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#1
Posted to alt.binaries.schematics.electronic
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Using a photoresistor and light to turn a transistor OFF...
As per my post in SEB, I am trying to use a photo resistor and sunlight to
turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave |
#2
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On 10/07/2011 06:36 AM, Dave wrote:
As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |
#3
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
"Phil Hobbs" wrote in message
... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net Oh, man. Something to WORK with. THANK YOU! Much appreciated... Dave http://electrooptical.net |
#4
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On 10/07/2011 07:13 AM, Dave wrote:
"Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Oh, man. Something to WORK with. THANK YOU! Much appreciated... Dave De nada. If you're planning to use that circuit for real, you might want an 0.1 uF cap from gate to source. That'll make it less twitchy and less vulnerable to electrostatic discharge. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |
#5
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
"Phil Hobbs" wrote in message ... On 10/07/2011 07:13 AM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Oh, man. Something to WORK with. THANK YOU! Much appreciated... Dave De nada. If you're planning to use that circuit for real, you might want an 0.1 uF cap from gate to source. That'll make it less twitchy and less vulnerable to electrostatic discharge. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net Gotcha. Thanks again. D |
#6
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On Fri, 07 Oct 2011 07:26:02 -0400, Phil Hobbs
wrote: On 10/07/2011 07:13 AM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Oh, man. Something to WORK with. THANK YOU! Much appreciated... Dave De nada. If you're planning to use that circuit for real, you might want an 0.1 uF cap from gate to source. That'll make it less twitchy and less vulnerable to electrostatic discharge. Phil has already answered the hard part but for the posting schematics part, try either AACircuit or LTSpice. AACircuit is available over at http://www.tech-chat.de/aacircuit.html A rendering of your right-hand snippet would look like (view with a fixed-pitch font): 2N3904 V- o-------o--------- ----------. | ^ / | | --- | | | .-. .-. | | | | | | | | 160 120 | | | '-' '-' | | | | | | | | o----------' | | | | | | | .-. - | | ^ - 680 | | | '-' | NTE 30045 | | | | V+ o-------o----------------------' (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Stylized but understandable -- and easier than trying to do it in a text editor or Usenet client's window. LTSpice is one of several free apps provided by Linear Technology http://www.linear.com/designtools/software/ It is a full Spice simulator but it's also used around here to pass the schematics as ASCII netlists. AACircuit is typically best for small snippets, and nice since they are directly viewable. LTSpice for the larger layouts. Version 4 SHEET 1 880 680 WIRE 128 -32 -16 -32 WIRE 208 -32 128 -32 WIRE 384 -32 304 -32 WIRE 128 48 128 -32 WIRE 384 48 384 -32 WIRE 128 160 128 128 WIRE 256 160 256 32 WIRE 256 160 128 160 WIRE 128 192 128 160 WIRE 384 208 384 128 WIRE 128 336 128 272 WIRE 128 336 -16 336 WIRE 384 336 384 272 WIRE 384 336 128 336 SYMBOL res 112 32 R0 SYMATTR InstName R1 SYMATTR Value 120 SYMBOL res 112 176 R0 SYMATTR InstName R2 SYMATTR Value 680 SYMBOL res 368 32 R0 SYMATTR InstName R3 SYMATTR Value 160 SYMBOL npn 304 32 M270 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL LED 400 272 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 TEXT -56 -32 Left 2 ;V- TEXT -64 336 Left 2 ;V+ -- Rich Webb Norfolk, VA |
#7
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On Fri, 07 Oct 2011 06:59:06 -0400, Phil Hobbs wrote:
On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* I couldn't find the original post, but if you're driving 20mA to an LED you should only need a mA (at most!) into the base of a BJT. So you could almost use Dr Hobbs's circuit above with an NPN, or use something like V+ o----------------o------------. | | | | .-. .-. | | R2 | | R5 | | | | '-' '-' | | | | .---------o | | | | | | V - | .-. - | | | R3 | D1 | | | | | '-' | | | | | | |/ | o----------| Q1 | | | | | | .-. .-. | ~ | | R1 | | R4 | ~ | | | | | '-' '-' | | | | | | | | | | V- o -----o---------o------------' (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Set up R2 and R3 to bias the transistor on, with R4 to lend a bit of authority pulling the base down. When R1 starts to conduct the junction of R2 and R3 doesn't have to get all the way down to 0.6V in order to turn Q1 off fully. Come to think of it, you could do this all with a jelly-bean comparator, and add some hysteresis to boot. Then D1 would snap on and off, instead of shivering on and shivering off as the light changes. -- www.wescottdesign.com |
#8
Posted to alt.binaries.schematics.electronic
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Using a photoresistor and light to turn a transistor OFF...
"Dave" wrote in message ... As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... There were several projects in the Philips EE kits based on a 2 transistor schmidt-trigger that produced a nice snap on/off with an ORP12 LDR. Haven't looked recently but there was some guy in the Nederlands running a Philips EE website with a collection of handbooks in various languages, between the schematics in the handbooks and the circuit overlay cards there's ample examples of a simple circuit that will do the job. |
#9
Posted to alt.binaries.schematics.electronic
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Using a photoresistor and light to turn a transistor OFF...
"Dave" wrote in message ... As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave Some 2-transistor LDR switches among this lot: http://ee.old.no/library/ |
#10
Posted to alt.binaries.schematics.electronic
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Using a photoresistor and light to turn a transistor OFF...
"Dave" schreef in bericht ... As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave Why use a photo resistor while you have a solar cell at hand? Increase the 120/680 voltage divider to at least 1k2/6k8 and place it across the solar cell. You may need to change one of them to find the right switching point (though it's more a traject the a point) or use a 10k/lin potmeter for experimenting. petrus bitbyter |
#11
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On Fri, 07 Oct 2011 07:26:02 -0400, Phil Hobbs
wrote: On 10/07/2011 07:13 AM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? I've seen LDRs fry from too much light+current. I humbly suggest Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | R R R R R R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* John |
#12
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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Using a photoresistor and light to turn a transistor OFF...
On 10/08/2011 06:06 PM, John Larkin wrote:
On Fri, 07 Oct 2011 07:26:02 -0400, Phil Hobbs wrote: On 10/07/2011 07:13 AM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? I've seen LDRs fry from too much light+current. I humbly suggest Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | R R R R R R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* John I haven't seen one fry itself on a 5V supply, but I suppose it's possible. The extra resistor is good insurance, for sure. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |
#13
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Using a photoresistor and light to turn a transistor OFF...
On Sat, 08 Oct 2011 15:06:56 -0700, John Larkin
wrote: I've seen LDRs fry from too much light+current. I humbly suggest I've done that... cobbled together a circuit with zero calculating and it worked like a champ- until summer came then direct sunlight was enough to lower the resistance and raise the ambient and poof no more LDR. |
#14
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Using a photoresistor and light to turn a transistor OFF...
default wrote in message ... On Sat, 08 Oct 2011 15:06:56 -0700, John Larkin wrote: I've seen LDRs fry from too much light+current. I humbly suggest I've done that... cobbled together a circuit with zero calculating and it worked like a champ- until summer came then direct sunlight was enough to lower the resistance and raise the ambient and poof no more LDR. Your LDR turned into a poof?! |
#15
Posted to alt.binaries.schematics.electronic,sci.electronics.basics,sci.electronics.design
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
On Fri, 7 Oct 2011 05:36:05 -0500, "Dave" wrote:
As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... --- While Petrus' suggestion to use the PV array as the sensor is excellent, it has the drawback that setting the switching point and getting a nice "snap" into the LED is difficult, if not impossible, using a single transistor. Using a comparator capable of driving a 50 mA load solves both problems at once. I've attached an LTspice circuit list as a .asc file, and it should run if you click on it and you've got LTspice installed on your machine. If not, here it is for all of you folks who might be interested but can't get to abse: Version 4 SHEET 1 1260 680 WIRE -256 -32 -304 -32 WIRE -128 -32 -192 -32 WIRE -32 -32 -128 -32 WIRE 208 -32 64 -32 WIRE 480 -32 432 -32 WIRE 704 -32 544 -32 WIRE 800 -32 704 -32 WIRE 944 -32 800 -32 WIRE 976 -32 944 -32 WIRE 1088 -32 1056 -32 WIRE 800 0 800 -32 WIRE 1088 16 1088 -32 WIRE 208 32 208 -32 WIRE 944 80 944 -32 WIRE -304 112 -304 -32 WIRE -96 112 -304 112 WIRE 16 112 16 32 WIRE 16 112 -16 112 WIRE 800 112 800 80 WIRE 912 112 800 112 WIRE 1088 128 1088 80 WIRE 1088 128 992 128 WIRE 432 144 432 -32 WIRE 480 144 432 144 WIRE 608 144 560 144 WIRE 880 144 608 144 WIRE 912 144 880 144 WIRE -304 176 -304 112 WIRE -128 176 -128 -32 WIRE 16 176 16 112 WIRE 208 176 208 112 WIRE 432 176 432 144 WIRE 704 176 704 -32 WIRE 928 192 928 176 WIRE 944 192 944 176 WIRE 944 192 928 192 WIRE 608 224 608 144 WIRE 800 224 800 112 WIRE 880 256 880 144 WIRE 976 256 880 256 WIRE 1088 256 1088 128 WIRE 1088 256 1056 256 WIRE -304 288 -304 256 WIRE -128 288 -128 256 WIRE 432 288 432 256 WIRE 704 288 704 256 WIRE -304 400 -304 368 WIRE -128 400 -128 368 WIRE -128 400 -304 400 WIRE 16 400 16 256 WIRE 16 400 -128 400 WIRE 208 400 208 240 WIRE 208 400 16 400 WIRE 432 400 432 368 WIRE 608 400 608 304 WIRE 608 400 432 400 WIRE 704 400 704 368 WIRE 704 400 608 400 WIRE 800 400 800 304 WIRE 800 400 704 400 WIRE 944 400 944 192 WIRE 944 400 800 400 WIRE -304 448 -304 400 WIRE 432 448 432 400 FLAG 432 448 0 FLAG -304 448 0 SYMBOL res 1072 -48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 150 SYMBOL LED 1072 16 R0 SYMATTR InstName D1 SYMATTR Value NSSWS108T SYMBOL voltage 432 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky 480 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage 704 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 12 SYMBOL res 688 160 R0 SYMATTR InstName R2 SYMATTR Value .1 SYMBOL res 784 208 R0 SYMATTR InstName R3 SYMATTR Value 50k SYMBOL Comparators\\LT1011 944 128 R0 WINDOW 0 53 20 Left 2 WINDOW 3 46 47 Left 2 SYMATTR InstName U1 SYMBOL res 816 96 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res 416 160 R0 SYMATTR InstName R5 SYMATTR Value 10 SYMBOL res 576 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL pnp 64 32 M270 SYMATTR InstName Q1 SYMATTR Value 2N3906 SYMBOL res 224 128 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R7 SYMATTR Value 150 SYMBOL LED 192 176 R0 SYMATTR InstName D3 SYMATTR Value NSSWS108T SYMBOL voltage -304 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky -256 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D4 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -128 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 12 SYMBOL res -144 160 R0 SYMATTR InstName R8 SYMATTR Value .1 SYMBOL res -320 160 R0 SYMATTR InstName R9 SYMATTR Value 10 SYMBOL res 0 96 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 1k SYMBOL res 32 272 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R11 SYMATTR Value 100k SYMBOL res 1072 240 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 1meg SYMBOL res 592 208 R0 WINDOW 0 -52 32 Left 2 WINDOW 3 -55 59 Left 2 SYMATTR InstName R13 SYMATTR Value 150k TEXT -290 424 Left 2 !.tran 12 Notice that R10 R11 sets the switching "point" for Q1, but also smears the ON to OFF period of D3 over a very wide range. R4 R3 sets the switching point for U1, which then switches D1 ON and OFF very quickly, no matter where the switching point lies. BTW, I've crossposted this to sed and seb. -- JF |
#16
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
"John Fields" schreef in bericht ... On Fri, 7 Oct 2011 05:36:05 -0500, "Dave" wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... --- While Petrus' suggestion to use the PV array as the sensor is excellent, it has the drawback that setting the switching point and getting a nice "snap" into the LED is difficult, if not impossible, using a single transistor. Using a comparator capable of driving a 50 mA load solves both problems at once. I've attached an LTspice circuit list as a .asc file, and it should run if you click on it and you've got LTspice installed on your machine. If not, here it is for all of you folks who might be interested but can't get to abse: Version 4 SHEET 1 1260 680 WIRE -256 -32 -304 -32 WIRE -128 -32 -192 -32 WIRE -32 -32 -128 -32 WIRE 208 -32 64 -32 WIRE 480 -32 432 -32 WIRE 704 -32 544 -32 WIRE 800 -32 704 -32 WIRE 944 -32 800 -32 WIRE 976 -32 944 -32 WIRE 1088 -32 1056 -32 WIRE 800 0 800 -32 WIRE 1088 16 1088 -32 WIRE 208 32 208 -32 WIRE 944 80 944 -32 WIRE -304 112 -304 -32 WIRE -96 112 -304 112 WIRE 16 112 16 32 WIRE 16 112 -16 112 WIRE 800 112 800 80 WIRE 912 112 800 112 WIRE 1088 128 1088 80 WIRE 1088 128 992 128 WIRE 432 144 432 -32 WIRE 480 144 432 144 WIRE 608 144 560 144 WIRE 880 144 608 144 WIRE 912 144 880 144 WIRE -304 176 -304 112 WIRE -128 176 -128 -32 WIRE 16 176 16 112 WIRE 208 176 208 112 WIRE 432 176 432 144 WIRE 704 176 704 -32 WIRE 928 192 928 176 WIRE 944 192 944 176 WIRE 944 192 928 192 WIRE 608 224 608 144 WIRE 800 224 800 112 WIRE 880 256 880 144 WIRE 976 256 880 256 WIRE 1088 256 1088 128 WIRE 1088 256 1056 256 WIRE -304 288 -304 256 WIRE -128 288 -128 256 WIRE 432 288 432 256 WIRE 704 288 704 256 WIRE -304 400 -304 368 WIRE -128 400 -128 368 WIRE -128 400 -304 400 WIRE 16 400 16 256 WIRE 16 400 -128 400 WIRE 208 400 208 240 WIRE 208 400 16 400 WIRE 432 400 432 368 WIRE 608 400 608 304 WIRE 608 400 432 400 WIRE 704 400 704 368 WIRE 704 400 608 400 WIRE 800 400 800 304 WIRE 800 400 704 400 WIRE 944 400 944 192 WIRE 944 400 800 400 WIRE -304 448 -304 400 WIRE 432 448 432 400 FLAG 432 448 0 FLAG -304 448 0 SYMBOL res 1072 -48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 150 SYMBOL LED 1072 16 R0 SYMATTR InstName D1 SYMATTR Value NSSWS108T SYMBOL voltage 432 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky 480 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage 704 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 12 SYMBOL res 688 160 R0 SYMATTR InstName R2 SYMATTR Value .1 SYMBOL res 784 208 R0 SYMATTR InstName R3 SYMATTR Value 50k SYMBOL Comparators\\LT1011 944 128 R0 WINDOW 0 53 20 Left 2 WINDOW 3 46 47 Left 2 SYMATTR InstName U1 SYMBOL res 816 96 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res 416 160 R0 SYMATTR InstName R5 SYMATTR Value 10 SYMBOL res 576 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL pnp 64 32 M270 SYMATTR InstName Q1 SYMATTR Value 2N3906 SYMBOL res 224 128 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R7 SYMATTR Value 150 SYMBOL LED 192 176 R0 SYMATTR InstName D3 SYMATTR Value NSSWS108T SYMBOL voltage -304 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky -256 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D4 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -128 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 12 SYMBOL res -144 160 R0 SYMATTR InstName R8 SYMATTR Value .1 SYMBOL res -320 160 R0 SYMATTR InstName R9 SYMATTR Value 10 SYMBOL res 0 96 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 1k SYMBOL res 32 272 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R11 SYMATTR Value 100k SYMBOL res 1072 240 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 1meg SYMBOL res 592 208 R0 WINDOW 0 -52 32 Left 2 WINDOW 3 -55 59 Left 2 SYMATTR InstName R13 SYMATTR Value 150k TEXT -290 424 Left 2 !.tran 12 Notice that R10 R11 sets the switching "point" for Q1, but also smears the ON to OFF period of D3 over a very wide range. R4 R3 sets the switching point for U1, which then switches D1 ON and OFF very quickly, no matter where the switching point lies. BTW, I've crossposted this to sed and seb. -- JF I considered the use of a comparator though not the LT1011 but the LM393 or similar. FAIK more popular, almost everywhere available and maybe cheaper as well. The next thing could be a two transistor Schmitt trigger. I ever calculated every component of it and I can still do so. It's just a matter of setting the threshold and the hysteresis to the required values. But the one transistor solution struck me for it's simplicity, low component count and light effect. So when the (sun)light is fading, the LED starts to glow faintly to come to full brightness when it grows really dark. Next morning the other way around if there's enough energy left in the battery that is. petrus bitbyter |
#17
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
On Sun, 9 Oct 2011 23:15:44 +0200, "petrus bitbyter"
wrote: "John Fields" schreef in bericht .. . On Fri, 7 Oct 2011 05:36:05 -0500, "Dave" wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... --- While Petrus' suggestion to use the PV array as the sensor is excellent, it has the drawback that setting the switching point and getting a nice "snap" into the LED is difficult, if not impossible, using a single transistor. Using a comparator capable of driving a 50 mA load solves both problems at once. .. .. .. I considered the use of a comparator though not the LT1011 but the LM393 or similar. FAIK more popular, almost everywhere available and maybe cheaper as well. --- Indeed, but incapable of handling, by itself, the 50mA load current the OP was asking for. The LT1011 is an improved LM311 clone and I used it because it was in Linear's library, but an LM311 would work just as well for about 1/4 the price, qty 1. --- The next thing could be a two transistor Schmitt trigger. I ever calculated every component of it and I can still do so. It's just a matter of setting the threshold and the hysteresis to the required values. --- Post a schematic, please? --- But the one transistor solution struck me for it's simplicity, low component count and light effect. So when the (sun)light is fading, the LED starts to glow faintly to come to full brightness when it grows really dark. Next morning the other way around if there's enough energy left in the battery that is. --- Yup! -- JF |
#18
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Using a photoresistor and light to turn a transistor OFF... -Night light.asc
petrus bitbyter wrote:
"John Fields" schreef in bericht ... On Fri, 7 Oct 2011 05:36:05 -0500, "Dave" wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... --- While Petrus' suggestion to use the PV array as the sensor is excellent, it has the drawback that setting the switching point and getting a nice "snap" into the LED is difficult, if not impossible, using a single transistor. Using a comparator capable of driving a 50 mA load solves both problems at once. I've attached an LTspice circuit list as a .asc file, and it should run if you click on it and you've got LTspice installed on your machine. If not, here it is for all of you folks who might be interested but can't get to abse: Version 4 SHEET 1 1260 680 WIRE -256 -32 -304 -32 WIRE -128 -32 -192 -32 WIRE -32 -32 -128 -32 WIRE 208 -32 64 -32 WIRE 480 -32 432 -32 WIRE 704 -32 544 -32 WIRE 800 -32 704 -32 WIRE 944 -32 800 -32 WIRE 976 -32 944 -32 WIRE 1088 -32 1056 -32 WIRE 800 0 800 -32 WIRE 1088 16 1088 -32 WIRE 208 32 208 -32 WIRE 944 80 944 -32 WIRE -304 112 -304 -32 WIRE -96 112 -304 112 WIRE 16 112 16 32 WIRE 16 112 -16 112 WIRE 800 112 800 80 WIRE 912 112 800 112 WIRE 1088 128 1088 80 WIRE 1088 128 992 128 WIRE 432 144 432 -32 WIRE 480 144 432 144 WIRE 608 144 560 144 WIRE 880 144 608 144 WIRE 912 144 880 144 WIRE -304 176 -304 112 WIRE -128 176 -128 -32 WIRE 16 176 16 112 WIRE 208 176 208 112 WIRE 432 176 432 144 WIRE 704 176 704 -32 WIRE 928 192 928 176 WIRE 944 192 944 176 WIRE 944 192 928 192 WIRE 608 224 608 144 WIRE 800 224 800 112 WIRE 880 256 880 144 WIRE 976 256 880 256 WIRE 1088 256 1088 128 WIRE 1088 256 1056 256 WIRE -304 288 -304 256 WIRE -128 288 -128 256 WIRE 432 288 432 256 WIRE 704 288 704 256 WIRE -304 400 -304 368 WIRE -128 400 -128 368 WIRE -128 400 -304 400 WIRE 16 400 16 256 WIRE 16 400 -128 400 WIRE 208 400 208 240 WIRE 208 400 16 400 WIRE 432 400 432 368 WIRE 608 400 608 304 WIRE 608 400 432 400 WIRE 704 400 704 368 WIRE 704 400 608 400 WIRE 800 400 800 304 WIRE 800 400 704 400 WIRE 944 400 944 192 WIRE 944 400 800 400 WIRE -304 448 -304 400 WIRE 432 448 432 400 FLAG 432 448 0 FLAG -304 448 0 SYMBOL res 1072 -48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 150 SYMBOL LED 1072 16 R0 SYMATTR InstName D1 SYMATTR Value NSSWS108T SYMBOL voltage 432 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky 480 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage 704 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 12 SYMBOL res 688 160 R0 SYMATTR InstName R2 SYMATTR Value .1 SYMBOL res 784 208 R0 SYMATTR InstName R3 SYMATTR Value 50k SYMBOL Comparators\\LT1011 944 128 R0 WINDOW 0 53 20 Left 2 WINDOW 3 46 47 Left 2 SYMATTR InstName U1 SYMBOL res 816 96 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res 416 160 R0 SYMATTR InstName R5 SYMATTR Value 10 SYMBOL res 576 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL pnp 64 32 M270 SYMATTR InstName Q1 SYMATTR Value 2N3906 SYMBOL res 224 128 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R7 SYMATTR Value 150 SYMBOL LED 192 176 R0 SYMATTR InstName D3 SYMATTR Value NSSWS108T SYMBOL voltage -304 272 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value PULSE(0 16 0 12 0 0 24) SYMBOL schottky -256 -16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D4 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -128 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 12 SYMBOL res -144 160 R0 SYMATTR InstName R8 SYMATTR Value .1 SYMBOL res -320 160 R0 SYMATTR InstName R9 SYMATTR Value 10 SYMBOL res 0 96 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 1k SYMBOL res 32 272 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R11 SYMATTR Value 100k SYMBOL res 1072 240 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 1meg SYMBOL res 592 208 R0 WINDOW 0 -52 32 Left 2 WINDOW 3 -55 59 Left 2 SYMATTR InstName R13 SYMATTR Value 150k TEXT -290 424 Left 2 !.tran 12 Notice that R10 R11 sets the switching "point" for Q1, but also smears the ON to OFF period of D3 over a very wide range. R4 R3 sets the switching point for U1, which then switches D1 ON and OFF very quickly, no matter where the switching point lies. BTW, I've crossposted this to sed and seb. -- JF I considered the use of a comparator though not the LT1011 but the LM393 or similar. FAIK more popular, almost everywhere available and maybe cheaper as well. The next thing could be a two transistor Schmitt trigger. I ever calculated every component of it and I can still do so. It's just a matter of setting the threshold and the hysteresis to the required values. But the one transistor solution struck me for it's simplicity, low component count and light effect. So when the (sun)light is fading, the LED starts to glow faintly to come to full brightness when it grows really dark. Next morning the other way around if there's enough energy left in the battery that is. petrus bitbyter 47 ___ +---------+-----+-|___|+-----------+ | | | + + | 3V bat--- | | - - | | ^ Vf 50 LED V - | + Sch - === | | GND | + | | +------------------+ + | | | 10K | | | ___ + | PNP |--|___|-+ | | /| | - | + | --- 3 Volt PV | | | | | | | | + | GND | GND | | | | | +-----------------+ Something like that? P.S. That circuit should also charge. Use 50mv Vf Schottky diode. The only problem is, you need at least 3 volts from the PV |
#19
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
On Sun, 09 Oct 2011 19:32:36 -0400, Jamie
t wrote: 47 ___ +---------+-----+-|___|+-----------+ | | | + + | 3V bat--- | | - - | | ^ Vf 50 LED V - | + Sch - === | | GND | + | | +------------------+ + | | | 10K | | | ___ + | PNP |--|___|-+ | | /| | - | + | --- 3 Volt PV | | | | | | | | + | GND | GND | | | | | +-----------------+ Something like that? P.S. That circuit should also charge. Use 50mv Vf Schottky diode. --- 50mV??? Got a part number? --- The only problem is, you need at least 3 volts from the PV --- 3V from the PV won't cut it, since the Schottky's in the way and you'll need more than 3v to charge the battery. -- JF |
#20
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Using a photoresistor and light to turn a transistor OFF... -Night light.asc
John Fields wrote:
On Sun, 09 Oct 2011 19:32:36 -0400, Jamie t wrote: 47 ___ +---------+-----+-|___|+-----------+ | | | + + | 3V bat--- | | - - | | ^ Vf 50 LED V - | + Sch - === | | GND | + | | +------------------+ + | | | 10K | | | ___ + | PNP |--|___|-+ | | /| | - | + | --- 3 Volt PV | | | | | | | | + | GND | GND | | | | | +-----------------+ Something like that? P.S. That circuit should also charge. Use 50mv Vf Schottky diode. --- 50mV??? Got a part number? --- The only problem is, you need at least 3 volts from the PV --- 3V from the PV won't cut it, since the Schottky's in the way and you'll need more than 3v to charge the battery. it's 50mv with low load...that of course goes up as the current does. for low I, a 1N5817 will reach that point. It depends on how you use it. I actually meant to say the Rs = 0.050; Much better than the usual 0.5xxxx found in others. As for the PV voltage, how else was this suppose to work? I didn't see a voltage multiplier in the request, and they do make multi cell PV's, I have a whole drive way full of LED lights with multi-cell PVs in them. Jamie |
#21
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
"John Fields" schreef in bericht ... On Sun, 9 Oct 2011 23:15:44 +0200, "petrus bitbyter" wrote: "John Fields" schreef in bericht . .. On Fri, 7 Oct 2011 05:36:05 -0500, "Dave" wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... --- While Petrus' suggestion to use the PV array as the sensor is excellent, it has the drawback that setting the switching point and getting a nice "snap" into the LED is difficult, if not impossible, using a single transistor. Using a comparator capable of driving a 50 mA load solves both problems at once. . . . I considered the use of a comparator though not the LT1011 but the LM393 or similar. FAIK more popular, almost everywhere available and maybe cheaper as well. --- Indeed, but incapable of handling, by itself, the 50mA load current the OP was asking for. The LT1011 is an improved LM311 clone and I used it because it was in Linear's library, but an LM311 would work just as well for about 1/4 the price, qty 1. --- The next thing could be a two transistor Schmitt trigger. I ever calculated every component of it and I can still do so. It's just a matter of setting the threshold and the hysteresis to the required values. --- Post a schematic, please? --- But the one transistor solution struck me for it's simplicity, low component count and light effect. So when the (sun)light is fading, the LED starts to glow faintly to come to full brightness when it grows really dark. Next morning the other way around if there's enough energy left in the battery that is. --- Yup! -- JF The LED mentioned by the OP can handle a maximum current of 30mA. The series resistor of 160R reduces this to about 10mA, depending on the forward voltage of the LED. So a LM311 would be a good option using a comparator. A two transistor Schmitt-trigger is a classic. See below. I'm sure it'll work though I made no extensive calculations this time. + solar-----+----|------+----------------------+-------+ cell | 1N5817 | | | | | V LED | | | - | | | | | | | | | .-. .-. .-. | | | | | | | | | |22k | |1k5 | |47 | +4V8 '-' '-' '-' --- | | ___ | - | +-----|___|----+ | | | | 3k3 | | | | | | |/ --- | ___ |/ +-----| BC547 - +--|___|---| BC547 | | | | 680 | | | | | | | | --- | +-----+--------)-------+ - | | | | | | | | .-. .-. .-. --- | | | | | | - | |3k9 | |100 | |3k9 | '-' '-' '-' | | | | | | | | | - solar---+------------------+--------+---------------+-- GND cell created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de petrus bitbyter |
#22
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
On Sun, 09 Oct 2011 20:13:31 -0400, Jamie
t wrote: John Fields wrote: On Sun, 09 Oct 2011 19:32:36 -0400, Jamie t wrote: 47 ___ +---------+-----+-|___|+-----------+ | | | + + | 3V bat--- | | - - | | ^ Vf 50 LED V - | + Sch - === | | GND | + | | +------------------+ + | | | 10K | | | ___ + | PNP |--|___|-+ | | /| | - | + | --- 3 Volt PV | | | | | | | | + | GND | GND | | | | | +-----------------+ Something like that? P.S. That circuit should also charge. Use 50mv Vf Schottky diode. --- 50mV??? Got a part number? --- The only problem is, you need at least 3 volts from the PV --- 3V from the PV won't cut it, since the Schottky's in the way and you'll need more than 3v to charge the battery. it's 50mv with low load...that of course goes up as the current does. for low I, a 1N5817 will reach that point. It depends on how you use it. --- I just measured the current through a 1N5817 with a 50mV drop across it, and it turned out to be 23 microamps, so if you're planning to charge the battery with that I'm afraid it's going to take more than just a day, even at full sun in the middle of the summer. --- I actually meant to say the Rs = 0.050; Much better than the usual 0.5xxxx found in others. --- Rs??? What are you talking about? --- As for the PV voltage, how else was this suppose to work? I didn't see a voltage multiplier in the request, and they do make multi cell PV's, I have a whole drive way full of LED lights with multi-cell PVs in them. --- Your schematic clearly states "3 Volt PV", so if you meant more voltage than that you should have shown it. Personally, I think you're trying to bull**** your way out of the corner you've stupidly painted yourself into. -- JF |
#23
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Using a photoresistor and light to turn a transistor OFF... - Night light.asc
On Mon, 10 Oct 2011 11:04:04 -0500, John Fields
wrote: On Sun, 09 Oct 2011 20:13:31 -0400, Jamie wrote: John Fields wrote: On Sun, 09 Oct 2011 19:32:36 -0400, Jamie t wrote: 47 ___ +---------+-----+-|___|+-----------+ | | | + + | 3V bat--- | | - - | | ^ Vf 50 LED V - | + Sch - === | | GND | + | | +------------------+ + | | | 10K | | | ___ + | PNP |--|___|-+ | | /| | - | + | --- 3 Volt PV | | | | | | | | + | GND | GND | | | | | +-----------------+ Something like that? P.S. That circuit should also charge. Use 50mv Vf Schottky diode. --- 50mV??? Got a part number? --- The only problem is, you need at least 3 volts from the PV --- 3V from the PV won't cut it, since the Schottky's in the way and you'll need more than 3v to charge the battery. it's 50mv with low load...that of course goes up as the current does. for low I, a 1N5817 will reach that point. It depends on how you use it. --- I just measured the current through a 1N5817 with a 50mV drop across it, and it turned out to be 23 microamps, so if you're planning to charge the battery with that I'm afraid it's going to take more than just a day, even at full sun in the middle of the summer. --- I actually meant to say the Rs = 0.050; Much better than the usual 0.5xxxx found in others. --- Rs??? What are you talking about? Diode series resistance, the ohmic part of a diode's behavior. It usually only matters at higher currents. It has a positive TC, the opposite of the junction's TC. John |
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My God, it WORKS!
"Phil Hobbs" wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. The whole thing goes into a mushroom lawn ornament, with the LED inside the mushroom cap to shine down on the fairy sitting underneath at night. Gonna look nice between the sage and Mexican Mint Merigold, which is a weed down in Mexico, but grows great in Texas and tastes just like Tarragon (which absolutely will not grow in Texas.) Dave |
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My God, it WORKS!
On Mon, 17 Oct 2011 17:53:01 -0500, "Dave" wrote:
"Phil Hobbs" wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. The whole thing goes into a mushroom lawn ornament, with the LED inside the mushroom cap to shine down on the fairy sitting underneath at night. Gonna look nice between the sage and Mexican Mint Merigold, which is a weed down in Mexico, but grows great in Texas and tastes just like Tarragon (which absolutely will not grow in Texas.) Dave A likely story ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
#26
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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My God, it WORKS!
On 10/17/2011 06:53 PM, Dave wrote:
"Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. The whole thing goes into a mushroom lawn ornament, with the LED inside the mushroom cap to shine down on the fairy sitting underneath at night. Gonna look nice between the sage and Mexican Mint Merigold, which is a weed down in Mexico, but grows great in Texas and tastes just like Tarragon (which absolutely will not grow in Texas.) Dave You're welcome. As the wise man said about beer, 2N7000s are "Good for what ails ya, and if nothing ails ya, it's good for that too." Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |
#27
Posted to alt.binaries.schematics.electronic,sci.electronics.basics
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My God, it WORKS!
"Phil Hobbs" wrote in message ... On 10/17/2011 06:53 PM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. The whole thing goes into a mushroom lawn ornament, with the LED inside the mushroom cap to shine down on the fairy sitting underneath at night. Gonna look nice between the sage and Mexican Mint Merigold, which is a weed down in Mexico, but grows great in Texas and tastes just like Tarragon (which absolutely will not grow in Texas.) Dave You're welcome. As the wise man said about beer, 2N7000s are "Good for what ails ya, and if nothing ails ya, it's good for that too." Cheers Phil Hobbs LOL! And thank you for that belly laugh. shaking head Cheers to you, sir! D -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |
#28
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My God, it WORKS!
On Mon, 17 Oct 2011 20:41:06 -0500, "Dave" wrote:
"Phil Hobbs" wrote in message ... On 10/17/2011 06:53 PM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. --- Geez, I feel kind of miffed since my (Jan's) solution would allow you to rid yourself of the LDR and its associated circuitry. With that in mind, why would you find Doctor Phil's circuit, which is wasteful of power and money by having it drive an unnecessary LDR, superior to mine? -- JF |
#29
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My God, it WORKS!
"John Fields" wrote in message ... On Mon, 17 Oct 2011 20:41:06 -0500, "Dave" wrote: "Phil Hobbs" wrote in message ... On 10/17/2011 06:53 PM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. --- Geez, I feel kind of miffed since my (Jan's) solution would allow you to rid yourself of the LDR and its associated circuitry. With that in mind, why would you find Doctor Phil's circuit, which is wasteful of power and money by having it drive an unnecessary LDR, superior to mine? -- JF Hey John. No offense intended, believe me. Your ASCII description translated into a schematic where my tiny photocell (I'm guessing that's what V3 was) was set up as 4 VDC, rather than .4 VDC, which is what it actually put out. And even then, when I set it all up, it looked like it ought to work, but it didn't. No idea why, other than that there is something about the tiny photocell that I don't know. Finally gave up on using that component. When my Digikey parts came in I put them together and they took off. That version worked, so I used it. Now I'm trying to find a 6V solar cell smaller than the 6"X6" behemoth I currenty have in place. Will probably go with one from Amazon that is 4"X3" and flexible. Take it easy... Dave |
#30
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My God, it WORKS!
On Wed, 19 Oct 2011 13:05:27 -0500, "Dave" wrote:
"John Fields" wrote in message .. . On Mon, 17 Oct 2011 20:41:06 -0500, "Dave" wrote: "Phil Hobbs" wrote in message ... On 10/17/2011 06:53 PM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. --- Geez, I feel kind of miffed since my (Jan's) solution would allow you to rid yourself of the LDR and its associated circuitry. With that in mind, why would you find Doctor Phil's circuit, which is wasteful of power and money by having it drive an unnecessary LDR, superior to mine? -- JF Hey John. No offense intended, believe me. Your ASCII description translated into a schematic where my tiny photocell (I'm guessing that's what V3 was) was set up as 4 VDC, rather than .4 VDC, which is what it actually put out. And even then, when I set it all up, it looked like it ought to work, but it didn't. No idea why, other than that there is something about the tiny photocell that I don't know. Finally gave up on using that component. When my Digikey parts came in I put them together and they took off. That version worked, so I used it. Now I'm trying to find a 6V solar cell smaller than the 6"X6" behemoth I currenty have in place. Will probably go with one from Amazon that is 4"X3" and flexible. --- No problem, but the circuit I was referring to wasn't the one with the tiny PV, it was the one with a PNP driving the LED which I posted as an LTspice circuit list along with two other circuits. Here it is in ASCII: .. 2N3906 .. +-[1N5817]-+---------E C-+ .. | | B | .. +-----------|-----+ | | .. | | | | [42] .. |+ |+ [POT]--+ | .. [PV] [BAT] |10k [LED] .. | | | |K .. +-----------+-----+---------+ Notice no LDR and its associated resistor. :-) Anyway, as long as you have something that works, that's what matters. BTW, make sure that you get a PV array with the capacity to charge the battery enough, during the day, so that the LED stays on for as long as you need it to at night. -- JF |
#31
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My God, it WORKS!
"John Fields" wrote in message ... On Wed, 19 Oct 2011 13:05:27 -0500, "Dave" wrote: "John Fields" wrote in message . .. On Mon, 17 Oct 2011 20:41:06 -0500, "Dave" wrote: "Phil Hobbs" wrote in message ... On 10/17/2011 06:53 PM, Dave wrote: "Phil wrote in message ... On 10/07/2011 06:36 AM, Dave wrote: As per my post in SEB, I am trying to use a photo resistor and sunlight to turn off a transistor that would otherwise be conducting like crazy, but can't quite make the leap of comprehension as to how to actually do this. Please see attached schematic parts that show more or less what I am trying to do this with. No part number for the photoresistor, sorry. It drops from multi-megohms in the dark to single-digit Ohms in the light and seems perfectly capable of carrying the 30 to 50 mA current I am working with at the voltages indicated. Would really appreciate it if someone could offer a hint as to how I should proceed with as few components as possible (small circuit board.) I hope that my method of posting the schematic portion of what I a working with is not too obtuse. Couldn't figure out any other way to do it... Many thanks... Dave You're wasting a gross amount of current in that bias network. How about a nice MOSFET? Say a 2N7002, source to V-, drain to series resistor+LED, LDR plus pot to set turn-on level: (V+)----*----------------* | | | R | R | R | R *---* | | | --- | R \ / ----- *- R ----- ----- R | R | | D | | |---* | | |--; 2N7000 *----------J |---* | | | S | | L | D | R | | | | | (V-)----*----------------* Man that was easy. Just had to get the MOSFET. Thank you, Phil Hobbs. I spent so much time wrestling with that other configuration, and this just flew together. And damn, but it works nice. Much appreciated. --- Geez, I feel kind of miffed since my (Jan's) solution would allow you to rid yourself of the LDR and its associated circuitry. With that in mind, why would you find Doctor Phil's circuit, which is wasteful of power and money by having it drive an unnecessary LDR, superior to mine? -- JF Hey John. No offense intended, believe me. Your ASCII description translated into a schematic where my tiny photocell (I'm guessing that's what V3 was) was set up as 4 VDC, rather than .4 VDC, which is what it actually put out. And even then, when I set it all up, it looked like it ought to work, but it didn't. No idea why, other than that there is something about the tiny photocell that I don't know. Finally gave up on using that component. When my Digikey parts came in I put them together and they took off. That version worked, so I used it. Now I'm trying to find a 6V solar cell smaller than the 6"X6" behemoth I currenty have in place. Will probably go with one from Amazon that is 4"X3" and flexible. --- No problem, but the circuit I was referring to wasn't the one with the tiny PV, it was the one with a PNP driving the LED which I posted as an LTspice circuit list along with two other circuits. Here it is in ASCII: . 2N3906 . +-[1N5817]-+---------E C-+ . | | B | . +-----------|-----+ | | . | | | | [42] . |+ |+ [POT]--+ | . [PV] [BAT] |10k [LED] . | | | |K . +-----------+-----+---------+ Notice no LDR and its associated resistor. :-) Anyway, as long as you have something that works, that's what matters. BTW, make sure that you get a PV array with the capacity to charge the battery enough, during the day, so that the LED stays on for as long as you need it to at night. -- JF Hey again. Oh, sorry, I missunderstood. Will have to go back and take another look at that particular circuit. I didn't know if I had any 2N3906s, and didn't push it past that. Will definetly check it out though. And yes, I am working to make sure that I am able to charge the batteries sufficiently to keep things running as long as possible. Thanks for mentioning that though, and the encouragement. Take it easy... D |
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