Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave, but -
nothing. When power is applied, it goes to ground, and I have checked and
rechecked all my connections. Somebody please tell me what I am doing
wrong. I used the same setup for a transistor tester, and it worked fine.
Keep thinking something has failed to make contact with the solder applied
to it, but that doesn't seem to be the trouble. I guess I'm asking if this
*looks* right, cause that would mean I do have a wiring error. Or is there
something here I don't know about the 555? Pin 3 should have a square wave
on it, even if it is not connected to anything but a scope, right?

Thanks,

Dave

Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave, but -
nothing. When power is applied, it goes to ground, and I have checked and
rechecked all my connections. Somebody please tell me what I am doing
wrong. I used the same setup for a transistor tester, and it worked fine.
Keep thinking something has failed to make contact with the solder applied
to it, but that doesn't seem to be the trouble. I guess I'm asking if this
*looks* right, cause that would mean I do have a wiring error. Or is there
something here I don't know about the 555? Pin 3 should have a square wave
on it, even if it is not connected to anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred.

"Fred Bartoli" " " wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Okaaay. Thanks Fred. Just out of curiousity, what made you think of this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave

On Mon, 12 Apr 2010 15:52:09 -0500, "Dave" wrote:




Okaaay. Thanks Fred. Just out of curiousity, what made you think of this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave


Hi Dave

Go here and read the part "Selecting External Components". You'll find
the answer to your ?

http://www.williamson-labs.com/555_apps.htm

"Fred Bartoli" " " wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a 1KHz
signal but that was okay. Problem is, the same problem persists. When the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave

"Hammy" wrote in message
...
On Mon, 12 Apr 2010 15:52:09 -0500, "Dave" wrote:




Okaaay. Thanks Fred. Just out of curiousity, what made you think of
this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave


Hi Dave

Go here and read the part "Selecting External Components". You'll find
the answer to your ?

http://www.williamson-labs.com/555_apps.htm

Hey Hammy. Checked it out, but it didn't really tell me anything I didnt
already know. If the problem were simply the signal being out of expected
parameters, or the resistors/cap being high or low in value, I would still
have some kind of signal to work with. Instead pin 3, which is the output,
goes to ground as soon as the power is turned on. As I told Fred I think I
have to have something hooked up wrong. Just have to figure out what it
is...

Thanks anyway.

Dave

On 4/12/2010 4:29 PM, Dave wrote:
"Fred Bartoli""" wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a 1KHz
signal but that was okay. Problem is, the same problem persists. When the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave



Dave,

I think everyone has been trying to tell you that your 47 ohm and 1uf
parts are just wrong. (but they are more polite)

Yes, I see that you "figured" that your numbers should work. But it does
not. You said so yourself.

I have no clue where 1000uf came from.

1nf = .001uf = 1000pf

For future reference: http://www.justradios.com/uFnFpF.html

hamilton

PS: do you have a scope ??

On Mon, 12 Apr 2010 17:32:47 -0500, "Dave" wrote:


"Hammy" wrote in message
.. .
On Mon, 12 Apr 2010 15:52:09 -0500, "Dave" wrote:




Okaaay. Thanks Fred. Just out of curiousity, what made you think of
this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave


Hi Dave

Go here and read the part "Selecting External Components". You'll find
the answer to your ?

http://www.williamson-labs.com/555_apps.htm

Hey Hammy. Checked it out, but it didn't really tell me anything I didnt
already know. If the problem were simply the signal being out of expected
parameters, or the resistors/cap being high or low in value, I would still
have some kind of signal to work with. Instead pin 3, which is the output,
goes to ground as soon as the power is turned on. As I told Fred I think I
have to have something hooked up wrong. Just have to figure out what it
is...

Thanks anyway.

Dave

Then you missed the part where it says "there are certain minimum
values of resistors......" and "it is recommended a 5kohm resistor be
the min for RA....."

You may have already damaged the timer. The timer charge/discharge is
current limited but it still may be damaged depending how long it was
running with those low resistor values.

Usually you would select as a high a value resistors as possible and a
low nF (nano farad) capacitor.

You might want to try it without your load ,first get the timer
working into a resitive load , then attach your JFET.

On Mon, 12 Apr 2010 17:29:49 -0500, "Dave" wrote:


"Fred Bartoli" " " wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a 1KHz
signal but that was okay. Problem is, the same problem persists. When the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave


My first thought, without looking at the data sheet or app note, was
that your resisters were too low in value, and that the capacitor was
much too large for your desired frequency.

The app note that was mentioned gives a minimum value for the timing
resistors of 5K, about 100 times what you used. Assuming you got the
math right, this means that the capacitor should be 0.01 uf. Using
47K resistors and a 0.001 uf (1000 nf) capacitor would be better, as
it gets the resistor value away from the recommended minimum value.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

"hamilton" wrote in message
...
On 4/12/2010 4:29 PM, Dave wrote:
"Fred Bartoli""" wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3
of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what
I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with
the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a
1KHz
signal but that was okay. Problem is, the same problem persists. When
the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave



Dave,

I think everyone has been trying to tell you that your 47 ohm and 1uf
parts are just wrong. (but they are more polite)

Yes, I see that you "figured" that your numbers should work. But it does
not. You said so yourself.

I have no clue where 1000uf came from.

1nf = .001uf = 1000pf

For future reference: http://www.justradios.com/uFnFpF.html

hamilton

PS: do you have a scope ??

AAaaaah. Crap. Well, I said I was ignorant. My apologies. And I guess
I did miss the part about 5K being the min for RA. Will have to go back and
look at that again, more slowly.

And I have plenty of .001uF disks. Damn. I'm sleep deprived right now, and
when I let that happen I get stupid.

Many thanks for the up front and plain-spoken answer. I frequently miss
hints. (Ask the wife.)

And yes, I have a scope. It's a 100MHz Tektronix (sp?). Can't remember the
model # but it's a rugged, militarized version of an already reliable model,
as I understand it.

'Preciate the help...

Dave

Back to the workbench.

On Mon, 12 Apr 2010 14:30:11 -0500, "Dave" wrote:

Building the attached schematic, only I have no signal output on pin 3 of
the 555. My calculations tell me it should be a 10.2 KHz squarewave, but -
nothing. When power is applied, it goes to ground, and I have checked and
rechecked all my connections. Somebody please tell me what I am doing
wrong. I used the same setup for a transistor tester, and it worked fine.
Keep thinking something has failed to make contact with the solder applied
to it, but that doesn't seem to be the trouble. I guess I'm asking if this
*looks* right, cause that would mean I do have a wiring error. Or is there
something here I don't know about the 555? Pin 3 should have a square wave
on it, even if it is not connected to anything but a scope, right?

Thanks,

Dave


Lose the 47 Ohms and the 1uF capacitor.

Tie pin 4 to +5V

Ground pin 7

Tie pins 2 & 6 together
^^^^^^^^^^
From there, 1nF to ground

From there to pin 3, a 72K resistor

...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 |

The only thing bipartisan in this country is hypocrisy

"Peter Bennett" wrote in message
news
On Mon, 12 Apr 2010 17:29:49 -0500, "Dave" wrote:


"Fred Bartoli" " " wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3
of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me what
I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with
the
solder applied to it, but that doesn't seem to be the trouble. I guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a
1KHz
signal but that was okay. Problem is, the same problem persists. When
the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave


My first thought, without looking at the data sheet or app note, was
that your resisters were too low in value, and that the capacitor was
much too large for your desired frequency.

The app note that was mentioned gives a minimum value for the timing
resistors of 5K, about 100 times what you used. Assuming you got the
math right, this means that the capacitor should be 0.01 uf. Using
47K resistors and a 0.001 uf (1000 nf) capacitor would be better, as
it gets the resistor value away from the recommended minimum value.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Hello Peter,

Yes, I see what you are saying now. I totally missed it from Fred and
Hamilton at first. Fortunately, Hamilton was persistant...

Dave

"Dave" wrote in message
netamerica...

"hamilton" wrote in message
...
On 4/12/2010 4:29 PM, Dave wrote:
"Fred Bartoli""" wrote in message
...
Dave a écrit :
Building the attached schematic, only I have no signal output on pin 3
of
the 555. My calculations tell me it should be a 10.2 KHz squarewave,
but - nothing. When power is applied, it goes to ground, and I have
checked and rechecked all my connections. Somebody please tell me
what I
am doing wrong. I used the same setup for a transistor tester, and it
worked fine. Keep thinking something has failed to make contact with
the
solder applied to it, but that doesn't seem to be the trouble. I
guess
I'm asking if this *looks* right, cause that would mean I do have a
wiring error. Or is there something here I don't know about the 555?
Pin 3 should have a square wave on it, even if it is not connected to
anything but a scope, right?

Thanks,

Dave




Change R1&R2 to 47K and the 1uF cap to 1nF.


--
Thanks,
Fred

Hey Fred,

I didn't have a 1000 uF cap, or anything reasonably close, so went with
a
10uF tantalum cap and the same 47 ohm resistors, figuring I would get a
1KHz
signal but that was okay. Problem is, the same problem persists. When
the
power comes on pin 3 of the 555 goes to ground. I have to be wiring it
wrong, is all I can figure. If it was configured properly, I should have
some type of signal on pin 3. Will look into it some more...

Thanks for the idea on changing the values.

Dave



Dave,

I think everyone has been trying to tell you that your 47 ohm and 1uf
parts are just wrong. (but they are more polite)

Yes, I see that you "figured" that your numbers should work. But it does
not. You said so yourself.

I have no clue where 1000uf came from.

1nf = .001uf = 1000pf

For future reference: http://www.justradios.com/uFnFpF.html

hamilton

PS: do you have a scope ??

AAaaaah. Crap. Well, I said I was ignorant. My apologies. And I
guess I did miss the part about 5K being the min for RA. Will have to go
back and look at that again, more slowly.

And I have plenty of .001uF disks. Damn. I'm sleep deprived right now,
and when I let that happen I get stupid.

Many thanks for the up front and plain-spoken answer. I frequently miss
hints. (Ask the wife.)

And yes, I have a scope. It's a 100MHz Tektronix (sp?). Can't remember
the model # but it's a rugged, militarized version of an already reliable
model, as I understand it.

'Preciate the help...

Dave

Back to the workbench.





Okay, I went back looking for what I obviously missed. And I did
*completely* miss that section. shaking head Thanks again, Hammy. And
now I know not to use ceramic disks for the timing cap. Fortunately I also
have plenty of silver mica caps, which is one of the alternatives that
article recommends. And I am sure I have damaged the 555 chip. But I have
another. Maybe this time I'll do it right.

I'm learning, slowly.

Many thanks,

Dave

On Mon, 12 Apr 2010 17:32:47 -0500, "Dave" wrote:


"Hammy" wrote in message
.. .
On Mon, 12 Apr 2010 15:52:09 -0500, "Dave" wrote:




Okaaay. Thanks Fred. Just out of curiousity, what made you think of
this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave


Hi Dave

Go here and read the part "Selecting External Components". You'll find
the answer to your ?

http://www.williamson-labs.com/555_apps.htm

Hey Hammy. Checked it out, but it didn't really tell me anything I didnt
already know. If the problem were simply the signal being out of expected
parameters, or the resistors/cap being high or low in value, I would still
have some kind of signal to work with. Instead pin 3, which is the output,
goes to ground as soon as the power is turned on. As I told Fred I think I
have to have something hooked up wrong. Just have to figure out what it
is...

---
Well, according to:

Version 4
SHEET 1 880 788
WIRE 224 192 -272 192
WIRE 544 192 448 192
WIRE -272 256 -272 192
WIRE -224 256 -272 256
WIRE -112 256 -144 256
WIRE 224 256 -112 256
WIRE 512 256 448 256
WIRE -112 320 -112 256
WIRE -80 320 -112 320
WIRE 48 320 0 320
WIRE 160 320 48 320
WIRE 224 320 160 320
WIRE 608 320 448 320
WIRE 480 384 448 384
WIRE 48 432 48 320
WIRE 608 480 608 320
WIRE 160 560 160 320
WIRE 512 560 512 256
WIRE 512 560 160 560
WIRE -272 592 -272 256
WIRE 480 592 480 384
WIRE 480 592 -272 592
WIRE -272 608 -272 592
WIRE -272 704 -272 688
WIRE 48 704 48 496
WIRE 48 704 -272 704
WIRE 544 704 544 192
WIRE 544 704 48 704
WIRE 608 704 608 560
WIRE 608 704 544 704
WIRE -272 768 -272 704
FLAG -272 768 0
SYMBOL Misc\\NE555 336 288 M0
SYMATTR InstName U1
SYMBOL voltage -272 592 M0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL res -96 304 M90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 58 VTop 0
SYMATTR InstName R1
SYMATTR Value 47
SYMBOL res -240 240 M90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 47
SYMBOL res 624 464 M0
WINDOW 0 -45 40 Left 0
WINDOW 3 -59 71 Left 0
SYMATTR InstName R3
SYMATTR Value 1000
SYMBOL cap 64 432 M0
WINDOW 0 -33 32 Left 0
WINDOW 3 -39 58 Left 0
SYMATTR InstName C1
SYMATTR Value 1e-6
TEXT -104 728 Right 0 !.tran .001 uic

it will oscillate, but that's for a bipolar 555, and at a frequency of
about 8.7 kHz.

If I had to guess, which I do, I'd guess that if pin 3 goes low when Vcc
goes high, and stays low, then you've either got the RESET pin wired to
GND or...


JF

On Mon, 12 Apr 2010 18:41:30 -0500, "Dave" wrote:


Okay, I went back looking for what I obviously missed. And I did
*completely* miss that section. shaking head Thanks again, Hammy. And
now I know not to use ceramic disks for the timing cap. Fortunately I also
have plenty of silver mica caps, which is one of the alternatives that
article recommends. And I am sure I have damaged the 555 chip. But I have
another. Maybe this time I'll do it right.

I'm learning, slowly.

Many thanks,

Dave

Others have pointed out some possible wiring errors you may want to
check.

The glaring thing to me was the low resistor values.

On Mon, 12 Apr 2010 20:12:08 -0400, Hammy wrote:

On Mon, 12 Apr 2010 18:41:30 -0500, "Dave" wrote:


Okay, I went back looking for what I obviously missed. And I did
*completely* miss that section. shaking head Thanks again, Hammy. And
now I know not to use ceramic disks for the timing cap. Fortunately I also
have plenty of silver mica caps, which is one of the alternatives that
article recommends. And I am sure I have damaged the 555 chip. But I have
another. Maybe this time I'll do it right.

I'm learning, slowly.

Many thanks,

Dave

Others have pointed out some possible wiring errors you may want to
check.

The glaring thing to me was the low resistor values.

---
Nice catch.

JF

On Mon, 12 Apr 2010 16:33:41 -0700, Jim Thompson
wrote:



From there to pin 3, a 72K resistor

...Jim Thompson


Where in the hell do you buy a 72K resistor without going to
precision? ANd why would you use a precision resistor when you will
have trouble getting capacitors better than 5%?

68K? 75K?

Jim

On Tue, 13 Apr 2010 09:52:36 -0700, RST Engineering
wrote:

On Mon, 12 Apr 2010 16:33:41 -0700, Jim Thompson
wrote:



From there to pin 3, a 72K resistor

...Jim Thompson


Where in the hell do you buy a 72K resistor without going to
precision? ANd why would you use a precision resistor when you will
have trouble getting capacitors better than 5%?

68K? 75K?

Jim
68k plus a 10k trimmer would do the job. A 10k trimmer would provide
some adjustment.

PPS film caps are +/2 % cheap and readily available.

RST Engineering wrote:

On Mon, 12 Apr 2010 16:33:41 -0700, Jim Thompson
wrote:


From there to pin 3, a 72K resistor

...Jim Thompson

Where in the hell do you buy a 72K resistor without going to
precision? ANd why would you use a precision resistor when you will
have trouble getting capacitors better than 5%?

68K? 75K?

Jim


No one expects you to stop using 20%, '40s parts.


--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'