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| Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Dropping 1V from a Regulated 6V Wall Wart
I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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#2
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 09:28:53 -0800, the renowned Watson A.Name - "Watt
Sun, Dark Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. Or just hang a dummy load on the output.. 1K0 or a bit higher (2K0) ought to do it. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
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#3
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Dropping 1V from a Regulated 6V Wall Wart
"Watson A.Name - Watt Sun, Dark Remover" wrote in message m... I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ Why not a 5volt zener and a resistor?....Just a thought... |
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 09:28:53 -0800, Watson A.Name - "Watt Sun, Dark
Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. Try this... + From wall wart --+ | +---+------+ | | \ | / | 20 \ / 2SC2334 or TIP31 ohm | |/ NPN power TO-220 o------| Heatsink optional | |\ | E\ | | | | | | | | | | | o----- + | | output | / to load | \ | / 2.2K __|___/ | / /\ | / \--------o / \ | -------- | | TL430 / | \ 2.7K | / | | | | | | - --o----------o------ - You may need a compensation cap between cathode and control pin. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice  480)460-2350 | || E-mail Address at Website Fax 480)460-2142 | Brass Rat || http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 09:28:53 -0800, Watson A.Name - "Watt Sun, Dark
Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, .... 6VDC------+-----------------+ | | [R1] | | | +-----|+\ C | | ------B | +--| / E | | | | +----+---------+ | |+ | [R2] [C1] [RL] | | | GND-------+-------+---------+ R1/R2 = 5 C1 = Whatever you need to keep the thing from oscillating; 100µF is probably a good guess. -- John Fields |
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#6
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 12:18:19 -0600, John Fields
wrote: R1/R2 = 5 --- R2/R1 = 5 -- John Fields |
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#7
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Dropping 1V from a Regulated 6V Wall Wart
I read in sci.electronics.design that John Fields jfields@austininstrum
ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 12:18:19 -0600, John Fields wrote: R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! |
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#8
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 19:07:59 +0000, John Woodgate
wrote: I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 12:18:19 -0600, John Fields wrote: R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) --- I'm sure there's a joke in there somewhere... :-) I meant that for 6V in and 5V into Rl, R2 = 5R1. -- John Fields |
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#9
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Dropping 1V from a Regulated 6V Wall Wart
I read in sci.electronics.design that John Fields jfields@austininstrum
ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 19:07:59 +0000, John Woodgate wrote: I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 12:18:19 -0600, John Fields wrote: R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) --- I'm sure there's a joke in there somewhere... :-) I meant that for 6V in and 5V into Rl, R2 = 5R1. OK, let's go on in the same vein. R2 is not always 5R1; it might be 5R6 or even 47K. (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! |
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#11
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Dropping 1V from a Regulated 6V Wall Wart
What about using a 5V low-dropout voltage regulator?
Bob Watson A.Name - "Watt Sun, Dark Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. |
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#12
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 20:12:23 GMT, the renowned Active8
,invalid wrote: I'm thinking 4.3V Zener and a series pass transistor. Wrong way. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
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#13
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Dropping 1V from a Regulated 6V Wall Wart
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#16
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 19:54:47 +0000, John Woodgate
wrote: I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 19:07:59 +0000, John Woodgate wrote: I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 12:18:19 -0600, John Fields wrote: R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) --- I'm sure there's a joke in there somewhere... :-) I meant that for 6V in and 5V into Rl, R2 = 5R1. OK, let's go on in the same vein. R2 is not always 5R1; it might be 5R6 or even 47K. (;-) GROANNNN... OK, it arteried: "In order to assure a voltage of 5VDC across Rl the resistance of R2 should be five times the resistance of R1." ?^) -- John Fields |
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#17
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Dropping 1V from a Regulated 6V Wall Wart
Watson A.Name - Watt Sun, Dark Remover wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. You almost had it- put the Vbe multiplier inside the feedback loop and buffer like so: Please view in a fixed-width font such as Courier. 6V ---+------+---------+ | | | | / | | 22 | | / | | \ c | | |/ | +-------| TIP31 | | |\ | | e----+-- 5V | | | === | +----+ | c | | | \| / | | |----- \ | | /| / === | e \ 1000U | | | | | | | | | | | | GND--+------+---------+----+-- GND |
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#18
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 09:28:53 -0800, Watson A.Name - "Watt Sun, Dark
Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) [snip] See also "4V-Regulator.pdf" on the S.E.D/Schematics Page of my website, for a similar application. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice 480)460-2350 | || E-mail Address at Website Fax 480)460-2142 | Brass Rat || http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
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#19
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Dropping 1V from a Regulated 6V Wall Wart
On Mon, 29 Dec 2003 20:46:53 GMT, Active8
,invalid wrote: But Mr. Wizard, this *package* says 502 and this one's on psychedelics. Why won't this magnet pick up this floppy disk? --- It will, Timmy, you just have to know how to do it. For a clue, check out "Magnet lifting floppy" on a.b.s.e. -- John Fields |
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#20
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Dropping 1V from a Regulated 6V Wall Wart
Fred Bloggs wrote: Watson A.Name - Watt Sun, Dark Remover wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. You almost had it- put the Vbe multiplier inside the feedback loop and buffer like so: Please view in a fixed-width font such as Courier. 6V ---+------+---------+ | | | | / | | 22 | | / | | \ c | | |/ | +-------| TIP31 | | |\ | | e----+-- 5V | | | === | +----+ | c | | | \| / | | |----- \ | | /| / === | e \ 1000U | | | | | | | | | | | | GND--+------+---------+----+-- GND Then you can work a common 5.1V zener into the equation like so: Use a 2N3906 for the pnp for Vbe,max=6V rating. Please view in a fixed-width font such as Courier. 6V ---+--------+----------+-------------+ | | | | | / / | | 22 51 | | / / | | \ \ c | | | |/ | +----------|-----------| TIP31 | | | |\ | | | e----+-- 5V | c | | | \| | pnp | | npn |--+-----|-------- c e---+ | /| | | \ / | | e | | ---- | === | | | 180 | | | | | +----/\/\---+ | | | | | | | | | | | | | | | / _/ / === | | 1K /^ 5.1v 1.2K 1000U | | / - / | | | \ | \ | | | | | | | GND--+--------+----+-----+-----------+------+-- GND |
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#21
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Dropping 1V from a Regulated 6V Wall Wart
"Fred Bloggs" wrote in message ... : : Fred Bloggs wrote: : : Watson A.Name - Watt Sun, Dark Remover wrote: : : I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried : a 3 amp rectifier, but it varied by more than .2V over a range of : loads. So I tried this: (view with courier font) : : + From : wall : wart --+ | : +---+------+ : | | : | | : 400 \ / 2SC2334 or TIP31 : ohm / |/ NPN power TO-220 : WW \-----| Heatsink optional : pot / |\ : | E\ | | : | | : +----+-----+ : | | : +------ + output : to load : - -------------- - : From wall wart : : This has some advantages and disadvantages. It's simple and cheap, : and keeps the output at 5V within a tenth of a volt over a current : range. But it has a minimum current below which it loses regulation : and the output starts to go up to 6V, because the transistor is not : conducting and the current is being supplied thru the ww pot. This : circuit is sometimes used in the bias circuit for the output : transistors in high powered amplifiers. Also Win Hill showed us here : how to use a similar circuit to maintain the voltage steady for a : current regulator circuit used on four AA cell rechargeable batteries. : : I'm thinking about putting a 5.1V zener on the output so that if the : voltage climbs above that, it just shunts the excess current. Oh, : yeah, I set the pot to various values to see what the output voltage : was with various loads. The two resistances were 120 ohms for the : upper and 280 ohms for the lower. I suppose the 400 ohms total could : be raised to a higher value, but the transistor needs enough base : current to do its job. There's only 1V available minus the ..6V E-B : voltage, so even at 400 ohms, that's not a lot of current. : : : : You almost had it- put the Vbe multiplier inside the feedback loop and : buffer like so: : : Please view in a fixed-width font such as Courier. : : : 6V ---+------+---------+ : | | | : | / | : | 22 | : | / | : | \ c : | | |/ : | +-------| TIP31 : | | |\ : | | e----+-- 5V : | | | : === | +----+ : | c | | : | \| / | : | |----- \ | : | /| / === : | e \ 1000U : | | | | : | | | | : | | | | : GND--+------+---------+----+-- GND : : : Then you can work a common 5.1V zener into the equation like so: : Use a 2N3906 for the pnp for Vbe,max=6V rating. : : Please view in a fixed-width font such as Courier. : : : : : : 6V ---+--------+----------+-------------+ : | | | | : | / / | : | 22 51 | : | / / | : | \ \ c : | | | |/ : | +----------|-----------| TIP31 : | | | |\ : | | | e----+-- 5V : | c | | : | \| | pnp | : | npn |--+-----|-------- c e---+ : | /| | | \ / | : | e | | ---- | : === | | | 180 | | : | | | +----/\/\---+ | : | | | | | | : | | | | | | : | | / _/ / === : | | 1K /^ 5.1v 1.2K 1000U : | | / - / | : | | \ | \ | : | | | | | | : GND--+--------+----+-----+-----------+------+-- GND It's getting bigger. Soon he'll need a 2nd breadboard to build and test this thing. ;-) Bill @ GarberStreet Enterprizez };-) Web Site - http://garberstreet.netfirms.com Email - Remove - SPAM and X to contact me --- This email ain't infected, dude! Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.544 / Virus Database: 338 - Release Date: 11/26/03 |
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#22
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Dropping 1V from a Regulated 6V Wall Wart
Fred Bloggs wrote: [snip] This one will make the output tempco essentially that of the zener which is not bad for the 5.1V's. Ripple rejection is lacking due to the low overhead -at 14dB, but your 6V is regulated anyway. Please view in a fixed-width font such as Courier. 6V ---+--------+----------+-------------+ | | | | | / / | | 22 51 | | / / | | \ \ c | | | |/ | +----------|-----------| TIP31 | | | |\ | | | e----+-- 5V | c | | | \| | pnp | | npn |--+-----|-------- c e---+ | /| | | \ / | | e | | ---- | === | | | 1N4148 | | | | | +----||----+ | | | | | | | | | | | | | | | / _/ / === | | 1K /^ 5.1v 1.2K 1000U | | / - / | | | \ | \ | | | | | | | GND--+--------+----+-----+-----------+------+-- GND |
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#23
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Dropping 1V from a Regulated 6V Wall Wart
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#24
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Dropping 1V from a Regulated 6V Wall Wart
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#25
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Dropping 1V from a Regulated 6V Wall Wart
Watson A.Name - Watt Sun, Dark Remover wrote:
I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. I've tried to do this on numerous occasions. If you need any amount of current at all, the big lump of stuff makes it too unweildy, even if you do bite the bullet and put in a complex circuit that works. Now, for regulated warts, I crack the case and shunt a resistor inside the wall wart. You can add a switch if you have multiple applications. If you need both voltages at once, it's still easier to use two warts than to have this lump of regulator stuff hanging about. I'm a little confused by your requirements. If you even considered a diode, you can't be too concerned about the actual voltage...but you're concerned about the .2V variability. Sounds like there's something in there that's important but not disclosed??? mike -- Return address is VALID. Bunch of stuff For Sale and Wanted at the link below. Toshiba & Compaq LiIon Batteries, Test Equipment Honda CB-125S $800 in PDX TEK Sampling Sweep Plugin and RM564 Tek 2465 $800, ham radio, 30pS pulser Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/ |
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Dropping 1V from a Regulated 6V Wall Wart
In article uMZHb.254877$Ec1.8820445@bgtnsc05-
news.ops.worldnet.att.net, lid mentioned... "Watson A.Name - Watt Sun, Dark Remover" wrote in message m... I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. Why not a 5volt zener and a resistor?....Just a thought... Well, the output of the wall wart is already regulated to 6V at 200 mA. But 1V at 200 mA is going to require a 5 ohm resistor. And the zener will have to dissipate a lot of wasted power. And the wall wart may not like being run at its max and overheat. Using the 1 amp rectifier in series with the output dropped about .6 to .8V, depending on current, which isn't all that bad a regulation. But the circuit I drew above gives a voltage closer to 5V over a wider range of load currents. I suppose I could've used a LDO 5V regulator, but then the output's already regulated. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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Dropping 1V from a Regulated 6V Wall Wart
In article ,
mentioned... On Mon, 29 Dec 2003 09:28:53 -0800, Watson A.Name - "Watt Sun, Dark Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, ... 6VDC------+-----------------+ | | [R1] | | | +-----|+\ C | | ------B | +--| / E | | | | +----+---------+ | |+ | [R2] [C1] [RL] | | | GND-------+-------+---------+ R1/R2 = 5 C1 = Whatever you need to keep the thing from oscillating; 100µF is probably a good guess. Thanks, but I think someone snipped the part where I said that I was trying to get this to fit across the pins of the RF modulator, and that the wall wart was already regulated. I guess I could do it if it was surface mount parts, but I'm not experienced with those. What kind of opamp works down to only 6V? A LM358? In order to put out 5V at the emitter, it would have to swing the base to 5.7 or more volts at 200 mA, so the opamp would have to swing close to the positive rail. Maybe a better idea would be to use a PNP for the emitter follower. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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#28
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Dropping 1V from a Regulated 6V Wall Wart
In article t,
mentioned... On Mon, 29 Dec 2003 19:54:47 +0000, said... I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 19:07:59 +0000, John Woodgate wrote: I read in sci.electronics.design that John Fields jfields@austininstrum ents.com wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Mon, 29 Dec 2003: On Mon, 29 Dec 2003 12:18:19 -0600, John Fields wrote: R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) --- I'm sure there's a joke in there somewhere... :-) I meant that for 6V in and 5V into Rl, R2 = 5R1. OK, let's go on in the same vein. R2 is not always 5R1; it might be 5R6 or even 47K. (;-) But Mr. Wizard, this *package* says 502 and this one's on psychedelics. Why won't this magnet pick up this floppy disk? Man, what did I start? Buncha pedants. BTW, I scrapped a couple old half gig hard drives, and took out the magnets. Those things are powerfull little devils! Made out of Nicodemus or some other exotic sounding materials. ;-) But I held the magnet to the platter and it literally won't even attract the plated coating on the aluminum. I guess it's so thin that it's like it's not even there! -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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#29
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Dropping 1V from a Regulated 6V Wall Wart
In article t,
mentioned... On Mon, 29 Dec 2003 20:36:46 GMT, said... On Mon, 29 Dec 2003 20:16:37 GMT, what said... On Mon, 29 Dec 2003 20:12:23 GMT, the renowned Active8 ,invalid wrote: I'm thinking 4.3V Zener and a series pass transistor. Wrong way. Best regards, Spehro Pefhany Why? NEver mind. I tried to cancel this but Gravity thinks I didn't post this. Still at TARFU level, I guess. OK 5.6V zener, solly. I think the emitter to base voltage will be something like .6 to .75V, and this has to be subtracted from the 1V diff, leaving something like ..4 to .25V. This very low voltage is what you have to work with when coming up with the resistor value to limit the current to the zener. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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#30
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Dropping 1V from a Regulated 6V Wall Wart
In article ,
mentioned... Watson A.Name - Watt Sun, Dark Remover wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. You almost had it- put the Vbe multiplier inside the feedback loop and buffer like so: Please view in a fixed-width font such as Courier. 6V ---+------+---------+ | | | | / | | 22 | | / | | \ c | | |/ | +-------| TIP31 | | |\ | | e----+-- 5V | | | === | +----+ | c | | | \| / | | |----- \ | | /| / === | e \ 1000U | | | | | | | | | | | | GND--+------+---------+----+-- GND I'll toss one together, but what value should I use for the Pot? 10k? Lower? This looks a lot like the current limiter circuit, 'cept for the pot. I'm wondering if it's such a good idea to have such a large cap on the output. When the wall wart is powered off, all that current tries to go backwards thru the pass transistor. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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#31
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 02:46:55 -0800, Watson A.Name - "Watt Sun, Dark
Remover" said... In article , mentioned... On Mon, 29 Dec 2003 09:28:53 -0800, Watson A.Name - "Watt Sun, Dark Remover" wrote: I needed to drop 1V from a 6VDC 200 mA regulated wall wart, ... 6VDC------+-----------------+ | | [R1] | | | +-----|+\ C | | ------B | +--| / E | | | | +----+---------+ | |+ | [R2] [C1] [RL] | | | GND-------+-------+---------+ R1/R2 = 5 C1 = Whatever you need to keep the thing from oscillating; 100µF is probably a good guess. Thanks, but I think someone snipped the part where I said that I was trying to get this to fit across the pins of the RF modulator, can't find that spec anywhere. and that the wall wart was already regulated. I guess I could do it if it was surface mount parts, but I'm not experienced with those. What kind of opamp works down to only 6V? A LM358? In order to put out 5V at the emitter, it would have to swing the base to 5.7 or more volts at 200 mA, so the opamp would have to swing close to the positive rail. Maybe a better idea would be to use a PNP for the emitter follower. -- Best Regards, Mike |
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#32
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 02:52:49 -0800, Watson A.Name - "Watt Sun, Dark
Remover" said... snip massive headers. christ on a crutch! did we need all that info?  R1/R2 = 5 --- R2/R1 = 5 Not always. (;-) --- I'm sure there's a joke in there somewhere... :-) I meant that for 6V in and 5V into Rl, R2 = 5R1. OK, let's go on in the same vein. R2 is not always 5R1; it might be 5R6 or even 47K. (;-) But Mr. Wizard, this *package* says 502 and this one's on psychedelics. Why won't this magnet pick up this floppy disk? Man, what did I start? Buncha pedants. Nyuk, nyuk, nyuk. BTW, I scrapped a couple old half gig hard drives, and took out the magnets. Those things are powerfull little devils! Made out of Nicodemus LOL i love it! Neodymium or Neodium (either a misspell or a TM). Good one, man. Nostrildumbass. I love playing with woids. Bone swar, moan sewer. or some other exotic sounding materials. ;-) But I held the magnet to the platter and it literally won't even attract the plated coating on the aluminum. I guess it's so thin that it's like it's not even there! Yup. I read an article about IBM developing a new process where it's so excruciatingly absoposifriggintutely thin that it doubles the density. They should've been out by now. Another article/AD (EDN or something) described a process to photoetch(?) the R/W heads, too. I think it was a matrix of heads. BTW. I said I was "thinking" series pass reg b4. I think I've never seen one drop 6V to 5V, either. I figgered since you already had a trans and a hulking ww pot and were thinking zener... Now you're talking about size and RF modulator which you never mentioned. What gives, Watson? -- Best Regards, Mike |
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#33
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 03:19:37 -0800, Watson A.Name - "Watt Sun, Dark
Remover" said... In article t, mentioned... On Mon, 29 Dec 2003 20:36:46 GMT, said... On Mon, 29 Dec 2003 20:16:37 GMT, what said... On Mon, 29 Dec 2003 20:12:23 GMT, the renowned Active8 ,invalid wrote: I'm thinking 4.3V Zener and a series pass transistor. Wrong way. Best regards, Spehro Pefhany Why? NEver mind. I tried to cancel this but Gravity thinks I didn't post this. Still at TARFU level, I guess. OK 5.6V zener, solly. I think the emitter to base voltage will be something like .6 to .75V, and this has to be subtracted from the 1V diff, leaving something like .4 to .25V. This very low voltage is what you have to work with when coming up with the resistor value to limit the current to the zener. Rough guess... ---+------------------+ | | | 10 | | ___ |/ +---|___|---+----| | | | | - | 5.6 500mW ^ +--------- | -------------+---------------- I kinda like JT's deal with the programmable zener which ain't much different. -- Best Regards, Mike |
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 01:32:13 -0800, Watson A.Name - "Watt Sun, Dark
Remover" wrote: I suppose I could've used a LDO 5V regulator, but then the output's already regulated. --- Yes, but the 5V output isn't at low currents, as you've already stated. The LDO will make that problem go away. -- John Fields |
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Dropping 1V from a Regulated 6V Wall Wart
"Spehro Pefhany" bravely wrote to "All" (29 Dec 03 20:16:37)
--- on the heady topic of " Dropping 1V from a Regulated 6V Wall Wart" SP Xref: aeinews sci.electronics.misc:8735 sci.electronics.design:31375 SP sci.electronics.repair:16164 alt.binaries.schematics.electronic:7314 Would "you people", please, stop crossposting into sci.electronics.repair? Thanks In Advance! .... # --- electrocuted tribble |
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 12:36:45 GMT, Active8
,invalid wrote: Rough guess... ---+------------------+ | | | 10 | | ___ |/ +---|___|---+----| | | | | - | 5.6 500mW ^ +--------- | -------------+---------------- --- Closer guess: Ib ~ Ie/ß = 200mA/100 = 2mA IZt = 20mA R = (Vin-VZ)/(IZt+Ib) = 0.4V/0.022A = 18.18...R ~ 20R -- John Fields |
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#37
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Dropping 1V from a Regulated 6V Wall Wart
In article ,
mentioned... On Tue, 30 Dec 2003 12:36:45 GMT, Active8 ,invalid wrote: Rough guess... ---+------------------+ | | | 10 | | ___ |/ +---|___|---+----| | | | | - | 5.6 500mW ^ +--------- | -------------+---------------- --- Closer guess: Ib ~ Ie/ß = 200mA/100 = 2mA IZt = 20mA R = (Vin-VZ)/(IZt+Ib) = 0.4V/0.022A = 18.18...R ~ 20R Yeah, I was thinking something really low like that. But these approaches have been to establish a new regulated voltage, dependent on the value of the zener. There's nothing wrong with this, but it would be simpler to just use a LDO 5V regulator as someone suggested. I figured that since the 6V input was already well regulated, that it would be easy to just drop a single volt. My subject: line kind of said that. And if I use a 1N4002 inline with the input, it gives me 5.4 to 5.2V or so, over most of the current range, which is not all that bad. And I did say I wanted to keep it simple. It's not that I'm unappreciative of all the input others have given, it's been a good learning experience seeing these neat little circuits. I've saved many of them to disk, to experiment with later. So I thank all who contributed. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
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Dropping 1V from a Regulated 6V Wall Wart
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Dropping 1V from a Regulated 6V Wall Wart
Watson A.Name - "Watt Sun, Dark Remover" wrote in message om...
I needed to drop 1V from a 6VDC 200 mA regulated wall wart, so I tried a 3 amp rectifier, but it varied by more than .2V over a range of loads. So I tried this: (view with courier font) + From wall wart --+ | +---+------+ | | | | 400 \ / 2SC2334 or TIP31 ohm / |/ NPN power TO-220 WW \-----| Heatsink optional pot / |\ | E\ | | | | +----+-----+ | | +------ + output to load - -------------- - From wall wart This has some advantages and disadvantages. It's simple and cheap, and keeps the output at 5V within a tenth of a volt over a current range. But it has a minimum current below which it loses regulation and the output starts to go up to 6V, because the transistor is not conducting and the current is being supplied thru the ww pot. This circuit is sometimes used in the bias circuit for the output transistors in high powered amplifiers. Also Win Hill showed us here how to use a similar circuit to maintain the voltage steady for a current regulator circuit used on four AA cell rechargeable batteries. I'm thinking about putting a 5.1V zener on the output so that if the voltage climbs above that, it just shunts the excess current. Oh, yeah, I set the pot to various values to see what the output voltage was with various loads. The two resistances were 120 ohms for the upper and 280 ohms for the lower. I suppose the 400 ohms total could be raised to a higher value, but the transistor needs enough base current to do its job. There's only 1V available minus the .6V E-B voltage, so even at 400 ohms, that's not a lot of current. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ I did this a while back. Replaced the 7806 in the wall wart with a 7805. Wade |
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Dropping 1V from a Regulated 6V Wall Wart
On Tue, 30 Dec 2003 08:28:53 -0800, Watson A.Name - "Watt Sun, Dark
Remover" said... In article , mentioned... On Tue, 30 Dec 2003 12:36:45 GMT, Active8 ,invalid wrote: Rough guess... ---+------------------+ | | | 10 | | ___ |/ +---|___|---+----| | | | | - | 5.6 500mW ^ +--------- | -------------+---------------- --- Closer guess: Ib ~ Ie/ß = 200mA/100 = 2mA IZt = 20mA R = (Vin-VZ)/(IZt+Ib) = 0.4V/0.022A = 18.18...R ~ 20R Yeah, I was thinking something really low like that. But these approaches have been to establish a new regulated voltage, dependent on the value of the zener. There's nothing wrong with this, but it would be simpler to just use a LDO 5V regulator as someone suggested. I figured that since the 6V input was already well regulated, that it would be easy to just drop a single volt. My subject: line kind of said that. And if I use a 1N4002 inline with the input, it gives me 5.4 to 5.2V or so, over most of the current range, which is not all that bad. And I did say I wanted to keep it simple. I'll trade a pot for a zener and R anyday, but I haven't looked at what this thing will do over the full current range. It's so close to what you started with, I thought it would be a snap to check out. It's not that I'm unappreciative of all the input others have given, it's been a good learning experience seeing these neat little circuits. I've saved many of them to disk, to experiment with later. So I thank all who contributed. I'm just glad to find an electronics post or 2 lately. Lots of long OT stuff I'm guilty! I feed it, but it's fun. -- Best Regards, Mike |
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