sorry about this
- Adverse Effects
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sorry about this
sorry about this but i didnt want to sing up to yet another forum for a one time question
i am looking for the smallest circuit possible to do this
3 to 8 Vdc in
out what ever the input Vdc is with a % of a duty cycle on / off
and i want to pules it sort of like we are doing with the car controller
if it could fit in side a area of no more than circler 25mm across and no more than 15mm high but the lower the better
what i am trying to do is replace a controller that controls the voltage up and down from 3 to 8 input to modify it to 5 volt out constant
but i want to replace it with something that will give me verifiable volts but control the amount of time it is on instead as we do in DC cars
this has to be able to do up to 3amps as well
[EDIT] that makes more sense now
i am looking for the smallest circuit possible to do this
3 to 8 Vdc in
out what ever the input Vdc is with a % of a duty cycle on / off
and i want to pules it sort of like we are doing with the car controller
if it could fit in side a area of no more than circler 25mm across and no more than 15mm high but the lower the better
what i am trying to do is replace a controller that controls the voltage up and down from 3 to 8 input to modify it to 5 volt out constant
but i want to replace it with something that will give me verifiable volts but control the amount of time it is on instead as we do in DC cars
this has to be able to do up to 3amps as well
[EDIT] that makes more sense now
Last edited by Adverse Effects on Wed, 20 Jul 2011, 08:47, edited 1 time in total.
- Richo
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sorry about this
Sounds tricky.
Probably need some SEPIC controller chip.
Here is a module in the ball park:
ZY1207 7A
Probably need some SEPIC controller chip.
Here is a module in the ball park:
ZY1207 7A
So the short answer is NO but the long answer is YES.
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- Adverse Effects
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sorry about this
umm no that is
3V to 14V Input 0.5V to 5.5V Output
i am trying to have same v input as output
like 7vdc in 7 vdc out but only on X% (veritable) time on adjustable with a small trimpot
i was looking at something useing a 555 chip but its going to be a bit to big and it wont take the amperage i need
3V to 14V Input 0.5V to 5.5V Output
i am trying to have same v input as output
like 7vdc in 7 vdc out but only on X% (veritable) time on adjustable with a small trimpot
i was looking at something useing a 555 chip but its going to be a bit to big and it wont take the amperage i need
- coulomb
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sorry about this
Adverse Effects wrote: I was looking at something using a 555 chip but its going to be a bit too big and it wont take the amperage i need
555 chips are pretty small, especially SMD versions. I would consider a small PCB with a CMOS 555 (for the very variable voltage) driving a smallish low threshold MOSFET (so it would turn on properly at 3 V). The PCB could be mounted vertically if necessary. The PCB could just be Veroboard, if using a through-hole 555C.
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- Richo
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sorry about this
Just be careful as some 555 won't do 3V-14V.
Also you may not get true full 0-100% duty cycle.
Also you may not get true full 0-100% duty cycle.
So the short answer is NO but the long answer is YES.
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- Adverse Effects
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sorry about this
Richo wrote: Just be careful as some 555 won't do 3V-14V.
Also you may not get true full 0-100% duty cycle.
that is cool
i am looking at inputs from 3 to 9 or 10VDC (depending on battery configuration)
and anything from say 20% to 99% would be good
- Adverse Effects
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sorry about this
ok like i said b4 i know almost nothing about about electronics
but with a lot or research i think i have made a circuit that SHOULD work can someone tell me if i have wasted all my time (almost a full day)
the red area id the unit i am trying to power and control with the unit

but with a lot or research i think i have made a circuit that SHOULD work can someone tell me if i have wasted all my time (almost a full day)
the red area id the unit i am trying to power and control with the unit

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sorry about this
Do you only want it to operate when the "touch switch" is touched?
Why not just use a miniature momentary contact switch?
Then you don't lose 0.7V through the transistor.
Why not just use a miniature momentary contact switch?
Then you don't lose 0.7V through the transistor.
Last edited by Squiggles on Fri, 22 Jul 2011, 18:22, edited 1 time in total.
- Adverse Effects
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sorry about this
yes i can cut out the touch switch its in there just because its "cool" lol
but the rest of the circuit should work as a PWM ?
but the rest of the circuit should work as a PWM ?
- coulomb
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sorry about this
Adverse Effects wrote: but the rest of the circuit should work as a PWM ?
Yes. However, the frequency will change as the potentiometer is changed; if that matters, you could rearrange the potentiometer and limit resistor(s) to connect the wiper to pins 2 and 6. The capacitor charges through the top 2 resistors, and discharges through R2.
You should use a low threshold MOSFET instead of a bipolar transistor to drive the load; at 3 V you will lose proportionally way too much voltage across a bipolar.
I'd lose the touch switch. But if you decide to keep it, get the touch transistor to drive another MOSFET for lower voltage drop. You will need very high gain with just one transistor, and you will lose too much voltage across a Darlington pair.
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5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
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- coulomb
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sorry about this
I looked briefly at a 555 and 555C datasheet, and they both listed 4.5 V as the minimum supply voltage. You will have to hunt a bit to find a 555 equivalent that runs on as low as 3.0 V.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
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Patching PIP-4048/5048 inverter-chargers.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
- Adverse Effects
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sorry about this
ummm ok i lost you about 1/2 way through your first line lol
any chance you could redraw the pic for me?
like i said i am a total noob at this and that is the first time i have drawn a circuit and i just copped each component off other things
do you know a smaller way to do it as it needs to be as small as possible
it will be driving a heating element of about 2.4 to 3 omes like these Atomizers
i dont think the voltage will get as low as 4.5 volt so as long as the lowers is not much higher than they it will be ok
any chance you could redraw the pic for me?
like i said i am a total noob at this and that is the first time i have drawn a circuit and i just copped each component off other things
do you know a smaller way to do it as it needs to be as small as possible
it will be driving a heating element of about 2.4 to 3 omes like these Atomizers
i dont think the voltage will get as low as 4.5 volt so as long as the lowers is not much higher than they it will be ok
Last edited by Adverse Effects on Fri, 22 Jul 2011, 21:21, edited 1 time in total.
- coulomb
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sorry about this
Adverse Effects wrote: any chance you could redraw the pic for me?
Not much to it:

You want a low threshold MOSFET that can handle at least 3 A. Digikey (and not Element14 or Mouser) have the gate threshold in their parametric search. This one is 2.0 V threshold, TO220, 12 A continuous:
http://search.digikey.com/scripts/DkSea ... 055VLFS-ND
You may need to search for one in a smaller package. TO220 transistors are about 15 x 10 x 5 mm plus leads. It probably won't need a heatsink.
Last edited by coulomb on Sat, 23 Jul 2011, 06:11, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
- Adverse Effects
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sorry about this
thanks for that
so that will do what i want then?
so all i need to do now look for thew smallest of each component i can get to do the job
i need to make it fit in to 1/2 the top part of one of thes torches

so that will do what i want then?
so all i need to do now look for thew smallest of each component i can get to do the job
i need to make it fit in to 1/2 the top part of one of thes torches

Last edited by Adverse Effects on Sat, 23 Jul 2011, 19:02, edited 1 time in total.