1.2v = 3v ??

[PeterDove]

Hi All,

Can anyone explain how you can get a 1.2V battery to power a 3V LED ? Is there a way to step up the voltage to power the LED?

Thanks

Peter

 

[PeterDove]

BTW, thats how do I make 1.2V DC up to 3V DC - the only examples I have found on the web so far are from AC to DC

 

[em2006]

https://www.electro-tech-online.com...running-a-3-3-v-led-with-one-1-2-v-nimh.1842/

 

[bloody-orc]

search for joule thief on google

 

[kchriste]

Can anyone explain how you can get a 1.2V battery to power a 3V LED

It can't get any easier than this:

http://cappels.org/dproj/ledpage/leddrv.htm

 

[Top Cap]

If you want to just flash the LED then the LM3909 can be useful

**broken link removed**

Also see:-

http://www.qsl.net/yo5ofh/hobby circuits/led_circuits.htm

Les

 

[k7elp60]

The LM3909 may be difficult to obtain as it has been discontinued.
The attacted schematic should work fine

 

[audioguru]

The LM3909 has not been made for many years. There are discrete replacement circuits for it on the web. I have seen voltage doubling circuits that use only two transistors but I didn't save one.

 

[ante]

Hi Guys,

This one is built and tested, works on a single NiCad cell down to 0.85V.

 

[Top Cap]

Gee sorry Guys, had no idea the 3909 had been discontinued. I still have one in its wrapper from RS (300-372) I notice that they have discontinued it from stock. That's the trouble with getting old, all the devices you used to have fun with at an earlier age are now obsolescent, I don't suppose it will be far off before I join them
Les G4CNH

 

[The Mad Professor]

Oh I would not worry Top Cap , I here there is a guy in England who still makes a tidy living servicing punch tape readers and three computers built using discrete 7400 logic chips that run some multi axis jig borers.

 

[RODALCO]

Joule Thief

Build the circuit for the Joule Thief ( google )

only small coil to be wound (about 20 turns bifilar) and one transistor required plus LED !

I built a couple of them and they drain a battery down till 0.35 volts.

Your 1.2 volts application will be perfect to drive a white or blue led at the 3.4 volts required.

 

[RODALCO]

Joule Thief

**broken link removed**

Here is the link and the very simple circuit with all details how to built it.

Good luck

raymond

 

[dog812]

i have been reading and reading and posting all over..
I might aswell try here aswell. I cant seem to get a schematic that will work with my application from anyone..

I need to power 21 LED's either RGB 3.2v - 3.6v @ 30ma. Or a mix of 21 single color LED's , red, pink, blue, green, etc..

I want to be able to power it with a single AA rechargeable battery...

Can it be done? Can i get a joule thief to have a constant power so i dont fry my led's?
Any other info would be awesome.

 

[HarveyH42]

i have been reading and reading and posting all over..
I might aswell try here aswell. I cant seem to get a schematic that will work with my application from anyone..

I need to power 21 LED's either RGB 3.2v - 3.6v @ 30ma. Or a mix of 21 single color LED's , red, pink, blue, green, etc..

I want to be able to power it with a single AA rechargeable battery...

Can it be done? Can i get a joule thief to have a constant power so i dont fry my led's?
Any other info would be awesome.

Should start your own thread, this is called 'Hijacking', frowned upon...
You are of course, joking about 21 RGB LEDS and a single AA rechargeable. It might happen for a few seconds, but that's a huge load. Joule Thief will light two, maybe three LEDs (never tried a fresh battery). Haven't tried more than one Joule thief off the same battery either. Make about 10 of them and see what happens. They are very simple and cheap to build, great project for child labor, if you have kids. Winding the coil doesn't even need to be done neatly.

 

[wcsur]

I have a 8 LED flashlight that runs on a single AA battery. Will draw the circuit out and post. Have ran this flashlight for days because it turns on with twist of the base and did not know it was on. I don't know what the inductor value is.

 

[duffy]

In theory, you could power the 21 3.4V leds at 30ma for about 2 hours off 1 AA battery.