Hey all, I'm not 100% sure how to ask what I'm looking for. But I wanted to use a Cree xqe led, or two, to light up a small camp light.

The problem is that I want to run it off of either 2, 2032 coin cells, or a capacitor array, or some combination of the two. So i need a driver. I would like to use some type of super simple pwm to keep efficiency higher.

Essentially im wondering if there is a way to power the led (2.9v 350mA) using minimal components. Possibly 3 transistors, two alternating the trigger for one to supply current, but allowing a capacitor to buffer the current draw from the power source? I don't want to run the led at 100% power. And I'm looking for a few hours run time.

The alternative to the Cree led is using an array of 0402 leds (3V 1mA), im not sure how many yet. But draw would be much less than the Cree chip. If I do this route. I would like to utilize capacitors and a charging circuit. I believe I have a way to charge the capacitors to +-5v with a few solar cells.

But again. I would prefer a simple minimal component circuit to provide pwm.one which I could change the duty and cycle with a couple passives. I would like to stay away from 555...

If I'm missing details, let me know!

 

This is a simple solution. It supplies 5V from a 1 to 5V input. Connect battery, supercap, or ultracap to the input and the LED with your chose series resistor to the output.

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• https://www.ebay.com/itm/DC-DC-1-5V...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649​

 

I like this driver. I can't tell if the output is pulsed though.

I'll see if I can look up that main sot23 ic?

 

Hey all, I'm not 100% sure how to ask what I'm looking for. But I wanted to use a Cree xqe led, or two, to light up a small camp light.

The problem is that I want to run it off of either 2, 2032 coin cells, or a capacitor array, or some combination of the two. So i need a driver. I would like to use some type of super simple pwm to keep efficiency higher.

Essentially im wondering if there is a way to power the led (2.9v 350mA) using minimal components. Possibly 3 transistors, two alternating the trigger for one to supply current, but allowing a capacitor to buffer the current draw from the power source? I don't want to run the led at 100% power. And I'm looking for a few hours run time.

So what has led you to believe that you can power a 350 mA load from a couple of 2032 coin cells at all?

The typical draw for these cells is a fraction of a milliamp continuous up to about 15 to 30 mA or so for low duty cycle pulsed applications. The capacity is typically 100 to 200 mAh. At "heavy" current draws the capacity is generally at the lower end of that range. But even if you are in the upper region at 175 mAh, your two-cell (assuming in parallel) would only last for about an hour at a 350 mA load.

With a "fresh" internal resistance that is typically somewhere north of 10 Ω, you probably couldn't get 350 mA out of a 2032 coin cell even if it were shorted.

 

It is DC. It uses the same or at least functionally the same chip as in the PFM Module (document below).

 

Hey all, I'm not 100% sure how to ask what I'm looking for. But I wanted to use a Cree xqe led, or two, to light up a small camp light.

The problem is that I want to run it off of either 2, 2032 coin cells, or a capacitor array, or some combination of the two. So i need a driver. I would like to use some type of super simple pwm to keep efficiency higher.

Essentially im wondering if there is a way to power the led (2.9v 350mA) using minimal components. Possibly 3 transistors, two alternating the trigger for one to supply current, but allowing a capacitor to buffer the current draw from the power source? I don't want to run the led at 100% power. And I'm looking for a few hours run time

The alternative to the Cree led is using an array of 0402 leds (3V 1mA), im not sure how many yet. But draw would be much less than the Cree chip. If I do this route. I would like to utilize capacitors and a charging circuit. I believe I have a way to charge the capacitors to +-5v with a few solar cells.

But again. I would prefer a simple minimal component circuit to provide pwm.one which I could change the duty and cycle with a couple passives. I would like to stay away from 555...


If I'm missing details, let me know!

I wonder how much light you really need. As WBahn points out the batteries you plan on using will not supply much power for the light load you mention. I use cr2032 batteries all the time for LED projects. I have some regular 5mm white LEDs that are very bright with onl 2 Ma of current, and some 10mm with 2 connected with a current of 6Ma ea and they almost light up a room. I match LEDs and then connect them in parallel and use one resistor to control the current for the batch