Problem with DIY LPM

Hi all, I have build the <50$ LPM from MarioMaser, but I have got now a problem. The TEC I use is too big. If I use a bigger heatsink, I get better results, but now I use a CPU cooler and measure something about 450mW with my 1W laser.
Is there any other way to calibrate it? I don't want to build a dry ice heatsink .

Here's a pic:

Can you tell us exactly what you are doing get your measurements?

First of all, inorder to calibrate an LPM, you need a laser of a known power. Forget the opamp right now, that comes after you have figured out the power of your laser. Once you know the power (for example) just supposing [ it's a1100mW laser] and it holds at 1100mW there for 10 seconds but you get a signal off the TEC at the same time only showing 450mV, you'd have to assume the sensor is 2.444x reading in mV = X mW. 900mV = 2.2W etc ... then set your mariomaster LPM pots accordingly.

Thanks, yes I use my spartan for calibration. It's with full batteries at 1100mW. I have the 5K poti at 0R and still get too less output. Not it tells me it is something about 220mW

try switching the 5K pot to a 10 or 20K resistor

What are you powering your circuit with...:thinking:
I can't tell from the pic..


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

I use the 5V out of my arduino. But I have solved the problem already . I have put a 2K resistor behind the 5k poti, so i could calibrate it. Thanks MarioMaster! +1 :beer: