My LPM for less than $ 5

[Borislav@87]

Hi from a video on YouTube, I made an LPM meter, which is very close to the real power and I can say that it shows very accurately. The price is very low and I think that everyone who is passionate about lasers should have something similar in order to be able to measure the power of their laser. For this purpose I use Thermoelectric Cooler Peltier TEC1-12704 30x30 for measurement. You must paint it black on the front and mount it on a radiator with thermal grease. You also need a multimeter. The formula is that 100mw = 1W. In this case mine is 735mw = 7.35W without lens. My laser in these power values and the results are very accurate in this case.

TEC1-12704 Thermoelectric Cooler Peltier 30X30

4.89US $ 24% OFF|DC 12V TEC1 12715 TEC1 12710 TEC1 12709 TEC1 12703 TEC1 12704 TEC1 12706 TEC1 12705 Thermoelectric Cooler Peltier 30X30 40X40MM|Instrument Parts & Accessories| - AliExpress

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[Borislav@87]

today i did a test of fully charged batteries at 100% and here is what it shows with lens and without lens

 

[bostjan]

Wow!

TEC's of that size are rarely that cheap!

I've tried similar with a TEC from American Science and Surplus, a Radio Shack heat sink (and thermal paste, and some matte black "chalkboard paint" from the dollar store. No idea how accurate it is, since I only have a fairly cheap and crummy LPM with which to calibrate it, and I'm not sure if discrepancies among different wavelengths are from the DIY LPM or from the cheap LPM. It could be also true that both are out of tolerance. I guess that, either way, it gives you a decent idea of how much power there is. Both meters can make it clear that my super cheap 532 nm pen is outputting more than 5 mW, even though it optically looks like a 5 mW green (it has a bad IR filter).

So, definitely worth the $5 investment (or $25 for that matter, assuming you have to also buy thermal paste, a heat sink, and black craft paint - two of which you can use for plenty of other projects afterward).

 

[Borislav@87]

Wow!

TEC's of that size are rarely that cheap!

I've tried similar with a TEC from American Science and Surplus, a Radio Shack heat sink (and thermal paste, and some matte black "chalkboard paint" from the dollar store. No idea how accurate it is, since I only have a fairly cheap and crummy LPM with which to calibrate it, and I'm not sure if discrepancies among different wavelengths are from the DIY LPM or from the cheap LPM. It could be also true that both are out of tolerance. I guess that, either way, it gives you a decent idea of how much power there is. Both meters can make it clear that my super cheap 532 nm pen is outputting more than 5 mW, even though it optically looks like a 5 mW green (it has a bad IR filter).

So, definitely worth the $5 investment (or $25 for that matter, assuming you have to also buy thermal paste, a heat sink, and black craft paint - two of which you can use for plenty of other projects afterward).

Yes, that's right. It definitely gives a clear idea of strength. It can't be 100% accurate. I had a radiator from an old video card, there are also thermal pastes I used a black marker. In Aliexpress one radiator is about $ 3-5. I glued Peltier glue to the radiator and it turned out great.

I did a test with a G8 lens and it shows very accurate losses. With the G8, the losses are about 10% and showed the device. 7.7W-10% = 6.9W