Laser Calorimeter take 2

A project log for MultiBot CNC v2

A low cost 3D printed CNC that can be built with minimal tools yet is capable of great things.

David TuckerDavid Tucker 04/04/2021 at 18:440 Comments

So my previous laser calorimeter topped out at 50% because it could not handle the heat.  I was eating a bowl from Chipotle and noticed that the tin lid was a nice compromise between too thin and too thick so I thought I would try swapping it in to my rig in place of the tinfoil.  That worked great, and I was able to get readings from across the full power range.

It is not shown in this picture but the foil is taped onto the points of the holder with tiny pieces of double sided tape.  If I made this again I would have the foil slide into the holder rather than mess with tape...

I used a 20mm square piece of the lid painted flat black.  I mounted it 100 mm away from the laser with the laser set to a 5mm focal length.  That spread the beam across almost all of the target surface and minimized the chance of hurting the target.  I then placed my IR thermometer about 8 mm behind the target and placed it in continuous mode.  Using my test program I triggered the laser for exactly 3 seconds (+/- 1 ms) and read the temperatures by hand from the display.  Reading the temps is the biggest issue, the display updates probably 10 times a second, so the accuracy is not great.  The thermometer has a max mode, I should experiment with that, but I would need to find a way to hold the button down for that to work.

Anyway the results look as linear as the previous ones.  This is surprisingly linear across the whole power range.  I was expecting some serious degradation at the top since we are overdriving the laser.  I would still stay away from 100% power to try and extend the life of the laser.