TEC update

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
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Colin Kaminski

TEC update

Post by Colin Kaminski »

I just returned from dinner after leaving the laser diode and TEC on. When I returned I was stable to 1/2 of a fringe!

Perhaps if I can double the performance two or three more times I will have a usable active system.

Tom B.

TEC update

Post by Tom B. »

I take it that you still have low level temperature oscillations. Is the oscillation frequency about the
same as before? (1 Hz, I think it was)
Colin Kaminski

TEC update

Post by Colin Kaminski »

No, improving the thermal assembly completely eliminated the oscillation. I need to re-tune the PID and see what I have. If I can believe the thermistor I have stability to +- .01 degree C.
Colin Kaminski

TEC update

Post by Colin Kaminski »

I drilled out the block that mounts the diode and used longer stainless steel screws and put nuts and another washer assembly like on the heat sink side. This stabilized things very well. I have also insulated the entire laser side with 1/4" neoprene foam earlier.

PID tunning is quite and art. I really don't understand it very well. I think I can get a little more stability and a faster response to drafts when I have the PID tunned correctly.

I have been letting the temperature settle and then blowing on the heatsink to see how the laser temerature responds but I think I really should be looking at the TEC voltage to see what corrections it is trying to make. I'll work on it more today.
Tom B.

TEC update

Post by Tom B. »

Here's a couple of PID tutorial links:
http://newton.ex.ac.uk/teaching/CDHW/Feedback/
http://www.geocities.com/chemforum/pidcontrol.htm

I seem to recall one of the TEC manufacturers having good tuning instructions but I can't find the link anymore.
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