Hi, heatsink compound is not as conductive as you think.

It should be used sparingly, I have a small straight edge and I use it to wipe the compound over the surface.

It is surprising how little you need to use.

http://www.youtube.com/watch?v=zPJspil1HJo

Tom..........

If I take it all apart and fix it right this instant, WILL SOMEONE PLEASE EXPLAIN EXACTLY HOW THIS IS CAUSING MY PROBLEM???

I've gotten a lot of "this isn't right" comments BUT NOT ONE PERSON HAS YET TO EXPLAIN A SIMPLE WHY TO ME ON ANY OF IT.

If I don't have a great thermal transfer, how exactly is that making it so that this happens:

Test 1:

PWM: 0; Temp: amb

PWM: 500; Temp: t

PWM: 0; Temp: amb

PWM: 250; Temp: g

PWM: 500; Temp: x

Test 2:

PWM: 0; Temp: amb

PWM: 500; Temp: t

PWM: 0; Temp: amb

PWM: 250; Temp: g

PWM: 500; Temp: x

and I will specify this as part of the example, "amb" is ambient temp, "b" is slightly warm, etc all the way up to "fz" which is as hot as it can possibly get. Thus, the above reads that PWM of 0 gives ambient temp, I get a slightly hot temperature of "t" every single time I go directly from 0 PWM to 500 PWM, I get a temp "g" if I go from 0 to 250, and I get a fourth temp "x" (which is higher than "t") when I go from 250 to 500.

Within probably a half a degree Celsius, ambient, g, t, and x are all the same every time I repeat this. I'm doing these tests in a closed off room, the humidity is the same from start to finish, the ambient air temp is usually 24.0*C (+- .2*C), I'm measuring by comparing to a known black body (accurate to within .001*C) with an infrared camera (14-bit raw data from it) and matching the peltier and the black body to within at most 4 or 5 14-bit units. If this was a small deviation (say, from t to v) I'd be more open to these little things but I'm talking like 12*C difference between t and x. This isn't a simple "well the air was on" explanation.

I don't care what explanations get thrown out there, because I really probably do need to address the amount of heat sink compound used, but if I'm going to fix this, I really need explanations of WHY. Why is it (whatever you're pointing out) causing this problem?