Tuesday, March 18, 2014

Summer is Coming

And my camera is hot.

I don't want it to be hot, really.  I've been using a peltier device to try to cool the camera with fair success.  Recently, I pulled apart the bottom of the camera to re-paste the finger to better transfer heat from the chassis.

On testing in the thermal extremes of the shed, I had some challenges.
  • First, the extension cord I used initially had too much voltage drop and was appearing to cause problems. To solve this, I've put the power supply at the source of AC and use my heavy extension cord to provide 12V.  This method is similar to the way the system is used in the field.  
  • Secondly, there has been a failure in the PWM controller.  It appears to no longer work, not powering the TEC/Peltier at all.  The failure could have been from a short across components. Thus, I removed the controller from the system and hard wired the fan and TEC together.  
  • Third, even with the thermal control at full power, the camera continued to heat up.  With strategic temperature probing, I was able to see that the cold finger wasn't very cold.  To solve this problem, I pulled the heatsink again and replaced the thermal compound on the cold side of the TEC with the silicon mat that I've used.  I think the thermal compound that I have is not very good at cold temperatures.  I think it needs heat to "set."  After I made this change, the cold finger worked much better.  However, the camera still didn't get cooler.
  • Fourth, while checking, I did see/feel that the base of the camera gets too cold.  The dovetail mounting bracket acts as a place for heat intrusion.  This is a massive leak.  I've removed the bracket and will have to try to protect the area.  Right now I'm using the old sock method.  Because I've removed this firm mounting point, I'll have to re-solve the issues with flexure, specifically rotation as the T ring has a lot of slop on the mounting pin.

I think the remaining issue with ut is that the air cooling just can't dump heat fast enough and the whole setup builds heat.  I'll need to look at optimizing things.  I've left it running overnight and I'm hoping that the cool air of the evening will show better results.  There might be an ambient temperature where it starts working.

All this has me thinking again about water cooling.  Nothing else I know can handle 100 Watts of waste heat in a light form factor.  I do have an old water block that I could press into service.  Would need a radiator with fans and a 12V pump.  I did a little searching online for parts and have some ideas.  The idea of water cooling makes sense to me since I use the method for my desktop computer.

While the idea of having a system that allows the introduction of ice to speed things up, I recognize that this setup is not very portable.  I think that using just a radiator, pump, hose, and water block will be all I can do.  I may be able to mount it on a dovetail clamp for riding piggyback.

EDIT: As a followup with more thinking, I believe that I may be using the wrong thermal compound.  I'll open it all back up and recompound with some better stuff I already have (Arctic Silver).  Will also try a smaller TEC since the system is running flat out with no PWM.  To facilitate the ease of changing components, I'll put a terminal strip on the board.