Saturday, March 22, 2014

Data from Cooled Camera

I think the current issue with the stacked Peltier devices is that once they cool, they start generating too much of their own heat.  This becomes a problem and it keeps the camera from cooling further.  Also, the hot air from the heatsink fan blows onto the camera body. 

To be tested:
1. Put a physical barrier between the camera body and the airflow.  I'm wrapping the camera in an old sock to act as a thermal blanket.  If this works, then I can use adhesive material and wrap the closed-cell foam tape I have around the critical bits.  Once stabilized, I'm seeing that the bottom of the camera is 55.4F as measured under the thermal layer.  I'll check it periodically and see how it changes.

55.4 at 9:00     (EXIF 17C)
57.8 at 9:55     (EXIF 21C)
59.5 at 10:48    (EXIF 22C)
60.8 at 11:34    (EXIF 23C)
61.4 at 11:53    (EXIF 24C)
62.1 at 12:13    (EXIF 24C)
61.7 at 12:40    (EXIF 24C)
62.2 at 12:57    (EXIF 24C)    TEC powered off to replace cord
62.8 at 14:06    (EXIF 24C)    Ambient is 74.6

2. I've ordered replacement thermistors for the controller.  Once I have these in hand, I'll put the sensor into the camera at the place where the finger touches the chassis.  That will give some information about the performance of the cooling and may be able to throttle the devices, letting them work less hard and thus not heat up as much.  I would have preferred to find the device locally, but I was not able to find it online at Frys or Halted. 

3. Still bench testing to see if the camera holds the warm temperature or if it doesn't change.  The new dark data is useful as there are hot pixels that have developed over time.  Over the coming months I'll be adding more darks to the library. 

I've looked at the data from the darks of the same EXIF temperature measured last August vs yesterday.  Aside from the hot pixel outliers, the range is still very similar across the whole frame.  In other words, much of this effort hasn't changed things.