QHY183 cooling control working improperly

[Former user]

The min. duration function to let camera cooling or warming gradually seemed to be not working well when cooling power is over 50%. In this case I set target temp. to -20 or -15 degrees. At room temp. at about 27C, it need about 50% to cool the chip to -5C(My target temperature was set to be -5C, it won't show the problem at this session) But if I set the target to -15 or -20(the power need to rise over 50%)The cooling power will suddenly drop to very low level and then rise up to over 50% but stay near 50% for a while, then it show the same thing(see the pic, it show very strange power curve over and over again) (If I set -15 or -20C at room temp 27C at first(chip near room temp.), the cooling session seemed OK before cooling power gradually climb up to about 50%, then it show strange thing I mentioned above)

I have read the log file, it seems that the command sent to the camera do have some problem, but the log file also show nothing "[Message] QHYCCD: Got Control CONTROL_CURPWM = " suddenly drop then climb up.

I have some screenshot and log file attached at the link. https://drive.google.com/open?id=1rhIiDxmCfKLCAZGzZHB9cdFDycpNsas-

[Dale Ghent]

Hi, I have a 183M and a 294C. I was able to reproduce the issue you described with the 183M, however the 294C did not exhibit the problem. Looking at the logs, this appears to be some sort of SDK issue. NINA just sets the target temperature progressively lower until the intended target temperature is reached no earlier than the desired duration. All TEC power levels are managed by the SDK and the camera’s own firmware. It could be that we are triggering some sort of bug in the SDK/firmware with the temperature steps… a bug that is specific to the 183M.

I would like to note that duration-based cooling and warming is kind of a pointless thing on modern cameras. On QHYs specifically, the sensor cover glass is constantly heated as a part of the anti-dew function of the camera. Worries about thermal shock breaking the cover glass are a bit overblown… there would be a lot of broken cameras if things were that fragile! Imagine your battery suddenly dying, or a power outage removing power from the camera and it breaking as a result.

[Stefan B]

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