QHY268M Cooling problem AND THE SOLUTION

[MarsG76]

Hi Astronomers,

This post is mostly for owners for the QHY268M coldmos astro camera, possibly other QHY cameras, particularly the newer models, BUT might help other if it has a similar protection measure.

I noticed that my QHY268M camera had a big problem in cooling the sensor than keeping the temperature at the set point.
I set the camera to cool to -10C (from an ambient of 17C) and it took a very long time, about 15 minutes, to reach -10C, cooling power was sitting solid at 100%. BUT as soon as I started exposing (Dark frames during this night), the temperature started to rise... cooling still at 100%
I stopped the exposures, but the temperature did not resume to cool... I stopped and restarted software controlled cooling and still the temperature did not drop... it didn't drop until I did a power cycle of the camera, but the behaviour of the camera was the same.

I use APT 3.99.1 for my imaging control, BUT I want to say at this point that APT was NOT the problem. 

I tried the same procedure in QHY's EZCam with exactly the same results, except when I connected the camera I got a dialogue message ”Camera may not be able to reach the maximum cooling power”... I did suspect the PSU, the QHY supplied 12V 6A unit, and it might contribute to the problem but this PSU delivers enough power to run the QHY268M cooling at 30C below ambience.

This QHY camera has a Under Voltage Lock Out (UVLO) protection which will stop or limit cooling when this condition is set in the camera. This condition is set when the PSU voltage drops below 11V. 

The solution to this is to reset the UVLO condition is in the latest version of the EZCap software, under the "Adventage Menu" (I'm sure that was meant to be "Advanced" but what do I know... there you can check the UVLO status and reset the UVLO status by clicking on the "Reset Flash Code" within the EZcap_QT app shown below:

 When I did it, the "Sensor UVLO Status" still reports the same value of 1, as it did before the reset, but the ”Camera may not be able to reach the maximum cooling power” dialog message did not show up when connecting the camera to EZcap, which was displayed every time I connected the camera to the program before the reset. So something has effectively been reset or changed.

After the reset, the camera cooled to -10C in about 5 minutes, sustained the temperature at -10C during my darks exposures and this was with 63% cooling power, in an ambient environment which was 1.5C warmer than before.

Now for the reason of my camera's UVLO. The action that (I think) triggered my UVLO condition was that I changed the temperature cooling steps to 6C (from the default 3C) in the cooling setting in APT Cooling Aid, hoping to cool the camera faster, but this just made the cooling power go straight to 100%, drawing power from the PSU too fast, causing the voltage to drop below 11V momentarily...
Since I reverted back to 3C steps, the cooling power increases steadily, the temperature is reached in a few minutes and I never had the cooling issue since.

 

QHY268M Camera UVLO Codes:

The QHY programming documentation defined the following UVLO status codes:

• 0 = init
• 1 = good
• 2 = checkErr
• 3 = monitorErr
• 8 = good
• 9 = powerChipErr

Hopefully this will help someone with this problem and they wont have to waste possible months waiting for  a camera replacement thinking that its faulty when it might not be... I had to write this because I did see someone with this problem on the QHY's own forum and their response was "I can replace it for you..." totally unnecessary....

Clear Skies,

Mariusz

 

Edited April 24, 2022 by MarsG76

[Starflyer]

I haven't experienced this with my 268M but do remember seeing a similar issue posted on the CN forum.

Great info, thanks for posting.

[tomato]

Thanks for posting. Under NINA my 268c goes to 100% cooling upon start of cool down momentarily,  but the cooling behaviour is normal after that. I did see a low supply voltage warning a while back but the camera was fine after a restart and it has not recurred since. 

[John Fletcher]

I too had the exact same issue MarsG76 describes but did not have the same outcome after going through the steps he outlines.  I did everything that was listed but found the temperature still did not reach the correct level.  Instead, everything is connected via a Pegasus Ultimate Powerbox, I disconnected all the USB plugs whilst the AstroPC was off, switched it on again and, one by one, reconnected everything.  Each time I reconnected, I then went into NINA and connected there too.  This has so far appeared to solve the problem.  What happens now is that I select -10c and it reaches this temperature but shoots past it to around -11.3c to -11.5c but then springs back and settles at -10c.  All works so far, touch wood.  Hope this helps somebody else.

 

Edited October 29, 2022 by John Fletcher