USB Current for MC1600MC Cooled

mcgillca

Hi - I'm trying to create a mobile imaging set up using an MC1600MC Cooled camera, and a 120mm-S, controlled by The Sky X on a raspberry Pi.

I have been measuring the current and voltage input to the Pi - I found that unless I had a v high quality power cable, I was having problems.

I have found that as the power for the cooling for the MC1600 cooled camera increases, more current is required by the Pi. Without cooling on, the Pi uses about 0.6A when running the camera. With the camera running at 100% power, I was surprised to see that the Pi uses about 1.5A.

Is this normal? I was not expecting more USB current to be required to run the camera, just current for cooling from the separate 12v supply.

When I add the autoguider and scope control, I get about 2.4A, which is well over the spec of 1.6A for the Pi.

Colin

jrmcvey

mcgillca wrote:
Hi - I'm trying to create a mobile imaging set up using an ASI1600MC Cooled camera, and a 120mm-S, controlled by The Sky X on a raspberry Pi.

I have been measuring the current and voltage input to the Pi - I found that unless I had a v high quality power cable, I was having problems.

I have found that as the power for the cooling for the ASI1600 cooled camera increases, more current is required by the Pi. Without cooling on, the Pi uses about 0.6A when running the camera. With the camera running at 100% power, I was surprised to see that the Pi uses about 1.5A.

Is this normal? I was not expecting more USB current to be required to run the camera, just current for cooling from the separate 12v supply.

When I add the autoguider and scope control, I get about 2.4A, which is well over the spec of 1.6A for the Pi.

Colin

Hi Collin,

I'm not using a Raspberry Pi, but I can tell you that my ASI1600MC-cooled camera uses about 0.22A from my Android tablet USB port when the camera is active, but that drops to zero when I plug in the 12VDC power cable for the cooler.

So, I believe the camera uses the 12VDC as the sole primary power source to reduce drain on the USB host! That is a great thing!

Keep in mind that ZWO states the camera cooler should be driven by a 2A or even greater 12VDC power source. That may explain the load on the R-Pi you are seeing.

I hope this helps,

John

mcgillca

jrmcvey wrote:

Hi Collin,

I'm not using a Raspberry Pi, but I can tell you that my ASI1600MC-cooled camera uses about 0.22A from my Android tablet USB port when the camera is active, but that drops to zero when I plug in the 12VDC power cable for the cooler.

So, I believe the camera uses the 12VDC as the sole primary power source to reduce drain on the USB host! That is a great thing!

Keep in mind that ZWO states the camera cooler should be driven by a 2A or even greater 12VDC power source. That may explain the load on the R-Pi you are seeing.

I hope this helps,

John

Dear John,

Hi - that was what I was expecting - but not what I found!

I use a 5A power supply, so that should not be the problem. I'll try again from my windows PC and see if that has the same thing.

Colin

mcgillca

Well, I played about with this some more. When I used a separate power supply for the Pi and the camera, I got the result you described (and I expected). No additional usb current is used to power the camera.

However, when I powered the pi from the same 12v source (via a step down transformer), the current goes up to 1 amp when using the cooler.

In the circuit design, is there a link such that if the two power sources have e.g. a common ground that the USB could draw more current?

Colin

Sam@ZWO

the camera and cooler and hub draw current from 12V if you plugin it

mcgillca

Thanks, Sam - I realised that the problem was the system I had used to distribute the 12v power - I have replaced this and the current going from the Pi to the camera is now nearly zero.

Colin