ParamountObservatory
Port 3 - ZWO DC to RCA Y Splitter Cable 2 X Dew bands
Port 4 - ZWO DC to RCA Y Splitter Cable 2 X Dew bands
I would recommend (1) powering the cooler separately, and not through the ASIAIR power port. Make sure it is powered a second or two before booting the ASIAIR.
(2) likewise, moving the dew heaters off of the ASIAIR power outlets. If moving the dew heater outlets works, and you still want remote control of the dew heaters, what you can do is use a relay between the 12V source and the dew heaters, and energize the relay with one of the ASIAIR power ports.
Then (3) [although this is not your immediate problem, it may eventually become a problem, and will cause you to make frequent walks out to your dome], find a USB 3 powered hub (which does not back-power the Raspberry Pi). Use a single shielded USB cable from the ASIAIR to the hub. Do not connect anything else to the ASIAIR. Then let the hub connect to your other USB devices. You do not have to worry about USB 2 vs USB 3 since a UBS 3 hub will allow them to coexist (unlike the USB 2 days, where the Hub need to be an MMT to allow coexistence of USB 2 and USB 1).
Most hubs will come with a shielded cable that you can use to connect to the ASIAIR. Make sure it is shielded. USB and WiFi co-interferes, and any USB cable that is close to the WiFI antenna (or internal WiFi circuitry when they are not properly shielded) can cause the USB connection to fail.
Do not, ever, ever, use the flat USB cables that comes from ZWO. They are not shielded and should not be allowed anywhere near where there is a strong WiFi signal. I throw mine away each time I open a ZWO box, just to be sure I don't get tempted to use them.
The hub that I found to not back power is this Anker one (also listed in one of the web sites that discuss Raspberry Pi back powering):
https://www.amazon.com/gp/product/B005NGQWL2
It is important that the powered hub does not back power the Raspberry Pi (you can find lots of articles about it on the web). The cheaper powered hubs simply tie the input and output +5V USB pins together. They either don't allow the Raspberry Pi to boot, or becomes flakey with temperature drops (when the 5V in the hub exceeds the 5V bus in the Raspberry Pi).
You can use a back power preventor (simply severs the 5V line) with cheaper powered hubs. But I have not found any USB 3 back power preventor (there are a number of USB 2 ones at Amazon); I had constructed my own with a trivial board layout with AutoDesk Eagle. I use one with my INDIGO Sky/ Raspberry Pi 4 set up.
![](https://bbs.astronomy-imaging-camera.com/assets/files/2022-04-08/1649438425-475354-packpower.jpeg)
Chen