convert USB dew straps

[sinbad40]

Hi All, again.

So when i came back to the hobby last year, My lads got me a couple of SVbony dew straps, they work very well and happy with them, but due to the number of other cables etc i am looking at going for something like the Pegasus Astro Pocket Powerbox.  I would like to use the USB ports for controlling the auto focusers and filter wheel, so would like to use the onboard rca ports for the dew straps (the power points i hope to use to power the mount/camera etc hence this model)  I have checked the wire diagrams and seems that they can be converted but wonder if anyone has done this before, any advise etc.

[Clarkey]

The RCA ports are 12v pwm outputs whereas the USB few bands are 5v, so I suspect they will be overloaded. You could get a 12v usb port to do the job with a bit of DIY. The other option is a 12v powered usb power hub and put an RCA plug on it.

[Carbon Brush]

Running the dew straps at a low PWM setting won't harm them.
However, the high pulse current may cane the power supply if they turn on together.
Now if you told us the resistance of the straps and the PSU capability.....

An easier fix?
Why not wire the two USB dew straps in series and connect to a 12V supply?

[david_taurus83]

I'd sell the USB ones and get 12v ones with the RCA plug. FWIW I also have the USB ones on my portable setup and they are very good despite my initial scepticism when I decided to try them. 

[sinbad40]

Thanks for all the info guys.  I have them running from a small powered USB hub at the min, and was thinking of trying to minimize the USB ports needed.  I will get some new RCA ones for the setup at home and keep these to use when we are away, excellent idea.