Re: AP1100 voltage

Christopher Erickson

The actual top recommended voltage isn't an absolutely precise number because variables like altitude, ambient temperature, relative humidity and localized air movement play significant roles in heat dissipation. 

14.5V is a reasonable, average suggestion. Personally I would de-rate that a bit in high, dry, hot environments. Maybe 12 to 13.7 volts.

In some cases I might even consider putting an auxiliary heat sink plate with a fan on the back of some hotter electronic devices in those kinds of extreme environments. Or use liquid cooling and propylene glycol or some other heat conductive fluid with extended temperature specifications.

Usually not issues that most amateurs have to deal with.

I hope this helps.

-Christopher Erickson
Observatory engineer
Waikoloa, HI 96738

On Wed, Jul 14, 2021, 7:05 AM ap@... <ap@...> wrote:
  • You can use anywhere from 12.5 to 18 volts on the 1100 mount. So if you have a variable voltage supply, dial it in to about 14.5 volts. It will work at up to 24 volts but will get quite hot, so it's not recommended. The controller will not get fried unless you exceed about 28 volts on the input. Best to stay below 18 for long term health.


Thanks, Rolando, 14.5v.  Perfect, I was hoping for a dial-in number.   Though I am confused by the 18v,24v; the manual says not to exceed 16v (e.g. page 50 of the referenced document below).  But not an issue, 14.5 looks good. It’s not like I’m trying to overclock a PC.


So back to the second half – when on batteries, I’ll be closer to the 12.5, probably starting the night at a bit over 13 and dropping.  If I hit 50% capacity I will be more like 12.2v less resistance loss.  So do I need a buck converter to get back up?  Or is the difference for a few hours occasionally moot?


I am somewhat resisting the buck converter because since it will hold the voltage up it’s a switching device and introduces some noise.


  • There is a lot of great information in the GTOCP4 Servo Motor Drive System manual that is posted on the AP1100 product page.  Appendix B is titled Power Considerations and has a lot of useful information regarding power for the 1100 in different scenarios.


Dean, thanks for that pointer, I thought I had downloaded all the manuals but missed that one.  There’s a LOT of documentation, which is good, but it does make it easier to miss pieces.  Thank you.


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