hi all,
its been a long time since ive posted anything here - real life has been keeping me busy.
since this summer ive had a TBS Discovery flying with APM 2.5 and generally things have gone very well. as things have developed and ive got more and more systems connected though ive run into a bit of a power supply quandry:
currently i have:
- APM powered with Power Module - also powers radio rx - all good
- Video TX powered directly from main battery - also powers FPV camera - perhaps not ideal but has worked well enough so far
- RCTimer Gimbal Controller powered directly from main battery - here is where the problems start
- Micro servo for FPV camera pitch - not connected
APM powered with the power module has worked great for months sharing the common connection to main battery with the video TX.
The brushless gimbal controller when first connected to the main battery refused to work (it worked fine by itself, connected straight to a 3S Lipo with no other systems). finally i got it to initialise and work properly adding a capacitor across its power in pins.
The problem ive just noticed is that the gimbal controller is causing a significant voltage drop at the main battery, something in the order of 1V or more, which is enough to really feel a lack of power after 5 minutes in the air.
The pitch control servo is not powered yet, obviously its going to need 5V from somewhere and signal from channel 6.
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so, several things to think about:
- would it be better to power the gimbal controller with a 12V ubec connected to the main battery or add a small battery dedicated to this controller?
- regardless of the power source for the gimbal controller, should i move the video tx to this source as well?
- any reason not to move all the eletronics to a secondary battery? power module would get power from this battery but measure voltage of the main flight battery?
- can i power the micro pitch servo directly from APM output rail or will i need a 5V ubec as well?
- any problem "sharing" the channel 6 signal? - ideally i would like to connect it to the pitch servo, the gimbal controller, and possibly even APM too.
so, thats pretty much it, all suggestions gratefully received as electronics is pretty much witchcraft as far as im concerned. im not just looking for the simplest solution, but one thats going to be robust and reliable.
regards,
james
Replies
I would suggest to use two different power sources. One for the APM, the Rx and the motors. And another for the Cam, the Video Tx and the Gimbal. I think that is more reliable and you get a longer flight time (a little bit).
My TBS Discovery is powered by a 4S 4000mAh battery (Motors, Rx, APM) and a 3S 600mAh battery (Cam, VTx, Gimbal). I never had any problems. Flight time is about 11 minutes.
All the best, Markus
Finally it would be nice to keep the ch6 input to apm, in case I ever want to trim some parameter in the air again. Though really it's a long time since I've used that.
Just wondering if there's any electrical reason not to connect these three signal pins together and have the same ch6 signal everywhere.
James
markus,
yes its certainly starting to look like a good option. i have some nice 1300mAh 3S batteries which might be just right for powering all electronics (APM+rx+gimbal+Vtx+servo), im not keen on changing two batteries with every flight so a slightly larger battery than your 600mAh should allow me to keep APM running and just change the flight battery. the only real problem there is where to put it, ive got absolutely everything crammed into a subframe that "floats" inside the discovery frame and theres almost no space left - perhaps this secondary battery will end up just stuck on the main frame somewhere.
how about the channel 6 signal? i wonder if you have that implemented, and whether ill be ok sharing it across different systems?
thanks,
james
Hi James, I don't have to change my 600mAh battery every flight. Actually I change it every 4th or 5th flight. But in my case it doesn't have to power the APM (which is powered by the big battery) nor any servos (but two brushless gimbal motors). At first I attached the small battery to one of the front arms, which worked great, but then - with the gimbal - I needed more weight at the end of the Disco to maintain the CG. So now I let the big battery stick out of its cage a little bit and put the small battery on top of the big one. Doesn't look superb but works.
What do you mean with CH6? I use it to move the gimbal.
All the best, Markus