Re: [Paparazzi-devel] Electrical connections in the airborne equipment.
From:
Helge Walle
Subject:
Re: [Paparazzi-devel] Electrical connections in the airborne equipment.
Date:
Wed, 14 Jul 2010 18:26:39 +0200
Thanks for all comments. I am trying to learn, and there is a lot to learn from this great project.
Felix,
I can see that it will be wiser to connect the servo (-) directly to the BEC (-) and keep only the signal wire from the TWOG. It should make a better power loop for the servos and avoid leading the current through the TWOG and PPM encoder.
I would beleive there is a potential for simplifying the ground connections, and by that avoid possible ground loop problems.
This raises a question that might have an easy answer, but I am not sure myself:
Do we know that the battery/LiPo input (-) on the ESC is hardwired to the (-) on its 5V out supply ?
Would that also be the case for the BEC?
In that case the ground leads TWOG==>PPM encoder and TWOG==>ESC should not be necessary (and avoided).
That should work great. For those that want to save on wiring and keep it a little simpler, there was a discussion a while back (on the RCgroups thread I believe?) about separating the 5V rail powering the servos from the rest of the 5V on the TWOG/Tiny. This is doable by severing a 5V trace. I'll have to see if I can find the schematic I MS-painted to show where I did it in a test. This setup allowed you to simply plug in the 5V from the ESC's BEC and use it to power the servos.
It's important to stress yet again that you should never hook up the 5V from your ESC unless you've severed that trace. Some people expressed concerns that high currents are still flowing through the AP board, but I never had any problems with my test board.
Buzz
On 07/14/2010 03:17 PM, Helge Walle wrote:
Here is a simple sketch showing how I would like to power the onboard electronics in a TWOG setup.
The plan is to use these connections for my next plane. On my current TwinstarII I use +5V from the TWOG to power the servos. Compared to the sketch the difference is that +5V is now taken from the BEC.
There is a jumper on the PPM board for separating the +5V connection, but I kept it in place and just left out the +5V lead between the PPM board and TWOG.
I use 6-7cm long servo cables between the R/C receiver and PPM board. Do you think that the +5V and Gnd in parallell in each servo cable represents a problem?