Navigator - Powering servo rail

Blue Robotics Products Flight Controllers
1

Hello Blue Robotics community !

I have a question about powering the servo rail of the Navigator board with 5V.

For a bit of context, I am working with Blueboats for my robotics research and I will have, at some point, the need to add servos to the vehicle.
From my understanding, the servo rail of the Navigator board needs to be powered with 5V to allow driving servos, which makes sense.

Then, my question is: where can I take this 5V from ?

I see a couple of simple solutions:

  • The second 5V output of the powerswitch
  • One of the V2 5V outputs of the fuse board
  • Adding a new UBEC in parallel of the 16V circuit to generate a new, decoupled 5V
    What is the safe way to do this ?

Thanks a lot,
Loïck

2

Hi @Loick -
I would recommend the third option, an additional UBEC, for powering the servo rail. The V2 5V outputs are limited by the 5V supply of the Basic ESC 500, and the power switch powers the Raspberry Pi 4, so you would not want to risk interfering with the quality of this power during servo usage!

3

Hi @tony-white ,
Thank you for your answer ! It also answers the underlying question of why it wasn’t a standard feature of the blueboat hatch.

Cheers,
Loïck

4

We’re updating the documentation, but the current limit for the Basic ESC500 should be fine for 4A at 5V - with sufficient cooling.

5

Hi Tony,
Do you mean that my second solution would work for 4A loads ?

I’ll be powering quite buffy servos so, either way, it feels safer to add an UBEC. It is good to know and could be useful for someone else though.

Cheers

6

Hi @Loick -
Correct - the ESC 500 BEC powers the V2 5V fuse board rail.
I would agree that a high in-rush current load like a servo is better served by a dedicated power supply though!

7

Thanks for your very clear and useful answers @tony-white !

8

This topic title seemed appropriate for this question:

I the PWM 1-16 servo power rail isolated from the rest of the navigator circuitry? I’d like to connect a higher voltage (+12vdc) to the Aux power pin in order to power some servos that run at a high voltage. There will be no other servos, or devices connected to that rail.

9

From the schematic and a couple of quick multimeter continuity tests it does indeed seem like the SERVO_5V signal / SERVO_BEC line is not connected to anything other than the “+” rails on the 16-pin servo connector and the RGB / AUX 5V / PWM0 connector.

That should be ok, assuming you’re also not connecting things to the PWM0 / Neopixel RGB ports that are expecting that central rail to be 5V.

10

No, that’s perfect!

Thanks.