Power to the servo rail?

Hi,

We’re using a Navio+ with a Raspberry Pi 3.

We read in the documentation that we need to use a BEC to power the servo rail. But when we attached the PPM the red LED on the X8R receiver is ON as shown in the picture below:

Does this mean that there is power on the servo rail?

When trying to bind the transmitter to the receiver we had no luck, does this mean that the receiver does not get enough power?

If we connect an SBEC to the power rail, do we risk damaging any components?

Regards
Kenneth

yeah, navio2 provides power to receiver port, but thats the only port on the rail that gets power from navio2![quote=“kenneth.f, post:1, topic:4349”]
When trying to bind the transmitter to the receiver we had no luck, does this mean that the receiver does not get enough power?
[/quote]

together with your usb device a 500mah input (eg usb2) could be not enough - try with your BEC![quote=“kenneth.f, post:1, topic:4349”]
If we connect an SBEC to the power rail, do we risk damaging any components?
[/quote]

you can power Navio2 (that would be: rpi’s usb ports, rpi, navio2 board and only receiver port on servo rail) from following sources
-usb
-navio power port
-servo rail
ALL simultaneously without damaging anything; (diode protection)

but your servo rail always needs to be powered separately - as it is not powered by Navio; (with the exception of the receiver port as you noticed!

–> so go ahead and connect your BEC to the servo rail (not to your receiver) - you don’t need USB and try to bind again!

Hi @panky

Thanks for your reply :slight_smile:

But we’re not using Navio 2, we’re using Navio+. Does the information you provided above count for Navio+ as well?

Regards
Kenneth

totally missed that point :blush: [quote=“kenneth.f, post:3, topic:4349”]
Does the information you provided above count for Navio+ as well?
[/quote]

you can connect 3 power sources (https://docs.emlid.com/navio/Navio-APM/hardware-setup-navio-plus/#powering-navio) (receiver is an exception) --> you can check that by connecting your receiver to channel nr 1-13 (–>no power while usb (or navio power port) is powering navio+)
don’t connect any high load devices (e.g. servos) to your receiver while powered through usb;

for binding: make sure you have enough power and set correct jumpers and mode (D8, D16) for recceiver and your transmitter (there are a lot of docs on the web for binding x8r! (for example: https://www.fpvblog.com/rctech/how-to-bind-x8r-to-the-frsky-taranis-in-different-modes)

Hi @panky[quote=“panky, post:4, topic:4349”]
you can check that by connecting your receiver to channel nr 1-13 (–>no power while usb (or navio power port) is powering navio+)
[/quote]

We checked the other channels with a multimeter, and there is definitely power on the pins, as shown in the image below:

The reason we’re so careful is that we had an incident a couple of days ago… Where the UBEC emitted white smoke and the receiver and the Raspberry Pi 3 died.:worried:

This is the setup we used during the incident:

In hindsight, the only thing we know we did wrong was connecting the UBEC to the AUX pin (something we did several times before without a problem).
We have replaced the Raspberry Pi 3 with another one, and checked in Mission Planner that it still works.

So we wonder if we destroyed something in the Navio+?
Are there other ways we can troubleshoot and check if it works?

Regards
Kenneth

i don’t know if there’s a diode on aux port! if there’s not: your BEC got heated by the other power source and then failed:
but if there’s a diode or not, following sounds logical to me:
you had overvoltage because of the failing BEC (diode became closed (punch-through)); and that would explain rpi and receiver failure! (rpi might work again - it has a self repairing fuse - so you might want to wait some time before you trash it)
you could add diodes manually if you need redundancy…and test output ports with a servo…

Thanks for your answer @panky :slight_smile:

@mikhail.avkhimenia could you help us clarify this? or do you know who could?

We’re working on a octocopter, so we’re not using any servos and the ESCs get power from another battery.

Regards
Kenneth

hope your ESCs are fine!

There was no power connected to the ESCs at the moment, so I think they are fine, but thanks for your concern :slight_smile:

There should be no power on Navio+ servo rail if BEC is not present. It is possible that the receiver drains power from the signal circuit.

Was that with Navio+ installed? If yes, then there’s a chance that come circuit is damaged and allows current to flow to the servo rail.

In any way - on Navio+ BEC is a must to power the RC receiver.

Thanks for your reply @mikhail.avkhimenia

We tried powering the servo rail using an SBEC, and it works fine. It seems like the receiver was indeed drawing power from the signal circuit.

We have completed two test flight with the Navio+ and it works great :slight_smile:

Regards
Kenneth Fjukstad

1 Like

Great to hear that everything is fine!
Please feel free to ask any questions:)