Can I disable the receiver power supply on the VESC 6.4?

I am starting to configure the VESC and I found out that it supplies 9.5V to the Arduino which acts like the receiver. Normally I have a switch that is supposed to turn off the UBEC which will turn off the Arduino and with it the batteries, but the Arduino is currently powered by the PWM pins from the VESC. Can I dissable the power supply to the receiver on the ESC and only send the signal across?

You should only connect Ground and Signal pins to the Servo connector. On this servo connector there should only be GND, 5V, and the Signal pin coupled via a 100Ohm resistor to the microprocessor on the Vesc. I checked the schematic for Vesc 6.4. If you get 9.5V there something is a bit odd. It is possible that an arduino gets enough power through signal pins (e.g. UART/serial pins connected to another microprozessor). But this would only supply enough for running the prozessor only and nothing else. You could add a much larger resistor to the signal line (e.g. 10’s of kiloohms) and see if your problem persists. If you connect the arduino to it’s own powersupply, don’t connect the 5V pin from the VESC.

Thanks. I wil remove the +5V pin from the VESC.

It was very strange. The Arduino and even the Big Relay had power even though I had the leads of the UBEC in my hand.

The VESC has a 5V 1.5A BEC through the DRV. I guess you just powered everything through the 5V and GND from the servoplug.

Well, I measured and it was 9.5 V! Could it be that the UBEC received 5 V from the VESC and then changed it up to 9.5?

Well, you didn’t change the wiring, right?
There are Buck (step down) + Boost (step up) converter chips, where you just set a output voltage and within a range they will take any input voltage (lower or higher). But still they have just 1 input and 1 output. So maybe your chip can do 9.5V from 5V but only from “in” to “out”, and sure not from “out” to “out” (if you didn’t changed your wiring and unplugged the battery in should be “open”).

I know. Its super strange. The Arduino and big Relay had power! 9.5V even with the UBEC leads not connected. I had them in my hands! They powered down only when I disconnected the VESC PWM cable (servo cable).

I did some more testing today. As long as the GND and/or 5V pins from the VESC PWM port are connected to the Arduino, it will power the Arduino and Relays when I turn off the UBEC.

Even with no power supply at all, the VESC stores enough charge to keep the Arduino Power LED on for a few minutes. And that only witht the Signal cable connected!! I don´t get it.

I burned 2 Arduinos today because the VESC would power the Arduino if I turn off the UBEC. Can I solve this with some diodes?

It‘s hard to give a precise answer without knowing your wiring exactly. If you draw a schematic, even crude handdrawn, with all single wires it will be much easier to spot the problem. Diodes could help, but I think you should analyse the problem first.

The Arduino itself is quite loaded because I use 13 out of 14 digital pins, 4 Analog pins and the header pins.

The UBEC is connected to the main battery with a switch. The Arduino gets power from the UBEC. Once the Arduino has power, it will activate the big relay which then connects the batteries to the VESC. If I turn the UBEC off, it will power off the Arduino which will power off the big relay and diconnect the batteries from the VESC.

But, if GND and 5V+ from the VESC are connected to GND and 5V+ of the Arduino, it will keep supplying power to the Arduino and the relay when the UBEC is switched off! This causes so much current to flow through the Arduino that it breaks after a few seconds.

There are no other connections between the VESC and the Arduino apart from PWM: GND, 5V and SERVO.

Are you saying you are powering the arduino with5V from the UBEC as well as 5V from the VESC? This wouldn’t be good.

Yes, but I don’t want to. Is the signal cable enough?

Yes if the arduino is powered (5V) from the UBEC then you should ONLY connect GND and SERVO (signal) to the VESC.

Unless of course the VESC requires external power?

As Flo mentioned a handdrawn drawing would help understand exactly what is happening, a picture paints a thousand words.