Fixing phantom powering

Projects General Guidance
1

I posted about this before but I didn't have much info on the issue. That is until I found a similar thread. This thread is about an Arduino and NRF24L01 being phantom powered and I think that is happening with my device because there is 5V across D12 and GND, and I have no communication with my NRF24L01.

I will post schematics if they are asked for but I don;t have them made yet. The system involves a brushless ESC and RF nano.

My question is: Can I fix phantom powering by placing a resistor and/or diode on pin 12 (the ESC signal pin)?

EDIT - Schematics posted below

2

Geez, do we really have to ask?

And why are you doing things without a schematic?

Please post a schematic of this.

a7

3

Give me a bit and I'll have them to you.

4

Don’t rush on my account, off to the beach just now.

a7

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requested
requested767×409 7.19 KB

Two notes. 1, the ESC is actually connected to a BLDC motor right now. 2, I currently have the circuit configured with a 10K resistor in between ESC signal and D12. I have not tested it.

6

It's working now but the ESC isn't initializing. Wondering if I killed the pin.

7

OK I made some modifications and now there is a new issue. The signal pin was moved to D2 with a diode allowing the electricity to flow from D2 to the signal pin and not the other way around. Now the Arduino is not powering on at all.

EDIT - I'm also using a new ESC because the old one was dead apparently.

EDIT - Now this one is reading a dead short between the main power line and the motor windings.

8

I'm making popcorn. Please keep up the running commentary, which is unlike anything that happens to all of us every day we throw ourselves at this stupid hobby.

a7

9

I'm giving updates to assist troubleshooting.

EDIT - I stopped because I have given up and am going to try an entirely different wiring scheme.

10

I would warn against using a BEC to power the Arduino, ESCs all too often explode in flames and you wouldn't want that to take out the microcontroller too.

Use separate, clean, power for the microcontroller if you can.

Try more like 2k2 or 4k7 resistors on the signal lines to guard against phantom powering but be more noise-rejecting.
A diode on its own blocks the signal unless you have a pull-up for it to work against.

Anyway the normal generic protection circuit for CMOS inputs/outputs is a pair of Schottky diodes to the rails plus a small value series resistor.
CMOS_output_prot
This diverts any phantom power current from entering the pin too.

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I'm not pushing it that hard.

I tried 10K without success.

I do not speak electrical engineer.

12

Nor do you have google, evidently.

schottky diode

resistor

series

rails, ok maybe that needs a few extra terms for focus. Take a look at the schematic and make a guess about why rails might be.

a7

13

So what sort of answer do you expect when you ask an electrical engineer question?

Maybe you would like the answer expressed in the form of dance?

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@alto777 I understand the terms, I just don't understand why that circuit works.

@Grumpy_Mike One that makes more sense to someone who isn't an electrical engineer.

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How is an electronic engineer going to know what a none engineer will find makes sense?

I will tell you.
Only by the none engineers asking questions about the specific parts he doesn't comprend.

The way you do not do it is to say alll that went completely over my head, or say you are just speaking gobbledegook, which in effect is what you did.

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Thank you for the advice. I will ask a more cohesive question.

@MarkT I only partially understand why that schematic does what it does. Why is there a resistor there? What is the phantom powering current doing upon trying to enter the pin?

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The resistor limits the current so the Schottky diodes aren't burnt out and the voltage rail isn't pulled too high.
The on-chip protection diodes are tiny, designed to protect against mild static discharge only (from careless handling), and if they pass high currents for too long they will fry. And if they pass very large currents the chip may go into CMOS latchup and cook the entire chip.

In commercial designs its common to see devices like BAT54S (dual Schottky diode) being used in this protection circuit. https://www.vishay.com/docs/85508/bat54.pdf

1 Like
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