ADC Current sensor problem ?

[Tibor1111]

Hello. I want to ask you for help.
If the drone is disarmed, the current in the OSD shows about 3-5 A. which is a lot if it is in idle mode. Before it showed (disarm inav 7.1.2) 0.66 Ampere. Also, when arming and the subsequent flight, I had to adjust the current meter scale from 268 to 375 so that the mAh values ​​​​sit with the battery recharge.

I did not change the hardware at all. Everything is basically the same. I just moved from inav 7.1.2 to inav 9.0.1
Board: matek f405 mini te
ESC: Diatone MAMBA F30 MINI dshot 300

thanks for your help

Inav 9.0.1 osd lua script

Inav 7.1.2 disarm

Inav 9.0.1 disarm

[sensei-hacker]

Hmm, the code that calculates that hasn't changed in eight years. 🤔

I do notice you have the offset at zero, in both cases.

[Tibor1111]

I have been using this drone since version 3.0 and I have not noticed this problem. Until now. I have never edited the offes. I do not know how and do not know what values ​​​​to enter there?
In 9.0.1 and also in previous versions I adjusted the scale using the calculator https://www.mrd-rc.com/tutorials-tools-and-testing/inav-flight/inav-current-sensor-calibration/
I changed the value from 268 to 355. Now the energy consumed during the flight matches what I add to the battery again.

The problem is only if the drone is disarmed then the current is very high.

I have an ultra-light drone. During the flight it consumes an average of 6 Amps. Therefore, it cannot consume so much in disarm mode. In lower versions it was about 0.6 A in idle mode.
I don't know what the problem is
Thanks for your willingness to help

[sensei-hacker]

The zero / idle current would be largely controlled by the offset parameter.
That is with the battery connected, not just USB, correct? Trying to measure battery current with no battery connected will give random-ish numbers.

[Jetrell]

@Tibor1111 Are you sure you have the main battery connected when you view this current reading in the script.
If I only have the FC powered via USB, which drives the RX by 4.5v. Then the current shows 2 - 3.5amps. But as soon as I plug in the flight battery. The current value drops to 0.4amps as expected.

[Tibor1111]

The photos are taken with the drone connected to the battery.

edit: I noticed that it only does this when I turn on the radio. Even if the rc radio is off and the drone is connected to the PC with the battery on, the current is about 0.5 A
If I turn on the rc radio, the current jumps to 4-6 Amperes. If I shade the buzzer with my hand, the current drops to 0.5 A
I admit that I moved the buzzer from the shoulder to the top plate of the drone.
I will have to move the buzzer somewhere else, further from the RX antenna.
Sorry for bothering you. You can end this conversation.

You are doing an amazing job. Inav it is great. Thank you for your willingness to help. Because I don't know how to work with code at all.

[Tibor1111]

I have another drone here. flash is Inav 7.1.2
I don't have this problem there even though the installation is the same type of buzzer and the distance from the RX antenna is the same??? (battery and rc radio on)

[sensei-hacker]

Ah mystery solved! (Mostly).

I noticed that same type of buzzer messes with my magnetometer. So that means the coil makes a magnetic field. As coils do.

Your first aircraft may have a Hall effect current sensor, which works based on a magnetic field. Buzzer causes magnetic field; Hall sensor treats magnetic field as current reading, mystery solved.

--

Fun bit of trivia related to the tangent we went on:
If you need random numbers, such as for encrypting the radio link, one good source of random numbers is to read the current, voltage, or RSSI values from a pad that's not connected. The small side of the numbers after the decimal will be very random. PrivacyLRS uses this, among other sources of randomness.

[Tibor1111]

If the drone is plugged into the battery and connected to the pc and the radio off. the value is good about 0.5-0.8 A. The change happens if I also turn on the rc radio. Then it jumps to 4-6 A.

The buzzer somehow affects the crossfire rx receiver which sends bad data in the telemetry.

I then see them in the telemetry on the radio.

I don't know for sure, I just think and maybe I'm wrong. If the buzzer affects the hall sensor current, then the drone with the battery connected and connected to the PC without connecting to the RC radio should have the value increase to 4-6 A. But that doesn't happen. It only happens when I add the radio on.

If I peel the buzzer off the top plate of the drone and move it to, for example, the shoulder, I see in the RC radio's telemetry that the value drops sharply to 0.5 - 0.8 A (battery and radio connected)

I've already moved the buzzer to the shoulder. And now the current is 0.7 A and it doesn't fluctuate.