Protecting the tablet's USB port on the V2 board


Today I tested the work of the AOG program with the sprayer sections. I noticed a strange behavior of the V2 board. When connected to a computer and the absence of +12 volts, from the power source, both Arduino were powered. Although I only connect the main USB connector. When I started to understand, I found that the stabilizer +5 volts (LM7805) passes current in the opposite direction. It turns out that the USB port of the computer feeds not only the arduino but also through IC3 and IC2 the entire board. Until the power supply +12 volts from the tractor current source appears. I decided that it was a malfunction of the LM7805 and replaced it, but everything was repeated on the LM from another manufacturer. I think, in order not to overload the USB port of the computer, insert a 7805 diode into the power gap.



Did that help?
I would suggest to put the diode between ads 5v and nano 5v, and also destroy the PCB connection there.
This way no power to ads or 5v out, when only on USB.
As you I see at the nano, 5v in goes directly to the usb 5v

1 Like

Yes, it helped and it works.
We can’t put the diode on +5 volts. It will take some of the voltage and current and we will not get +5 volts on the Arduino. The voltage will drop on the diode.

What if germanium diode is used? Around 02-03 volts.

1N4004 is already used in the circuit and it is not expensive. It is designed for a current of up to 1 ampere. You can use any diode for a current of 0.4, 0.5 amperes.

I didn’t mean it, I wrote it for Larsvest’s answer. For a small voltage drop on the diode. 5volt> germanium> 4.8 volts.

All right, got that.