# Overvoltage protection for Raspberry Pi with Zener Diode

I am aiming to power 2 Raspberry Pis via their GPIO pins. As there is no protection on GPIO, I would like to add one on my PCB (that will deliver the 5 V thanks to a TRACO, which can deliver 6 A maximum).

I looked on the internet how to do it, but I am a bit lost in the dimensioning part. I am following this tutorial, and I don't know how to deal with point 2 in section 4 in my case:

Calculate the load current that is linked across the circuit of overvoltage safety. This is 50mA for our example discussed above. Other than the load current, biasing current is required by Zener diodes. Therefore, the total current, plus the Zener diode biasing current, should be equal to the load current. For the above-mentioned example, it can be total current=50mA+10mA=60mA.

How can I know the load current of my RPi? Should I use the maximum (2*3 A)? Here is the diagram of what I planning to do.

• power 2 Raspberry Pis via their GPIO pins Why would you use the GPIO pins for powering the devices? The GPIO pins are not designed for that. I do hope you mean that you will be using the GPIO connector and power the devices via the VDD and VSS pins on that connector. Jun 14, 2021 at 6:47
• You should be adding a series resistor like you added R1, the current consumption of an RPi varies a lot so you'd need to use a low value resistor but then you'd need a very high power zener diode. You would do much better by replacing R1 with a fuse so that when the input voltage gets too high, the fuse will blow. Suffice to say that you should be using a good quality 5V power supply and then no protection is needed. Jun 14, 2021 at 6:51
• Sorry, yeah through misuse of language I called them GPIO. Yeah, I am planning to use the VDD and VSS of the GPIO connector, the +5 V and GND pins. Jun 14, 2021 at 6:53
• Oh, I didn't think about a fuse instead of resistance! I read that TVS diode can absorb more power than Zener Diode, should I use that instead? I don't know how the TRACO is good to avoid additional protection. Jun 14, 2021 at 6:55
• I'll check the TRACO datasheet Jun 14, 2021 at 6:56