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I built a retropie arcade system for my father-in-law as a Christmas present. Since then, I have noticed that whenever one of my nephews plugs in a USB controller there is an ESD discharge on the USB Terminal from whoever is plugging in the controller. This discharge causes the raspberry pi to reboot. I am looking for some way to isolate the USB plug ground from the raspberry pi ground so that this doesn't happen. I haven't been able to find anything online, what most people suggest is to just use a grounding strap. This isn't a viable option because my nephews won't remember to put the strap on every time they want to play pacman.

I am using a Raspberry Pi 3B+, and from what I have read the chip itself is protected from ESD discharge. I am more trying to stop the chip from rebooting every time someone gets shocked.

Any help is appreciated!

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Question

USB controller there is an ESD discharge on the USB Terminal from whoever is plugging in the controller, ...

This discharge causes the raspberry pi to reboot, ...

Some way to isolate the USB plug ground from the raspberry pi ground? ...

Recently I have the same trouble when using an USB to TTL cable/adapter as a 5V power source to a ESP8266 module. A nearby Rpi3B+ has a floating (from mains ground) switching power supply (220VAC to 12VDC to 5VDC 5A).

When I switch 5V relays connecting mains appliances, from time to time, perhaps some back EMD or EMI causing Rpi to reboot, and in some worst cases even the switching power supply experienced a huge voltage spike (my guess) and even the 12V 5A PSU shuts down (neede to manually power off/power on to restart), by triggering PSU short circuit protection (my guess).

I have two prevention measures:

  1. Use a dedicated 200VAC/12VDC PSU for Rpi. Sometimes I use a rechargeable battery pack (18650 3.7V x 3 = 11.1V) instead of the mains powered PSU. I also used optoisolated 5V Songle relay modules, and optoisolated L293D/L298N DC/Stepping motor driver modules. Then the Rpi intermittently self rebooting problem disappeared.

  2. I also used USB cables with ferrite beads. I read that this prevents the USB cable picking up EMI from spikes caused by ESD or relay contact sparks/spikes.

ferrite bead cable

  1. If using a USB/TTL cable, I often use one that has a big cap on the circuit board. I read that this kind of cable prevents many untended Rpi/ESP8266 reset because of UART signals switching.

ch340 usb ttl cable

  1. And when in doubt or to play double safe, I have double beads! :)

ferrite bead

I once tried to use my scope to display the mains voltage wavform when switching something. But the scope immediately triggered the home MCB and the whole house went dark, ... I know I don't know many things I don't know about mains grounding, so from then on I avoid using the scope to check anything connected to the mains. (I do have a hand held scope with everything floating to check the mains though).

References

Ferrite bead - Wikipedia

A ferrite bead or ferrite choke is a passive electric component that suppresses high-frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ high-frequency current dissipation in a ferrite ceramic to build high-frequency noise suppression devices. Ferrite beads may also be called blocks, cores, rings, EMI filters, or chokes.

Ferrite beads prevent electromagnetic interference (EMI) in two directions: from a device or to a device.

A conductive cable acts as an antenna – if the device produces radio-frequency energy, this can be transmitted through the cable, which acts as an unintentional radiator. In this case the bead is required for regulatory compliance, to reduce EMI. Conversely, if there are other sources of EMI, such as household appliances, the bead prevents the cable from acting as an antenna and receiving interference from these other devices. This is particularly common on data cables and on medical equipment.

Large ferrite beads are commonly seen on external cabling. Various smaller ferrite beads are used internally in circuits—on conductors or around the pins of small circuit-board components, such as transistors, connectors and integrated circuits.

Ferrite beads are used as a passive low-pass filter, by converting RF energy to heat, by design. (Contrast this with inductors, which by design do not convert RF energy to heat, but rather offer a high impedance to RF.)

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You can not "isolate the USB plug ground".

USB -ve pin is connected to Pi Gnd, and the shield is also connected to Pi Gnd.

Your fundamental problem is that most switch-mode power supplies are double insulated and float WRT real Ground and often are capacitatively coupled to mains voltage.

Use an earthed power supply, or bond the Pi Gnd and all other exposed metalwork to Gnd. NOTE there are good practices in grounding, and also safety issues to consider - e.g. do not plug into a Mains Ground pin.

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