Induction Capacitors and such

I have the following configuration working great, but have some questions.

PR16-4-1a 8-Channel DPTP Relay Shield with IOT
PR-2-8 MCP23008 8-channel Digital I/o with I2C Interface
PR-54-2 Feather To IOT Adapter - Using a Particle Photon 2

The Relays are switching 24VDC to USSolid 5-way 2 pos 24VDC 200ma Pneumatic Solenoid
Inputs on 8-channel board are pullup manual toggle and push button switches, shorting to ground to activate. Two of the relays are switching 24VDC to SSR module blocks to provide 120VAC to drill motors and a vacuum.


  1. Should I be using Induction Suppression Capacitors to protect the relay board? If so, which ones, and is that what the solder pads are for next to the relays that I would solder them to?

  2. Do you have a Solid State Relay IOT I2C board I could use to handle switching for these outputs?


Given your description I don’t think induction suppression capacitors are necessary. You aren’t switching the motors directly but rather through external solid state relays so that should isolate the board. Also you would not damage the the devices from induction, they could just cause anomalies in operation.

These are the solid state I2C interface relay boards:
But to be honest you are doing it the way I would(external Solid State relays).