Relays and Solenoid Valves

Using Arduino Motors, Mechanics, Power and CNC
4

Wawa:
In general, three things are important.

  1. Snubber diode across the solenoid, on the solenoid.

  2. No solenoid wiring near Arduino/relay wiring. No solenoid near the Arduino.

  3. Use opto isolation if possible, which gives you a second layer of isolation.
    a) Relays need a separate supply
    b) JD-VCC jumper must be removed
    c) NO ground wire between Arduino and relay board.

Leo..

The relay boards are exactly like these:

What does the "JD-VCC" jumper actually do? How should it be wired if that jumper is pulled? How do the control signals work if there is "NO ground wire between Arduino and relay board?"

Regards,
Ray L.