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Topic: Flyback diode required for relay board and 12v solenoid? (Read 18367 times) previous topic - next topic


The fact that each channel has a transistor and diode is obvious even from the fairly low-res photograph.
Is your unit like the photograph?  In front of each relay is a TO92 packaged transistor and a glass diode.
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I have a similar setup but another problem.

I'm controlling multiple valves in the same way by using an UNO board and a MCP23017 to control 2 8xRelay modules.

Then each relay control a 12V solenoid valve. Powered by a separate 20A power supply.
Positive wire going through the relays and all ground connected back to the power supply.
note: valves wires are not polarized.

My problem is when I'm turning on 5 relays in the same time (this is the maximum I need to turn on simultaneously), all leds on modules turn ON and some others valves also.
It seems that there is a kind of "bleeding" of current through the common GND who turn on other solenoids.

So I want to :
- connect a secondary 5V power supply for the modules, connected on the jumpers, as described earlier here.

- add some diodes in there, to block this "overflow" (I don't know how to call that) but where?
I have some 1N4007, and I feel to put them between the coil and the GND terminal block I'm using, so nothing can come back on the coil.

Should I add two diode /coil?
or the one to protect the relay should be enough?

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