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Topic: Can I use this relay to control 12 V DC? (Read 1 time) previous topic - next topic

Grumpy_Mike

That wiring is wrong.

You need to connect the solenoid directly to the 12V line not back to the arduino pin 13. You are connecting the arduino output into a very low resistance and overloading the pin possible damaging it.

JimboZA

The way I read that diagram, the relay is switching a 5v 40ma max supply from pin 13 which is supposed to trip that solenoid?

But I thought from earlier posts the solenoid is 12v? Surely you should be putting 12v into the common on the outpit side of the relay and switching that? I think the  DFRobot tutorial puts 5v in there just as an example, since that's all you need to drive the LED. (I'm curious why they didn't source that from the 5v power pin though, rather than an i/o pin which they switch on and leave on.)
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Grumpy_Mike

Quote
I'm curious why they didn't source that from the 5v power pin though, rather than an i/o pin which they switch on and leave on.)

Simple - they are idiots.

PedroDaGr8

#18
Jan 18, 2013, 09:43 pm Last Edit: Jan 18, 2013, 09:54 pm by PedroDaGr8 Reason: 1
It sounds like a power supply problem. The relay isn't the fault here. If it is switching (and works for the LED) then you are fine. The Amperage of your power supply is much lower than the rated valuse for the relay (once again the relay is fine). Therefore I would look at the power supply.

Edit just read the above:

Yes, your 12V power supply should come in to the Common pin on the relay. You should NEVER be sourcing the power form the arduino, that defeats the point of the relay.

Also I don't see if the relay has a reverse diode to take care of back EMF when the relay disengages. If it doesn't I would wire one in (I have a feeling arduino's don't like 300V pulses too much).

JimboZA

Quote
I don't see if the relay has a reverse diode


Well the pic of the module certainly shows there are diodes, but the narrative in silent on the matter and it would be a guess that they are fly-backs
No PMs for help please. Not active on this forum any more.

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