Aaaaaargh!

29 Aug 2017

So I got everything hooked up/soldered together and it was all working great. The relay was clicking on when I wanted it to. The power supply had everything going without any smoke or flames. And then I hooked up the solenoid valve to the relay. It clicked on once and then the relay stopped working. The light on the Nano is still on and yet the relay light is no longer blinking. I guess I should see if there is any voltage coming from pin 8 (the one hooked up to the relay.

The solenoid power was coming directly off of the power supply, not from the Nano. Should I have put a diode in there somewhere? I'm really new to electronics as I am a logger.

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jw0752 over 8 years ago

Hi Clinton,
If the power supply was supplying the solenoid as well as the Nano then it would be a good idea to have a flyback diode across the solenoid. In fact it is probably always a good idea to have a protection diode across any inductive load. Just using the Nano for a connection point for the relay board would probably not cause the problem you have encountered as long as you were taking the power from the input voltage line Vin (Pin 30) and not trying to use a voltage that is regulated on the nano such as the 5 volt or 3.3 volt points. The fact that you had no problems until the solenoid clicked tells me that you got a voltage spike and killed your nano. Sorry
John
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sasquatch84 over 8 years ago in reply to jw0752

Awesome thanks. Good thing I bought those Nanos in a 3-pack! As far as the diode goes, where can I look to learn 1. How to put one into the circuit 2. How to figure out the size of diode needed. I have a decent assortment of components including diodes so I may have the one I need. Again, thanks so much for the help.
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jw0752 over 8 years ago in reply to sasquatch84

Hi Clinton,

Here is a link with some info.:

https://electronics.stackexchange.com/questions/110574/how-to-choose-a-flyback-diode-for-a-relay

The diode goes across the contacts of the solenoid with in a reverse biased orientation. Banded end of the diode toward the + side of the supply. This way the spike from the collapsing magnetic field will be dissipated by the diode and not your nano. The recommendation is for the voltage and current specs of the diode be twice the voltage and current of the solenoid. Of course anything higher is just fine. The link recommends the 1N400X series of diodes but for your application any general purpose diode will likely work.

John
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sasquatch84 over 8 years ago in reply to jw0752

Thanks! I'll check that out!
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sasquatch84 over 8 years ago in reply to jw0752

Thanks! I'll check that out!
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