SOLVED relay controled valve fail

Other Hardware General Electronics
1

Hello,

I've been working on this projects for a while and, about an hour ago, it was supposed to be the nice moment when you see everything working all alone, and of course, I'm back on the forum...

Shortly, I have a 12vdc solenoid valve controlled by a Arduino Uno through a 3vdc relay with this circuit. I also have a LCD display hooked-up.

When I turn on the set-up, all goes well, then the valve opens, but then when it closes, by the sound of it I know it's not right, the sound is not snappy enough. And, above all, the LCD starts displaying in Inuit letters (or maybe symbols, I don't know).

when I try it without the valve hooked-up, only the naked relay, all is good.

I redid the part with the relay and valve on a breadboard with new parts (except the valve) to see, same problem. But, when the power is on, if I trigger the relay from the NC side of the relay, just by pluging the wires into the breadboard and out, the valve works fine, no Inuit incantations, the LCD is fine. (I mean, if I don't wait for the arduino to trigger it, I just hardwire it)

I even pushed everything as far as possible from the valve, since it operates through a magnetic field, I though something might have come from there...nope.

What should I look for?

I need guidance, thanks

2

Sounds like you may be encountering an inductive spike when the solenoid magnetic field collapses.

Try putting a snubber in parallel to the solenoid coil. 0.1 uF capacitor in series with a 100 ohm resistor seems to be a popular choice - though sure to use a capacitor with voltage rating well in excess of the voltage used to control the solenoid.

3

Try putting a snubber in parallel to the solenoid coil

I did put a snubber on the coil of the valve, and all is working well. But, in the meantime, the 110vac to 12vdc transformer died! So I now use my benchtop power supply. So I can't really know which fixed the problem...

Then, it happens that I had just learned about snubbers doing this project, so I found the suggested capacitor and resistor in my used parts bin, but I didn't know which went where so I looked it up and stumbled upon this:

RC Snubbers: A simple snubber uses a small resistor (R) in series with a small capacitor (C).

this looks like what was suggested

and

Diode Snubber: When the current flowing is DC, a simple rectifier diode is often employed as another form of snubber.

this is what I had done with the relay, which is DC

both quotes are from this wikipedia article

So I tried to put a Diode Snubber in parallel with the coil of the valve, and voilà! all is ticking and I'm happy.

Question: would the capacitor + resistor have worked or is it only for AC use?

Thanks for the hint!