Thread: Relay question

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I have another post dealing with something like this but I wanted to break out a basic level question for anyone looking for clarification like me. I believe I understand the concept of a relay, the NO, NC, Common, etc but I'm looking for clarification.

Here's an example:

I have an air cannon that I would like to fire but any board you plug it into suggests a relay so I'll leave it at that.

Here's what I'm wondering... The only thing on the air cannon that requires power is the valve which has two wires coming off of it. The adapter I bought goes into the wall at 110 and it's output is 26.5V 650 mA and also has two wires. Hook the two together and the valve opens. No issues.

I have a few things that confuse me here...

1. I plug the adapter into the wall, two bare wires and I can't get a reading on my multimeter but I don't know why. I set it to 200V, 20V, 10A and it doesn't register anything? Test it on say a 12V and it works fine.

2. The second part is where the relay comes in... If I run power to the prop then there's nothing that the relay would plug into so I'm guessing that one wire goes to the prop, the other goes to the board? So basically I have one wire come from the wall into the board, then one from the board into the empty wire of the prop thereby completing the circuit?

I realize that the normal voltage is 12V so if the voltage is the issue I'm still confused on the actual configuration.

I'll try to help , First off is the adapter. Is it an AC or DC adapter. The 26 volt sounds like it maybe 26 volts AC. A multi meter will give you strange readings if you have it set to the incorrect range , trying to measure AC voltage when the meter is set to DC.
On a relay you need 2 things , 1 is the energizing voltage, that is what operates the coil of the relay. Most relays will have the coil voltage on the case or coil itself. #2 is the device voltage, thet is the voltage that actually runs the device in your case the coil if the solenoid. That also has to match the coil of the solenoid. If I now have you totally confused , I can draw out a diagram for wiring a relay. Hope this helps

What is the output voltage of the adapter per the label? It sounds as though you have an unregulated supply as 26.5VDC is pretty unusual. And what voltage does the valve require to operate?
I have a couple of 12VDC warts that were sold with those Razor scooters a few years back, the ones that had small battery-powered motors on them. I don't get any reading on a DMM with them, but they work fine when there's a load applied.

sorry, here is a pic of the adapter and my MM doesn't have an AC or DC setting, just V.

As for the explanation I get the theory of it all and understand the need for the separate power sources, I think I'm confused as to how everything comes together and how to not mix power sources. For example if I have AC doesn't that mean that both wires are technically hot at some time? If not, when you have an adapter that doesn't really indicate a hot wire, how do you know which one to pick?

Also, on that adapter, it was matched to the valve so I know I'm using the right one and it did work fine when I hooked it all up together. The other thing is that when I do hook it up I can match any wire without issue which is why I wonder about which wire is hot, how it all works with a relay, etc. Does that make sense?

What is on the end of the adapter ,a plug ,spade lugs? If you're using a watering system valve in a pneumatic application I would strongly advise against it . Thay don't mix.

just two bare wires. As for the application the valve is rated to 120 psi and I'm only pushing 80.

you connect the output from your controller to the relay coil, and then back to the neutral on the controller. This gives you power to the relay. attach one of the wall wort cables to the NO term of the relay then on other side attach a wire from solenoid. Hook other solenoid wire to the other wall wart wire. I have drawing but dont know how to post it.

As bfjou812 says. Your adapter is AC, but you're trying to measure with DC. Since the AC is toggling between + and - very fast, it averages to 0V. The DC setting on a meter measures the average, over time, of the voltage - that's why you're getting 0.

Take a look at page 2 on this diagram. It might help understand how to wire your solenoid valves.

- Hook

If you do some research you will find that there is a difference between water pressure and air pressure. I am NOT trying to belittle you or anything like that. I was injured by an exploding pvc pipe that was intended for a water or liquid application and it was used in a pneumatic application. I used to work for a company that built Gauges, pressure ,vacuum ,etc. Just my 2¢.