That looks like what I was suggesting, but I also see what you mean about the valve now being shorted to ground so obviously this configuration won't work. Is there any configuration of this that will work? There's not a whole lot of parts to play around with.

I don't see the short. Where is it?

 

Right where the arrow is pointing to " - jumpered to ground" there is a connection that extends from the positive output to the valve directly to ground.

 

Right where the arrow is pointing to " - jumpered to ground" there is a connection that extends from the positive output to the valve directly to ground.

What's wrong with that? The other end of the valve is still free. One side of the valve has to be grounded if you want to drive a relay, or any other type of load. You could use an optocoupler to avoid grounding the valve, but that would draw a few milliamps from it (which I can't imagine would be a problem). Why are you so concerned about stealing a couple of milliamps from the valve supply?

 

I suppose a few milliamps wouldn't be a huge loss. In general a small loss in my current means the valve opens a little less, which means my pump output is a lower, which means I lose a lot of driving capability. It amounts to about 40mA for every gallon of output/min. I haven't actually sat down to try designing said optocoupler circuit, but I would think it would require more components and be more difficult to work with since the voltage can vary so widely and the LED side of the optocouplers I've worked with don't take a much voltage very well.

 

I see your point about optos.
Did you come to grips with the "short"?
I think the 2N5434 will work. The relay coil may only have 22-23V across it, but this should be more than enough to pull it in. 2N5432 or 2N5433 would be a better choice, if you could get them.

 

I'm still not sure why the "short" isn't actually a short. I could see why the electrons would preferentially go back towards the positive terminal to maintain a balance since you can't just pump electrons out one end without getting them back in the other end. But what's to stop them from also just shooting straight into the ground as it is my understanding this is what they like to do.

 

I'm still not sure why the "short" isn't actually a short. I could see why the electrons would preferentially go back towards the positive terminal to maintain a balance since you can't just pump electrons out one end without getting them back in the other end. But what's to stop them from also just shooting straight into the ground as it is my understanding this is what they like to do.

That is not what electrons like to do.
Current won't flow to ground unless there is a return path.

 

So if I also made a connection from the other side of the valve to ground in addition to what is there THEN it would be a short?

 

So if I also made a connection from the other side of the valve to ground in addition to what is there THEN it would be a short?

If you mean, in addition to the connection that I showed in my schematic, the answer is definitely yes.

 

haha, well yes definitely in that case. So if ground is a common line or point or what have you then how exactly would you ever use it in a circuit? I could see it working for say static charges where you have an excess of electrons in a certain part and those electrons would then drain and everything would be good again.

 

haha, well yes definitely in that case. So if ground is a common line or point or what have you then how exactly would you ever use it in a circuit? I could see it working for say static charges where you have an excess of electrons in a certain part and those electrons would then drain and everything would be good again.

Ground is generally just a reference node in a circuit, and in the general case does not connect to earth. Think of any portable device. They don't connect to earth, but the schematic will have one or more ground symbols. All ground symbols connect to the samr node, even if the connection is not explicitly shown as a wire.

 

That does make sense. You learn something new everyday. Now I just need to order a few components and I'll be ready to go. Thank you.