Hey all,

So I am using a ASCO Red Hat 8223G027:120/60 AC, 2-way, 17.1W solenoid valve to control some gas flow for a project of mine. I have searched these forums and other parts of the internet looking for clarifications on how to control the valve. I have come away with using things like relays and microcontrollers and what not. I only know basic things about AC circuitry.
Basically, I am just really confused by all of this info and I have no idea exactly what I should be looking for or where to start in designing my circuit. I don't want to be spoon-fed, but I am quite confused.

Thanks.

 

Why don't you explain what you're trying to accomplish? Give details like constraints and budget too.

 

Ok. Well this is controlling the flow of Nitrous Oxide to an injector for a hybrid rocket motor. It is open to the air and is being tested statically. I will be standing at a safe distance where I will be controlling all of this. Budget wise, I have already put several hundred dollars into this project. I don't want to spend too much more on this part of the project, but I do want to make sure I do it right and don't waste money on the wrong parts.
Does that help? Let me know if you need more info.

 

Since you say it is 120VAC, 60Hz, then you look at the inrush current, which is 70VA, and the holding current, which is 40VA.
70VA/120V = 0.58333... Amperes when first energized.
40VA/120V = 0.333... Amperes to hold it open.

If you are going to be controlling it from a microcontroller, you will need to use something like a relay or SSR (solid-state relay).

That valve is only rated for 1,500 PSI, and I don't know whether the valve is brass or SS construction; those are options you have not mention.

I have no clue what you are using for a fuel. Nitrous oxide oxide is a heck of an oxidizer.

I get the idea that you are "on your own" in this development effort, which makes me quite concerned for your safety.

I was an avid model rocket builder in my youth. Before I found "safe" rockets like Estes, I managed to blow up my Mom's brand-new kitchen making rocket fuel on the stove. I later worked on missile systems and spacecraft, among other things.

Since it sounds like you are interested in high-powered rocketry, I very strongly urge you to seek out a NAR section/club near you. Their website is here:
http://www.nar.org/

Things are very different today than they were back in the 60's. Back then, you could get away with having something blow up, or launch a rocket into the stratosphere, and not much if anything was said about it. If you do something like that nowadays (without being in an organization like NAR), you will very quickly find yourself in very, very deep trouble with "the authorities", and they will have absolutely no sense of humor about it. They will want your head, and they will probably get it. I am not kidding.

 

Thanks for your feedback and concerns. However, I might add that I used to be part of a club that built and launched our own hybrid rockets. I also chose a hybrid system due to it being safer that solids and less complex than liquids. I am an AE major myself and was doing this as a summer project mainly. I wanted to try to do as many things as I possibly could by myself before I turned to professors and such for advice/help. I have been reading up on safety and other pertinent info. When I was in the club, we had a long list of safety procedures we went through before we fired. Basically I am not doing this trying to fool around and such. I am quite serious about it and want to do everything properly.
BTW, I am using a brass constructed valve and the fuel is paraffin wax.

 

OK. Brass valves have a tendency to be porous. They are generally sand-cast before machining; if the pour didn't go just right, the valve body will leak. While I really like brass due to it's self-lubricating properties and that it won't spark if struck, stainless would probably be a better choice.

While our primary activity around here is helping people with electronics projects, our overriding concern is safety.

I have no clue as to what pressure nitrous oxide tanks are pressurized to. Oxygen, acetylene, nitrogen and CO2 tanks are routinely pressurized to 3,000 PSI; or double your valves' pressure rating.

I probably don't have to tell you how dangerous it could be if the valve failed with that kind of pressure behind it. However, we had a nitrogen bottle fall over in a shop many years ago (70's) because someone failed to put a safety chain on it, and didn't have the safety cap screwed on. The valve hit something on the way down to the floor, and was broken off. The tank took off like a rocket, and went right through a concrete block wall. We were just really lucky that nobody was injured.

 

Crazy story there. Glad everyone was safe in the end.
Nitrous oxide is actually self pressurizing. One property that makes it appealing as an oxidizer. This pressure depends on the temp. of the nitrous oxide. I think its around 750-800 or so for safe operating conditions.

Anyways, what would be the best way to control this thing? I am a bit confused about relays and such. Do you know any good references for this kind of thing that would help me to better understand this?

 

Well, electromechanical relays are inexpensive and readily available. If you're going to use a uC to control it, then you would likely need one with a coil rated for operation with 5VDC. The contacts must be rated for at least 120VAC @ 1 Ampere.

You should use a 1A fuse in series with the relay contacts.

Here is our E-book introduction to relays:
http://www.allaboutcircuits.com/vol_4/chpt_5/1.html

 

Thanks. This should be good. You've been a great help. I appreciate it