Hi - total utter right-off-the-boat newbie here working on a little pneumtics project for my house. I've probably already made half a dozen mistakes that you can easily point out, so please be don't eat me alive over them.
Right now, I'm just working on the absolute basics. I purchased a couple 220V solenoid valves of different varieties (I live in Europe) and am trying to get one to fire off by providing current manually, no control circuitry involved. I read the documentation which came with it, which was bare minimal and included nothing about the wiring, but I'm pretty sure I did it right. Here's the solenoid:
Here's the internals:
Here's how I wired it:
Green-yellow to ground (the lead is red, but the wire on the plug is green/yellow), blue to plus, brown to the unlabeled port that obviously should be minus.
When I plug it in, the red light comes on, I hear an electrical pop followed by an electrical hum that sounds like little transformer. But nothing happens. The solenoid doesn't switch which path air can flow through. I unplug and the light goes off and the hum stops. I plug back in and I get another pop, light, and hum - but no result. I have a couple more similar solenoids and I get no results with any of them.
Okay, so I'm sure I'm majorly screwing up here, probably in some fundamental-understanding issues that you can easily point out. Maybe I've already destroyed my solenoids somehow due to my lack of understanding! Or maybe it's not that simple. I have no clue, so I'm hoping one of you can point me in the right direction.
Also, another super-basic question: Is it okay for the solenoids to be left engaged for a long period of time? Or is it important that they not be left open for more than X seconds because, say, overheating risk or something?
nafnlaus:
When I plug it in, the red light comes on, I hear an electrical pop followed by an electrical hum that sounds like little transformer.
I'd expect to hear the solenoid operate, and a hum wouldn't be unusual while it's energized. If the "pop" is a mechanical sound rather than say, that of an electrical arc, it's probably OK.
Also, another super-basic question: Is it okay for the solenoids to be left engaged for a long period of time? Or is it important that they not be left open for more than X seconds because, say, overheating risk or something?
You need to refer to the manufacturer's information, i.e. datasheet or whatever. Surely there are solenoid valves that are rated for continuous duty, but there are probably also types that have a limited duty cycle. The manufacturer's doc should say.
I don't actually have any experience with pneumatic valves like this, but I have used similar solenoid valves for liquids. Some rely on the pressure of the working fluid to operate. The inscription on this one (1.5~8kgf/cm2) would seem to indicate a minimum pressure. I wouldn't think that operating this type of valve dry would harm anything, but without some pressure on it, it's possible that it won't appear to actually open.
There was very little information for them - just basic specs like the voltage, dimensions, etc and the flow paths taken when open and closed. And googling doesn't provide any more.
The pop was electrical. It happens each time it's plugged in. There is no mechanical motion (that being of course the goal). Is it possible that these solenoids are just defective or something?
Hmm, maybe they need pressure. I'll give that a try next.
nafnlaus:
There was very little information for them - just basic specs like the voltage, dimensions, etc and the flow paths taken when open and closed. And googling doesn't provide any more.
Maybe the mfr. has a contact email for technical questions.
The pop was electrical. It happens each time it's plugged in. There is no mechanical motion (that being of course the goal). Is it possible that these solenoids are just defective or something?
I might also ask the mfr. about the sound. Mechanical motion may not be visible but internally the solenoid plunger should be moving or at least exerting some force. Brand-new but defective equipment is always well down my list of suspects. Possible, but not very probable.
Measuring the current drawn when energized against the mfr. spec would be one indication whether things are OK electrically.
Do you know how much air flow and how much pressure you want ?
What kind of air pump are you going to use ?
What kind of tubing ?
Some valves are direct acting, other use the air pressure to open and close.
Wikipedia has a nice drawing : Solenoid valve - Wikipedia
The small solenoid is used to operate a larger valve. The pressure of the input does all the hard work to open and close the valve.
Those valves are used inside a washing machine, and in industrial projects.
You have such an industrial value. It needs (a lot) pressure at the input to open and close.
There are standarized drawings and notations for the number of inputs and outputs (but I have forgotten most of it).
They are very useful for a pneumatic actuator to make it move in both directions.
Thanks everyone - the minimum pressure is probably the explanation! Duh - I didn't even think about that aspect. Unfortunately I just checked and my connectors for hooking up to either my compressors are wrong so it's going to take a trip to the hardware store before I can try again. But that definitely looks like the likely culprit!
I want to get as close to the maximum pressure as possible, which is 8 kg/cm²; both of my compressors can handle it. While the ultimate goal is a pneumatic tube system with electronic route selection, right now I'll be happy if I can merely achieve blowing air into a tube on command I've sketched out the plan for what solenoids I'd need and where (and I understand how to read valve diagrams), but I have zero experience working with them.
I don't need the valves open that long, maybe a dozen seconds or so, so it's good to know that won't be a problem.
I've discovered one (likely) flaw in my initial design when playing around with my hardware. I had initially been planning to use a venturi pump to handle return of the cylinder, so the single switching center could both blow and suck requiring only a single compressed air line to do both. But after I got my venturi pump and tried it out I was quite disappointed by how little flow rate it seemed to give and how much air it consumed to do so. I knew they're inefficient but I expected better than that.. I'm not going to give up on it until I try it out in practice, but I have a feeling I may need to rework my design, and potentially may need to add a real vacuum pump to my shopping list. :Þ Either that or make my end stations more complicated.
(normally I'd have done the calculations in advance but I don't know the payload weights, tube lengths, or tube diameters yet, I wanted to experiment first before locking into a single design)
Do you want the Arduino to control the 230V valves ?
You can use relays or SSR (Solid State Relays).
That means that you gonna need many wires along the tubes to the valves ?
The way I sketched out for it to work was to have one central switching station and a number of end terminals. Each end terminal would have a single solenoid (plus control electronics), open to the air or closed, and that's how the route would be selected - only one would be allowed to be open at a given point in time so there would only be one route for airflow. But to get it back would thus require either suction in the tube or some source of pressure (or way to store pressure) at the bottom of each end terminal below the canister. And I want the terminals to be as simple and cheap as possible, so I naturally felt that drawing a vacuum at the switching station would be easiest. But if the Venturi would prove to be insufficient then I'd also have to have a vacuum pump / cylinder in the garage and a vacuum line into the house, a lot of extra cost and hassle. Hmm...
Concerning noise: yes, they are noisy. But I have a spot in a semi-detached garage that I was planning to soundproof and run a high pressure line from there into the house. I read that it's not recommended to use plastic on long permanent high pressure runs, but that shouldn't be a problem, I have both a tube bender and a flare tool for end fittings so I can use metal.
Okay, I understand. You want to send canisters/cans through tubes.
When I think about that solenoid valve, the pressure, the tubing... it doesn't seem to fit.
That valve is for high pressure, low flow. The path for the air is only small. You might need 10 minutes to pressurize a tube. Do you know the force on a tube at 8 bar ? That are huge forces.
I think you need low pressure, high flow. For example a vacuum cleaner with an inlet and outlet. Perhaps 0.5 bar is enough to make a canister go 'flying' through the tube. The valves can be those valves that rotate a round disc inside a tube (I forgot the name).
Okay, I'll rethink it - thanks Hmm, I guess I should go run some calculations.
Okay, just did some calcs. I calculated the force on a 10-centimeter diameter (just picking an example) cylinder, and it'd be 628kg; with a half kilogram payload that'd be 128 Gs acceleration, minus losses. So yes... point well taken That'd be more air cannon-level pressure than a pneumatic tube system. I calculated flow rates... assuming the solenoid is a simple orifice and is the only bottleneck and pressure differentials remain constant, to oversimplify, a 20 meter long section of tube would take 24 liters of compressed air (expanding to 157 at near ambient pressure) which would take 16 seconds through my larger solenoid type and 35 seconds through my smaller solenoid type. Longer in a real-world situation. Again, point well taken.
I'd just been assuming that pressure would be the limiting factor and with high pressure flow rate would be sufficient through the solenoid. But this is why it's good to be able to talk to people with actual experience, something I as previously mentioned totally lack in this field. It's also why I just bought a few parts to experiment around with first rather than buying all of the parts I'd thought I'd need.
What would one look for to find a high flow rate / low pressure air valve? I can think of a number of search terms I could search for to find a high flow rate / low pressure air pump - "blower", "duct fan", "vaccuum cleaner motor", etc - but I don't know what to search for in terms of valves. They'd need to have a reasonably good seal when closed.
Try "duct valve". But I can only find big ones. Now something smaller and electrically operated and one that can withstand more pressure than only the house ventilation.
Finding lots of results for the search term "electronic duct damper". Only problem is, all that I've seen so far cost $70-100 US, so it's like 4x what I can get solenoids for :Þ
GENERAL INFORMATION
Standard solenoid models are assembled for “Internal Pilot” operation; that is, the valves derive shifting pressure for the spool from the valve inlet port.
So, from what I understand, the solenoid opens up a tiny jet internally that then allows the compressed air (on the inlet) to actually moves the internal bobbin to complete the switch. Without a compressor, it's just not going to switch.
But that is the problem, I think that high pressure is not okay in this situation.
nafnlaus, you have to do some tests. Can you use a tube (metal or PVC) of a few meters, and try with your compressors or a vacuum tube (with inlet and outlet) and see what pressure you need to make the canister start moving and how much air flow is needed to keep it moving.
I haven't purchased any canisters or tubing yet because I didn't want to lock myself into a single design without testing first (which increasingly looks to have been a wise decision), given that I'm such a newbie. But I can rig something temporary up with a trip to the hardware store this weekend.
Running the math, to overcome gravity (not friction) would on a loaded 10cm-diameter canister weighing half a kilogram would take only 0,1 psi / 0,6 kPa. Surprisingly little. A 20 meter run of such pipe would contain 157 liters, so 160 liters per second (340 ) cfm at 0,1 psi, plus extra for friction losses, should be more than reasonable.
But I'm concerned about the cost of those electronic duct dampers. I'm going to need to watch Ebay for a while to see if they're consistently expensive or if they're ever cheaper. 4x-ing my end station costs wouldn't exactly be a good thing. :Þ
Hmm, here's a crazy idea. 4" 100CFM blowers seem to sell for as little as $23 USD - in the ballpark of solenoids and not a ridiculous price. What if instead of electronic dampers I put a blower on each terminal? On triggering to send a canister from point A to point B, the first phase would to blow from the source and suck from all other terminals in the house, and then the second phase would be to blow from all terminals except the destination, which would suck. Not sure how that would affect the switching dynamics I had planned, but I'm thinking it might work... what do you think?
The only thing is, I don't see any pressures listed for duct fans.
The neutral was labeled "+", so that's what I was referring to as positive. That was connected to blue (neutral), while the other was connected to brown (live)
Good point about reversibility - I'll need to inquire about that.
, Jack Christensen already wrote about air pressure to operate)
I've sketched out the plan for what solenoids I'd need and where (and I understand how to read valve diagrams), but I have zero experience working with them.