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Basic Electronics » How to Switch a Solenoid?

February 20, 2011
by Ralphxyz
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This will probable be a similar answer as to Lusitania's question "How to switch a relay?" but I really need to ask.

I have these great solenoids (at least I am impressed with the apparent quality) that I got on

ebay.

Of course once they made a sale they increased the price which is to bad as I am going to need a lot more of them. They went from $5.00 to $8.00.

Anyway how would I turn these solenoids on and off?

Speed will be important the solenoids have a 5 - 8ms response time.

They have a 24 volt coil pulling 6 watts.

Would a transistor be faster than a relay? Also what about cost?

I would appreciate a part number with your recommendations.

This switch will possible be on continuously so might heat sinks be required if a transistor is suggested?

Now as if I didn't have enough to do with my weather station project I have to be thinking and sourcing another project.

Of course coming off ebay there is no enclosed documentation, datasheet or wiring guide so I was intimidated by the three prong connectors but in searching the web I found the manufacturer and while these were probable made for a OEM as there is no label on them with any information I was able to come up with a similar valve from there catalog. It appears the #1 prong is + and #2 -. I do not have a 24 volt power source at the moment so I can not test.

Thanks,

Ralph

February 20, 2011
by mongo
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A transistor would be a little faster than a relay but I don't know if it would really make enough of a difference. The relay appears to draw 250 ma, (1/4 Amp) if it's 6 watts at 24V.

I am familiar with these types of coils, as they are common in the industrial equipment I work on. The coil terminals are the two on either side and the other is just a ground terminal. That's a tiny valve setup, so I would assume it is not intended for anything of higher flow rates.

February 20, 2011
by Ralphxyz
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Thanks Mongo, I am picturing a low flow rate but I really do not know what I will be using volume wise I should be able to get enough water through a 1/8" device and I'll vary the flow with a pressure regulator if needed.

Here is the specsheet or at least the closest in their catalog. It is the only 6w value they list.

It is rated for a .5 - 12 bar pressure range I haven't the slightest idea what that means.

So what would be a recommended transistor and what about the continuos service would a heatsink be needed?

Since I am going to be in a wet environment a solid state relay might be more wet resistant that a transistor, so that might be a consideration. The solenoids have a watertight connector so I do not need to worry about them.

Some part numbers or even a transistor type would help get me started.

Ralph

February 20, 2011
by Ralphxyz
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Oops wrong valve. Here is the correct one.

It has a 17 orifice marking so i assume that is 1.7 which gives a bar rating of 0 - 9.

I googled bar pressure ratings and came up with 1 bar = 14.5038psi so this will give me a pressure range of 0 to 130.5342psi

Which gives me a good range of flow volume.

Now for what transistor might I get?

Ralph

February 20, 2011
by mongo
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Good job researching it... Yeah, 1 bar is the average pressure of the atmosphere at sea level, roughly 14.5PSIA (absolute) When working at other altitudes, the pressure is in PSIG (Gauge) which just allows for the difference in pressure over altitude. Still one PSI is still one PSI either way you look at it. so the solenoid is good for fairly low pressure as well as typical industrial air pressure supply too.

Almost any switching transistor will work but I would go with something in the TO-220 type packaging just in case it gets a little warm. They dissipate the heat pretty well.

If you are going to use a logic "high" to turn on the circuit, an NPN transistor will do. The solenoid coil would connect between the +24V supply and the collector of the transistor. The emitter would go to ground. Because there is a difference in logic and work voltages, make sure they share the same negative ground and use a 10K resistor in series with the transistor base and your output on the MCU. That will limit any possible feedback from the higher voltage supply. Don't forget to put a clamping diode across the coil of the solenoid, anode side to ground.

Transistors like the 2N3055 or 2N5190 are popular for these applications.

The 3055 is in a TO-3 case while the 5190 is a TO-220 case. Either one is more than capable.

You can also use the smaller transistors like the 2N2222 or 2N3904. I think they are capable of 100mA. (the others are good for much higher currents)

February 21, 2011
by 6ofhalfdozen
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Ralph,

Looks like you have another cool project going there! I just wanted to pass along my 2cents worth. As usual, Mongo is right about those plugs. Those 3 prong adapter plugs are pretty common on industrial solenoids and sensors. At work we have a bunch of solenoids that use that style of plug and they are pretty decent to work with. It looks like you have one of the better ones with the screw to hold both halves together. Some of the cheaper ones don't have that and the two halves can come loose from time to time especially if there is vibration around. If you are going to be using the solenoid in a wet area, I would definately recommend wrapping the seam between the two halves with electrical tape, heat shrink or something. We had one valve get moisture between the two clamshells and corrode the pins pretty badly. And the price on those valves will probably jump around due to the brass/bronze prices, so you might be able to time it right and buy more when/if brass prices go back down.

February 21, 2011
by Ralphxyz
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These Flo control P2B-B solenoid valves really look high quality.

They are water resistant if not water proof they use a rubber gasketed DIN 43650/B connector.

I am "going" to try to build a animated water curtain.

Picture the | as a drop of water falling:

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I saw a YouTube video of a mall in China that had the most spectacular animated water curtain, but I can not find the link.

Here is a water curtain but not as dramatic as the one I saw before, but still impressive.

I definitely am going to need help with this. I used to be a plumber so the physical setup I "should" be able to handle.

The timing algorithm will be very interesting.

So I purchased 10 solenoid valves to start I wish I had bought more they increased the price to $8.00 from $5.00.

I am thinking that 32 would be a nice demonstration but would really like at least 64 but for now the 10 will have to do.

I think that once the timing is figured out, then it "ought" to scale up to any number.

I am going to start out using the Nerdkit mcu,probable I will serialize a couple like the Expanded Array project does.

Ultimately I would like to capture a sketch from a tablet and then produce the effect on the curtain. That will be my rational for purchasing a iPad.

So I have 10 solenoids. I have a 24 volt power supply coming and a batch of transistors all of ebay.

Any one wanting to help please let me know. rhulslander gmail.com

Ralph

February 21, 2011
by mongo
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That's a cool idea! Kinda like the Bellagio only from the top down...

February 21, 2011
by devinsbusiness
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Sounds like a great idea and a fun project. Good luck with it.

February 23, 2011
by Ralphxyz
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Mongo or 6ofhalfdozen, what is the correct way to take those connectors apart to get to the wiring?

There is a little slot at the top left that looks like it would be a pry spot.

Thanks,

Ralph

February 23, 2011
by Ralphxyz
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Oh I found the answer the secret is to remove the mounting screw completely from the connector.

The screw not only holds the connector to the solenoid but holds the connector internals together.

Ralph

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