80 mA x 24v = 1.92 watts You should be OK...

Thanks! I did hook it up and try it and it worked, but I just don't know how electrical components, especially solid state have as far as built in longevity. I'm old school, if a 10-32 will hold, I opp for a 1/4-20, but this will be right on the edge so I had my worries. I'll try it and report back in a month or so. Thanks again!

The power looks OK. I'd put a back diode on the solenoid valve to eliminate any arcing on the reed switch, if speed isn't critical.

So I put a diode (like a check valve?) on the ground side of the valve? This prevents bounce back? As you can see I'm clueless as to what your telling me.

Jack, It's a solid state switch, I shouldn't have said reed in the title, I don't know how a solid state device works, I assumed it would be like a reed.

Thanks all!

Jack, It's a solid state switch, I shouldn't have said reed in the title, I don't know how a solid state device works, I assumed it would be like a reed.

A reed switch is a mechanical switch where as a solid state device is an electronic switch. Generally the solid state switch is more reliable (as long as it is operated within its recommended parameters).

With regards to the diode, from Wikipedia......

The diode across the coil is is a diode used to eliminate flyback, the sudden voltage spike seen across an inductive load when its supply voltage is suddenly reduced or removed.

Flyback diode

More information can be found in the solid state switch literature off the manufacturer's website.

Put the diode across the solenoid valve in the direction where it doesn't conduct when the valve is operating. When the switch opens, the inductive current in the valve will discharge through the diode, eliminating any chance of producing an arc across the switch. It does slow down the dropout of the valve slightly.

If it's a solid state switch, it should have protection built into it, but the diode isn't a bad idea anyway.

Thanks to all! Dave, I checked the switch specs and it has a "zener diode on the output side" to protect against surge, but it says if it is to be used to power a solenoid additional precautions should be taken. Also the valve itself has a built in "surge voltage suppressor diode". Additionally the switch can only be used in a PNP output mode. I'll look more into what your suggesting, I still don't fully understand how to do it. Do the specs above sound like it already has the diode your describing built in?

uweka, As you can see from above, I can't even understand an apparently simple approach, your solution is well above my level, but thanks for your time!

Is it a solid state switch or a mechanical reed switch, there is a difference?

The reed switch data sheet (or manufacturer's website) should give you a good indication as to the expected life of the device, which can vary greatly depending on the type of reed switch you are using.

Regardless, the diode mentioned in post #3 is a good idea as back EMF (an inductive load after all) will likely reduce the life of such a sensitive switching component.

80 mA is not so less for a REED-contact. The lifetime decreases significantly with higher currents and - paradox but true - very low currents.

I would prefer a semiconductor solution like follows. Its a photocoupled driver which makes 60V at 5A and you can forget all trouble.

Regards Uwe

You'll find that using a 33Vdc MOV instead of the diode will get you a faster rate of de-energizing of the solenoid valve.

My biggest concern after that would be how often you will be driving the air valve. These are not meant to be driven very rapidly. Do so will quickly degrade the mechanics of the valve and will lead to a much shorter life of the air actuator.

You should be OK.

If not try a 400mA switch:- http://www.diodes.com/datasheets/AH266.pdf

Which device are you using?

Randall, I'm using an SMC D-7P solid state switch and a SMC NVZ3140 valve. I already have the switch as it came with the valve.

BDT, Cycle time is from 60/min to 120/min. I'm doing that at present using micro switches.

From the spec sheet, this air solenoid has a operating frequency of at least 3 Hz, so at 120/min you're still good.

However, what is the operating frequency of the air actuator? Driving this at 2 Hz seems rather high to me. Our air actuators are quickly wearing out and we're driving them at 0.5 Hz.

BD, The strokes are 1.5" or under, bores are 2" or under. I have one cylinder that is getting a little loose after 10 million cycles, but it's one of the most cheaply made cylinders. I did have one Festo cylinder with a 12" stroke running at 50 cycles per min, it was still good and tight after 7 million cycles.

I'm not sure we're talking about the same thing, because we're not having any longevity problems. You might be running 24/7 and 10 million isn't anything to you.