The PWM is getting a little beyond me. Let me make a few additional comments if it will help identify the proper solution.

A slight delay in the time to energize and de-energize the solenoid is not a problem. They operate hydraulic cylinders and I can live with as much as 150ms of slop.

There is no problem with 25 watt resistors. However, I noticed you can purchase inductive and non-inductive resistors. If I use the resistors, which version do I need?

The power supply is a 100 Watt industrial power supply. Usually, only one solenoid will be firing at a time, but it is possible to have as many as two at once. On average, there will be no more than (4) 3-second firings per minute among 12 solenoids and no more than (2) firings per minute on any one solenoid.

The components must be able to withstand being in a metal box in the summer (in the shade) and must be reliable.

I would like to use the resistor solution, but if the PWM is the correct solution, then I would need a complete circuit (because it would be a little bit beyond me to design such a circuit).

Thanks,
Dale

 

You really need the specs on the solenoids.

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Ron

 

just an idea to test out
use a 7812
output from the device in the input of the 7812
output from the 7812 to the solenoid
other wire from the solenoid to the - terminal of the 7812 and device
might work

 

Ron,
To whom does the "he" refer? Did you mean me or "six bullets"?

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Len

 

I still think your best solution is with resistors. You could use either as the inductance of the inductive riesotors is a fraction of the inductance of the solenoid because the resistor is made from a highly resistive wire like nichrome, whereas the solenoids are most likely wound with copper wire. If vibration is a problem because of the solid wire on the resistors, there are resistors that have solder terminals and mounting flanges so you could use stranded wire for the connections.

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The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
Show me a different way. I have an open mind.

 

Hi Len,
The "he" was referring to six bullets. My reply was in response to your comment:

__________________
Ron

 

Thanks everyone for your help. I am waiting to find out the manufacturer and manufacturer's part number so I can lookup the coil specifications. I will then use equivalent resistors in series.

I will also put a diode in series with the resistor (for when the other vendor is operating the solenoids). Is there any other protection I should add to the circuit?
Thanks,
Dale

 

You need a diode across the coil to limit the back EMF.

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Len

 

If you put the diode across the solenoid-resistor series circuit, the solenoid will turn off marginally faster, which could be good or bad, but probably doesn't matter.

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Ron

 

Ron,
That's what I had in mind but did not know how to explain it in words.

The solenoid will release in about half the time as the time contant is half what it would be if the diode is across the coil only. (since the resistor will be equal to the coil resistance)

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Len

 

LJCox,
What kind/size of diode would be necessary? Is it OK to have the diodes mounted inside near the controls rather than outside near the coils? I was thinking of mounting them from the series resistors to common. Would before or after the resistors be better?

Sometimes the diodes are built into the DIN connector for the coil, but I will check to make sure. It would be a good idea to take the diodes along just in case and I guess it wouldn't really hurt to have the extra diodes in the circuit.

Roff,
While replying to LJCox, I was notified of your response being posted. Thanks, I think that answered my mounting location question. I just need to know that kind of diode to use now.

Thanks everyone,
Dale

 

What current does the solenoid draw?

The diode will have to pass that current at the moment that power it turned off.

So if it say 1 Amp, then a diode such as the 1N4004 would suffice. But if it is say 2 Amp, then you would need a diode capable of passing 2 Amp.

Remember that the cathode must be connected to the positive supply and the anode is connected either to the other end of the coil or to the other end of the resistor. I don't believe it will make any difference in practice except that the solenoid will release slower if the diode is across the coil.

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Len

 

as the discussion here is abt the supply and solenoids,(i don't want to start just another thread for it)
i had a problem,which i never able to solve.

my application involves AC solenoid which operates at 220V.which is as per its SPEC.in our country rates voltage is 230-240VAC.but we used to get 250 to 270 which is not good i know.bcz of which the solenoid used to get too hot.
so is there any solution for this problem.imean is it possible to lower the AC voltage like..from 260-270 to 210-220 AC?

 

Do you know how much current the solenoid would draw on 220V?

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Ron

 

That's true but it wouldn't need to be rated for 100% duty, it depends on how long it takes for the current to decay and the maximum frequency of actuation. A 1N4004 can take 50A in short pulses so the current really shouldn't be a problem.

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