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Hi Len,
The "he" was referring to six bullets. My reply was in response to your comment:
I would not use the PWM solution since the soleniod is designed to operate with a 12 Volt supply, if you apply 24 V pulses, it will reduce the operating life since the solenoid will move faster and hit the stop harder.
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
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
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.
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)
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.
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.
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?
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?
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.
i was browsing around for some data abt this issue.and came across this article from silicon chip. https://www.siliconchip.com.au/cms/A_103140/article.html
look at the last post.
i wonder is it really possible.say if my application draw 2AMPS then if i use a 12-0-12 2A transformer,it will solve my problem.
what do u guys think abt it.
i was browsing around for some data abt this issue.and came across this article from silicon chip. https://www.siliconchip.com.au/cms/A_103140/article.html
look at the last post.
i wonder is it really possible.say if my application draw 2AMPS then if i use a 12-0-12 2A transformer,it will solve my problem.
what do u guys think abt it.
of course i'll connect the output supply to the coil once i confirm the voltage.
(i have plenty of voltmeters,ready to spoil ;-))
but still iam little bit confused.
say if i connect the supply to one end and take out put from other end,result will be reduced voltage
and if i connect the input to center tap and take output from (any?) end,the result will be higher voltage.
so choosing the input line(end or center tap) decided whether to drop or increse the output?
AC line voltage has amplitude, and it has phase. From the center tap to one end of the secondary, the voltage will be in phase with the line voltage, and from the center tap to the other end, it will be out of phase. If you use one half of the secondary, you can either add 12V to or subtract 12V from the line voltage. If you use the entire secondary, you can either add or subtract 24V. You can't easily measure the phase of the output relative to the line, so you have to use trial and error to determine which connection increases the voltage and which decreases it.
This has turned into two threads, but I just want to check on something for the original question for a moment because I now have solenoid specifications (I think).
The coil is 12VDC, 28 ohms, 430mA (at 70F).
This works out to be about 5.2 watts.
I would like to use 24VDC.
I am thinking of using a 27 ohm series resistor.
A 30 ohm resistor is the other available choice, but there is a long cable distance so I opted to go with the lower value.
Any one solenoid would fire at the most for about 3 or 4 seconds twice per minute with the maxium ambient temperature in the enclosure of 150F. Would a 5 watt resistor work or do I need something larger?
There will also be a 1 amp series diode (to 'OR' the outputs of two different systems together) as well as a reverse protection diode to the common (also 1 amp to make them all the same).
A 5 watt resistor would be safe. You could probably go smaller. It would be easy for you to test on the bench, with a power supply, your resistor, a couple of clip leads, and your finger for a thermometer.
Ron,
5 watts is small enough for construction. I just wanted to make sure I didn't need something larger.
Do you think I could I put heat-shrink tubing (135C max working temperature) over the resistor or would it provide too much insulation for heat to dissipate?
Thanks,
Dale
thanks for the explanation audio guru.i got the solution.
@DSGarcia
as the resistor is the main part here.i think its better to place it in a small AL make enclosure(say 1.5*1.5*3inch lngth).this will protect the resistor and works as heat sink.
Ron,
5 watts is small enough for construction. I just wanted to make sure I didn't need something larger.
Do you think I could I put heat-shrink tubing (135C max working temperature) over the resistor or would it provide too much insulation for heat to dissipate?
Thanks,
Dale
One caveat - if there is any possibility that the solenoid drive will get stuck ON, you need to consider that - although I your solenoid may also not be rated for continuous duty.
Steev, Thanks for the suggestion, but the heat shrink was to protect them electrically inside a junction box. I was going to bend one lead on each of the 12 resistors down along side the resistor to make it a radial part and have one long Euro-style terminal strip, but I decided to mount them axially going from one terminal strip to another so now the heat shrink would only be on the leads.
Ron, Good point. I will have a watchdog on the outputs so they will be shut off automatically if the I/O block looses communication with the controller.
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