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Old April 15th, 2019, 03:17 PM   #16
ASF
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Thanks for all the info, this place is a godsend sometimes

I'm already using an interposing relay to drive the solenoid, I'm just more worried about the effect on my other electronics when the solenoids switch on and off (well, mostly off). And to a lesser extent, the relay - as much as the whole idea of an interposing relay is for it to be the sacrificial lamb, I still prefer not to blow them up unnecessarily

I did find the plugs with the built in suppression last night - and on further reading it looks like they're an optional extra for this solenoid, but I didn't pick up on it in time, and I probably don't have time now to get them ordered. But maybe I'll order a few anyway, to retrofit if we have any issues or just to have on hand for next time.

Thanks again!
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Old April 15th, 2019, 03:30 PM   #17
PLC Pie Guy
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Great thread.
Ill be swapping my 1N4001 out for 1N4007 promptly.
I'm also operating on a 24VDC system as the OP described. I was reading the reverse bias rating as the ability to handle the voltage across the coil, and it does, however it must be rated for the peak voltage generated by the inductive kick as well. As iv learned here today.

Cheers!
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Old April 15th, 2019, 03:42 PM   #18
Chilliwack Murray
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Quote:
Originally Posted by PLC Pie Guy View Post
Great thread.
Ill be swapping my 1N4001 out for 1N4007 promptly.
I'm also operating on a 24VDC system as the OP described. I was reading the reverse bias rating as the ability to handle the voltage across the coil, and it does, however it must be rated for the peak voltage generated by the inductive kick as well. As iv learned here today.

Cheers!
You original assumption is correct, the max reverse bias rating need only be higher than the operating voltage to the coil. The induced voltage returned from the coil will be in the forward direction and will therefore be shunted by the diode so no significant voltage will be developed. The diode is not blocking this voltage so the break over rating is not applicable.

That said, always go with the highest rated device you can practically apply to any problem.
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Old April 15th, 2019, 03:45 PM   #19
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Quote:
Originally Posted by Chilliwack Murray View Post
You original assumption is correct, the max reverse bias rating need only be higher than the operating voltage to the coil. The induced voltage returned from the coil will be in the forward direction and will therefore be shunted by the diode so no significant voltage will be developed. The diode is not blocking this voltage so the break over rating is not applicable.

That said, always go with the highest rated device you can practically apply to any problem.
Thank you Sir!
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Old April 15th, 2019, 04:08 PM   #20
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I don't know if anybody looked at the data sheet for the valves but they are AC voltages
220VAC or 24VAC
you can not use a diode on these in fact putting a diode on them will damage the output card
what you need is an MOV of the correct value.
either way the best place to install them is as close to the coil as possible any wire between the diode / MOV will induce inductance and resistance to the circuit and educe the effectiveness of the suppressor
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Old April 15th, 2019, 04:13 PM   #21
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Quote:
Originally Posted by GaryS View Post
I don't know if anybody looked at the data sheet for the valves but they are AC voltages
220VAC or 24VAC
Guilty!!!
I simply assume it was 24VDC. I strive to make everything I do 24VDC so it just becomes second nature to think that way.
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Old April 15th, 2019, 04:13 PM   #22
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That is a generic spec sheet, the OP stated he was supplying it with 24VDC.

If in fact the solenoid is driven with AC voltage, you are absolutely correct.
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Old April 15th, 2019, 09:33 PM   #23
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We use 1N4007 as suppressors for 24VDC and 30Vrms varistors for 24VAC/DC for all devices like small dc/ac motors and coils.
We solder them directly into the double deck terminal blocks with the lower being the -24V and the upper +24V. We could also buy presoldered terminal blocks but it's much much cheaper to make our own.
It's possible to use varistors as suppressors not only for AC but for DC as well but theoretically diodes work better with DC.
On all of our solenoid valves coils (dc or ac) we also install plugs with varistor as suppressor.

https://www.digikey.com/product-deta...70K-ND/2407528



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Last edited by kallileo; April 15th, 2019 at 09:48 PM.
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Old April 16th, 2019, 01:01 AM   #24
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Quote:
Originally Posted by Chilliwack Murray View Post
That is a generic spec sheet, the OP stated he was supplying it with 24VDC.

If in fact the solenoid is driven with AC voltage, you are absolutely correct.
Correct - they're 24VDC. There is no data sheet for the 24VDC version, apparently they're a pretty unusual request. The data sheet just has the standard voltages listed for AC and then says DC: Contact Us. So I contacted them
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Old April 16th, 2019, 03:23 AM   #25
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A diode is just a P N junction foward biased by .6 volts. The options in the other replies with built in diodes are best. If you use a stand alone diode get the anode and cathode connected in the right direction. In navy ET school they taught us that the arrow always points in. Meaning to the n-type material (neg) --->|---Hope this helps
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Old April 16th, 2019, 04:04 AM   #26
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So.. if we go off the specsheet, the max current of your solenoid is 78VA -> 3.25A, the minimum is 35VA -> 1.5A. Would you use a 6A10 diode instead of a 1N4007? Otherwise if you are turning this off-on-off-on you might fry your diode.

Note the operating on many of these diodes is -65C, so have a think about where you mount them.
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Old April 16th, 2019, 10:19 AM   #27
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Quote:
Originally Posted by kallileo View Post
We use 1N4007 as suppressors for 24VDC and 30Vrms varistors for 24VAC/DC for all devices like small dc/ac motors and coils.
We solder them directly into the double deck terminal blocks with the lower being the -24V and the upper +24V. We could also buy presoldered terminal blocks but it's much much cheaper to make our own.
It's possible to use varistors as suppressors not only for AC but for DC as well but theoretically diodes work better with DC.
On all of our solenoid valves coils (dc or ac) we also install plugs with varistor as suppressor.

https://www.digikey.com/product-deta...70K-ND/2407528



Personally I'd rather see the component out in the open and not hidden inside a terminal block. Hopefully the terminal block clearly identifies the component located within.
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Old April 16th, 2019, 10:53 AM   #28
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You are using interpose relays on these aren't you
79VA is a large load for a direct output as stated 3.75 Amps in rush remember it could be even higher
most solid stated outputs limit the current to a max of 2A on each output with a card limit of 5 or 10A total. Even the interpose relays will need a rating of 6A most are only 2A
Careful selection of the hardware will make a big difference in the life of the machine
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Old April 16th, 2019, 11:44 AM   #29
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Quote:
Originally Posted by AustralIan View Post
So.. if we go off the specsheet, the max current of your solenoid is 78VA -> 3.25A, the minimum is 35VA -> 1.5A. Would you use a 6A10 diode instead of a 1N4007? Otherwise if you are turning this off-on-off-on you might fry your diode.

Note the operating on many of these diodes is -65C, so have a think about where you mount them.
The only time your diode is doing work is when the coil is switched off. At that point is time the magnetic field collapses generating a voltage and current through the diode. The 1N4007 is good for 1 amp average and 45 amps peak for 1 ms. In a high cycling environment you may want to figure out the size of your coil in Henrys, and then compute the current generated during the collapse of the field. However I think you will find that the current generated and the duration are pretty small.

If you do a google search you can find some fairly detailed direction an how to measure the size of your coil and some nice o-scope pictures showing the effects with and without a diode installed.

A couple more notes.
First, you can put a resister in line with the diode to limit the current during operation. To size it correctly you would need to figure out the size of your coil as mentioned above.
Second, there is also a device called a bi-polar TVS diode that can be used for this sort of thing. Putting it very simply, they have a sort of built in resistance that limits the current while at the same time keeping the voltage at a safe level. And because they are bi-polar, you don't have to worry about polarity.
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Old April 16th, 2019, 03:32 PM   #30
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Quote:
Originally Posted by GaryS View Post
You are using interpose relays on these aren't you
79VA is a large load for a direct output as stated 3.75 Amps in rush remember it could be even higher
most solid stated outputs limit the current to a max of 2A on each output with a card limit of 5 or 10A total. Even the interpose relays will need a rating of 6A most are only 2A
Careful selection of the hardware will make a big difference in the life of the machine
Yes, in post #16 I mentioned that I was using interposing relays. They're rated to 6A.
Quote:
Originally Posted by AustralIan
So.. if we go off the specsheet, the max current of your solenoid is 78VA -> 3.25A, the minimum is 35VA -> 1.5A. Would you use a 6A10 diode instead of a 1N4007? Otherwise if you are turning this off-on-off-on you might fry your diode.

Note the operating on many of these diodes is -65C, so have a think about where you mount them.
If I'm reading the rest of the thread right, the current rating of the coil doesn't really come into the equation, because that current doesn't go through the diode. Only the inductive spike when the coil power is removed. These solenoids will be operated very infrequently - most of the time it'll be a case of "okay, today we're running this product, so these two solenoids will be on and this one will be off for the next 8 hours".



Good catch on the operating temperature, I hadn't thought of that - though the coils themselves are only good for -20C ambient anyway, it's only the process that can go down to -196C. The solenoid body is quite tall to allow for thermal separation, and the pipework will be insulated - ambient temperature will likely be around 20C.
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