12vdc solid state timer-relay

Are the commonly available octal base industrial timer relays (NCC, Dayton, ect.) compatible with a 12vdc load? Can find listings with 12vdc coil (input or control circuit) but all the outputs are rated for some motor HP rating, which I take to mean AC voltage. My load is a 12vdc solenoid (10A draw) that activates a pneumatic cyl., the release of which I need to time delay (delay on break).

If not, does anyone know of a combo timer-relay (min.adj. .01s, max adj. 5s) that will work in this app.? Have done a forum search, but did not find an answer. Many thanks in advance for any suggestions or advice.

Keith LeBlanc

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voodooracer
Reply to
voodooracer
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HP is commonly about 745 Watts, watts =3D volts x amps, so you can figure it out if you can multiply and divide.

Reply to
hrhofmann

Sorry if I sound ignorant of some basic electrical knowledge, but in all honesty, I am. I have learned long ago that the only dumb question is the one that goes unasked. Have learned much on my own, but have learned many times more from others. Thanks again for any help you can give.

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voodooracer
Reply to
voodooracer

Easiest is to put a cap across the relay, adjust the value of the cap to hold the relay for the extra time you need.

If you want precision, then use a 555 timer kit to drive the relay.

Or you can do some research, and scrabble up a 555 delay circuit yourself.

John :-#)#

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Reply to
John Robertson

You have at least two problems. Whatever you use to drive the relay needs to withstand the inductive kick when you turn it off. To fix that, you add a diode or some kind of snubber. But what does that do? It causes the current to continue flowing in the relay until the energy is dissipated in the coil resistance and/or snubber. That keeps the relay closed for some period of time.

Same thing happens on the contact side. You need some kind of snubber to keep the inductive kick of the solenoid from arcing the relay contacts. Causes more delay for the same reason as above.

You can get a rough estimate of the amount of extra delay from Td = L/R where L and R are the inductance and DC resistance of each of the coils involved.

Bottom line: 10ms is kinda short for a reliable time delay for a mechanical relay.

Reply to
mike

You could use the timing relay to drive a conventional DC rated relay which in turn would activate the solenoid.

And see the section on "Protection diodes for relays" at

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Reply to
Bennett Price

Thanks for all the replies and advice, great info! That link to the electronics club was just what I need! Will be spending lots of time there in my endeavor to become more "electronical".

Thanks again to all. Keith LeBlanc

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voodooracer
Reply to
voodooracer

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