Solid State Relay - 72V coil

[fett5]

Hello All,
I am in need of a 72VDC control signal relay. I'm only passing 10A at 12VDC through the contacts. All I'm finding online is 36VDC control. Does anyone have any relays they've worked with that can handle this? Yes, I know a voltage divider would work, but my company just wants to put in one panel mounted relay, no extra pieces.

Thank you,
Mike

 

[fett5]

Oh, i mean 72V control, not coil, hehe. No coils in solid state.

 

[OperaHouse]

These relays basically have an internal LED with a resistor in series. The lower end of the voltage is the minimum to turn on and the upper end is the maximum current. Figuring that 10ma is a typical current, just install a 4,700 ohm 1W resistor in series with the input and you should be fine. If your input voltage doesn't go to ero, you will have to also play around with another resistor across the input to insure the relay turns off.

 

[Comcokid]

The other option to a resistor is to use a 3 or 5 watt zener diode. If most solid state relays are designed for a 24 volt control with 20 ma, then 72-24 = 48 volts. Use something like a IN5368 47 volt zener which will dissipate about a watt at 20 mA.

 

[fett5]

zener, thats a good idea, thank you.

 

[itsmoked]

Why would you use an expensive zener when the resistor is simpler, more robust, and simpler to aquire? I don't understand....

 

[Comcokid]

Yes, a zener is 50 cents and a resistor less than 5 cents. However, with a zener you don't need to know the equivalent resistance of the input side of the relay - only that the max current is less than the V*I dissipation of the zener.

With a zener, IF the control voltage fell to less than about 50 Volts, then the relay would not operate. With a resistor, it might still operate. In your application if such a situation were to occur is one preferable over the other?

 

[fett5]

I still the zener idea, but I found a 74VDC mechanical relay that will do the job in our inventory.

Thank you all.