Question on 12V 30A relay

Hi There!

I have a 12V 30A ( JQX-15F T90) relay and I want to operate it at 9V DC. Is it OK to operate at 9V? Will less contact pressure generate heat and cause problems?

BTW, I want to switch a 1HP motor with it.

Thanks in advance!

To activate it, the voltage can be a little lower, but 9V might be too low. I advise not to use it at 9V. I don't worry about the contact pressure, but reliable operation under any condition.
Once activated, the voltage can often be half of the specified voltage.

What about sparks ? I think you need a snubber circuit over the contacts.

Do you want to activate it with an Arduino ? A 12V relay is 155 ohm, that is 77mA. You can do that with a normal transistor or mosfet.

How much current do you want to switch ?

Do you know the Solid State Relays (SSR). Search for example for: SSR-40 DA


I have to second that. For that particular relay 9v is pushing it a little. Some relays might work at that voltage some may not because 9v is the spec for the maximum required voltage to operate properly. If you can get a 9v relay or other that would ensure proper operation. If you try the 12v relay at 9v it may work for a while and then not work some time in the future too.
There are tricks to get around this, but it requires more electronic parts such as a large electrolytic capacitor of say around 1000uf at 25v or so.

A reasonable tolerance for the coil voltage would be +/- 5%,
-25% is just asking for trouble.

What is wrong with just trying it? You can't hurt it.


Whatever you use to energize the relay will drop some voltage, so the coil will see less than the minimum 9.00V required to activate it. If you have access to the unregulated DC rail on your supply, it should have sufficient voltage to for the driver (NPN transistor or logic level N-Channel MOSFET) to activate the relay.

Yes u can use 9v to operate the relay
But if you are using 9v
U must maintain a constant current supply