# Solid State Relay Off Voltage

1. ## Solid State Relay Off Voltage

I have a Solid State relay that is controlled by a digital output which turns on and off 120Vac supply to load.

When I enable the relay with digital output (SSR = ON), the measured AC voltage on the load = 120Vac.
When I disable the relay with digital output (SSR = OFF), the measured AC voltage on the load = 12Vac.
I know that an SSR has leakage current when = OFF.

The off case is still turning the load on lightly.

When the SSR = OFF, how do I make the AC voltage on the load = 0Vac so that the load does not turn on at all?

Thanks!

•

2. ## Re: Solid State Relay Off Voltage

Hi,

Find out at what maximum voltage the load is safely OFF.
Then find out leakage current of relay.

Then use Ohm's law to calculate a what (maximum) load is neede to make the load stay OFF.
Calculate the power dissipation of this resistor with full voltage (120V).
Connect this resistor in parallel to the load.

If the power dissipation of the resistor is too high, then you may replace the resistor with a series RC combination.
Calculate the C to meet the impedance value.
Use a resistor with about 1/10 of the impedance.

Klaus

1 members found this post helpful.

•

3. ## Re: Solid State Relay Off Voltage

Originally Posted by KlausST
Hi,

Then use Ohm's law to calculate a what (maximum) load is needed to make the load stay OFF.
Calculate the power dissipation of this resistor with full voltage (120V).

Klaus
KlausST,

Just to be certain, the equation to calculate the resistor value would then be:

R = (Vmax load off)/ (I leak)

I leak = leakage current of relay

Is this equation correct?

Thanks for you help.

•

4. ## Re: Solid State Relay Off Voltage

Hi,

Yes, I think it is correct.

in other words: The max voltage where the load safely is OFF.

Klaus

5. ## Re: Solid State Relay Off Voltage

Mind you if I ask two questions??