The 3950 DC Solid State Relay can be used to switch loads of up to 50A at 30VDC using the digital output from a Phidget I/O board.

The Relay comes with an optional protective cover to protect people from touching the exposed high power wires, and a diode to protect your SSR from harmful transients. All wires connect to this relay by screw terminals.

If you are switching a high power load or find the relay is getting hot, please consider a heat sink.

Heat sinks 3955 and 3956 are designed for use with this relay.

Electrical Properties

Physical Properties

Other Properties

Have a look at the Data Sheet for a complete set of specifications.

When choosing a SSR, check the actual load current and the working ambient temperature. Refer to the characteristic curve in the Data Sheet and select the proper heat sink if required. Use the heat transfer pad between the SSR and the heat sink. Failure to do so can cause overheating and could damage the relay. Make sure that the SSR terminal screws are tight. If the screws are not tight, the SSR will get damaged by heat generated when the power is ON. Check the Data Sheet for recommended tightened torque. When an SSR fails, it most often fails permanently closed - leaving your load powered, and possibly creating a fire or safety hazard. You can use a fuse to protect your circuit from wiring mistakes and accidental short-circuits. Make sure that you use the relay within the product specifications.

Have a look at the relay's characteristic curve in the Data Sheet to decide if you need a heat sink.

Without a heat sink, the maximum current that can be handled by this relay is 18A up to an ambient temperature of 40°C.

To switch currents between 18 and 50A, you have to use the 3955 - Heat Sink.

- Data Sheet

- Solid State Relay Primer

This relay connects to the 1012 - PhidgetInterfaceKit 0/16/16.
Just connect the positive control terminal of the SSR to the +5V terminal on the 1012,

and connect the negative terminal to an open collector digital output on the 1012.