Products for USB Sensing and Control

Products for USB Sensing and Control


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DC Solid State Relay - 50V 80A

ID: 3951_0

This SSR switches up to 50VDC/80amp and connects to a PhidgetInterfaceKit 0/16/16.


Quantity Available: 496

Qty Price
5 $24.00
10 $23.00

Replaced by the 3958, an SSR with similar characteristics.

The 3951 DC Solid State Relay can be used to switch loads of up to 80A at 50VDC using the digital output from a 1012 - PhidgetInterfaceKit 0/16/16. 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.

Comes Packaged with

  • A Protective Relay Cover
  • A Heat Transfer Pad
  • A Diode


  1. 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.
  2. Use the heat transfer pad between the SSR and the heat sink. Failure to do so can cause overheating and could damage the relay.
  3. 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.
  4. When an SSR fails, it most often fails permanently closed - leaving your load powered, and possibly creating a fire or safety hazard.
  5. You can use a fuse to protect your circuit from wiring mistakes and accidental short-circuits.
  6. Make sure that you use the relay within the product specifications.

Product Specifications

Electrical Properties
Relay Output Type MOSFET
Isolation Method Photoelectric
Dielectric Strength 2.5 kV AC
Control Voltage Min 4 V DC
Control Voltage Max 32 V DC
Load Voltage Max (DC) 50 V DC
Load Current Min 20 mA
Load Current Max (DC) 80 A
Load Surge Current 200 A
Turn-on Time Max 1 ms
Turn-off Time Max 0.5 ms
Physical Properties
Length 58 mm
Width 45 mm
Height 25 mm
Operating Temperature Min -30 °C
Operating Temperature Max 80 °C
Other Properties
Manufacturer Part Number KS33/D-50D80-L

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

Relay Output Boards


This SSR can be controlled using our relay output boards; ordinary digital output boards usually don't have sufficient power to activate the relay. Just connect the positive control terminal of the SSR to the +5V terminal on the relay board, and connect the negative terminal to an output on the relay board.

Product Relay Properties Electrical Properties
Image Part Number Price Number of Relays Load Current Max (DC) Load Voltage Max (DC)
1012_2 $100.00 16
REL1100_0 $25.00 4 8 A 30 V DC
REL1101_0 $50.00 16 8 A 30 V DC


If you're switching high current devices or circuits, we recommend that you use a heatsink. In some applications, you may be able to mount the relay to a metal surface which can act as a heatsink by itself. This relay comes with a heat transfer pad that you can sandwich between the relay and the heatsink or mounting surface. When screwed on tight, it will eliminate any air gaps and ensure that the heat conducts from the relay to the heatsink. In cases where the heatsink cannot dissipate heat fast enough, you should add a fan to one end of the heatsink so that air is constantly moving through the fins.

Product Heatsink
Image Part Number Price Thermal Resistance
3955_0 $5.50 2.4 K/W
3961_0 $18.00

Here's a list of our DC solid state relays:

Product Electrical Properties
Image Part Number Price Control Voltage Min Control Voltage Max Load Voltage Min (DC) Load Voltage Max (DC)
3957_0 $22.00 3 V DC 32 V DC 5 V DC 120 V DC
3958_0 $45.00 3 V DC 32 V DC 5 V DC 120 V DC