GS-401 Photoelectric Relay


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This is a control device that provides ON-OFF relay output in response to the presence or absence of light falling on a sensor.

It can be used in a variety of applications such as turning on house lights when evening falls or starting and stopping a motor, solenoid, relay, etc. when a light is directed at the sensor.

The sensor is a photocell that is mounted in the tube at the opposite end from the lens.

When light is aimed more or less directly at the lens, the beam is focused on a photocell whose electrical resistance then falls dramatically. This change in resistance is used in a sensitive electronic circuit to activate (pick up) an output relay when the light level is high.

When the light is removed, the cell will return to its high resistance state and the relay will then drop out.

When the cell is dark, it will typically have a resistance of about 10 megohms.
When the light level rises to 2-foot candles, the resistance will drop to about 50K Ohms.

The photocell (GS-550) is included as part this system but also may be purchased separately. When purchased separately the cell includes the twisted wires and a horizontal mounting post, however, the upright clamp and vertical post are not included.

Additional information

Weight 1.25 lbs
Dimensions 7.75 × 7.75 × 7.75 in

Cell only – Voltage Not Applicable, 115 v Plug, 220 v Other Plug, 220 v UK Plug, 220 v EUR Plug

Replacement Parts

We have had no request for replacement parts for this product, but please be assured that whatever you might need is readily available.

Please contact us for any replacement part that might be needed.