FAQ: Can adjustable light sensor switches be used to control 12v circuits?

A light sensor switch can be used to activate DC and AC circuits. This article provides instructions on how to set up our SPLS-12-30W adjustable light sensing switch.

The SPLS-12-30W switch is typically used to activate 12v DC control circuits for lighting, motors, actuators, etc. Although most use it for 12 volt devices, it actually has a wide range of operation, from 5v to 18v DC.

Caution: it is always advisable to fuse both the input and output circuit to prevent damage to the unit.

If the output is used to control a relay, this switch can be used to control much bigger loads than the rated 30 watts (about 2.5 amps @ 12v), such as 110v AC and 220v AC motors.

Light sensing switches can be purchased in our online store, click here to view in a new window

The normal mode of operation of the SPLS-12-30W is for the output to be turned on when it is dark, and it is typically used to turn lights on at night and turn them off during the day. However, a simple double pole relay with both normally open and normally closed contacts can be used to reverse the operation of this switch. In that case, you might have a motor operating a circulation fan during the day, but switched off at night.

The SPLS-12-30W has an advantage over other designs in that the trigger threshold for switch activation can be adjusted.

If you need to adjust the threshold trigger point for these light sensor switches, the first step is to remove the cover, exposing the backside of the circuit board. This is accomplished by inserting a small flat blade screwdriver into the slot at the end of the housing, where the wires exit. A twist of the blade will pry the cover off.

There are two slots on either side of the light sensor that accept a flat screwdriver blade. When you rotate the screwdriver blade in each slot, it will pop the clamps inside the unit, releasing the top cover.

You can then lift off the cover, exposing the underside of the circuit board. To get to the threshold adjustment, carefully remove the circuit board by lifting it gently as you push the 4 wires back through the hole to release the tension on the board.

The circuit board will come out of the housing and you can connect it back into your circuit for adjustment purposes, but take care not to short the board out on anything metal. If you plan to adjust it frequently, you could drill a small hole through the cover to provide better access.

Note that the light sensor itself is on the end of the unit; there is also a dual color LED status indicator on the top of the board that is exposed though a hole in the housing. If it is green, the output is off. A red color indicates that the ouput is switched on.

There is a yellowish color screwdriver adjustment potentiomter on the circuit board, as shown in the picture. Rotate this clockwise or counter-clockwise to set the light threshold trigger to the level you want.

PLEASE NOTE: You might think (as we did) that covering the unit with your hand would be enough to simulate a dark environment for adjusting the trigger level, but it is not. You need to cover the switch so that there is no light leaking through to it.

Wiring Connections:

There are 4 wires leading out of the housing. The two longer wires are for the input power: 5v to 18v, red(+) and black(-). The two shorter wires are for the switched output circuit: 5v to 18v, orange(+) and black(-). Note that this switch provides power to the output circuit, you do not have to connect power separately, unless you wish to switch a separate cicuit using an output relay.

Light sensing switches can be purchased in our online store, click here to view in a new window

We sincerely hope you enjoy using these advanced devices; if you have any questions, please feel free to contact us at any time!