How can I reverse the operation of a photocell using the ST01 timer?
How to reverse the photocell circuit for 120-277V AC and 12-24V DC load circuits using the ST01 timer?
A normal dusk lighting or night photocell circuit works by turning the load on at night and turning it off in the morning. In today’s wiring tutorial, we will learn how to reverse a photocell circuit so that a 120V and 24V AC/DC load turns on during the day instead of at night and vice versa.
Consider the following ordinary photocell circuit, in which a 120V 277VAC night lamp with an automatic daylight sensor is additionally controlled by a programmable digital timer (ST01, EJ500, Ei600, etc.).).
Since the light sensor (which can be mounted in a normal switch box) automatically turns on and off during the day and night, an additional programmable timer can be used to turn off/delay the operation of the night lighting (e.g. if you wish to turn off the light 4 hours later than the standard twilight setting).
A similar circuit is shown below for a 24V DC load, with the timer connected to a 120V to 24V DC supply. The same objective also applies in the case of a twilight control circuit.
Now we want to reverse the circuit from sunset to sunrise and sunset. Let’s see how it goes.
In the following circuit, a 24V AC or DC night lamp (corridor or outdoor) is controlled by both a photocell (photocell with brightness sensor) and an ST01 timer.
Check the normal operation of the photocell with a digital timer
In normal operation, the light switches on in the evening and switches off automatically in the morning.
You may have noticed that the red wire on the timer is covered (with a cap).
Now if you want to reverse the circuit, just connect the blue and red wires of the timer together and connect it to the photocell (as shown in the picture).
Now the circuit is reversed; For example, the light turns off at night and turns on again in the sun (during the day).
How to reverse the operation of a photocell using the ST01 timer
- Good to Know: It is recommended to add a relay or contactor when the load (e.g. motors, water heaters, etc.) exceeds 4A at 120V AC or 2A at DC.
- Programmable digital timer and functions
- These are twilight and dawn clocks that, like photocells, can be used in both AC and DC circuits. The
- Ei600 and ST01 timers have a built-in CR2 battery (long lifespan of 2 to 5 years). Therefore, they do not require an external 120V power supply or a neutral wire.
- These programmable digital timers can be used in 6-24V DC circuits. The
- ST01 can be connected to 2A at 28VDC and 4A at 12VDC. The
- ST01 can be connected up to 6A at 120V/208V/277V.
- For motor loads, 1 HP at 120V and 2 HP at 240V can be connected.
- Can be connected for ohmic loads up to 20 A at 120-277 V AC. For a power supply, the safest limit is 16A at 120VAC. The
- Intermatic Timer ST01 automatically adjusts to the time zone.
- They can be adjusted to allow slightly longer or shorter missions at dusk and dawn.
- Before sunset and sunrise, put the cap on the red wire and connect the blue wire to the load.
- From morning to evening, connect the red and blue wires together and connect them to the charging station.