Need 240 Volt, 50 Amp, timed and light sensitive controller reccomendation


Thread Starter

Paul Bode

I need to help someone control power to several lights on the same circuit. I need a basic timed function so the power is available only at nights. Being light-sensitive would be an added bonus but not as important as the timed function.

One 'on' and one 'off' function.
Consider using any standard timing device, along with a controllable circuit breaker. Square D makes this type of breaker that can be controlled via discrete inputs to turn on or off.
Contact your local electrical distributor (They are often forgatten as a source of information).

You can get a cheap and dirty time clock (from Paragon or Intermatic) and a photo-cell. Another choice is a lighting contactor (Square D class 8903 type L), a "smart relay" (Square D/Telemecanique type SR1) and a photo-cell.

Steve Myres, PE

The usual device for this is called a "lighting contactor". It is a magnetic power relay with one to many sets of output contacts. It is placed between the output of the circuit breaker and the power feed to the light. You can design a simple control circuit using any PLC that has an internal time of day clock. It can accept the input from the sunlight sensor and can even have different operation on the weekends if needed. You can contact me off list if need more suggestions.

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James Ingraham

Moeller makes a micro-PLC with 120VAC inputs and relay outputs. It has an option for a real-time clock, which is better than a pure timer. You can actually say "Turn on at 7:12pm" if you like. It is programmed in ladder logic, but it has a screen and buttons so you can write the program directly on the PLC rather than having to hook it up to a PC. These devices are also sold by entrelec, Siemens, and A-B. The Moeller version is called an easy Control Relay, the A-B is called picoLogix, and entrelec calls it logotron. (Can't remember the Siemes brand name).

Total cost for one with a real-time clock should be around $300, and that's all you have to buy. No special cables, no programming software, nothing. We've used them at work, at one of our guys liked them so much he bought some to control the lights at his house. Exact same situation; wanted the lights to come on at a certain time and then go off later.

-James Ingraham
Sage Automation, Inc.