How to Switch Up To 600w Lighting? - Page 1
Forum section: electronics / projects

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: September 10, 2019, 08:36:51 pm
content: I want to replace the wall-mounted toggle switches that control overhead lighting in several rooms of my house with switches than can be actuated remotely over a CAN bus. What kind of switching element is appropriate for this task? The overhead lights controlled by these switches range from incandescents to LEDs. The largest arrangement is in the main living room and consists of ten incadescent floods totaling about 600w. Other rooms have LED floods totaling about 100w per room. Dimming would be desirable, but not mandatory. I'm in the U.S., so the voltage is 120v 60Hz AC.I plan to design a small PCB that will have a microcontroller, CAN transceiver, and the switching element. I'm not sure yet whether to supply power to these units as DC over the CAT-5 I plan to run to each outlet (for the CAN signals) or tap it from the AC line. In any case, I want the PCB to be small enough to mount in a standard size wall switch receptacle housing.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 10, 2019, 08:43:39 pm
content: There are dozens of off-the-shelf solutions for this. Why make it yourself?Eg: insteon. But eaton and Schneider have it as well.Anyway, nothing beats a decent relay. But you may also use a triac.

author: themadhippy
author_rank: Super Contributor
timestamp: September 10, 2019, 09:05:59 pm
content: QuoteOr the entertainment industry standard, DMX.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: September 10, 2019, 09:12:51 pm
content: Quote from: Jeroen3 on September 10, 2019, 08:43:39 pmWhy? Because I like DIY rather than always going with an off-the-shelf solution. It's a combination of learning experience and the satisfaction of having done it myself rather than having just bought something from a store.

author: Kjelt
author_rank: Super Contributor
timestamp: September 10, 2019, 09:19:12 pm
content: In the lighting devices I have opened they use a small relay but with so called pre-make contacts. Esp smps drivers and cold incandescent bulbs have large inrush currents and smps with switching off arcing.These relays have a double contact the first is Wolfram that will take "the heat" switching on and off the second is standard AgSnO2 material.An example of such a relay is Schrack RTS3Txxx (xxx is coil voltage).

author: nctnico
author_rank: Super Contributor
timestamp: September 10, 2019, 09:25:56 pm
content: A decent relay is by far the most reliable and cheapest solution.BTW: you should check the building regulations whether it is allowed to mix low and high voltage wiring in a junction box or outlet. Running cat5 and mains wiring through the same conduit is probably a big no-go.

author: Ian.M
author_rank: Super Contributor
timestamp: September 10, 2019, 11:20:01 pm
content: Incandescents pull a massive surge current when you switch them on from cold as the cold resistance of a tungsten filament is typically an order of magnitude lower than at its normal operating temperature. Therefore whatever you choose for the 600W 120V lighting needs to be able to handle 50A for a couple of cycles tapering off to the 5A running current over the next ten or so cycles.Also, they've got a nasty habit of dying at end of life by the filament breaking and arcing at switch-on. The arc rapidly eats the rest of the filament and the highly conductive arc plasma directly shorts the terminals, (while working on melting its way up the bulb stem and out of the bulb) until the fuse or breaker trips. Meanwhile the current is only limited by the circuit impedance and the relatively small arc voltage drop, so can easily reach high hundreds of Amps. Bye-Bye under-rated TRIAC or SSR and even a mechanical relay is likely to weld its contacts if they are still bouncing during the arc event.