SwitchMote++

[dwenrhod]

I have had an uncannily similar project to SwitchMote brewing in my mind for a while now, and finding SwitchMote is a big inspiration. My project basically replaces the 3 pushbuttons with a motorized fader, and the solid state relay with a triac-based dimmer.

I would love to beta test SwitchMote, and either way I will probably still be buying a few of your SwitchMote kits. I'm an Android developer and look forward to designing a SwitchMote app too.

[Felix]

The reason I abandoned the triac SSR was because it was getting too hot with anything more than a few light bulbs and would require a large heatsink. For large loads - more than a few Amps you will need a very efficient triac circuit. You may get inspired from a commercial product but typically those are not isolated and people will complain

[Simon]

I was having a similar thought but what if you limited the power draw to 1A? That would be sufficient to power over 20 dimmable LED bulbs. Incandescents are no-longer sold and CFLs are waining in popularity so why not just build for the growth market- LEDs! 

[Felix]

The current SwitchMoteR2 can drive 5A.
The SwitchMote2x10A can drive two 10A loads.
The SwitchMote1x30A is can drive 30A. I think that covers a lot of needs.

[Simon]

None of them are capable of dimming

[Felix]

So here's your chance to design one that is capable

[Simon]

I found this circuit on electroschematics.com. It uses an analog approach which gets over concerns with the arduino's PWM frequency being audible. It also isolates the low and high voltage circuits from eachother using the light-dependent resistor optocoupler.

http://www.electroschematics.com/9368/arduino-multiple-lights-dimmer/

[Felix]

The TRIAC will have to be very special, otherwise you will need a big heatsink. Same problem that was found in SwitchMote R1 where I used a TRIAC based SSR which would start to heat up when there is a larger load on it. It has to handle 15A which is a LOT of current, although most residential lights are much much less than that and even the R1 would support a large-ish lights load (like a chandelier with 10 CFL bulbs).

[Simon]

I took apart one of my Lutron 600W incandescent dimmers to confirm that the triac is a BT137/600 as per this article http://www.dimmers.net/dimmer_switch.htm . I have another that dimms 8 75watt PAR30 lamps in my family room. Compare that with the LED equivalent of 11 - 14.5 watt lamps and you have a maximum load of 116W/1.05A. I'm not an electronics engineer by any means but this seems fairly straightforward and with the triac at around 55c in quantities of 100+ it's not expensive either - as long as the load-limit is well-defined and never exceeded.

I would defintely recommend a fuse be incorporated - I blew one dimmer (the one I dismantled) when I swapped 6 MR16 60W lamps for 4.5W LEDs and found one was defective. 

[Felix]

The TRIACS do heat up. I use some commercial ones in my house.
The fuses will blow once you exceed a certain low limit. This is a problem. There will always be someone that will want a 5A load or 8A load. What do you tell those people?