Light dimming

Discussion of the online video show SuperHouseTV, where Freetronics co-founder Jonathan Oxer hacks on his house using various Open Source hardware and software. [SuperHouseTV site]
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Joined:Sun Jan 31, 2016 6:33 pm
Light dimming

Post by kamenyev » Sun Jan 31, 2016 7:11 pm

First of all, I would like to mention that I'm happy to find this site and really thankful for the inspiration I've got from SuperHouseTV.

In another topic Jonathan mentioned the lack of dimming control caused by the relays in the system. What would be the ideal/practical solution to make the system able to dim the lights?
As far as I can imagine, it would require modifications in the high voltage and the control side as well.

Joined:Mon Apr 20, 2015 5:49 pm

Re: Light dimming

Post by Sixfold » Tue Jul 05, 2016 8:28 pm

Instead of using a relay to control the mains voltage you will need to use a triac with a zero cross detection circuit. You need the zero cross because of how the triac interacts with the AC voltage. There are some premade boards on eBay.

Joined:Sat Aug 30, 2014 7:45 am

Re: Light dimming

Post by lemmings » Wed Jul 06, 2016 12:42 am

If your light fixture uses AC, then some of the TRIAC dimmers available at:

may do the trick as long as your light fixture is dimming compatible (i.e. either incandescent, LED corn bulb, or LED bulb/driver that is TRIAC dimming compatible, some fluro).

In the specific case of an AC lighting circuit connected to an LED driver, there are drivers on the market that can be wired up with an extra wire pair for a dimming signal (DALI, PWM, 0-10V, or resistor) but that is going to be difficult unless you are renovating.

If your light circuit is instead low voltage DC connected directly to an LED, you will need to dim by either:
  1. Digital dimming (PWM the DC voltage)
  2. Analog dimming (Adjustable constant current source)
PWM will be easier to implement, gives dimming from 0% to 100%, but will flicker if you don't have a high enough PWM rate. I haven't looked into high current PWM dimmers that can easily be controlled by a micro controller. Any product suggestions would be great (otherwise will look at using a MOSFET on a protoshield).

Analog dimming will be harder to implement and I wouldn't try that unless you can find a constant current driver that has an input for dimming control (like some Meanwell models).

Joined:Mon Apr 20, 2015 5:49 pm

Re: Light dimming

Post by Sixfold » Tue Nov 29, 2016 1:38 am

OK I am having a problem, and thought others may as well, so adding it to this highly relevant thread.

The setup:
I am using one of these ... e-arduino/ triac boards with zero cross detection.

Along with that, my fixture is a dimmable driverless 120v (USA) AC LED light. Specifically the Intertek led-sm6dl.

Im not sure that it matters but I am driving the triac with an esp8266 (wemos mini).

The Problem:
So I wrote out my code and everything works fine when I am only using 1 light fixture. No noticeable flicker, good dimming range, no noise. However, when I connect 2 or more lights, I get horrible flashing. Like seizure inducing.

Another wrinkle. I bought a leviton 6672 dimmer switch. And that thing works great. No flashing at all. No matter how many lights I connect. So I opened it up and from what I can tell its just a triac controlled by a pot. But, it has a huge inductor in there along with some capacitors. I was wondering if I am just missing a smoothing circuit of some sort on my setup? I dont believe its a software issue but anything is possible.

Any thoughts would be appreciated.


As a side note, this is for my home automation project. I am planning a lengthy write up eventually, so you dont all have to waste hours troubleshooting like I did.

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