Lighting control 12v switching vs 240v switching

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]
Joined:Sat Nov 08, 2014 1:52 am
Re: Lighting control 12v switching vs 240v switching

Post by aitken85 » Sat Nov 08, 2014 2:25 am

I am retrofitting/ renovating my house to be automated, starting with the lights.
Found it quite a headache to be able to control the dimming/driving the LEDs.

So, I found a great solution: DMX LED downlights. Which there's an Arduino shield for, DMX master. Added bonus is that the LEDs are RGB, which means they're dimmable and can be set to any colour. The LED driving is all sorted for me. Takes DC power input per slave. I run ethernet cable to each lamp/slave to carry the DMX signal, which is daisy chained.

I'm using Raspberry Pi as a MQTT server as well as an Apache server for a browser GUI. It then communicates to the Arduino DMX master via MQTT, sends RGB values for each slave(lamp) that needs actioning.

Code: Select all

DmxSimple.write(address, brightness); // x3 per lamp: R,G,B.
// 512 addresses = 170 RGB lamps on the one system
The DMX slave chips are separate from the actual LED lamp, so if either the LED lamp or slave unit dies, I can easily re-address a new slave unit (around $1O from china), which fits through the ceiling hole used to house the lamp.

DMX is fast, silent (no relay clunks), cheap. Just thought I'd add my 5cents worth, if someone is starting out :)

Joined:Mon Dec 22, 2014 11:01 pm

Re: Lighting control 12v switching vs 240v switching

Post by Bear » Mon Dec 22, 2014 11:39 pm

If the question is about power supply efficiency, most transformer style are not over 60% and most switching are not over 75% efficient with the device on all the time. For me this made the choice easy to make my primary switching on the (in the US) 120/240V side of the system. I use solid state relays which are effectively triac switching modules and thus essentially noiseless and can be switched fast enough to act as a PWM dimmer. Upfront cost can be a little high and heat sinks are a must, especially if you are switching the load at any frequency and expect any reasonable life, but they can be built into the network anywhere between the supply panel and the point of use, giving them unparalleled flexibility and far smaller losses than running a power supply when the lights are not needed. I prefer having my switching in my power room and easily accessible for new construction or where home run cables are more easily handled, but have built a box assembly which can slide into the ceiling like an old work recessed light fixture, leaving only the device connection box exposed for old work. These do not last as long due to high temperatures in the space where the heat sink is meant to shed heat and the heat sink size is limited by the hole size.

The only time I have switched low voltage is on a system for an off the grid cabin that had an entire power system based on 12 and 48VDC from solar, wind and batteries and that system was built to purpose with inverters powering the few devices which could not be obtained in 12V configurations. Every outlet, light and fixture was home run back to a power monitoring room and was monitored for usage and controlled to control battery usage, charging and demand shedding.

Joined:Fri Nov 27, 2015 10:21 am

Re: Lighting control 12v switching vs 240v switching

Post by AlexisnaveCA » Fri Nov 27, 2015 10:25 am

You can easily run a low voltage DC circuits and higher voltage 240V AC circuits in the same house. Be careful that you install the correct conductor sizes, especially for the 12V DC circuits, as they generally require thicker cabling in comparison to 240V. BTW for 240V you will need an electrician to install.

If your running your lighting from a DC source like a battery, especially LED lighting, you will require less equipment and increase the efficiency by not having to run an inverter for your lights. In general any direct consumption from the batteries is preferable, depending on the overall efficiencies of the devices connected, or inverter installed to convert to 240V AC.

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