Illuminated Projects

September, 2012

When I moved into my new home the kitchen seems a bit bland, and with it being a rental there isn't too much I can do. I've noticed there is a 1/2" gap between each of the cupboards that extends from top to bottom, the perfect place to discretely run wires without drilling any holes. There was also an outlet in the cupboard above the stove to power the microwave. I've decided to add some much needed ambiance to my kitchen, so I decided that I wanted to install multi-colored LEDs above the cabinets and warm-white LEDs under to illuminate the work space.

After doing some research on different LED control modules, I've decided that I wanted to build my own. I wanted to have four channels of control, three for the colored LEDs on top and one for the under-cabinet. I also wanted the system to turn it's self on and off automatically, and make sure the kitchen was always lit at night in a night-lite mode. After experiencing an extended power outage after hurricane Irene I also wanted the system to have a battery backup that will make sure the lights stay on long after the power goes out.

As far as off the self solutions, I could have gone with a simple Chinese made RGB controller, but they only offer a few fixed modes and offer little flexibility for configuration. There are also advanced DMX controllers that are more then powerful for what I need, but they usually require something to be feeding them a constant signal, such as a computer with a DMX interface or a lighting console. This is defiantly outside of my price range. For backup power, all of these solutions will have to run off an uninterruptible power supply, which are usually inefficient with the DC to AC conversion when running off of the battery.

I've decided to use a Belkin UPS to house the battery and the control board. The Belkin unit will act as the power supply and handle the battery backup functions of the setup. There is also enough empty space inside to house the control board for the LEDs.

This is the Belkin unit opened up. After removing the battery, unscrewing four screws, and using a screw driver to pry open a few plastic clips, the two halves and the front separate. The DC power cable and the wires to the newly added front button were routed inside the unit though the same slot the battery cables run. The new cables will connect to the LED control board.

In order for the controller to detect if the unit is running on battery or the AC mains. There are three jumpers on the main board that connect to the front panel status LEDs. JP14 is Fault, JP15 is on AC Mains, and JP16 is on battery. I've soldered a wire to the JP16 jumper so the controller will be able to tell if the unit has switched over to battery power. When the controller detects that the unit is running off the battery, it will switch to an energy conserving mode to extend runtime during a power outage.

This is the control board that is the heart of the system. It is powered by the ExtraCore Arduino board that I've bought during a Kickstarter campaign. There is a DS1307 real time clock for accurate time keeping for the automatic functions of the unit. Four PWM output from the Arduino drive the ULN2003 Darlington transistor array to control the four seprate LED channels. A small heat-sink is attached to the ULN2003 with a piece of wire to help keep it cool during normal operation. The top screw terminals connect to the front button, the UPS status, and the LED output.

The board is installed on the inside of the battery door behind the battery. The wires to the LED strips leave the unit though a small hole cut in the top of the battery door. The backup battery for the RTC is attached to the battery door with double sided tape. In this photo, a ribbon cable is attached to a terminal strip for serial debugging and programming.

The unit is plugged in and installed above the microwave. The cables for the LED strips run up though a small hole above the junction box. The small black button is used to manually switch between the different light modes.

The controller installed and fully working. The lights fade up automatically at 7:00pm and dim at midnight. While on, the RGB LEDs fade slowly between blues, greens, and purples. It adds some much needed ambiance in my home.

During a power outage at night, the unit will automatically turn on at %25 to keep the kitchen illuminated. With the on-board clock, the unit is smart enough to keep the lights off during the day to help conserve power and extend runtime. I get about ~20 hours in this mode with a fully charged battery. The front button still allows me to switch between Power Outage Mode and night light mode, with some conservation I can make the battery last a few days completely independent of another power source. The Belkin UPS automatically turns it's self off when the battery drops to 11.5 volts.

In the future I would like to add an external photo-sensor so the system can automatically adjust for the time it turns it's self on for cloudy days and adjusting for the sunset throughout the year. I would also like to have each cabinet section be individually addressable to allow for chase sequences and more interesting ambiance lighting.

KitchenLED.zip The Arduino sketch for my LCD control board.