Here are some pictures and video of my custom LED backlight controller. The controller gives you easy IR control of LED fixtures like the Cyron Media Highlighter and IKEA Dioder. It replaces the OEM controller with a new controller that provides an IR interface and discrete control over the colors, effects, and power of the color bars.

It provides the following features

• IR Control (Harmony, Pronto, etc)
• Discrete power on and off
• Direct control of colors; Choose a channel or combination of channels and set the intensity from 0-255 (8 bits of resolution)
• Adjustable speed for effects such as morphing and changing
• 500Hz refresh rate to avoid TV flicker
• 9 Presets, saves the pattern, sequence, color, and speed
• Small, slightly larger than a deck of cards
• Standard header spacing for screw terminals or stake pins

On this prototype I've used an extremely sensitive IR receiver so that it can detect the transmitted IR even behind my flat panel. For the purposes of these photos, I've placed the system against a white backdrop since my walls are not white. It is important to recognize that this is really for effect and "wow" factor rather than as a replacement for the ideal CRI backlight. The primary focus of this design is to enable IR control and as a result home theater integration rather color matching or rendition.

The LEDs are pulse width modulated to keep the power waste low and color accurate. The LEDs wavelength will shift if the current changes such as when a linear power supply is used to control LED brightness. PWM just keeps the current constant and pulses it quickly relying on the persistence of our vision to "average" the light level. The green operates at 500Hz and the red/blue at 250Hz. It has to be above 60Hz to avoid flicker with the flat panel. The next incarnation will run much faster. In fact, you can see the PWM if you watch the video carefully, but you will never see it during observation in operation.

The video is basic, but shows it working in its various modes. Although it looks like the colors are different brightness, that is mostly due to the sensitivity of the eye to certain colors and that my video camera has a Bayer color filter array rather than 3 independent sensors, so it is more sensitive to green. It does look much better on the wall though as can be seen in some of the still photos.

The electronics are designed to take from a 12-24VDC input depending on whatever your LEDs require. The internal electronics are very low power, so an inexpensive LDO linear is used to regulate the 24VDC to 5 to operate the control logic. The power is controlled by some logic compatible MOSFETs. The PWM and control state machine is all implemented in software contained within a (small) AVRs flash memory. The presets are stored to the persistent EEPROM. There is a custom PCB in the box, but it is from another project that was modified to support this application. I plan to spin a completely new board with the same power electronics but a larger size AVR and faster PWM.

The system is using the internal PWM units of the AVR. However, I've overloaded the PWMs and I also use the timers for other functions, hence the different frequencies of the PWM refresh. The code is based largely on the same code that operates the ps3toothfairy.