Mar 13

Low cost under cabinet lighting with the launchpad

This is my low cost under cabinet lighting system based around the Texas Instrument Launchpad and my PowerFet Booster Pack.

Booster pack PWM blog:


The video pretty much explains the highlights, but I'll go over it in text quickly in case you don't have access to youtube.

The power fet booster pack is a booster pack I designed as a plugin motor (load) controller for the launchpad. It will be up for sale as a kit (you would have to assemble) on the products page. This is more of a proof of concept for a low cost under cabinet lighting system though. I needed one, so I figured I would design an expansion board for a solution. The system shown exemplifies the ability to design a low cost and low power lighting controller. I did this because the home LED lighting and accent lighting markets are growing and most solutions for consumers are still fairly expensive, like LEDs are a brand new technology or something.

I'd like to get this write-up and video out to developers in the industry that are looking for a new, innovative, low cost, low power solutions for accent lighting similar to this because I can design custom hardware and software that I think would be much more palatable to their customers.

The budget I realized breaks down as follows:
LED strips - $15.00 x2
Power Supply - $25.00
Launch Pad - $5.00
Power Fet Booster Pack - $12.00

One problem I did have with this system when using the weak pull-up in the MSP430 was that other loads on my house's power system would create noise/ground shifts that produced noise on the pin that sensed the button push. This was because the internal weak pull-up in the MSP430 is not strong enough to keep the pin pulled up when noise occurs. To fix this, I just added and external pull-up (resistor) to Vcc on that pin. This solved the problem and the system works great now!

The firmware I'm using is very simple so we will just touch on that really quick. It's an interrupt driven system that interrupts on the falling edge of the digital IO pin connected to the push-button switch. This throws the processor into it's interrupt service routine and in there I flip the bits on the pins in POUT driving the gate of the power FET.