Hi,

I want to build an interactive christmas tree where I can precisely control which light is on or off. In order to keep the number of wires limited, I thought of a solution where each led has its own I2C enabled PIC operating in slave mode, with an additional master PIC that is programmed to tell which slave to enable or disable. A 4-wire cable would then be sufficient. Nevertheless it sounds a bit too complex...

The actual logic that I need is also a bit more simple. Instead of controlling each light individually, it would suffice to interactively increment the number of leds that are on. So first LED 1 is on, next step is 1 and 2, then 1, 2 and 3 and so on.

My knowledge of electronics is a bit limited, so I wonder if anybody over here has some illuminating ideas...

 

Controlling a single LED from a PIC would be a horrific mess and very wasteful of resources.

A better solution would be to control eight LEDs from one low pin count chip and networking all chips from a master controller.

Another solution would be to drive eight LEDs from a serial shift register and daisy chain as many shift registers you wish controlled by one MCU. This would be your simplest solution.

 

Thanks!

Yes of course I could add multiple LEDs to each PIC, it would actually safe me a lot of wire (and PICs!)

I'll look into these serial shift registers. They sound cheaper than PICs, for one

 

You might use a I2C or SPI multiplexer, which can be controlled by one line pair from a PIC.

 

Look into LED pixels; these have a driver chip with (or now inside) each RGB LED. Most use some sort of serial protocol, often a data/clock pair like a shift register.
You can get them at Adafruit or Sparkfun, or even cheaper if you get them directly from China.
http://www.adafruit.com/products/322 or https://www.sparkfun.com/products/11020

 

Hi,

I want to build an interactive christmas tree where I can precisely control which light is on or off. In order to keep the number of wires limited, I thought of a solution where each led has its own I2C enabled PIC operating in slave mode, with an additional master PIC that is programmed to tell which slave to enable or disable. A 4-wire cable would then be sufficient. Nevertheless it sounds a bit too complex...

The actual logic that I need is also a bit more simple. Instead of controlling each light individually, it would suffice to interactively increment the number of leds that are on. So first LED 1 is on, next step is 1 and 2, then 1, 2 and 3 and so on.

My knowledge of electronics is a bit limited, so I wonder if anybody over here has some illuminating ideas...

Last year or so I believe one company came out with individually addressable string of Christmas LED bulbs. I don't remember the interface details but it's all online.

Target already has their Christmas stuff up and I believe these LEDs are on display. Get the name and google it and you'll get the details.

I'd help start you but I'm three states from home as a powerless hurricane refugee.