I'm a fan of LEDs, lots of LEDs. So here's a slightly less crass way of using LEDs for decorative purposes.
While this is by no means a neat and polished solution, and probably not the first of its kind, however the pulse effect is as far as I have seen unique, and exactly what I wanted. I hope that this will inspire others to create similar.
The set-up It consists of a plain, unmodified vase, and a small battery-powered unit that sits behind a vase and shines three LEDs to give some nice ambient color.
The circuit is powered by a microcontroller, in my case, a PIC12F683, I've included source code for the PIC12F683, but presumably it can easily be ported to Atmel or other microcontrollers.
I am writing this instructable for those with experience with circuits and microcontrollers, I am happy to answer any questions anybody has.
The circuit can be split into 5 parts:
1. The brains - this will control the LEDs and produce the colours and pulses of light
2. The power - I use lithium-ion cells, but the circuit works perfectly well using 3AA or AAA batteries typically this will run the circuit from a week up to a month depending on battery.
3. Light detection - this is so that the circuit turns on only when dark
4. Voltage reference - this is needed for low-battery detection, for lithium-ion cells, this is important since over-discharging damages the cells. For AA or AAA batteries, this is less important.
The circuit diagram is below, there's also a PDF with the same diagram since the picture is a little small and blurry.
You will need:
- PIC12F683 or other microcontroller
- either 1x 18650 or 3x AA
- 220uF electrolytic capacitor (or any value larger than 1uF)
- 10k resistor + zener diode (or 1N4001, see later)
- 3x 150R resistor, 3x NPN transistors
- 3x high-intensity LEDs, 3x 20R resistor (see later)
- 40k resistor, phototransistor