Created
01/14/08

Once upon a time I was walking through the halls of the local Fred Meyer store and saw this "Funlamp" on sale for two dollars. This is a light bulb that cycles through a sequence of colors. I bought a couple to open up and play with. This is what I found...

A quick cut around the base with a sharp knife allowed me to remove the bulb and expose the electronics which are stuffed down into the Edison base. There are six LEDs arranged in pairs of red, green, and blue, held in place by a plastic bracket.

The IC is a Texas Instruments CD4060BE 14-stage binary ripple counter. The designers of the funlamp very cleverly hooked the counter input through a big resistor right to the AC power line - a nice source of 60 Hz clock. As the count increases, different combinations of the high bits occur so as to activate the LEDs in seven color combinations (the eighth combination is very brief because it triggers a reset of the count.) I think that this is a fascinating example of using a very simple circuit with great effectiveness.

Here I have photographed three color sets.

Unfortunately the visual intensities of the different colors vary wildly, which makes the funlamp a very distracting nuisance whenever it is turned on for more than a minute or so. I simply could not stand to be in the same room with the thing as its brightness changed each time the color cycled. The red state was pretty nice though, so I hardwired the circuit to always generate the activation signal for red and never the ones for green and blue, and sealed it back up with hot glue.

I then tried, unsuccessfully, to open the other funlamp with equal gracefulness. At first I suspected the bulb material was plastic. It turns out that it is actually a glass bulb coated with a plastic film. I know this because I embedded half a dozen tiny glass shards in the palm of my hand when the second bulb shattered at the first touch of my pocketknife...

This second unit was slated to become a nice blue floodlamp. I retained the Edison base and the power supply electronics, and stripped out the counter. I also demonstrated the importance of performing power calculations for all resistors when I accidentally ignited one. It was replaced with a less elegant parallel pair.

A handful of blue LEDs and a little scrap of perfboard became the heart of my new lamp. I connected this to the remains of the funlamp base and stuffed it all back into the crammed quarters of the Edison base, sealing it over with hot glue when it was all in place. The finished module became a ceiling light for my garage. In the last picture you can see the red bulb sharing garage illumination duty.