Tardis Light

So the wife and I throw a party every fall around Halloween, and we theme it. This year's theme was Time Travel, and I had intended to go as the time traveler from H.G.Well's book 'The Time Machine'. Well best laid plans of mice and men and all that, I was convinced to appear as Dr Who. Intrigued by the brilliantly geeky suggestion by someone who didn't even show up, I accepted the challenge. I don't have a Police Box. Neither do I have the time (given the amount of housework, homework, and... well, work I have at the moment) to build one. But the Doctor without a TARDIS is like being a vampire without teeth. Just ties the whole thing together. My origonial intent was to program a 'breather' on an ATTINY13, add power and enjoy the pulsing light of a TARDIS light atop my shed. I had a problem getting the program to do what I wanted it to, and then... for some reason (after I had several glasses of wine) I couldn't program the chip. (PROTIP: AVRDUDE cannot program a 555 timer). From nowhere I got a brilliant idea! I had found a spare 555 timer I had mislaid some time ago, I could use it! Next day at radioshack, I picked up one of these bad boys and figured I could use one of these too. I put the 555 in AStable mode the circuit looks something like this.




R1 is 1k, R2 (as you can see form the pics) is actually 2 10k in series. C is 100μF. So everything can be found at Radioshack. (and was). So your asking where the LED is... pin 3 outputs the signal, a 330 ohm resistor feeds the LED and the 4700μF inline cap that are connected in parallel. Caps don't like sudden changes in voltage, so when pin3 goes high, the cap robs some of the sudden voltage, and the effect is a slow turn on of the LED. the process is reversed when Pin3 is suddenly turned low. The Cap feels bad about having all the voltage, and lets it loose. The effect is a slow turnoff. It also makes people nervous to see a giant capacitor. Addmittedly its completly unneccessairy to have a 35V cap for a 5v chip... but that's whats at the shack. Actually there is only 4.5V, I used 3AAA batteries, it ran all evening with no probs. I was quite happy. Here's the effect while it was still on the Breadboard. By this point I had several stiff drinks, so instead of using the protoboard to solder on I deadbugged it... it's a miracle it works but it does.