so i decided to throw together a really simple 555-timer based LED flasher with a decent range of frequencies for an immersive art party we're having. It's around $7 in parts (going radio shack -- it's actually like $1 if you've got stuff lying around), so i figured i'd share it. This doesn't do audio, and it's a totally analog interface, but if anyone wants to play around with the basic light stuff, this may be a fun toy to throw together...

Parts:

- 555 timer
- 4.7uF capacitor
- 10nF capacitor
- 10k resistor
- 470 ohm resistor
- 50K potentiometer
- 2 x 47 ohm resistors
- sunglasses
- 2 bright red LED's
- wire
- 4 AA batteries, in holder
- small proto board (~$1.69 at rshack for pack of 2) makes it a bit easier.

i used a polyfilm capacitor for the 10nF and tantalum for the 4.7uF, but that's just cuz that's what i had lying around. with a circuit like this, tolerances are really pretty unimportant, feel free to adjust and use whatever you might have that's pretty close, within reason.

since ascii art won't format right, i'll just note connections between the 555 and other bits...


555 -
pin 1 : "-" side of battery pack, "-" side of 4.7uF cap, "-" side of 10nF cap
pin 2 : "+" side of 4.7uF cap, pin 6 of 555, center tap of potentiometer
pin 3 : side "a" of both 47 ohm resistors
pin 4 : pin 8, side "a" of 10k resistor
pin 5 : "+" side of 10nF cap
pin 6 : (pin 2, as noted above)
pin 7 : side "b" of 10k resistor, side "a" of 470 ohm resistor
pin 8 : (pin 4, as noted above), "+" terminal of battery pack

additional connections:

side "b" of 470 ohm resistor connects to one end of potentiometer (other end unconnected; wiper was connected to 555 as noted above)

LED's are connected, via 4' wire or so, between side "b" of 47 ohm resistors (one LED per resistor, cathode end) and "+" terminal of battery pack (anode end). drill holes in the sunglasses, trying to get them right at where your eyes naturally focus when looking straight ahead, for the LED's & hotglue them in.

this should flash the LED's for days, if not weeks, and gives a good range (from about 1-2 hz to 30+).

(note: there's a nice free 555 timer design program at www.schematica.com; download it if you need a graphical representation of where the parts go. this is set up as an astable, duty cycle > 50%; C1 is the 4.7 uF cap, C2 is the 10nF cap, R1 is the 10k resistor, R2 is the 470 resistor in series with the potentiometer, Vo goes to the 47 ohm resistors & on to the LED's)