6 LED Knight Rider
The famous visual effect from the TV-series Battlestar Galactica and Knight Rider

The ATtiny22 datasheet.
The AT90S1200 datasheet.

Part list: 6x high eff. LED 2x 330 ohm 1x ATtiny22* 2x 1N4007 1x 100n 1x 47uF/16V 1x 78L05

* The ATtiny22 is obsolete, replace with one of the folowing AVRs: AT90S2343 / ATtiny13 / ATtiny45. History of the back and forth flashers.... In the 80's the famous TV-series Battlestar Galactica and Knight Rider made the BAFF a well known visual effect. In the series Battlestar Galactica the so called Cylons had one for their eye, in the TV-series Knight Rider it was the car KITT who had one in it's grill. That time even electronics stores sold different kinds of BAFF kits. Even today people are still building these BAFF gadgets. On this webpage you will be able to build the smallest...

The smallest back and forth flasher ever.... (use SMD components)

How to make it work.... Take a small hobby-board or devellop your own PCB. First solder the 8 pin IC-socket on the print, then put the two 330 ohm resistors left and right, and make the connections with little wires, you can also take a breadboard and push the parts on it, and make it start functioning, it's up to you. This small BAFF can e.g. be fixed in the front of a toy-car, or you can make a disco-broche, etc.

Source code and more... Here you can download the sourcecode (ASM), which you can assemble to a hex dump with WAVRASM. You can upload this hex-dump to the ATtiny22s flash memory with this simple programmer. Upload the hex file with SP12, and use this DOS line: (SP12 Win2000/XP) sp12 -wpfC baff.hex When using WAVRASM do not forget to drop this definition file in the same map as where the assembling takes place: 2343def.inc.

8 LED Knight Rider
The famous visual effect from the TV-series Battlestar Galactica and Knight Rider

Part list: 8x low-current LEDs 1x 1k ohm 1x 10k ohm 1x AT90S1200 2x 1N4007 1x 100n 1x 47uF/16V 1x 78L05

8 LED knight rider with very little components

Another version: In this version I took PORTB of the AT90S1200 AVR microcontroller as you can see in the diagram, because this makes it simpler to let 8 LEDs flash back and forth. Set the Data Direction Register of port B as an output, the output will source current. What I did is loading an EEPROM-table in the AVR and reading each address into PORTB. There are ofcourse many ways to program this little gadget. If you use a 3 Volt battery and SMD components you can make e.g. an earring, e.g. set the LEDs in a circle, etc., just use your fantasy and something nice will come out of it. Here the complete assembly listing and also the hex-dump: baff8led.txt baff8led.asm

16 LED Knight Rider
This version is using logic ICs

Part list: 8x LED (red) 1x 180 ohm 1x 10k ohm 1x 33k ohm 1x 2u2/16V 1x 74HCT191 1x 74HCT132 2x 74HCT138 1x 78L05 1x 47uF/16V 1x 100n 2x 1N4007

16 LED knight rider with logic ICs

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Yet another version: Here an example with 4 TTL ICs. This is I think the cheapest solution with standard logic ICs. The 74HCT191 is a Presettable Synchronous 4-Bit Binary Up/Down Counter. Pin 14 is the clock input (from the osc.) Pin 5 is the Up/Down input, this lets the counter counts up or down (via the flip-flop) when reaching the last LED. Enable the counter by connecting pin 4 to GND. The counter generates 4 bits data at the 4 outputs (Q0 to Q3) The data goes to the two 3-to-8 line decoder/demultiplexers, the trick is this, you have 3 address inputs (btw 2^3 = 8) and two Enabling inputs (pin 4 and 6), with these you can enable each 74HCT138 individually. At the first clock of the oscillator (N3), the counter starts at 0001 (first LED on), so pin 4 and 6 are both 0, so only one 74HCT138 is enabled at a time. When reaching the 9th clockpulse, the two 74HCT138s flip, because the counter is at 1001.