Authentic Looking Knight Rider Led Project
*Update! V2 of this project finished (see end of page).
Well of course I had to make one of these at some point! There's something hypnotising about lights chasing up and down in a sequence isn't there!
I have looked through many websites from people who have built these and also magazines which have detailed there designs. But one thing has always been left out! When you watch the Knight Rider episodes (yes there re-running them here in the uk!), you see the red lights chasing up and down on the front of KIT, but in between each sequence there is a pause of about 1 second before it starts again! Almost all the other circuits I've come across just continually pulse a decade counter, so the leds go up and down continually.
Now, the challenge I set myself was to do this with out using a PIC microcontroller or any other fancy devices, so that it can be made easily by anyone.
The circuit is fairly easy and un-complicated. It uses 2 555 timers and 1 4017 Decade counter. One 555 control the flash rate for the led sequence (decade counting frequency) and the other is to turn the decade counter on and off. Once the led have gone up and down the row once (2 seconds) we switch the power to the 4017 off for 2 seconds and then back on again for another 2 seconds creating a break between each light chase. Fairly simple hey!
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I have not used diode on the outputs of the 4017 as I figured that the IC already has suitable protection on it's outputs. You could add them if you wish, just place them between the ouput and resistor to the LED. I have run mine like this continually and I can say it's fine without.
The circuit runs quite happily from 9V but could take 12V as it is, so you could mount it to say, a car! The true knight rider image! Although, I shouldn't the police will like you though.
The LED's I used were 10mm High brightness Red Leds of some 8000mcd. They were a great find on ebay at £4.50 for 10!
Trent Johnson has suggested a few modifications to my original circuit. It has been suggested that a 4071B OR Gate IC is added between the outputs of the Decade counter and LEDs, to stop the decade outputs from cross talking. Another modification is to move the 10nF capacitor that was connected to pin 15 (reset) and +V, to inbetween pin 16 and 15. This is changed to force a reset of the decade counter when the decade interupt becomes high.
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Here's some pics of my version:
In some of the above pictures you can see 2 green wire leading off from the board. I put these on to just tweek my chaser speed to match the original knight rider lights! Over doing it now aren't I... oh well. enjoy.
V2, even more Authentic:
Due to recent requests, I have designed a new version of the above circuit, that is still composed of logic circuits as it was more of a challenge to design (This could easily been done with Microcontrollers (PIC, Atmel), but not everyone has programmers). There are quite a few more components in this version, but as you will see, it is far more versitile and robust.
Why create a better version?
Well apart from the already stated facts, I have been informed that Knight Rider KITT car actually had 8 light phases, rather than the previous 6 of my early project. This was complex to implement in Logic as the Johnson counter (4017 decade) only counts to 10, and we need 6 to pulse up and 4 back down the light chain. So the obvious answer was to use a second 4017 counter to bring the light chain back down, leaving the first 4017 to pulse the light chain up.
To keep the running light wait time "authentic", I have used a JK flip flop in a T flip flop setup to toggle on-off and off-on every time the counting reaches one cycle. So it's on for one up-down cycle, off for the second up-down cycle and back on for the third up-down cycle and so on. The JK toggles the power and so the output from the OR gates to the LEDs.
The circuit can be scaled to suit anysize light chain fairly easily. The basic idea for expanding the Decade counter is shown here: (click to large)
(click to enlarge)
So enough of me typing, here is the circuit configured for an 8 LED chain setup.
(click to enlarge)
Main Parts required:
- 2x 4017 Decade counters
- 1x 555 timer
- 2x 4071 Quad OR gates
- 1x 4027 JK Flip Flops
- 1x 4081 AND gates
- Resistors, Capacitors, NPN transistor and LEDs.
- The NPN transistor can be anything, eg. BC108, BC547,C2120
- The LED running speed can be adjusted by changing the value of the 3k3, 4k7 or 10uF cap connected to the 555, you could exchange the 3k3 for a variable resistor.
- Capacitors have been added in parrallel to the LEDs to provide a short fade effect to smooth the transition between pulses.
- Power supply can be upto maximum 15v, minimum 7v.
- Outputs from the OR gates could be taken on to MOSFET gates to drive heavier current Lamps.
Please do not reproduce anything contained within my website, as it maybe hazardous to your health unless you fully understand what you are doing.
I cannot be held responsible. This website is copyright.
© Oliver Hunt 2006-2011