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Knight Rider with Halogen Bulb

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I have wrong.
It's Tip42, not Tip32. ::)

And it's for car.
With relay hear you all the time when it on. :o
It would not like it.

And this schematic from http://ratliff7.tripod.com/counsel.htm would not work best.

I have hear from other forum.
They say it does not work best, It would very heat.

So, how dit they do that?
Like as Knight-f2k4 scanner.

And could this work at first schematic?

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Look at the spec's of the transistors to see why it doesn't work.
The halogen bulb draws more than 4A when hot, much more when cold.
The TIP42 and most other power transistors need at least 400mA of base current to saturate with a 4A load and has a min current gain of only 12 at 4A.
The 1k base resistor allows only about 11mA of base current. A 27 ohm base resistor would give the output transistor enough base current but its 400mA is much too high for the BC547. A 2N4401 transistor can replace the BC547 and the 10k resistor must be replaced by a 390 ohm resistor for enough base current.

Your last posted schematic has the TIP31C upside-down.

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I have to agree with Windoze,
I don't like to add power transistors to car circuits. Especially where there will be multiple sets of this circuit.
The Emergency Response agencies have already figured this all out. They use lots of blinking bright lights. They use relays to make these blink. If you do not want to use a relay that will click and has a short life, use a Solid State Relay for this. There will be longer life and less waste. They will cost you more than a TIP32, but reliability will be built in. I have made several devices over the years that use solid state relays. Some are still used in an Industrial environment for better than 20 years.


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I wonder if this same effect could be made with a 4017 with some electrolitics capacitors at the output to make that flash trail behind or some delay when the light change from one channel to another.

But a "flash trail" means that the output transistor will be operating as a linear amplifier and getting very hot. You could do it with PWM and it would remain cool.
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  • 1 month later...

There are many applications where a resistor between base and emitter is not needed on a transistor.
"Always" is certainly an exaggeration.
Also note, protection from radio waves requires filtering. A resistor does not protect against radio interference.


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Schematic works  ;D 8)


Nice, i will make the same effect but for a break light for my car with very bright led's, but i will change some things to look like a normal break light (all led's on) and than after some time knight rider effect, you see here at Brazil we can't use any light effects outside the car, like flashes etc. Only Police, fire fighters, ambulance can use such a things.
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