LED 5 blinks and then a continuous light.

SimonFrisendal said:

Hello. I have been assigned a task of designing a brake light with the following specifications:
1. The circuit shall start when given voltage (Obviously!)
2. It must be operational within 10-16V.
3. It must blink 5 times, and thereafter light continously.
4. The Blinking frequenzy must be approximately 5 Hz or similar frequencies appealing to the eye.
5. As the system is designed to replace current brake lights the only signal coming from outside the circuit is the 12V from the car.

I tried sending a 5 Hz test signal into a CD4017B decade counter. I thought i could then take every second output into an or gate made up of diodes a transistor and resistors. I thought this would give the five blinks and that connecting the last output leg to the clock inhibitor would then make a continous signal after the five blinks. The circuit would be resettable by coupling the voltage off. The final circuit would then be made up of an NE555 delievering the 5 Hz.

But the problem is that i have hooked up the decade counter as i mentioned on a test bench, but i am only getting a high low shift on the legs of the decade counter and not on the rest of the diodes that only show a low signal. I thought this would work. What am i doing wrong and could i possibly add some pulse width modulation to make the circuit more efficient?

I'm sorry for this long post but i don't have anywhere else to go to. So thanks in advance.

Simon.

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