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direction indicators

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haris_216

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if you drive an older car and have the "bad" habit of using direction indicators for lane changing, eventually you come to the conclusion how nice it would be if you "hit" the direction stalk once and let the indicators flash for 3-4 times so you concentrate on the steering wheel. from what I hear this is a common feature in new cars.
I guess the circuit itself would be fairly simple but there is a catch. it must work the "auto" 3-4 times blink if you simply hit it once but it has to revert to the normal switch/blinker function if the stalk switch is pressed more or locked in position (like when you are about to turn in another street and be released after steering wheel straightens)
I did a fair search in the internet but didn't come up with anything apart from a unit sold by waeco. of course this is a solution but if we were satisfied with ready made solutions we wouldn't be around here, right?
 
This sounds like the perfect application for a PIC microcontroller. Set up an interrupt on Port change, flash the indicators 3 times, then check to see if the port pin has still changed (is the direction stalk still hit). Continue flashing if it is, stop flashing if it isn't.

Failing that, set up a dual 555 timer with the first one (as a monostable) triggering the second one (as an astable). Pulse the first one low, the output goes high which drives the second causing it to oscillate. If the pulse to the first is kept low, the output of the first will remain high keeping the second one flashing. If the pulse disappears, it acts as a normal monostable and its output goes low after a predetermined time, switching off the second.

If you understand that, you will understand anything
 
This sounds like the perfect application for a PIC microcontroller. Set up an interrupt on Port change, flash the indicators 3 times, then check to see if the port pin has still changed (is the direction stalk still hit). Continue flashing if it is, stop flashing if it isn't.

Failing that, set up a dual 555 timer with the first one (as a monostable) triggering the second one (as an astable). Pulse the first one low, the output goes high which drives the second causing it to oscillate. If the pulse to the first is kept low, the output of the first will remain high keeping the second one flashing. If the pulse disappears, it acts as a normal monostable and its output goes low after a predetermined time, switching off the second.

If you understand that, you will understand anything
I did understand it;) will give a try to einstain's theory but not today:)
thanks for your quick reply. your idea seems ok but I think there might be some small problem.
press momentarily the switch and it will flash for the predetermined period. so far so good. but if you press it more (or even "lock" for some 90 degrees turn) doesn't it mean that the blinking will continue even after you release the switch (or finished the turn)?
 
I vote for the dual 555 solution. That would be much simpler and work just fine.
 
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