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The conversion is not a problem. A zener diode with a resistor or a resistor divider on the power supply can easily solve that.
The voltage can rise, thats why I have noted it in the circuit before. But you have to check if the place from which you take the power supply has a regulator for "12VDC" or not. If it does not, it will be necessary to add a limit.
Please check the circuit I gave and see if it suits your needs. There is a switch on the power supply to account for turning off the timer when needed.
Hi, Thanks for the diagram. Can you explain the switch logic as I was hoping to use a momentary switch to initiate the counter. In addition a high from the brake light switch would keep the indicators running until it goes low and then timer count would start again.
There are a few options here. Since I don't exactly know your signals, please add your information so we can reach a solution.
0. I am not certain you want to repeat the indicator turning on/off, this is the only reason for the timer, otherwise the circuit can be simplified.
1. The idea is simple, when you receive a high from the brake(normally this is done for a parktronic device) this will activate the timer and the output of the timer will give a consecutive sequence of impulses at 5 sec period, 70% duty cycle(70% on, 30% off). When the brake is off (0V at the timer's power supply) you will turn off all indication at the output of the timer(buzzer or/and other).
-What will be the indication specs for the buzzer or other(voltage, current, frequency and duty cycle, activated by falling front or rising front)?
I am quite confused. The circuit I need supples the existing wiring loom (and the existing indicator electrics) with current.
I want to replace the existing on-off-on toggle switch with a momentary switch which activates a timed 5 second feed to the existing circuit - effectively a self cancelling power feed. In addition I need the circuit to provide a continuous feed if the brake light switch goes high and restart the timed feed when it goes low.
I do not need a buzzer as the car is driven with ear defenders and a helmet on. If I could use a sound then I could introduce a buzzer to the existing circuit and do away with the need for a self cancelling timer.
This covers the 5 sec self canceling part:
In that case the timer needs to be reworked. Its possible to give a 5 sec output(100% duty cycle) and then turn off, unless a second impulse is givien after the 5sec. If a second impulse is given before the 5 sec run out, then the output will not be affected(the 5 sec will run out and wait for an impulse then).
Does this suit your needs?
The second part - a continues feed if the brake also is on, will require some time to make.
You don't need a 556 timer IC for this idea. The technology already exists with a two-pin flasher and a time delay module from the ignition cylinder circuit ( mine is an Echlin AR-613 unit). I assume that applying the brake voltage would reset the timer and restart the time delay upon pedal release.