I am looking for a sensor that activates after the clicking noise of an automobile turn signal

Hello Forum,
I am looking for a sensor that activates after the clicking noise of an automobile turn signal solenoid stops. Similar to the "clap on clap off" device, but activates only after I choose to stop clapping.  Or like a heart monitoring circuit that activates an alarm when a heartbeat stops. I would like this circuit to activate for only three seconds then reset. I would like that sensor to be able to clip onto an adhesive pad just like the one doctors use for heart monitoring.

Thank you! Thank you! Thank you!

sort by: active | newest | oldest
TommyT13 years ago

your over complicating everything pull 12v down to 5v use an arduino. time the delay between claps and tell the arduino to Case1; when the digital pin is low for more then the delay between claps.

run a second digital input to a simple push button mounted anywhere Case2; when push button pin is high wait for clap sensor pin to be high

end loop

Thank you for your input. My research continues this week on finding someone who understands how to put your idea and the previous idea together. I will post the results when its done.
You guys are great!!!!
seandogue3 years ago

Erm...I think you're all over-complicating. This is far easier than it looks. Use an edge trigger device like a one-shot (74121, 74221, etc.), and set the timeout for 3 seconds.

Trigger it using the Falling edge instead of the rising edge, and using the"active" line (the line that feeds the turn signal light) on the flasher.

Since the voltage at that point is most likely 12V or thereabouts, use a 5V zener and a resistor, an op-amp, or other similar voltage division-clamp-compression-isolation-conditioning circuit (ie, there are several options for how to do it) to ensure you don't exceed the input V max on the one-shot. Me, I'd be inclined to use a 4 or 6-pin opto-isolator.

.. So, now you've designed, built, and installed the circuit. How does it work?

One-shot out is 0V

The turn signal light turns on...(don't care how long), then turns off

The one-shot has now been triggered

one-shot out => 5V

3 seconds.....

One shot turns off.

Now, to do this once and only once, it gets a bit more complication, but really not much. you simply generate a secondary circuit that locks out the one-shot once it's fired the first time. Or said another way, you simply apply a latching circuit. that severs the connection by pinning the input high and/or isolating the output. That way, the device will trigger only once until the circuit is reset by powering off and then on again,

to be complete...

The short answer is this:

What you're looking for does not exist. There is no "sensor that activates after the clicking noise of an automobile turn signal solenoid stops", although a technically literate person can easily design and build a circuit that will detect the action, as I noted in my first answer.

Thank you Seandoug,
I knew what I was looking for did not exist. But I knew it could be created and you proved that. In my patent application, and why it was approved is because I indicated that this product can be automatically or manually operated. I also think it would be a great selling point for the consumer and getting an endorsement from the High Patrol.

Getting it put together on a bread board then miniaturize is my next bridge to cross. Do have any suggestions on how to proceed? Is this something you are qualified to accomplish? If so I am willing to work with you.

Yes, I *am qualified, but I do not have time or interest. I'd suggest contacting a local university and asking to speak with the engineering department. They may be able to guide you to a qualified (senior level engineering or better) student with which you can work. They will be grateful for the employment and experience, and you will get dedicated local involvement at a cost that would likely be far more acceptable to you than what I'd charge.

Good luck with your project. I hope the outline gives you enough to proceed.

You have been a "God Send" I cannot thank you enough for all of your knowledge and your "Thinking outside the box" attitude. I will take your advice and proceed in that direction and check the forum at the couple of university in my local area. You are also correct about cost issues it will be more manageable.

I have enough to go on thank you again.

seandogue3 years ago

On the other hand, if you mean an audio trigger, then I'd have to ask what you're doing with this circuit, because the first thing that comes to mind is very very criminal and dasterdly.

iceng seandogue3 years ago


That's creepy !

It might be more reliable to sense the current in the clicker, or watch the flashing light ?

petercd3 years ago

a condenser mic would be able to sense the clicks if its right up against the relay, the finer detail of delays and activation would be up to you with the rest of the circuit design.

iceng3 years ago

You are going to have to use a micro processor to learn the turn signal frequency and time between your noise clicks to determine a missing pulse and therefore the end of the signal train and start your three second output.

Yes, I could do this with four LM555 ICs but it wold be very specific to one car's tick-tock ....

piezoSens.pngPiezoDiscs.JPGFlexForce Sensor.pngWaveSensor.jpg