Car Turn Signal Data Capture

Hi everyone,

As the title suggests, I would like to capture the position of a car turn signal at the neutral, up and down positions. The turn signal exterior would be left unaltered inside the interior of the car (the car is to be used in a motion simulator, hence the need to preserve the interiors). In addition to this, devices such as infrared proximity sensors that measure the distance of the turn signal in order to determine if it is up, down or neutral are not ideal.

What are some good methods to use an Arduino to receive turn signal position data, while maintaining stock exteriors? As I understand, the turn signal uses a switch to close/open required circuits in order to activate lights. What sensor could be used within this circuit in order to determine turn signal position?

Thank you

Hello GravityZ,

I am a certified electrician, and even I am very careful when working on the electrical systems of a car. The common ground (chassis) and the more frequently used electronics in cars are very easily confused and broken when there are suddenly more current drawn in circuits, or influenced by voltage drops.
If I had to build such a system I would remove the covers of the front or back where the signal turning light is housed, and put an LDR in there, working the cables back in to the trunk or motor bay and from there on use a voltage divider to get the signals to a digital input of the arduino.
Should you decide you don't like my proposed option, and would prefer to make a physical connection with the wires of the turn signals I would recommend using an optocoupler, because of its very low power usage, and if something goes wrong your system doesn't get damaged, in worst case you need to aquire new optocouplers, and those are very cheap. If you have further questions then don't hesitate to ask them.

With regards.


Can you get a wiring diagram for the car? (I've got a service manual for one of my vehicles and it's got a full set of wiring diagrams.)

It's probably just a [u]SPDT[/u] center-off switch. Typically, the common switch connection is grounded, so when either the left or right connection is grounded the appropriate blinker is activated.

If you leave the car wiring intact, you'll have 12V on the left & right contacts when it's not pulled-down (grounded) so you will have to be careful with the 5V Arduino. (Use an opto-coupler or a voltage divider, etc.)

Beware, if you should start the car's engine, not sure if you will or not, your voltage will increase to 14 Volt, because that's the output of your dynamo. An Arduino prefers a voltage between 7-12 Volt. The Limits are 6-20 Volt. Take this into account.

If the turn signal arm is metallic you might use an inductive proximity sensor.

That's a very good idea dougp, they could even glue a piece of metal on the back of the handle. Or glue a magnet on the handle and use a simple reed switch. These solutions don't have any galvanic connection between the car and the arduino.