Hello everybody, recently I have started a project where I’m attempting to outfit my current 2007 fj cruiser with a blind spot camera system. My plan is to install cameras in both the left and right mirrors, and when the subsequent turn signal is activated, the camera would turn on and display the blind spot to the head unit. I’ve already figured out most of the logistics in terms integrating this with the car and my head unit, my only issue is creating a system using arduino that detects the intermittent 12v signal provided to the turn signal bulb, and activates a relay that provides a decently stable 12v to camera from the car battery. From what I’ve researched so far I am aware that I would need to convert the 12v input signal into a 5v signal that would then be fed to the arduino, however in terms of the overall layout of the system and especially the code for the system I am lost. Any suggestions would be greatly appreciated, and If you are aware of any similar projects like this that already exist and it has code readily available that can be adapted to my situation, it would be greatly appreciated if that was shared as well. Thank you!
Your vehicle has a flasher relay. When you turn on the indicator lever, continuous 12V is send to the flasher relay. They are usually located in one of the fuse blocks. You could tap off that with a resistor to provide a signal to the camera.
Be aware that this voltage can go up to 14V so I'd use it with an optoisolator that can handle the 14V and on the other side of the isolator I'd loop VRef through a resistor into a digital pin.
I do not recommend making changes to your car's electrical system though. Do so at your own risk.
Seriously consider what you are trying to do. Automotive systems are not simple 12V battery systems. Your vehicle probably has a 60V to 80V load dump with 400V+- transients. Turn signals are part of a special class as defined by FMVSS.
I am not recommending this just something to consider. Use a fiber optic cable to sense the turn signal lamp, then trigger your system with a timer that will trigger each time it sees a pulse. The delay needs to be longer than the off time of the flasher. Look at something like a 74HC123 retriggerable one shot, that with a sensor would do what you want. When it triggers it will reset the timer and turn its output on, each pulse will reset the timer and the output will not go off until it is no longer getting pulses.
Yes, you would use a voltage divider made up of two resistors with the Arduino pin connected to the junction of the two resistors. One end of the resistor goes to ground and the other resistor goes to the turn signal line. Try it with your volt meter before connecting to any Arduino.
Thank you for your response! I have been looking into maybe isolating the continuous 12 volts sent from the turn signal stock, however finding the right wiring diagram has been nearly impossible. I’m probably going to just unplug the relay and test every pin in the connector with a multimeter, until I find it. Thank you once again for time.
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