So I have decided to do this project for my Senior design class. (found the idea at playground, sounds cool so i picked it)
I was going to use Distance Sensor to place it behind the car and when the car behind gets too close the LED will light up words like Tailgate and back off etc.
But then my professor asked a question about what if I am parking my car? The sensor will always sense the car behind and the LED will keep on. He asked me how to not make the LED light up while parking and cannot use a switch to shut down the LED. What are the ways to fix it?
If you wanted to get fancy you could interface with the obd2 port with a chip like the elm327 or similar. Assuming the car is an automatic, the ecu will tell you what gear you are in. You could also take the speed route with this interface as well.
Another, more universal, way to take the speed route would be a gps module to acquire vehicle speed.
Or you could take the simple route like posted above and send the back up lights through a voltage divider and use them as an input.
The speed sensor route is the best. You really do not want the display to "warn" people who pull up to your rear at a stop light... Another thing that would be good is a variable warn distance based on speed, higher speed farther distance...
Agree completely with #5. That would be a real safety enhancement.
You can get the speed from obd or gps. There might also be other options that are a little more adventurous:
There might be a pulse output from the transmission you can tap into. Or the abs sensors leave pulses. But be very careful not to affect these signals since that could compromise the cars function and/or safety. Since these signals most often are generated by hall sensors there might be a possibility to fit your wn sensor reading the same magnetic pulses