As an RC plane guy, or rather RC jet guy, I need to use a trailer to pull my jets to and fro. I built my own trailer using a base from Harbor Freight by building a box on top of it with barn doors on both side. That is a topic all its own but I digress.
One of the main issues I have is the wiring harness that connects from my Jeep to my Trailer. It is constantly getting corroded,so my trailer lights don't work. The other issue is sometimes I forget to plug it in or it comes unplugged while I am driving. perhaps a better plug is in order, but this is 2015. This is the wireless/Bluetooth era!
The current control box I have purchased hooks into my light wiring on my jeep, literally spliced in. It reads the current coming in and outputs the voltage to the trailer lights.
The main issue is that there are only two trailer lights, and these functions as running lights, brake lights, and turn signals! So the box is connected to my brake lights and turn signals and converts those inputs into the appropriate signals to emulate those functions on 2 lights.
What an "easy" task for an Arduino Pro Mini, or rather 2 of them. One on the jeep as the transmitter (Tx) and the other on the trailer as the receiver (Rx).
The issue of powering the lights on the trailer is easy, some mosfets and an external battery. Tricky part will be to emulate the brake lights. What happens is the lights are dimmer when in running mode, and when I hit the brakes they are simply brighter. Sounds like a job for PWM!
The issue of reading the lights a bit more complicated.
The Arduino pins have a 100M Ohm resistor in series with them and they can handle a max of 5.5V, but to play it safe I will assume 5V. This means the pin can sink .05uA, not a lot of current.
A car voltage can vary from around 12V to 15V. I see numbers in the 14V range when running and 12.6 when not running. While there are ways to use a resistor to drop the voltage, I think a 7805 is probably a good choice to regulate the voltage. It will still function in the car battery is below 12V and can handle up to 25V. So each input from the light, which is reading the voltage going to the light when it is on, will go through a 7805.
This will allow the Arduino pro mini to read the lights and process the signals to send out.
I'm open to other ideas but a 7805 seems like a good idea. I would need about 6 of these. more to come in the next post!
This is an early picture of my trailer, before I straightened out the side beams. The trailer has advanced quite a bit this stage an in my next post I will show better pictures.
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