Components needed to build a trailer light tester using Makita 18V battery

Community Projects
1

Hello all,

I am looking to build a trailer light tester that can be powered by a Makita 18V battery.

The tester should cycle through the brake lights, running lights, and blinkers when it is turned on. I have done a little research and have come up with a list of parts, but I wanted to run it by the community to ensure that I have everything I need. Or if someone has another idea as I am a novice.

Here is the list of components that I have come up with:

Voltage regulator: LM7805

Battery adapter: Keystone 248

Microcontroller: Arduino Uno or ATtiny85

LEDs: Red LEDs for brake lights, amber LEDs for blinkers, and white LEDs for running lights

Resistors: 220 ohm resistors for the LEDs

Transistors: NPN and PNP transistors

Do you see any issues with this list of components? Are there any other parts that I should consider? Any advice or feedback would be greatly appreciated.

Thank you!

2

Hi Justafella,

I’m assuming you are using a typical 4-pin trailer connector? If so, there isn’t a separate channel for directionals and brake lights. You have left directional control and right directional control pins. Brakes are done by energizing both simultaneously. If you have the less common 5-pin trailer harness, then you get a separate channel for brakes.

-Bill

3

Hey Bill,

Yes you are correct, it is for a 4-Pin connector

Mike (Justafella)

4

You really only need 3 SPST switches, a trailer connector and some terminals. Should be able to find all that at a auto parts store. I wouldn’t use a fully charged 18volt battery though, that might burn out your bulbs.

5

I’m also not opposed to having an internal rechargeable battery.