This Page will show how the High Side switching Module was Build.
Why not use Relays?.. you might ask. Well typically this is what you would do but unfortunately relays have a low switching frequency and can not be PWMed which means the output will be constant voltage and you could not dim an LED for example.
So we are going to go with Transistors...or are we? The typical implementation with an arduino to switch higher voltages, in this case 12V, looks something like this:
Here is the problem with this layout for my project: My Vehicle, like most, are driven by high side switches typically running around 12V with grounding points all over the place. I wont go into detail about high and low side switching but here is some very good info that should bring you up to speed:
What is high side switching?
My HSS (high side switch module) only needed three outputs. Namely my LED Brake Lights and 2x Led Signals in the Mirror.