I designed and built a custom light controller for my truck. My goal and reason for not just buying a commercially available device was adding some specific functionality. I wanted a controller that had 3 inputs:
1) A SPST switch controls each output
2) Two 12V nominal inputs that enables the output (output 1 & 2 connected, 3 by itself)
The two 12V inputs can come from a vehicle system (high beams for example), or from a SPST switch. They are protected by diodes so they do not ‘back feed’ each other. In application I have one of the inputs from my high beam, and the other from an override switch in the cab. My outputs go to lights.
To build myself the one circuit card I needed, I had to buy 3 versions of the circuit card. I am looking to sell the remaining 2 of the cards to help fund other projects. I can populate the electrical components, or I can give you the part numbers for everything and let you source and install them. I have been running my card in my truck for a couple months and I am convinced that it is working well and how I wanted, no issues. You will need to provide an enclosure, and a way to mount the board (a strategically cut piece of wood or plastic will do, or 3D printer).
Bare circuit card: $20
Assembled circuit card: $65
· 3 output circuits
· Fuse protected distribution built in (one input +12V line)
· Max 30A per output, total not to exceed 80A.
· Low current draw on trigger inputs (to reduce load on vehicle system or triggering overcurrent faults)
· Standard automotive relays handle "high" current, easily replaced
J1 – Bulk +12V input, feeds fuses F1, F2, and F3 (80A max, sum of output currents)
J2-1 – Trigger A for output 1 and 2 (~1 mA)
J2-2 – Trigger B for output 1 and 2 (~1 mA)
J2-3 – Switch for output 1 (~0.2 A)
J2-4 – Switch for output 2 (~0.2 A)
J2-5 – Switch for output 3 (~0.2 A)
J2-6 – Trigger A for output 3 (~0.5 mA)
J2-7 – Trigger B for output 3 (~0.5 mA)
J2-8 – Ground (~6 A)
J3-1 – Output 1 (30 A Max)
J3-2 – Output 2 (30 A Max)
J3-GND – Ground (common to J2-8)
J3-3 – Output 3 (30 A Max)
I have it connected to 2 sets of forward lights, and one set of rear lights. Input J2-1 is connected to the high beam +12V from the truck. Input J2-2 is connected to an “override” SPST switch in the cab. This switch turns on various outputs such as my HAM radio and now my lights. J2-3 is connected to another switch in my cab, this switch only controls output 1 (one of the forward lights). J2-4 controls output 2 (2nd set of lights), and J2-5 controls output 3 (rear lights). J2-6 connects to the reverse +12V circuit, and J2-7 is connected to the same override switch as J2-2.
With this setup, I can select which of the two forward lights I want on, and then turn them on and off with the high beams. Similarly, I can select if I want the reverse lights on, and then they will come on with the truck in reverse. Optionally, at any time I can turn on the override switch, and the outputs that are switched on will turn on.
I have this all wired up into a box mounted on top of my engine compartment fuse box. In the past I have accomplished this same thing with fuse blocks, relay blocks, and a rats nest of wiring. This implementation is much cleaner and well organized with the added low current triggers.