Dash Auxiliary Power Button

I have a better way of hooking up my dash auxiliary power button as right now the way I have it is a bit daffy and I'll explain why; The scenario works but what happens is that say I have the auxiliary power button turned on and I forget that it is on and then I turn over the cars ignition, well when I turn off the ignition key the car will keep running because power is still being supplied through the lower consoles auxiliary dash power button being turned on, I would then need to switch that off in order to turn the car off. This way is much better because that can't happen as the dash can only get it's power from one source or the other via the relay and not both at the same time which is how I currently have it wired.

Bread Board Experiments

Yesterday I was experimenting around a little with the Darlington Driver 50V / 500mA Transistor array chip model number ULN2803A. I wired up a simple circuit on my Bread Board with 2 mini Songle 12V 10 Amp relays, some resistors, micro tactile buttons, wires, a single red LED and the project 2 LED flasher circuit that came with the starter kit I got.

Now this is really simple setup using the Darlington Transistor

array chip in that my micro buttons (in this case) are switching on a stepped down 9V current through the resistors to simulate a low current input to the Darlington array chip. This is ideal since I intend on using an Arduino to control input signals to the chip, and Aduino uses a low 5V output, same as a USB device. On the other side (Outputs) of the Darlington array chip I have the necessary voltage needed to trigger the magnetic coils of the mini Songle 12V Relays and as you no doubt already know that on the switch side of the relay I can have anything I want to activate up to 10 Amps, which is a lot of current. I can use higher rated Relays if I need to power anything that requires more than 10 Amps.

So in the experiment yesterday I have it so when you press once of the micro buttons the single red LED turns on through the switch of one relay and when you press the other button the small 2 LED flasher circuit turns on through the switch of the other relay. Now keeping in mind that for a low power input of 5V (USB) I would not need the resistors in front of the input pins on the Darlington array chip, this makes for a very small space saving potential PCB board to control stuff from my dash software I have been developing in Unity 3D. I'm planing on using the Arduino because so far it's what I have found that communicates well with Unity 3D both as a means of controlling from the Arduino and sending information too the Arduino.