Arduino Controlled Auxiliary Relays Wiring Help

I am in the process of programming an Uno board to use capacitive touch sensors in my truck to toggle power to auxiliary relays. I pretty much have the coding down, just a little additional tweaking for that, and the coding is not the basis of my post.

I will be using the Arduino to control 5 separate relays and want to make sure i have the wiring down so that I do not fry something in the Arduino or my truck. Attached is a diagram of the intended wiring setup, but I wanted to make sure I have things run correctly to keep common grounds and correct component placement.

Any input would be greatly appreciated.

The first thing that jumps out to me is your power for the Arduino. I don't think you can put 5 Volts into Vin and get proper operation. I believe Vin needs to be at least 7 Volts or more for the onboard regulator to properly provide 5 Volts. Although rated for up to 12 volts for Vin I would preregulate that down to maybe 8 Volts with a small adjustable buck DC-DC converter, this will keep the onboard regulator from getting too hot if your current draw gets near maximum. It will also protect the regulator from voltage excursions in the vehicle electrical system, which may well exceed 12 Volts, especially when the vehicle battery is being charged.

Hi,
Put a fuse in line with the 12Vpos to the 12V to 5V converter too.

It will be interesting to see how well capacitive touch works in a vehicle.

Tom... :slight_smile:

Hi,
I would strongly suggest using prebuilt optically isolated relays like THESE

You could run twisted pair from the Arduino to each relay (Shielded Twisted pair if needed for Electromagnetic Interference issues).

See THIS: page about Arduino controlling Power. Follow links to areas people have problems with. Make sure you see the part about really isolating relays; you will also need 5V at the relay to power it.

DISCLAIMER: Mentioned stuff from my own shop...

TomGeorge:
It will be interesting to see how well capacitive touch works in a vehicle.

I know GM's got it in their Cadillacs. I'm not just talking about the infotainment touch screen, the radio and HVAC knobs and buttons are replaced with capacitive sliders and touch regions.

I hate it. Who wants to swipe the volume up when a good jam comes on the radio?

Jiggy-Ninja:
I know GM's got it in their Cadillacs. I'm not just talking about the infotainment touch screen, the radio and HVAC knobs and buttons are replaced with capacitive sliders and touch regions.

I hate it. Who wants to swipe the volume up when a good jam comes on the radio?

That is what the paddles on the back of the steering wheel are for :slight_smile:

In the automotive environment, you need to pay attention to putting filtering/limiting on any inputs as well as making sure the outputs are using decent drivers etc. In addition to the fact that the "12v" system can be anywhere between 11v and about 15v (13.7-14.3 is normal for a running engine), the automotive environment typically has all sorts of spikes and pulsed magnetic fields around that can cause all sorts of issues and induce strange things in any wires you have running next to other wires (you should see the magnetic pulse that happens in the battery cables when you hit the starter and draw several hundred amps from the battery)

Unfortunately I'm not wealthy enough (yet! cross my fingers) to own a Cadillac, I just have access to them where I work. My Cruze still has a knob for some good, old-fashioned "crank it up!"

I'm certainly aware of all those things. The recent motorcycle quickshifter thread in this very forum showed just how hellish engines are for electronics. He fried 2 or 3 gate driver chips, at least one Nano regulator, and also had a problem with EMI causing false detection of an input trigger.

Anything hooked up to an engine's alternator needs to be filtered, clamped, reverse-protected, current limited, all that jazz.