Can an arduino/Raspberry Pi do this?

Noob here, please be gentle.

I am attempting to find a solution to replace 2 very thick cables for wires, 27 wires in total, due to space constraints for my lightbar install (volunteer fireman). These are simply 12v+ trigger wires that control the different functions of the lightbar. Each wire needs less than 1 amp 12v+. The lightbar will have plenty of 12v power available inside it.

I am wondering if I can rig a simple (relatively) system of 1or 2 arduinos to pass the 12v signals from inside the cab of my truck to the lightbar, and activate a relay bank inside the lightbar itself using a much smaller USB or cat5 size wire for communication.

I’ve read a little about I2C, and have differing reports on the distance it can go, some say 1 meter, others much more.

Hoping someone can point me in the right direction.

I have run 5 I2C LCD displays at 10 feet, without pullup resistors

controlling the relays: bitwise operations & port manipulation.

investigate solid state relays, the modern replacement for mechanical relays

search the project hub for relay control

[quote author=Geek Emeritus link=msg=4413594 date=1576972921]
I have run 5 I2C LCD displays at 10 feet, without pullup resistors[/quote]

I2C, by definition, requires pull-up resistors.

You can not have a 12V trigger connected directly to an Arduino pin. You need to have a transistor and 12V supply on each line.

A Pi or Arduino are both capable of this but remember that a Pi will take about 30 seconds to boot up and start working and unlike an Arduino you can’t just cut the power when you want to stop it. You have to run a shut down program and then wait until it is finished before removing the power.

FFRNDAN:
Noob here, please be gentle.

I am attempting to find a solution to replace 2 very thick cables for wires, 27 wires in total, due to space constraints for my lightbar install (volunteer fireman). These are simply 12v+ trigger wires that control the different functions of the lightbar. Each wire needs less than 1 amp 12v+. The lightbar will have plenty of 12v power available inside it.

I am wondering if I can rig a simple (relatively) system of 1or 2 arduinos to pass the 12v signals from inside the cab of my truck to the lightbar, and activate a relay bank inside the lightbar itself using a much smaller USB or cat5 size wire for communication.

I've read a little about I2C, and have differing reports on the distance it can go, some say 1 meter, others much more.

Hoping someone can point me in the right direction.

Not quite sure just what it is you want to do.
If it is to install 27 signal wires to operate relays, then why the Arduino..?
Signal wiring to relays only need to be small gauge anyhow.
You say 2 thick wire with 27 wires in total....??
Something to do with selective switching over one cable pair perhaps..?

How many different functions can the lightbar have?

Hi,
Welcome to the forum.

FFRNDAN:
Noob here, please be gentle.

I am attempting to find a solution to replace 2 very thick cables for wires, 27 wires in total, due to space constraints for my lightbar install (volunteer fireman). These are simply 12v+ trigger wires that control the different functions of the lightbar. Each wire needs less than 1 amp 12v+. The lightbar will have plenty of 12v power available inside it.

Does that mean you have 26 LEDS in the light bar, each of the 27 wires goes to each of the LEDs and gnd?
The pattern is operated from a control unit in the cabin?
Is this a commercial unit?
Tom.... :slight_smile:

Thanks for the replies folks. Here is a link to the PDF of my specific lightbar. Its not a simple unit, and is usually used by police. I snagged it cheap from a government auction.

https://www.whelen.com/install/137/13745.pdf

The bar has its own internal flasher board that controls most of its functions. It is controlled by supplying +12v to a series of "control wires".

There are 27 of these wires in total that control all the possible functions of the bar. The 27 wires are simply just in a giant cable all together, like 1.5" thick, and I want to avoid making a hole in the roof of my truck that big if I can avoid it. I like the idea of 2 or three smaller 18 gauge wires through my roof for I2C much better.

I guess a Pi is out of the question for me just because of the startup/shutdown constraints. I need this to fire up within a few seconds at the flip of a switch.

FFRNDAN:
I want to avoid making a hole in the roof of my truck that big if I can avoid it.

Designers of these things very rarely ,if ever, make operation complex by running large amounts of large core wiring if it can be avoided. Simply doesn’t make economic sense.

Other aspect of your “hole in the roof” could be that in many countries it is illegal to use emergency vehicle signage, warning lights or whatever.
Might pay to check first.

Hi,
I2C will probably not be suitable, as it is a 2wire PCB communication system.
A simple canbus would be advisable as it is designed for the automotive environment.

The fact that the data sheet specifies 1A or 500mA fuses in EACH control line has me wondering what components are being driven in the light assembly.
An arduino at each end of you remote cable would work, BUT you will need some interfacing components between the Arduino in the light assembly and the light pattern controller to supply the current needed.

Tom… :slight_smile: