Wire required for sensors in an engine bay?

Using Arduino Project Guidance
1

Hi all.

First project, new to small electronics, and programming, so bare(bear?) with me.

Creating an engine moniter. Utilizing thermistors for temp and will be using some sort of sensor for things like oil pressure, intake/boost pressure.

I have a basic sketch done for the temp sensors. Took quite a while to get it to work.. But made it in the end.
I don't think the code is needed for the question, so I haven't posted it.

Using an arduino UNO at the moment.

Anyway. To my question.

I have been told i will need sheilded wire. Is that right?

The various sensors will be around an car engine bay. Reasonably close to ignition wires and such.

I went to jaycar (an electronics shop) and asked about sheilded wire. The guy tried to show me aerial co axial stuff. And said that's the only 'shielded' wire they have.

So will need it? Should I be asking for something in particular? Link to the type of wire I need?

Please let me know if I missed any relevant info and ill post it up :slight_smile:

2

I wire stuff in engine bays all the time and never used shielded wire or had any problems. I work in cars and tinker with electronics and always seem to mix the two. If you do experience issues you could get some cat 5 cable (like your computer network cable). That's shielded.

3

For straight forward analog sensors there's no need to use shielded wire. Shielding is needed if you're reading a pulsed signal such as a crank or cam position sensor, where even small amounts of noise can interfere with the pulse detection.

4

Thanks guys.

I thought as much. Im installing a Megasquirt ECU into a different car, and the only sheilded wire on it is the cam/crank sensor. All the other sensors are straight single core copper wire.

So I figured I wouldnt need it. But I thought it best to ask before I move to the next step in the project :slight_smile:

Thanks again.

5

Ok.

Not sure if im being an idiot or not..

Do I need 3 wires going to the thermister? or can I some how use 2?

I dont want to have to run 3 wires to every sensor.. Will start to get too bulky.

6

Ohhhh hang on.

If I use 2 wires out to the sensor, 5v and gnd, 5v straight from the board, but bring the gnd back to a bread board to the bias resistor which then goes to the input pin, and then the other side of the resistor to the ground on the board.

Is that the correct way of doing it?

7

In most cases you can ground everything to the car.

8

Yeah I thought of that as well.

Wasn't sure if it would effect things. For testing it's going to be in and out of the car alot so il do it with the bread board for now and see how we go.

I've just re wired it the way I said and it works perfectly. Matches within a degree C of my bought sensor 8) (don't know the accuracy of it, but it's good enough for me :))

9

One other reason to use CAT cables is the toughness of the sheath.