Car system

Hello everyone

Let me introduce myself first.
I'm Arnou and I'm in my final year of automation engineer, as a hobby I'm a car and bike enthousiast and pretty much everything with engines.

So as a side project I made some kind of monitoring system with an arduino. I have some temperature and pressure gauges which the Arduino just reads out (resistance measurements). These readings are then processed and shown on an LCD screen. This is the result.

Lately however, the system has become slightly unstable. Sometimes it seems like the LCD and the arduino lose communication and the LCD goes all crazy. As shown below.

Does anyone know why this is happening? It's pretty hard to reproduce myself and sometimes it doesn't even happen.

And a pic off my car :slight_smile: It's an 1986 Mazda RX-7 for those who wondered :slight_smile:

Does anyone know why this is happening?

Lack of supply decoupling.
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Grumpy_Mike:
Lack of supply decoupling.
De-coupling

Aha, thanks!

So basically it’s just the noise that needs filtering. How can I know how big the capacitor needs to be? Or do I just take 0.1uF as the example shows?
The voltage supply is tapped from the back of my radio and is just powering one Arduino.

How can I know how big the capacitor needs to be?

You don't, that is the Art of electronics. You have a 0.1uF ceramic minimum and then add extra capacitors.

Yeah my electronics isn't what it used to be :slight_smile:

So basically I start out with 1 capacitor, see if it works. If it doesn't work add more (in parallel right?)?

If it doesn't work add more (in parallel right?)?

Yes but you use large electrolytic capacitors 100 to 1000 uF. If that does not work you try the Pi circuit which was the last one on that page.

A car has a very hostile environment electrically speaking and you might need other things as well but this is the place to start.

Alright, thanks!
I'm going to find some parts now!

If you have soldered connections, they may be the problem. If you don't have soldered connections, they may be the problem.

Paul

Paul makes a great point as connection issues with cause havac, however one point id like to put out there is a poor ground if you are running off obd connection or possibly even a female pin connection if you made the harness urself. last but not least a resistor.

The supply voltage is split from the wires powering the radio, so same ground as the radio. Radio has no issues whatsoever so, not sure if that could be the case.

My resistors for my ohm measuring are soldered to a universal board, and the board is then connected to the arduino via the given jumper wires. Have been looking for a better solution to connect the two, but havent found anything yet.

Radio has no issues whatsoever so, not sure if that could be the case.

That is because the radio will have filtering inside it, protecting it's circuits.

Aha alright, i'll see what i can do with capacitors

Inductors help as well.