Voltage Reader for My Car (Car Electronics Basics)




Introduction: Voltage Reader for My Car (Car Electronics Basics)

About: Engineering student

Disclaimer: My car is not the one in the picture, mine is red and does not have a roll cage :-D

Hello everyone, in this instructable im going to show I installed a concealed voltage reader in my car.

My personal goal with this project was to enhance my understanding of the car wiring and how to pass wires between the drivers seat and the motor compartment, plus, it makes an excellent debug tool.

At the end of this instructable you´ll also find some interesting information about car electronics and parisitic capacitance

The material used in this instructable was:

  • a 8mm nut
  • A voltage reader that you can find in alot of eletronics stores
  • Red and Black wire (personal preference)
  • 2 connectors (8mm)
  • A switch

Step 1: Identify the Best Path to Pass Your Wire

The first thing you need to do is to identify the best path to pass the wire.

In cars with ECUs(Electronic control Unit) might be easier since there might be more paths for electric wires. My problem was that my car did not have an ECU and I wanted a clean path from battery to the display, so I passed the wire trough the space between the wheel enclosure and the up part of the wheel fender as you can see in the first image.

I wanted to install the reader and the switch in the door compartment that was meant for the windows motor controls so I passed the wire to the door and since the objective was not to make a user friendly device I did not care much about presentation (most of the time there is going to be a panel hiding the device) .

If you wanted to pass the wire to the dashboard the process should be equal to this one.

Always be sure not to bend and/or stretch the wire since it might break and cause really bad problems
Never leave pieces of the copper wire uninsulated or you´re going to have a bad time.

Step 2: Connecting Power to the Reader

With the use of the nut and the 8mm connector I connected the other end of the cable to the input of the fuse box in the motor compartment, the guys that made the car in 1992 were kind enough to let an extra screw for me :p

The earth connection is really REALLY important so make sure you have a solid connection to ground, usually there is one right by the battery where the negative terminal of the battery is connected but if there isnt make sure you make the earth of your circuit touch the bare metal of the car.

Make sure also that all of your connections are waterproof and solid since cars tend to shake a lot.

Step 3: Make Sure It Works

Go and test your system, my car regulates the voltage in the DC bus very loosely (I can get DC voltages from 12 V to 15 V) and this small project really allows to see those variations, the video presented here shows that range of voltage.

Step 4: Some Car Electronics Theory

In a car you have two main voltage sources (I say main since you might also have some big capacitors that can store a lot of energy during some time has Afrotechmods show in his video).

Those sources are the alternator and the battery. the alternator is responsible to sustain the DC voltage across the car when it is running (you can even remove the battery and the car will continue to work) and the battery is responsible of providing the inrush current needed to start the motor and when the car is running it provides extra juice when needed.

So, whenever you´re designing something that must work in a car, always make sure to protect your circuit against this inconsistencies

Any question please feel free to ask.

More projects involving my peugeot 106 coming soon :-)

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    4 years ago

    nice. I made one similar, see my instructables.