Automotive Project - Sensors & Others

Using Arduino Sensors
1

Hi,

I'm starting an automotive project and I need some help. My background in electronics is quite limited. Well let me start with what I've in mind.

My initial goal is to build a car monitor to provide real time information about coolant temperature, oil temperature, outside air temperature and battery voltage.

I would like to use my existing coolant temperature sensor that is connected to the car and shows the temperature in the instrument cluster.

My sensor has 4 wires connected to it. 2 designated for the ecu, and other 2 for the instrument panel.

With respect to power arduino input is 5v so how can I display my battery voltage of ~12v?!?

I've read several posts in the forum about reading info from automotive sensors, but standalone, that is, not in simultaneous with the existing wiring from the car. Can you please explain me what I have to do in order to read data from the sensors using arduino.

Any help would be appreciated,
Thanks,

Tiago

2

What car do you have? If it's a more or less recent model, use the OBD-II interface to read out all these values (and a lot more if you wish). The easiest way to do is to connect an ELM-327 (or compatible) to the OBD-II connector (in most cars below the steering wheel or near the pedals) and read the values over the serial interface.

3

pylon:
What car do you have? If it's a more or less recent model, use the OBD-II interface to read out all these values (and a lot more if you wish). The easiest way to do is to connect an ELM-327 (or compatible) to the OBD-II connector (in most cars below the steering wheel or near the pedals) and read the values over the serial interface.

VW Vento 1994, too old for that :). No OBD-II

Thanks anyway for your help

So what else? Come on guys, you help would be appreciated

4

Hi.

To measure 12v to the arduino you can use a voltage divider. Google it.
The divider will give a linear voltage 0-5v to the arduino representing a higher voltage.
This is done using resistors.
Your Head or coolant temp can be read out using PTC or more common NTC sensors wich also is used in a voltage divider method. however the values must be linearized or normalized in software, also Digital temperature sensors can be used on the engine block and fastened with JB WELD. just find a hole in the head around the thermostat and put the sensor in and JB WELD it in place, The same can be done for the oil. or the sensor can simply be taped onto the oil filter with som thermal insulation over it.

I would not recomend hacking the original sensor as it could induce a paracitic current into the sensor
and mess up your original sensor reading.

Helge.

5

And while you are at it you can get the RPM reading from tapping into the hall sensor(Frequency measure) on the distributor, and the speed from the pulse pin behind the indtrument cluster (Frequency measure), also the fuel gauge signal can be tapped of behind the instrument cluster, or at the fuel gauge directly.
You can also create a remote start feature or keyless entry :):slight_smile:

Helge.

6

https://dl.dropboxusercontent.com/u/8736419/sensor.rar

Some education stuff for sensors.

7

HelgeNodland:
Hi.

To measure 12v to the arduino you can use a voltage divider. Google it.
The divider will give a linear voltage 0-5v to the arduino representing a higher voltage.
This is done using resistors.
Your Head or coolant temp can be read out using PTC or more common NTC sensors wich also is used in a voltage divider method. however the values must be linearized or normalized in software, also Digital temperature sensors can be used on the engine block and fastened with JB WELD. just find a hole in the head around the thermostat and put the sensor in and JB WELD it in place, The same can be done for the oil. or the sensor can simply be taped onto the oil filter with som thermal insulation over it.

I would not recomend hacking the original sensor as it could induce a paracitic current into the sensor
and mess up your original sensor reading.

Helge.

Well thanks for the comments. So I was hopping to tap into the signal that comes from the coolant sensor, or at least tap the wire that provides info to the cluster. As for the oil sensor and outside air temp, since my car does not have them, i can do things without tapping, and connect them to the arduino directly.

So as I've mentioned my temperature sensor has 4 connections, 2 for the ECU and 2 for the cluster. Well yesterday I've measured things and it turns out that from the 2 connections used by ecu I've measured a voltage of 4,54V, when the key is in the ignition and the plug is disconnected from the sensor. When the plug is connected I've measured 1,94V...

For the other 2 connectors i've measures voltages above 5V I don't recall the values right now.

For resistance, I've measured 1MOhm in both cases, that is between the 2 connectors for the ECU and between the 2 connectors for the cluster, directly from the sensor with the plug disconnected.

These were taken with a cold engine.

So i'm guessing that my ECU provides 5V, can i tap directly to the wire, that goes to the sensor, and feed it to a arduino input?

HelgeNodland:
And while you are at it you can get the RPM reading from tapping into the hall sensor(Frequency measure) on the distributor, and the speed from the pulse pin behind the indtrument cluster (Frequency measure), also the fuel gauge signal can be tapped of behind the instrument cluster, or at the fuel gauge directly.
You can also create a remote start feature or keyless entry :):slight_smile:

Helge.

ok that is planned also :stuck_out_tongue: at a latter stage, but for that i intend to use an already existing project named mpguino, nevertheless i will have to connect things but i'll save that for later :slight_smile:

HelgeNodland:
https://dl.dropboxusercontent.com/u/8736419/sensor.rar

Some education stuff for sensors.

thanks for the literature

Tiago

8

Hey there again, had some time to dedicate to this :slight_smile:

I was reading about protection of arduino inputs, because I intend to measure the car battery voltage using a voltage divider, and i don't want to fry my arduino so I came across this post

http://www.thebox.myzen.co.uk/Tutorial/Protection.html

For clamping (signal) diodes can i use 1n4001 diodes?

Thanks