Hello to all! I am new here and I am working on a project making a monitor for my Sierra Cosworth.
I have succesfully connected and read from the tps sensor and the map sensor and I cannot find how to connect the arduino to the water and air temp sensors. All I found about sensors are with sensors with +5 volt supply but the marelli sensors and others I think works only with ground and measure the ohm resistance! Can anyone help me on how can I read resistance from the marelli sensor! If that helps the sensor code is marelli wts05! Thank you in advance! 
The sensor is just a thermistor with one side connected to ground/motor.
I assume you want to leave the sensor connected to the instrument in the dash.
The dash instrument and the sensor form a voltage divider.
Start by measuring the voltage across the sensor.
Both when the engine is cold and hot.
I expect the voltage to be higher when the engine is cold.
Report back with the voltage and the "cold" temperature.
Leo..
HI. the sensor works only with ground...so I cannot measure voltage. I can measure ohm resistance only at eny temp. How can I connect that to arduino input?
Panosrc:
HI. the sensor works only with ground...so I cannot measure voltage. I can measure ohm resistance only at eny temp. How can I connect that to arduino input?
Is it screwed in the radiator/engine block. And connected to the dash instrument.
Then you will have a voltage between the sensor wire and sensor ground when the "contact/key" is on.
If you don't use the sensor in the car, you have to provide your own sensor supply.
Looking at the graphs of the sensor, a 1k resistor could be used.
Sensor ground to Arduino ground.
Sensor wire to an analogue pin.
1k resistor from analogue pin to 5volt.
Read the A/D value, and convert that value to temp readings.
You might have to use a lookup table for that.
Leo..
So you mean like that!
But instead of puting the resistor to the groud I jave to put that to the 5v ? Right?
That will work, and swapping the resistor with the thermistor will also work.
Best to connect the resistor to 5volt, and the sensor to ground (safer).
The Fritzing diagram way increases A/D value with temperature.
Swapping the parts decreases the A/D value with temperature.
Code has to convert value to temperature anyway, so it won't make a difference.
Try this first.
int rawValue;
void setup() {
Serial.begin(9600);
}
void loop() {
rawValue = analogRead(A0);
Serial.println(rawValue);
delay(500);
}
I am using the sensor on the car but with the arduino ohm meter I cannot read ohms. So give it 5v supply and use 1k resisror? Do you habe any good code to use after for reading the ohms?
Panosrc:
I am using the sensor on the car but with the arduino ohm meter I cannot read ohms. So give it 5v supply and use 1k resisror? Do you habe any good code to use after for reading the ohms?
Arduino can read the voltage across the sensor (sensor in the car).
OR
Arduino can measure the resistance of the sensor (not in the car).
You can't do both without breaking something.
Now go to the car (if the engine is cold). Turn on the contact (don't start the car), and measure the voltage on the sensor. Black lead to the metal screw of the sensor, red lead to the wire of the sensor.
I hope you have a DMM (Digital Multi Meter).
Leo..
0 volt reading my friend...What is goin on?
Is it a single wire sensor, or two wires.
Did you measure both wires.
Could be that the sensor is connected to an onboard computer, and you can interface with that.
Not a car electronics expert.
Wait 'till someone else chimes in.
Leo..
I am doing a simular system but have chosen to run my own sensor system for both temp and pressure.
Also I am replacing my dash lights with a 0-25 volt sensor to read the trigger and a 8 channel relay to light up a 12 volt LED.
It all takes time and research, I am no where near finished.