I'd like to know something about the "specs" of an odometer signal in vehicles like trucks:
voltage and frequency range.

 

What is it you are trying to do? The vehicle speed sensor isusually produced by a 2 or 3 wire sensor on the output shaft of the transmission. It is generally sent to the ECM or PCM and cleaned up and sent to the odometer in the form of a square wave signal. It can also be sent via CANBUS. If you give me a specific vehicle, I can tell you more.

 

Hello! Sounds like it is measured by transmission speed, aka wheel speed. I would guess that the wheel speed is taken from the ABS sensors on each wheel as an averaged value of all wheels. If so, the value gives an number of impulses per turn and must be tranlated to km/h or mp/h.
Maybe i'm totally wrong, so please clearify!

 

Vehicle speed sensing can be taken from a VSS located on the output shaft of the transmission, a sensor mounted on the differential which works off of the crown gear, or from ABS sensors depending on the OEM. There is usually a tone ring of sorts which will have a specific number of teeth on it. As the vehicle moves, the sensor pulses a signal to an ECU which counts those pulses and sends a signal to the speedometer/odometer. Newer clusters have very complicated electronics in them which will not allow most people to change programming etc without specific information and programmers. The newest version of this is Global A vehicles which allow only a single write to a chip, meaning you can no longer run to the wrecking yard and throw in a used cluster to fix your problem. Welcome to cyber-security for your vehicle

 

Thank you for the answers,
i need to get a ON/OFF signal that is ON when the truck is moving,and OFF when it is stopped.
ON = Vbattery, OFF = GND
I think to use the same signal used for the odometer, rectified and filtered (given that it is a square wave of some frequency).

 

What is it you are trying to do? The vehicle speed sensor isusually produced by a 2 or 3 wire sensor on the output shaft of the transmission. It is generally sent to the ECM or PCM and cleaned up and sent to the odometer in the form of a square wave signal. It can also be sent via CANBUS. If you give me a specific vehicle, I can tell you more.

I am working on a IVECO EuroTrakker and an IVECO Magirus 410.

 

Perhaps I am not following correctly so correct me when I am wrong. You would like a square wave signal when the vehicle is moving and no signal when it stops?
Or do you just want solid 12v when moving and zero when stopped?
What are you connecting this to in the EuroTrakker? What are you trying to run?

 

Solid 12V (24V in this case) when it is moving, and 0V when stopped.

 

Perhaps I am not following correctly so correct me when I am wrong. You would like a square wave signal when the vehicle is moving and no signal when it stops?
Or do you just want solid 12v when moving and zero when stopped?
What are you connecting this to in the EuroTrakker? What are you trying to run?

I just want solid 12V (or the battery voltage) when moving and zero when stopped.
I'm trying to run an external RPM counter that counts only when the truck is moving.

 

Check to see if the intended vehicle is equipped with a Crankshaft Position Sensor. In certain modern vehicles, the CPS is the signal input source to the tachometer. The CPS should provide a definitive test regarding vehicle motion, without resorting to software manipulation. A high impedance interface with the CPS could feasibly trigger a capacitor charging transistor, ultimately providing an appropriate motion derived signal.

 

Why not use an accelerometer IC?

 

Taping into the CKP will not give him vehicle motion. It will give him engine revolution. He needs to tap into the Vehicle speed sensor and change a digital signal into solid 12v signal.

 

Taping into the CKP will not give him vehicle motion. It will give him engine revolution. He needs to tap into the Vehicle speed sensor and change a digital signal into solid 12v signal.

Right.

 

A "missing pulse detector" tied to the speed sensor output should give him an indication of motion vs stopped.

 

I don;t know what the signal looks like, but earlier signals were made with a reed switch on the conventional speedometer cable. I think when i looked briefly into my car, you get a pulse every foot.

I'd like to design something that would be a little better than the emergency brake on. With the tilt steering and the angle I see the dash, I have a hard time seeing the indicator. I'd like to combine emergency brake on with actual tire movement and a buzzer with timeouts.

 

Thank you all.
Reading some Iveco docs online, i found that is available a signal with name "shift netral" that is ON at 24V when the shift is in neutral position. I need to reverse its polarity, not a big issue, using a simple SPDT relè. Someone has already used this signal ?
I will post the link to the abovementioned docs.