Ideas for a vehicle speed sensor

sir
I am doing a small project for that I need a sensor which will be placed on the vehicle and it should measure the speed of the vehicle
please let me know about if you have any idea.

speed sensor

there are already a couple of sensors which can give you the speed, the VSS (vehicle speed sensor) located on the transmission, it can give you speed, some modern cars don't have this and they take the speed from the ABS sensor in the wheel, you can also use this.

Re: speed sensor

What type of vehicle is this? If it's a wheeled vehicle, you could use a sensor to measure the RPM of a wheel (optically or magnetically) and use that to figure out how much distance has been covered in X amount of time.

Another possibility is to use a pitot tube and a pressure sensor, such as is used to measure speed in aircraft.

Probably one of the simplest ways, is to read out the velocity data from a GPS receiver. With complete units now selling for $25 or so in single quantities, this might be something worth looking into.

Re: speed sensor

If your car has a J1850 bus or OBDII bus, you should be able to use micro with a UART or CAN to retrieve the speed information. For the J1850, there are transceiver that are available but are becoming obsolete so the alternative is to use discrete components Stern Technologies - OBDII Code Scanner. For the CAN, you should be able to request the data using the ISO-15765 or the other alternative decipher the data coming out of the OBDII. I have managed to decipher most of the OBDII commands from my car without requesting and one of them is speed but the code will vary between manufacturers. The code will be used in my vehicle tracker when GPS is poor and for dead reckoning. As for the VSS, I believe some car manufacturers are making the VSS obsolete from their cars. If you don't want to use a micro, use can232 or canUsb and notch up a cable with the OBDII connector. I written a C# application to filter out packets and find variation in the data bytes. I forgot to note, the ISO-15765 is a standard and the commands should work for most cars that has OBDII.