# Speed signal from speed sensor to microcontroller

How can I know the actual speed of a vehicle through arduino mega2560? By using the speed signal from the speed sensor? Also can I set it as variable in arduino, with that, I can set speed limits in places? Thanks

speed is relative to something in a car usually it is rotations of the transmission locations of the axial rotations of the drive shaft rotations of gearing inside the transmission some mechanical thing that does not relate to exact Road speed however it is generally pretty accurate. if you change the tires for a larger diameter then the speedometer will show a speed based on the old tires not the new tires. If you're trying to get an exact speed then you would need to see the road or some way to measure the passing of obstacles such as line markers in the road or some such. if you're just looking to see what the car thinks the speed is, you can tie into the computer system in the car. Google arduino obd.

Hi

Maybe you can try to calculate the speed of a car with GPS.
This way is nearly exact.

Daniel

Hi,

virus012:
How can I know the actual speed of a vehicle through arduino mega2560?
By using the speed signal from the speed sensor?
Also can I set it as variable in arduino, with that, I can set speed limits in places? Thanks

Yes, you can use the vehicles speed sensor output, but you must know its format, is it a pulse or from a CanBus system.
Yes, you can use it with an Arduino to make a speed limit alarm
Tom...

TomGeorge:
Hi,Yes, you can use the vehicles speed sensor output, but you must know its format, is it a pulse or from a CanBus system.
Yes, you can use it with an Arduino to make a speed limit alarm
Tom...

What if it is a pulse? How can I calculate for speed? Straight from speed sensor wire signal to my mega?

Daniel-S:
Hi

Maybe you can try to calculate the speed of a car with GPS.
This way is nearly exact.

Daniel

I`m thinking about this. If I`m able to display it in a LCD. There is still a chance to make the speed from GPS a variable and call it to another function. Right? Like making it a speed limit in a particular area.

Hi,

What is your electronics, programming, arduino, hardware experience?

Tom...

virus012:
What if it is a pulse? How can I calculate for speed? Straight from speed sensor wire signal to my mega?

Typically, the speed sensor will be some fixed ratio (+/- some small correction for tire size/wear). You will need to find what the speed sensor is in the vehicle you are working with. You will then also need to do some signal conditioning on the signal before feeding it into your board - it is unlikely that the output from the speed sensor would be directly compatible with the input to your board and microprocessor inputs do NOT like voltages that go over their specified input range (or go negative relative to ground) etc. You need to do some research and find just what is in the vehicle you are trying to interface to.