Speed Sensors?

Question

I'm Looking for advice on which speed sensor I should use to measure a small cart. the cart is hardly bigger than a human hand.

Answer 1

This method is commonly used in school experiments because it's so cheap. Attach a paper tape to the cart and run the tape between the clapper and bell of an electric bell, with carbon paper between the clapper and the tape. Each time the clapper strikes the bell, it makes a mark on the tape.

Another is to take a photographic time exposure as the cart moves against the background of a meter stick, using a stroboscope for illumination.

There's a myriad of techniques if accuracy is important and money is no object.

Answer 2

My best guess (without much information) wuld be to use some kind of small shaft encoder to measure how fast the drive wheel(s) are turning. Knowing the radius of the wheels yu can then convert that to speed.

Doug