View Full Version : whats a shaft encoder?

11-06-2004, 06:26 PM
hi all

I want to know what is a shaft encoder? Are there any ICs for this available in the markets.
I also want to thank all users and developers of this site because it is a very good learning resourse.


11-06-2004, 10:41 PM
Hey Rahul ... just open up an ordinary wheel mouse. Inside u will find rollers which rotate when the mouse is moved. One for the X - axis & other for the Y - axis. Even there is one for the scroll button.

Shaft encoders are used to measure the rotation of motor shaft.
It consists of a wheel with notches / holes along it's perimeter which rotates with the shaft. The number of notches passing is counted by optical detection such as LED / photo diode pair etc....hence we can get a measure of rotation and it's speed. The data can be further processed to excercise accurate control of the motor rotation.

There is no special IC as much as I know as it's a partly mechanical device. And just some basic electronic design logic is needed to design one of these.

11-06-2004, 11:04 PM
The detailed working of a shaft encoder is as follows:

The encoder is a wheel with holes at it's perimeter at fixed angular intervals. The counter is an IRLED / Photo diode pair. As u might guess that the IR falls on the diode when a hole passes between the pair. This gives a short impulsive signal accross the diode. This can be passed through a schimitt trigger which acts as a hard limiter. The signal now can be directly counted by a digital counter or can be passed through a monoshot and then integrated to give analog level corresponding to the speed of rotation.
(More the speed, more triggers to the monoshot, higher the integrated value)

11-07-2004, 11:08 PM
hi sumandeep

thanks for the information.
looking forward to learn more from you


11-08-2004, 12:53 PM
here are some links, which teach u how to make...


there is some article in www.migindia.com also

03-29-2008, 09:12 PM
thanks for posting the seattle robotics link