[UnWired]

Hi,

This is a very beginner question (its my first time using an encoder and building a robot).

I recently ordered an 300cpr and my friend told me that each count equals 4 ticks.

My question is, how precise can I get with the encoder? For example, if I have an encoder mounted on the shaft, and the shaft turns 360 degrees, is it 300 counts or 1200 ticks? When I want to turn the shaft 1 degrees can I just turn until the encoder reaches 3 ticks? Or does the encoder just go by counts? Do ticks even exist?

Thanks!

[Lon]

The encoder count is based on the rear shaft movement of the motor (for geared motors with encoders attached prior to the gearing). When used with our motors there is a 30:1 gear ratio. So the encoder count converts to Counts-per-motor-shaft-rotation = 300CPR*30 = 9000. 9000/360 = 25 counts per degree of motor shaft rotation.

Most controllers use decoder chips (see www.usdigital.com) to convert the quadrature signals to "upcounts" and "downcounts". These up and down counts are used to determine the position of the motor.

Example, Position = 10000 and you receive 5000 upcounts and 200 downcounts

Position = Position + (UpCounts - DownCounts)
Position = 10000 + (5000 - 200) = 14800

The decoder chips can often be set for 1X, 2X, or 4X decode. In a 4X decode you multiply the total counts by 4. For our motor and 300CPR encoder 1 motor shaft revolution would equal 36000 counts (9000x4). So you would then have 100 counts per degree of motor shaft movement. The higher the counts the better the resolution and smoother the movement (generally speaking).

Lon