FRC 2012

The official 2012 FRC Kit of Parts FIRST Choice description can be found on the US FIRST website. Additional encoders can be purchased at the AndyMark store or directly from US Digital. Please mention that you are a FRC team when ordering to receive the FIRST discount.

Other items that could be useful for FIRST teams:

MA3 - Absolute magnetic encoder
QSB - Quadrature to USB Adapter

How do I assemble the E4P?

See the E4P assembly instructions.

How do I connect to the E4Ps?

Use the provided cable(s). If you need other cabling options, browse our 4-pin cables.

What are the electrical signals I need to hook up?

1. +5 VDC power
2. Quadrature A channel
3. Ground
4. Quadrature B channel

What can the E4P measure?

E4Ps are incremental encoders outputting 2-channel quadrature. They are capable of measuring shaft position, speed and direction.

What encoders are included in my kit?

Your kit includes two E4P-360-250-D-H-D-B. These are miniature optical encoders with two-channel quadrature outputs. They are 360 codes per revolution and fit on a 0.25" shaft. See the E4P web page.

What is quadrature?

Most incremental encoders provide quadrature output signals. A single track optical disk encoder can provide speed information only. Adding a second track to the optical disk and offsetting it by 1/4 cycle from the first track is quadrature and provides two advantages:

1. Rotation direction can be determined by examining the relative phase of the two channels (i.e. whether A-leads-B or B-leads-A)
2. The encoder resolution is effectively increased since there are now 4 transitions for each line pair, instead of 2.

What is the difference between absolute and incremental encoders?

Absolute encoders can determine their position at power up. Incremental encoders only show relative movement after power up and would require a homing cycle in some applications.

What resolution are these encoders?

The encoders provided are 360 CPR. With 4X quadrature decoding, you get 1440 positions per revolution. Which gives you a unique position every 0.25 degrees. The maximum RPM for these encoders is 10,000 RPM.

Here is how maximum RPM is calculated:
For the E4P, the maximum output frequency is 60 kHz (60,000 cycles per second). A 360 CPR encoder produces 360 pulses on each channel per revolution. To solve for how fast the encoder's shaft must turn per second to reach the maximum output frequency, divide the maximum frequency by the pulses per revolution. 60,000 / 360 = 166 revolutions per second. To convert to RPM multiply by 60 (10,000 RPM).