Pololu ROMI User manual

1
https://eckstein-shop.de/
POLOLU ROMI ENCODER PAIR KIT, 12 CPR,
3.5-18V
USER’S GUIDE
PINOUT AND INSTALLATION
The encoder board is designed to be soldered directly to the back of the motor, with
the back shaft of the motor protruding through the hole in the middle of the circuit
board. One way to achieve good alignment between the board and the motor is to tack
down the board to one motor pin and to solder the other pin only when the board is
flat and well aligned. Be careful to avoid prolonged heating of the motor pins, which
could deform the motor case or brushes.
We currently have two boards that the these encoders can directly plug into: the Romi
32U4 Control Board and the Motor Driver and Power Distribution Board for Romi
Chassis. The encoder pins need to be installed pointing down toward the chassis in
order to be able to plug into this board.
The Romi Encoder can plug directly into
the Motor Driver and Power
Distribution Board for Romi Chassis.
Romi 32U4 Control Board with LCD on a
Romi chassis.

2
https://eckstein-shop.de/
For robots not using these boards, it might be more convenient to install the board and
pins facing up and connect to them with a cable made from our wires with pre-crimped
terminals.
The included low-profile headers are still long enough to work with our
pre-crimped jumper wires.
To later use the same encoders with a board that they can plug into, just pull the motor
portion off of the gearbox, rotate it 180°, and push it back in to make the encoder and
pins point down.
The motor can be removed from the
gearbox even when the encoder is soldered
to the motor.
The motor portion can be removed
from the gearbox and rotated 180° to
change whether the connector pins
point up or down.

3
https://eckstein-shop.de/
If you do not care about compatibility with existing or potential future boards, we
recommend soldering wires directly to the encoder or installing a standard-length male
header that works better with cables made from our wires with pre-crimped terminals.
A standard-length straight 0.1″ male header allows for compact cable connection.
Once the board is soldered down to the two terminals, the motor leads are connected
to the M1 and M2 pads along the edge of the board; the remaining four pads are used
to power the sensors and access the two quadrature outputs:
The sensors are powered through the VCC and GND pins. VCC can be 3.5 V to 18 V, and
the quadrature outputs A and B are open-drain digital signals that need to be pulled up
to the appropriate logic voltage of your system. The encoder boards have pads for
optional 0603 size surface-mount resistors to pull the outputs up to VCC, but in typical
applications, the pull-up resistors will be on the main electronics board.

4
https://eckstein-shop.de/
Encoder A and B outputs of a magnetic encoder on a high-power (HP) mini plastic
gearmotor running at 4.5 V.
The board’s six pads have a 0.1″ (2.54 mm) pitch, so they are compatible with common
0.1″ connectors, or you can just solder individual wires directly to the board.
Once the board is soldered to the motor, the magnetic encoder disc can be pushed
onto the motor shaft. One easy way to accomplish this is to press the motor onto the
disc while it is sitting on a flat surface, pushing until the shaft makes contact with that
surface. The size of the gap between the encoder disc and the sensor board does not
have a big impact on performance as long as the motor shaft is at least all the way
through the disc.

5
https://eckstein-shop.de/
SCHEMATIC DIAGRAM
This schematic is also available as a downloadable pdf (88k pdf).