Gamoto PID Motor Controller

DC Motor Controller, with closed loop PID control of speed and position.
Delivery date: 3-5 days

The Gamoto is a PID closed-loop servo motor controller. It uses quadrature encoder feedback to precisely controller the position, speed, and acceleration of almost any motor. It includes an on-board H-bridge (LMD-18200) capable of driving 6A peak, or 3A continuous load. The bridge requires a minimum motor supply voltage of 12V, and a maximum of 55VDC. The base processor is a PIC16F876, which is a 28-pin PIC processor, running at 20MHz. It is paired with an LMD18200 H-bridge, which can drive 3A continuous loads, 6A peak. The motion control capabilities have been modeled after the LM629 motion control chip, and include the following:

  • 32-bit registers to hold fixed point position variables (up to +/- 8 million encoder counts)
  • 16-bit factors to hold Kp, Ki, and Kd constants
  • 10-bit PWM resolution for motor output power/speed control, choose sign-magnitude or locked anti-phase
  • High speed encoder capture (1X and 4X) logic (up to 254,000 counts/sec, or encoder pulses as fast as 2us wide). For an encoder with 1200 counts/revolution, speeds up to 12,700 rpm are possible. With 4X setting, a 500ppr encoder will show 2000 positions.
  • True real-time PID control with adjustable filter constants
  • Trapezoidal Trajectory Profile processing (constant accel ramp, constant velocity cruise, then constant decel rampdown)
  • Storage of several trajectory profiles in flash EEPROM
  • Fast PID recalculation, updating approx every 510 usec. (~2kHz)


Pulse Control Options

  • Step/Direction pulse inputs can be used to emulate a stepper motor driver. Each step pulse jogs the setpoint in the given direction. Great for use in light duty CNC systems. Note that the Gamoto cannot drive a stepper motor - only DC brushed motors. The step/dir inputs allow you to replace a Stepper Driver and stepper motor with a Gamoto and DC motor with encoder feedback.
  • R/C (Remote Control) pulse inputs allow connecting the Gamoto to an R/C receiver. Convert a normal motor to a giant servo! Use this feature with the Analog Feedback option, and use a potentiometer instead of quad encoders for position feedback. Animatronics, robotics, automation applications.

Communications Options

  • Serial port, at 9600, 19200 or 115200 baud. Connect to any PC by using a Type 1 RS-232 converter from SuperDroidRobots. or other similar level shifter chip, such as the Dallas/Maxim MAX232.
  • RS-485-like network at 9600, 19200 or 115200 baud. Connect serial lines in parallel, and set the dip switch to an address from 0 to 7, and up to 8 Gamotos can share the serial network. No need for extra hardware. Broadcast commands supported.
  • I2C protocol, with the Gamoto as a slave device. Up to 8 Gamoto boards can be on the same I2C bus, with support for broadcast commands
  • Cricket Bus, a one-wire, mutlidrop bus protocol developed by MIT for use in their cricket controllers, also used by Gleason Research's HandyCricket controllers. Find out more at

Easy to Use

  • Easily removable fuse for the motor power, with an LED indicator if it blows
  • 5-position dipswitch to allow setting of baud rate, I2C address, etc.
  • Jumper selectable 1X/4X encoding
  • Analog Feedback option allows the use of either an analog voltage/potentiometer or a quadrature encoder for position feedback
  • Encoder connector with power and ground pins, and on-board pullup resistors and signal conditioning.
  • Expansion connector with four general purpose analog or digital I/O lines
  • Two extra inputs dedicated to upper limit and lower limit switches, for applications where limiting is important (CNC mill, etc)
  • Home switch option automatically zeros position registers and stops motor when home is sensed
  • On-board flash memory to permanently store things like the PID constants, configuration, and motion trajectories.
  • Two I2C connectors in parallel for easy daisy-chaining
  • CricketBus connector and pigtail in parallel for easy daisy-chaining
  • Separate motor power and logic power, for clean logic signals
  • LEDs for Overtemp of H-bridge, fuse failure, and power indication
  • Analog reading of motor current and position error available via software commands. Allows control of motor torque, sensing of obstacles / force feedback, etc.

Programming port connector, for easy firmware updates.

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