AmpFlow Motor Speed Controller

We offer two different speed controllers as optional equipment on our kits. The full-size AmpFlow controller (below) is designed for use in middle and heavy weight kits. You can also install the larger Ampflow in our light weight kit if you anticipate heavy current draw (by using multiple battery packs or the high-speed ratio).

We also offer a smaller controller for use in the light weight kits. Visit the Mini controller page for more information.

The AmpFlow is a high performance, microcontroller- based motor controller, loaded with numerous features and operating modes. It has two power output stages with dual H-bridges for full forward and reverse operation of two independent motors/wheels. The controller's two channels can either be operated independently or mixed together for "tank style" steering. A single channel version is also available with twice the rated current. The motors may be operated in open or closed loop speed mode. Using low-cost position sensors, they may also be set to operate as heavy-duty position servos.

The controller is packed with features including a safe power-on start, automatic stop in case of command loss, over-current protection on both channels, and overheat protection. These features ensure reliable and safe operation in the most demanding mobile robot applications.

For all its sophistication, the controller is very simple to install and operate. Its many options are programmed using only two switches and a LED display on the front panel. The controller may also be connected to a PC for setting current limits and other configuration parameters using a convenient graphic interface. Once programmed, the configuration data are stored permanently in the controller's nonvolatile memory, eliminating the need for cumbersome and unreliable jumpers. The 7 segment LED display also provides running and failure diagnostics.

Easy to Install

The controller is designed for simple installation in a variety of applications. It's fitted with heavy 8-gauge cables for direct connection to high current batteries and motors.



A convenient 15-pin connector includes mounting nuts to secure a permanent connection with the radio receiver or microcomputer and the various external sensors. You can use it for any of the following connections:
*   Radio receiver or microcomputer
*   Tachometer inputs for closed loop speed control
*   Potentiometer input for position control (servo mode)
*   Motor temperature sensing and protection with external thermal sensor
*   Input for an emergency stop switch
*   Input for detecting when a vehicle is turned upside-down, reversing the controls
*   A third channel with 2 Amp switched output for a brake, clutch, weapon or other device
*   Regulated 5V output for powering the R/C radio (Battery Eliminator Circuit)
*   Two additional low voltage inputs for connecting switches or sensors (RS232 mode)

Multiple Input Modes

The controller’s multiple command input modes (R/C Radio Pulse Width, Serial Port, or Analog), make it uniquely interfaceable to all types of microcontrollers, remote control radios, or other devices.

R/C Radio mode
R/C Radio is the most popular, simplest and least expensive method to build and operate a remote controlled robot. The controller supports many configurable options, including joystick calibration of min, max and center positions and deadband adjustment. Full optical isolation is provided on all R/C control inputs

Serial Port (RS232) mode
The controller may be interfaced to a microcomputer for autonomous operation. More advanced operations are possible, including remote control via the Internet, using a wireless modem or wireless network adapter (802.11).

Analog mode
A simple 0-5V analog control mode is also provided for direct connection to potentiometers or joysticks.

Multiple Command Modes

The controller may be connected to two motors which will react to commands received on two input channels. Using these two inputs, the motors can be commanded independently or in a combined fashion to accommodate the most common drive and steering methods.

Single Channel
In the single channel version the two outputs are combined to control a single motor. This doubles the rated current to 320 Amps for three minutes and 360 Amps for 20 seconds.

Independent Speed command
In this mode, each of the two motors is commanded independently of the other. This operating mode is best suited for generic motor control applications.

Mixed Speed/Steering command
In this mode, the motors work in combination to move and turn a vehicle by combining the forward/reverse command information and the left/right steering information. This mode of operation provides a cost effective method for moving and steering tank-style robots and underwater vehicles.

Speed and Position commands
In this mode, one channel is used to control the forward/reverse motion of the vehicle. The other channel is used to make the motor work like a position servo which can be then connected to a steering column.

Dual Position Commands
In this mode, each channel independently controls the angular position of one motor. The heavy duty servos built in this way can be used to control throttle, breaks, and steering of full-size vehicles or animate any large and heavy structure.

Programmable Throttle Curves

The controller can be adjusted to optimize the throttle response to your particular radio and motors.

Deadband adjustment (R/C mode only) The controller allows a selectable amount of joystick motion from its center position before it begins applying power to the motors. This feature ensures a safe start and smooth operation.

Exponentiation adjustment
After the joystick moves past the deadband position, the controller can be set to add an increasing (exponential) or decreasing (logarithmic) amount of power to the motor. The operator can tailor the controller's driving characteristic for a particular use.

Joystick calibration (R/C mode only)
With the push of a button, the min, max and center positions of the R/C joysticks can be captured and stored in the controller.

Multiple Motion Modes

For each channel, the controller supports multiple motion control modes. You can even set each of the two channels to a different mode.

Open Loop Speed mode
The controller delivers an amount of power proportional to the command input. The motor speed is not measured. This is the preferred mode for use in most robots.

Closed Loop Speed mode
A tachometer measures the motor speed. The controller automatically compensates the power output if the speed changes because of changes in load. This mode is often used in precision motor control and autonomous robotic applications.

Servo mode
The axle of a geared down motor is coupled to a potentiometer that is used to compare the angular position of the axle versus a desired position. This unique feature makes it possible to build ultrahigh torque “jumbo servos” that can be used to drive steering columns, robotic arms, animatronics, life-size models and other heavy loads.

Optional optical encoder inputs

The Ampflow controller is available with an optional built-in optical encoder module. This includes an extra 8-pin connector on the controller's faceplate. Click here for details.

Efficient Power Output Stages

The controller includes two high-efficiency power output stages which can operate from 12 to 40VDC and an optional 12V input to the controller so that it will continue to operate if the main battery voltage dips below 12V. High efficiency MOSFET “H-Bridges” are used for full forward and reverse operation. The controller uses Pulse Width Modulation at 16 kHz to generate smooth, variable output power in as little as 0.5% increments. Ultra-low “On” resistance of the 32 MOSFET transistors and synchronous rectification ensures operation up to 180A per channel with very little heat generated by the controller. The internal "on" resistance of .003 Ohms is comparable to the resistance of two 8-gauge battery cables just 2.4 feet long. The resistance of the single channel version is even lower at only .0015 Ohms. The extruded aluminum case, which doubles as the heat-sink, provides efficient cooling without the need for a fan.

Advanced Multi-mode Current Limiting

With careful current management the AmpFlow controller is able to survive abusive conditions that might otherwise destroy a bulkier and more expensive controller. The internal microprocessor is constantly on the lookout for over-heat and over-current conditions and it cuts the power back smoothly when it detects excessive current or heat. Use the default current limits or easily customize them for your application.

*   A sensor measures the actual current delivered to the motors and automatically reduces the power if the current goes over the preset limits.

*   Two temperature sensors located on the heat sink will cause the controller to adjust the maximum allowed Amps in case of controller overheat.

*   The controller can be configured to automatically smooth command changes (from forward to reverse, for example) to avoid sudden overloads on the controller, the batteries, and mechanical components. The controller’s programmable acceleration feature will automatically limit the huge current spikes that would otherwise occur.

*   The "SmartAmps" algorithm for automatic current limitation allows each of the two channels up to:
160 Amps continuous for three minutes
180 Amps for up to 20 seconds
500 Amps momentary peaks (less than one millisecond)
These figures are doubled for the single channel version and they can be increased if you choose to add a fan.

This array of current-limiting technology eliminates the need for oversizing the controller and allows the AmpFlow to perform better than other controllers that lack current limiting. It also helps to protect motors from over-current and overheating damage.

PC-Based Configuration and Monitoring Utility

You can run the controller with the factory default settings for true "plug and play" convenience. You can also fine-tune the settings using either the built-in switches and 7 segment LED display or through connection to your PC. The controller is delivered with a PC utility and connection cable that will allow you to read and set the programmable parameters with a user-friendly graphic interface and send precise commands to the motors.

In addition to the above, you will have access to advanced data logging capabilities including:
*   Read and chart real-time 12 internal parameters, including battery voltage, captured R/C commands, controller temperature, motor temperature, current, and more.
*   Save controller operating data to disk for analysis with MS Excel
*   Data may be logged in a PC, PDA or microcomputer
*   Data Logging Software is supplied for PC and Palm Pilot PDA

Using the PC and an internet connection, you can download software updates to improve existing features or enable new ones as they become available. This unique capability keeps the controller from ever becoming obsolete. Uploading the latest software to the controller is a very simple point-and-click procedure requiring no special computer or electronics skill.

You can download the latest software here. You can play with the slider controls and see how simple it is to customize the settings on your controller. You don't need to own the controller to download and experiment with the software.