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Scorpion XL Product Information 


The Robot Power Scorpion XL is a flexible high-performance two-channel speed controller for small robots in the one to twelve pound class. By using the latest automotive-rated power chips the Scorpion XL is able to offer features, power handling and load protection unprecedented in any controller of this size.

Robot Power,

As an online robot building club we are always finding products that work and sharing our findings. The Midwest region of R2 Builders started using the Scorpion XL over a year ago. Upon seeing one put to use I got one myself. WOW! I�m running two 100W Razor scooter motors off this thing and the control is dependable, fluid and smooth. The 24V scooter motors are being run at half voltage in my robot and friends are running theirs at full voltage, yet the Scorpion works just as well both ways. I also am impressed with the low amount of high pitched motor winding whistle noise from this unit�s low speeds, whereas other robots using different controllers with the same motors have a more annoying amount of audible pitch.

I love the BEC, I just charge my robot�s gel-cell battery bank and that�s it! No dying R/C receiver battery on a robot that has plenty of run time left.

Customer Craig from the USA

I purchased a Scorpion XL recently, and have just won a local robot tournament with it. It worked great, and was especially easy to install, and was not intimidating, even for someone fairly new to robotics. The control was excellent, to which I associate the majority my advantage in the competition. It's ability to easily calibrate and work right out of the package was also key. To everyone that asks I thoroughly recommend it, and deem it well worth the price, just by the extra features incorporated. (The flip switch saved my bot on a several occasions.)

Having done a massive amount of research for this project, I've come to realize the potential of this motor controller as a continually expandable device. I saw it mentioned on the website that there were possibilities for encoder support as well as other options for interface, specifically serial...

Overall, thanks for an awesome product, I'd recommend it to anyone.

Customer Andy B. from The USA

The Scorpion XL is designed for sumo robots, ant and beetle weight combat robots and other small robots such as firefighting robots, maze solvers and carpet rovers. It may be used on robots up to as much as 30 pounds or more as long as the motor current limits are respected.

The built-in drive and mixing functions allow an all-in-one solution for small robots previously unavailable at any price.


The Scorpion XL contains the following features:

  • Size: 2.7� x 1.6� x .5�
  • Weight: 28 grams with servo leads installed
  • Three R/C input leads for
    • Left and Right Drive - fully reversible H-bridge channels
    • Flip Control - reverses controls if robot is flipped over (optional)
    • Serial I/O - Flip input doubles as TTL serial I/O port
  • 4.8V to 28V battery voltage
  • 12.5A continuous current (45A peak) on each Left and Right drive channels. May be combined into a single 25A continuous forward/reverse channel. This is a real 12.5A rating i.e. you can put 12.5A through the output channels for several minutes with higher peaks for a few seconds
  • Full current limiting and over temp limiting. This thing is nearly blow proof!
  • Surface mount drive chips mounted on the bottom of the board for reliability and to reduce the size of the unit
  • Flip input reverses motor direction when the robot is inverted. May be operated via an R/C channel or via a mechanical (gravity) or optical etc. switch
  • 2 Indicator LEDs for Left/Right speed and direction. A status LED shows the R/C signal status and other information
  • Left/Right channel mixing is the default � many mixing modes are available set by jumpers
  • Receiver battery eliminator circuit (BEC) standard � may be disabled. This can provide up to 100 mA of current at 5V to the RC receiver and other attached electronic circuits.
  • Failsafe shuts off motors and weapon if R/C signal is lost
  • Calibration function to match Scorpion to your radio or other signal source - settings stored in EEPROM
  • FLASH-based microcontroller with upgradeable software via in-circuit programming header
  • Hardware support for I2C/SPI command interfaces
  • Hardware support analog current measurement and limiting
  • Hardware support for dual-channel quadrature encoders
  • Analog voltage feedback inputs built in

Scorpion XL back side

Optional Features

The Scorpion XL software is designed to work with most R/C systems out of the box. The most common options are set up as the default so no complicated configuration, calibration, or programming is required.

The following configuration options are available in the Scorpion software:

  • Mixing - by default the left and right channels are mixed. No external mixer unit is needed! This function allows one radio channel to be used as the "throttle" control and one as the "steering". This allows driving of differential drive robots in a natural and intuitive way using a single transmitter stick. For independent control of each output channel "Tank" mode is available. Tank mode is also suitable for programmed control by microcontrollers etc. which can do any needed channel mixing internally. The following mixing modes are available on the Scorpion XL as set by the "M" and "T" jumpers:
    • Left/Right Mix (default - right input acts as steering and left as throttle)
    • Mixed Mirror Left (left mixed output command sent to both output channels)
    • Mixed Mirror Right
    • Left/Right independent (Tank)
    • Mirror (both outputs mirror a single input)
  • Exponential - by default the steering response is linear in any mixed mode. Thus at 50% stick throw the output voltage will be set to 50% as well. With the exponential function the output response is related via an exponential curve to the input. This allows a softer response around the center point while still giving full power at the extremes of the control range. This setting helps when driving robots by eye as it makes control smoother when giving small control inputs. The mode is set by a jumper as shown above. Throttle response is always linear.

  • Flip - by default the flip function is controlled by an R/C channel. This allows easy control of the robot when running inverted or when driving backward in sumo or to present an alternate weapon to your opponent. The landing gear switch on an aircraft style radio or the 3rd channel on a pistol style are commonly used to activate this function. An alternative configuration is to use a binary signal to activate the motor flip function. In this configuration a switch is connected between the signal wire and the ground wire on the Flip R/C lead. When the switch is closed the flip function is activated. A logic level input from a microcontroller may also be used as long as the two units share a common ground wire.

  • BEC - the 5V regulator on the Scorpion XL is connected to the power wire on the servo leads by default. This allows the Scorpion to provide power to the R/C receiver and eliminates the need for an external R/C receiver battery. Cutting a jumper on the PC board disables this function and allows a separate 5V supply to power the R/C or master micro.

  • Calibrate - by placing a jumper on the proper pins during operation the Scorpion XL goes into calibrate mode. This mode records the range of values sent by the radio system or microcontroller signal source. Once the full range of values has been sent the Scorpion XL stores the values in non-volatile memory and retains them. It is also possible to reset the values to the factory defaults by entering calibrate mode with no signals present.

While the primary input mode of the Scorpion XL is the R/C interface, future versions of the Scorpion software will support a TTL serial and I2C interfaces for interactive command from PCs and microcontrollers such as the BasicStamp and others. Hardware support for analog and encoder feedback is built into the Scorpion XL. This allows it to be used in servo and other closed-loop applications. Contact us for details if you would like to use the Scorpion XL in a closed-loop application.

A Quick Start Guide for the Scorpion XL with details on setup and operation of the controller will be available soon from the downloads page. Contact us for any detailed questions about setup or use of the XL.

Robot Power offers the Scorpion XL in fully assembled units ready to install and use. Check the Web store for details on prices and special offers.

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