Published 07/02, Copyright 2002 ,

Controller Lingo:
Understanding the brain-box behind your powerchair
-Mark E. Smith

Offering finite control over one's mobility, electronics controllers (also known as power modules), are among the most vital and complex powerchair components - after all, they are the brains behind your powerchair.

Integral and Remote Controllers:
Put simply, the controller is the central processing unit of a powerchair, accepting joystick input and directing it to the motors.  Controllers come in two forms, "remote" and "integral."  An integral controller features the joystick and controller in one housing.  In years past, integral controllers were identified as very large joystick housings protruding from an armrest, and featured fewer programming options than a remote.  However, in recent years, integral controller technology has dramatically improved, to the point where some are comparable in size and features to remote controllers.

Remote controllers feature separate controller and joystick modules, connected by a wire, allowing the controller to be mounted underneath a body shroud or seat, while the compact joystick housing remains on the powerchair's armrest.  Most remote controllers have advanced programming and accessory capabilities, allowing you to operate power seating systems and lighting packages via the joystick.

In today's marketplace, there's no clear-cut choice as to which is a better system, integral or remote electronics.  If you use specialty controls like Sip-N-Puff or a head device to drive your powerchair, remote electronics will be needed due to complex interfacing.  Otherwise, for most users whom use standard joystick controls, the choice between integral versus remote controllers may merely be one of aesthetic and price, as both offer similar performance and features.

Profiled and Non-Profiled Programming:
Controllers feature programming parameters, allowing customization of handling characteristics such as acceleration, turn speeds, deceleration, and so on.  The way in which the programming is configured within the system is via two forms, "profiled" and non-profiled.  Profiled programming means that the controller allows each drive mode to be programmed individually, so that mode 1 can have entirely different program settings than mode 5.  Profiling is meaningful in that a powerchair's handling can be fully optimized toward a wide range of driving conditions, from indoor to outdoors.

Non-profiled electronics features a single set of programming parameters that are applied to all driving modes, with the only variation being top speed.  Mode 1 through 5, for example, may all use a single 50% acceleration program setting (by comparison, a profiled controller may have acceleration settings of 25% in mode 1, 35% in mode 2, 45% in mode 3, 60% in mode 4, and 80% in mode 5).  For slower, less aggressive powerchairs, non-profiled programming works well, allowing a single set of customized program settings.

Programming Parameters:
Changing the program settings in a controller can customize your powerchair's handling characteristics, better meeting your needs.  There're no less than a handful of controller brands on the market, with varying programming parameters; however, there is basic programming terminology, and knowing the defined parameters may help toward optimizing your powerchair:

Acceleration:  Adjusts the speed and force at which a chair accelerates in forward and reverse.  The higher the value, from 0 to 100, the more acceleration.  Some powerchair manufacturers limit the settings range.

Deceleration:  Adjusts the chair's breaking distance when the joystick is released in forward and reverse, from 0 to 100.  The higher the value, the quicker the chair stops.

Turn Acceleration:  Adjusts the acceleration of a chair when a turn is initiated.  The higher the value, from 0 to 100, the faster the chair accelerates into a turn.

Turn Deceleration:   Adjusts how quickly a chair stops turning when the joystick is released.  The higher the value, from 0 to 100, the faster the chair stops.

Forward Speed:  Adjusts the chair's top speed in the forward direction.  The higher the value, from 0 to 100, the faster the chair travels forward.

Reverse Speed: Adjusts the chair's top speed in the reverse direction.  The higher the value, from 0 to 100, the faster the chair travels backward.

Turning Speed:  Adjusts the maximum and minimum speed at which the chair spins in a circle, adjusted from 0 to 100.  

Controller Amperage Dynamics and Fold Back Conditions:
Amperage relates to powerchairs in a similar way as horsepower relates to automobiles - the higher the amperage rating within a controller, the more torque a powerchair has to overcome obstacles.

The way amperage draws work is based on the demands placed on a powerchair.  A typical powerchair draws between approximately 15A  to 30A, where 15A may be cruising on a flat street at full speed, and 30A may be turning from a dead stop on thick carpet (specific powerchair models and configurations may vary from this generalized example).  As power demand increases, the amperage increases, for example, climbing a very steep hill may demand 50A or more. If enough strain is placed on the powerchair, such as stalling the wheels against a curb, it will reach its peak output (this is the 50A, 70A, 80A, or 100A controller ratings that manufacturers advertise).  The peak output, however, is not constant, usually only lasting 5- to 15-seconds, at which time the controller "folds back" to a lesser amperage - say, 50A on a 70A controller - to protect itself from overload.  Similarly, "thermal fold back" reduces power if prolonged high amperage draws occur, protecting the controller from overheating (this is the occurrence described by many users when they are offroading and suddenly lose power - the system is protecting itself from heat due to long demands for high amperage).  

Whether fold back is time or heat related, allowing the chair to sit and cool or operate under reduced strain will allow the system to return to normal operation.  However, if strain on the powerchair continues, fold back will continue, causing the chair to operate at reduced power. Additionally, hot summer air temperatures and a user weight bordering on a powerchair's maximum capacity may increase the likelihood of fold back.  Users sometimes find their powerchairs in fold back, and attribute it to overheating motors, but it's almost always a function of the controller, as most electrical systems are designed for the controller to reduce power at a temperature or sustained amperage level well below the motors' tolerance levels.

Controller Amperage Ratings:
Integral controllers commonly range between 50A and 70A, whereas remote controllers commonly feature a range from 70A to 100A, depending on the model of controller.  Controller amperage ratings are peak output, meaning that a 70A controller will run, again, during everyday use at approximate levels between 15A and 30A, with momentary spikes up to 70A to meet power demands.  As a rule of thumb, if you are a frequent outdoor user, a 70A or greater controller rating is recommended; however, for light-duty powerchairs, a 50A controller may be entirely appropriate.  

While we often look for sleek lines and sexy MPH numbers when considering a new powerchair, the most important aspects of a powerchair - its power! - is often overlooked:  The black box tucked under the seat, or joystick housing on the armrest, known as the controller, may make all the difference toward a powerchair's performance.

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