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Incremental encoder ideal for low speed applications

06 April 2016

Rotalink is developing innovative, low-cost and user friendly motion control solutions for OEM’s and machine builders.

Rotalink’s incremental dual channel encoder is available across its range of modular brushed DC motors and gearboxes and is proving to be successful in numerous positioning applications. 

The addition of the incremental encoder, usually sandwiched between the motor and gearbox, provides the ability to position components with an accuracy limited only by the 2º backlash of the gearbox. The original purpose of the encoder was specifically to offer closed loop control and provide users with the benefit of feedback from the gear motor, where normally this would be impractical due to cost.  

Whilst the addition of an incremental encoder is unable to match the precision of a micro-stepping stepper motor, it is proving to be highly effective in a wide range of low-speed applications. These are typically those requiring speeds below 100rpm, where a brushed DC motor and gearbox achieve more torque than a stepper motor of the same size. 

One of the most common uses is precisely controlling the speed of a peristaltic pump, and hence the amount of fluid it dispenses. Without the encoder, the varying tolerances in motor output and wear in the pump tube can cause gear motor speed to vary by as much as 15 percent and so compromise pumping accuracy. Other examples of low speed applications include positioning rotary valves in water softeners, transferring filters from cinema projectors, panning CCTV cameras and positioning a chute in a cash dispenser. 

The encoder can also be used for basic closed-loop positioning and whilst is still requires a single limit switch, it has the ability to move to multiple positions as opposed to between two extremes defined by a pair of limit switches

Although this is not uncommon, a highly streamlined assembly process combined with the fact that Rotalink is also manufacturing the gearbox, results in lower cost.  

The incremental encoder offers a range of output options up to 48ppr, is available in single or dual channel configurations and size variants of 28, 42 and 52mm. This layout provides a ‘sandwich’ mount between the standard Rotalink single shaft DC motors and gearboxes which provides the dual benefits of protecting the encoder and making very efficient use of space. It features a capacitance design based around a custom ASIC with internal amplification, can directly drive TTL logic, is designed to operate over a wide range of temperatures and is unaffected by external magnetic forces. 

There is also the facility to use the dual channel encoder with Rotalink’s Red Drive programmable controller for more complex control applications.  


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