The RPM limit assembly is:

 A motor speed feedback + position tracking mechanism
used by the DorRoller 45 controller to determine:

• When the door is fully open
• When the door is fully closed
• How fast the motor is rotating (RPM feedback)
• Whether the door is moving correctly

It works together with the controller’s electronic limit system.

From DorRoller 45 specs:

• The system has “accurate limits” and electronic control features
• Limits are set electronically and stored in the controller logic

What it actually consists of

The “RPM limit assembly” is usually made up of:

 Motor rotation sensor (RPM pickup)

• Typically a Hall-effect or magnetic sensor
• Reads motor shaft rotation
• Generates pulse signals (RPM feedback)

 Reference mechanism

• Gear, magnet ring, or encoder disc
• Fixed to motor shaft or gearbox
• Creates repeating signal pattern

 Limit reference system (electronic memory side)

• Controller stores:
  • Open position count
  • Close position count
• Uses RPM pulses to “count travel distance”

How it works in the DorRoller 45 system

So instead of physical limit switches, it uses:
electronic counting of motor revolutions

Why RPM is used for limits

Unlike older systems with end switches, the DorRoller 45 uses:

• Electronic limit setting
• Soft start / soft stop
• Obstacle sensing

This requires:
Continuous RPM feedback to know exactly where the door is

From system features:

• “Soft Start Soft Stop”
• “Accurate Limits”
• “Obstacle sensing feature”

All of these depend on the RPM feedback loop.

Key technical characteristics

While Dortech does not publish a separate part sheet, the assembly typically behaves like this:

Electrical

• Low-voltage sensor system (5V–24V logic)
• Pulse output (digital signal)

Signal type

• Square wave pulse train
• Frequency = motor speed (RPM)

Mechanical interface

• Mounted on:
  • Motor shaft OR gearbox housing
• Coupled via:
  • Magnet ring / encoder wheel

How limits are actually set

The system does NOT use physical limit screws like older motors.

Instead:

Programming process:

1. Motor runs to fully open position
2. Controller records RPM pulse count
3. Motor runs to fully closed position
4. Controller stores second reference point
5. System calculates full travel range

This is why it is called:
“electronic limit setting system”

Failure symptoms (very important in real use)

If the RPM limit assembly fails:

Typical symptoms

• Door runs but does NOT stop correctly
• Door overshoots open/close position
• Stops mid-travel randomly
• “No limit set” or similar fault behavior
• Motor runs continuously without reference

Root causes

• Faulty RPM sensor
• Broken encoder magnet ring
• Loose wiring to control PCB
• Controller not receiving pulses

Testing method (field check)

Quick diagnostic:

1. Check motor rotation manually (service mode)
2. Measure sensor output:
   • Should show pulsing voltage on multimeter/oscilloscope
3. If motor turns but no pulses:
   RPM assembly is faulty