Description

12-Magnet PAS Sensor for Electric Bikes – Split Disc Cadence Sensor for eBike Conversion Kits

Name: PAS Pedal Assist Sensor for E-Bike Conversion Kits
Brand: All4ebikes
SKU: 25

Cadence PAS (Pedal Assist Sensor) with 12 magnets and split disc — the standard component included in All4eBikes MTX conversion kits. Detects pedal movement at approximately 15 degrees of rotation and sends a signal to the controller to engage motor assistance. Split disc: no crank removal required for installation. 1.2m cable, 3-pin connector, compatible with all UART controllers in the All4eBikes range.

12 Magnets Split Disc 1.2m Cable 3-Pin 15° Response UART Compatible

The cadence PAS sensor is the dominant type in conversion kits — simpler, more robust and easier to replace than torque sensors. It works by detecting the rotation step of the crankset: the 12-magnet disc mounted on the bottom bracket axle passes the sensor head fixed to the seat tube, generating pulses that the controller interprets as a pedalling signal. With 12 magnets, the sensor detects movement after approximately 15 degrees of rotation — significantly faster response than 5 or 8-magnet sensors.

12-Magnet PAS Sensor Technical Specifications

Technical Parameters

Sensor typeCadence (Hall)

Number of magnets12

Disc typeSplit (2 halves)

Motor response~15° rotation

Sensor-to-magnet gap1–3mm optimal

Cable length1.2m

Connector3-pin standard

Operating voltage5V (from controller)

LED indicatorYes (signal check)

Compatibility

Controller protocolUART / KT standard

Controller 17A–60ACompatible

Kit 250W–3000W MTXCompatible

Crankset typeSquare taper / BSA

BB shell width68mm / 73mm

InstallationNo special tools

Pedalling directionForward (reversible)

Compatible Kits

250W MTX KitIncluded / Compatible

500W MTX KitIncluded / Compatible

1000W MTX KitIncluded / Compatible

1500W MTX KitIncluded / Compatible

2000W MTX KitIncluded / Compatible

3000W MTX KitIncluded / Compatible

Why 12 magnets and not 5 or 8

The number of magnets determines how quickly the motor responds when you start pedalling. With 5 magnets, the motor engages after 30–40 degrees of rotation — noticeable as an initial lag. With 12 magnets, response reduces to approximately 15 degrees — almost immediate. At the same pedalling speed, the 12-magnet sensor generates 2.4 times more pulses per second, providing a more stable and precise signal to the controller.

Split disc — installation without removing the crankset

The magnet disc comes in two halves that clip around the bottom bracket axle without removing the crank arm or crankset. Installation takes 10–15 minutes with standard tools (screwdriver, zip-tie pliers). The sensor head is fixed to the seat tube with the included plastic zip ties, at 1–3mm from the magnet disc for optimal detection.

LED indicator — visual signal confirmation

The sensor head has a built-in LED that flashes each time a magnet passes. This allows quick field verification: if the LED flashes regularly when pedalling, the sensor is detecting correctly. Note: the LED being lit does not guarantee correct wiring — also check the wire order at the connector (GND / VCC / signal).

Direction note: if the motor engages when pedalling backwards but not forwards, flip the magnet disc over. This reverses the detection direction without changing anything else.

What It's Recommended For

Failed Sensor Replacement

A direct replacement for the PAS sensor in any All4eBikes MTX conversion kit 250W–3000W — same 3-pin connector, same protocol.

Upgrade from 5 to 12 Magnets

A quick upgrade for existing systems with a 5 or 8-magnet sensor — faster motor response at the start of pedalling, more stable signal at low speeds.

DIY eBike Builds

An essential component for any DIY build with a UART controller from the eBike parts range — compatible with all 17A–60A controllers.

Installation and Troubleshooting

Installation Steps

Clip the two disc halves around the bottom bracket axle
Fix the sensor head to the seat tube with the included zip ties
Adjust the sensor-to-magnet gap to 1–3mm
Connect the 3-pin cable to the PAS port on the controller
Check the sensor LED when pedalling before first ride
If the motor engages when pedalling backwards, flip the magnet disc

Common Troubleshooting

Motor does not engage when pedalling — check sensor-to-magnet gap (max 3mm)
Delayed assist — gap too large or magnets misaligned
LED does not flash — check wire order at connector (GND / VCC / signal)
Motor engages when pedalling backwards — flip the magnet disc
Inconsistent assist — check that the disc does not vibrate when pedalling

Frequently Asked Questions About the PAS Sensor

What is the difference between a cadence PAS sensor and a torque sensor?

A cadence sensor (this product) detects whether you are pedalling and how fast, providing consistent assist at a selected PAS level regardless of how hard you push. A torque sensor measures the force applied to the pedals and modulates assist proportionally to your effort — a more natural feel but significantly more expensive and complex to install. For standard conversion kits, the cadence sensor is the practical, reliable choice.

Can I install the PAS sensor without removing the crankset?

Yes — the split disc clips directly onto the bottom bracket axle without removing the crank arm. You only need a screwdriver and zip-tie pliers for the plastic clips. Full installation takes 10–15 minutes.

Is it compatible with All4eBikes MTX kit controllers?

Yes — all All4eBikes MTX controllers (17A to 60A) use the UART protocol and have a PAS port with a 3-pin connector directly compatible with this sensor. The sensor is in fact included as standard in all 250W–3000W kits.

How far should the sensor be from the magnet disc?

The optimal gap is 1–3mm. Under 1mm there is a risk of physical contact between disc and sensor. Over 3mm the signal becomes weak or intermittent. Check the gap after tightening the zip ties — pedalling vibration can shift the sensor position during the first few rides.