The NXT Force Sensor will enable you to build robots that can measure a physical force applied through a LEGO cross axle. The sensor has a LEGO cross axle receptacle and the value represents the force that is applied to an axle going into the sensor. Note that the force measured is the linear force going into the sensor.

This sensor can be thought of as an analog touch sensor. Unlike a touch sensor, which gives just a binary value indicating pressed or not-pressed, this sensor gives you a numeric value based on how hard the axle receptacle is pressed.

Note: The sensor value does not directly translate into force. With calibration the value can be used to determine the approximate weight of an object. Build the sensor into your robot so that the the weight of the object becomes a force pressing into the sensor. Now the sensor value can determine the weight of the object.

The HiTechnic Force Sensor measures the force applied to the cross axle receptacle and converts it into a signal that can be used by the LEGO Mindstorms NXT. The force can be read using LEGO Mindstorms NXT Software Force Sensor Block. When using other programming languages, the Force Sensor can be read as though it is a LEGO Light Sensor.

The sensor measures the force applied by a LEGO axle being pressed into the sensor as shown by the arrow below.

magnetic sensor

The chart shows the sensor value relative to the force applied, in grams, to the sensor.

Programming

Mindstorms NXT-G

The Force Sensor can be programmed using LEGO Mindstorms NXT-G Software by importing the Force Sensor Block. This and other HiTechnic sensor programming blocks are available from the downloads page.

The Force Sensor Block provides access to the sensor output in addition to other features.

The number shows which of your NXT's ports are connected to the Force Sensor. You can change this number in the configuration panel if you need to.
The block's data hub will open automatically when the block is placed in the work area. At least one data wire must be dragged from the block's output plug to another block's data hub.

Configuring the Force Sensor Block

The sensor may be connected directly to an NXT sensor port or via the HiTechnic Sensor Multiplexer (MUX). When configuring the sensor via the multiplexer, there are two port selections to make. The first is the NXT to MUX connection and the second, the MUX to SENSOR connection.

Other Programming Environments

The Force Sensor is an analog sensor like the LEGO Light Sensor. Therefore the same way you read the LEGO Light Sensor can be used to read the Force Sensor value.

Downloads

HiTechnic Force Sensor Block

HiTechnic EV3 Analog Sensor Blocks