In Stock    Accel    Acceleration & Tilt  Sensor    $59.00                 .

This sensor has been tested with NXT using the Lego NXT conversion cable (W770323). With NXT the sensor should be read in raw mode.

The Accel Sensor lets your robot measure it's acceleration.  The sensor can also be used to measure tilt.  This is a two channel device that lets you measure acceleration or tilt along two perpendicular axis.

Acceleration is a change in speed.  When you push the gas pedal of a car, and the car speeds up, this is acceleration.  I.  The Dual Acceleration/Tilt Sensor (Accel) measures acceleration by it’s effect on a small mass.  The sensing mass is also affected by gravity.  Because of this, the sensor can be used to measure gravity.

Gravity is constant, and points straight down.  Since the Accel sensor can measure gravity, you can use it as a tilt sensor.  The sensor is most sensitive to tilt when it is mounted so the sensing channels are perpendicular to gravity.  (the electrical connector is horizontal)  When mounted this way, the light sensor value will be 50, indicating zero acceleration.  The value will increase or decrease depending on the direction of tilt.
 
 

         Accel Sensor.
 

       Mounting the sensor.

You program the Accel Sensor just like the Lego light sensor.  Use the Light Sensor block in the Mindstorms program environment to cause program branches.  Remember this is a two channel product.  It is normally connected to two separate sensor inputs on the RCX.  You can use only one channel if you want, but it must be channel #1.

Dave Astolfo has written a review of this sensor and how he used it to build a balancing robot.

The Accel sensor must be programmed as a light sensor.
With zero acceleration, it has a RCX light sensor value of 50.  With one “g” (one gravity) of acceleration in the forward direction, the output will be around 90.  One “g” in the reverse direction will give an output around 10.  The sensor response is linear.

Specifications

• Size: 2 bumps by 4 bumps.  Height is one and one third bricks.  (one brick plus one flat plate)
• Size:  1.25 x 0.625 x 0.575 inch.
• Split Mindstorms electric plate connector on bottom.  (Two separate connectors)
• Range: + /- 1.1 g.  (gravity)
• Power required:  8.2 volts,  7 mA.     (Minimum Mindstorms battery voltage)
• Bandwidth:  50 Hz.

The sensor element is a micromachined polysilicon structure suspended over a silicon wafer by polysilicon springs.  The structure forms a differential capacitor with the wafer below.  Acceleration causes movement of the suspended structure relative to the wafer, and thus a change in capacitance.  The capacitance is measured and converted to an output to the RCX.  The sensor achieves high reliability in a small package by using surface mount parts using a reflow solder process.  A picture of what is inside the sensor is about 50K bytes.