Lesson 010 – Burglar alarm
You need:
iTriangle online, 4 in 1 sensor, buzzer
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4 in 1 sensor |
Buzzer |
Introduction:
An accelerometer is a sensor that measures how quickly an object moves from its rest position. The 3-axis accelerometer can simultaneously measure acceleration values in the x, y and z axes. An accelerometer can be used to construct a motion vector, i.e., the direction of movement in space and the acceleration value in the given direction. Acceleration is reported in units of G, which is the acceleration due to gravity. For humans, acceleration or deceleration of around 20G will result in internal organ damage and death.
Task:
Learn how a 3-axis accelerometer works. Use a long cable to connect the accelerometer to iTriangle online so you can move the 4 in 1 sensor away from the rest of the construction. Construct a movement detector and use it as a safety module to detect the movement of the object it is attached to.
Tutorial:
Step 1
- Construct a simple stand with iTriangle online and connect the sensors and components as pictured below. Connect iTriangle online and upgrade its firmware by following these steps.
- Choose an object you want the PIR sensor to detect.
- Start the graphical measurements.
- Try to move the sensor each time along one axis so that the measured value is constant – the acceleration along the given axis is constant. Another option is to move the sensor so that the acceleration value is zero – the speed is constant.
- What is the difference in sensor movements along different axes and at different speeds?
Step 2
- Re-use the stand and settings from the previous step.
- Attach the iTriangle online to an object of your choice that you want to have an alarm (cars usually have these alarms against burglars).
- Start the program (you can set limit values for the buzzer to start making noise – make sure it's not too low or high, some tweaking with the limit numbers might be needed)
- Challenge others to move your object from one place to another and hope that you set the alarm correctly!
Extra mile:
Place the sensor at rest in one place. If the value along one or more axes is non-zero, why? What is the value of the acceleration / negative acceleration (deceleration) you get by clapping your hands with the sensor in one of them?
Construct a movement detector and use it as a safety module to detect the movement of the object it is attached to.
Examples of good practice:
Technical notes:
The z-axis extends vertically upwards, the x-axis extends lengthwise from the connector across the sensor plate and the y-axis extends perpendicular to the x-axis along the description on the printed circuit board. Axis orientation is indicated on the printed circuit board for the following sensors: magnetometer, accelerometer and gyroscope.
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