This is a sensor module containing a microswitch that is always ON. When the operating arm of the microswitch is depressed (eg, by coming into contact with an obstacle) it turns OFF It is an INPUT device.
How does it work?
The secret of a microswitch is that a metal common contact is moved at high speed between two other contacts by using a very small force on a pre-loaded spring that forms the common contact.
As the picture below shows, in the idle, or normal state, the common contact is completing the electrical circuit between pin 1 (digital signal) and pin 2 (Vcc – the Kookaberry’s operating voltage). The Kookaberry interprets this as “ON” condition.
When the lever arm is depressed the common contact moves from pin 2 to pin 3 which is ground and removes the Vcc voltage on the signal wire. The Kookaberry interprets this as “OFF” condition.
A red LED lights up on the crash sensor when the lever arm is depressed and the circuit is opened.
Where are these switches used in real life?
Microswitches are used in control circuits everywhere. Some applications are
- Levelling and safety switches in elevators
- Door interlock on a microwave oven
- Vending machines
- Detect paper jams or other faults in photocopiers
- 3D Printer position feedback, etc…
Why is this microswitch called a crash sensor?
Imagine that it is mounted right at the front of a moving platform (like a model or real car) so that the first thing that makes contact when it get close to a wall or obstacle is the lever arm.
Now imagine that the power to the platform motor is dependent on the state of the crash sensor. Whilst the sensor is in its idle state (ON) the motor is ON. When the arm is depressed it is OFF.
That is why it is called a crash sensor……
How can the crash sensor be used to enhance lesson plan outcomes?
- To demonstrate the operation of a Burglar Alarm: Use the crash sensor as a digital input to the Alarm app to trigger an alarm when a box, drawer, window or drawer is opened. Fasten the crash sensor to the lid of a cardboard box using a VelcroDot or BluTac
- Control of a vehicle: Set up a Kookaberry and a crash sensor on a powered wheeled or tracked platform and either use or adapt one of the pre-coded apps (or code a new one) to make the platform avoid obstacles. Control can be either a simple ON/OFF of the motor(s) or a reversal of power to make the platform reverse backwards for one or two seconds; turn either left or right 90 degrees; and then continue. IMPORTANT: Use the crash sensor to control the motors of the platform though a separate power control circuit. Current flowing through peripheral circuits should always be less than 100 milliamps