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In this video I do the 11th project from the Maxitronix 20in1 (the Sensor Robot 20): Burglar Alarm.

This project uses the reed switch to trigger a bistable multivibrator that controls an alarm. The bistable multivibrator can be reset with the key. An astable multivibrator is used to generate the tone for the audible alarm.

In this project we get some more experience with transistors and how they can be used in various types of multivibrator circuit. Under the thermal camera we can see some of the transistors warming up as they conduct electricity. With the oscilloscope we can see the periodic waveform used to generate the alarm tone.

Note: while I was making this video I needed to make some banana plug to hook clip cables (so that I could test the reed switch). I made a video of my making those cables which you can see here: Electronics Project #9: Making Banana Plug to Hook Clip Cables | In The Lab With Jay Jay.

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Yum Cha KT-908 Digital Thermometer

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