Breakbeam Detector and Alarm Circuit Kit
If you’re a fan of making your own spy kit, then here’s another kit for you. The MK120 Infra-red (IR) breakbeam detector kit allows you to construct a gadget that sounds an alarm when the IR beam is broken by someone walking between the transmitter and the receiver unit.
The transmitter unit creates a pulsed beam of infra-red light that is detected by the matching IR receiver. When the receiver stops receiving the signal, the buzzer on the receiver sounds loudly. You typically put this device in a doorway or narrow corridor so that the beam is broken by someone walking through the beam. You see this sort of thing in with laser tripwires in the Hollywood movies too.
The range of the transmitter is between 1 and 4 metres. The kit requires soldering skills and comes with all components, but does not come with power supplies or enclosure boxes. You can easily power the devices from a 9V battery though. The MK120 kit is easy to obtain, either from Maplin in the UK or Apogee in the US.
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