electronic mouse trap

Posted on Feb 5, 2014

This circuit uses a conventional spring loaded mouse trap, available from hardware stores. However when a mouse is caught, the circuit triggers and transmits an interrupted tone on the commercial FM band to a nearby radio receiver. This circuit is a small battery powered transmitter which is activated by vibration from a mechanical mouse trap. Thi

electronic mouse trap
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s can be done using a microswitchpositioned so that the circuit is off (not transmitting). When the mouse trap is triggered the microswitch lever is moved and activates the transmitter. The transmitter is a standard hartley oscillator, designed to transmit across the FM band approximately, 87 to 108MHz. The transmit frequency is adjustableby means of trimmer C8. The combined capacitance of C4 plus C8 and L1 set the resonant frequency. IC1 is a CMOS quad 2 input AND gate. Gates U1a and U1b create a square wave astable oscillator ofabout 2Hz. The output of gate 1b is wired tothe input of gate 1c. Similarly gates 1c and 1d form another astable oscillator, this time about 2kHz. The 2kHz oscillator is activated only whengate 1b is high, all gates forming and interrupted oscillator. The tone of this oscillator is adjustable via the preset R2. The output of the oscillator now directly drives the transmitter comprised of Q1 and associated components. The transmitter will be on when the output fromgate 1c is high and off when gate 1c is low. As the input signal is a sqaure wave, there will be some cross modulation and the transmitter signal willbe heard at more than one point across the FM band. As the output power is limited, this is not really a problem and with just 5 inches of wire as anantenna, I could hear the transmitter with an ordinary radio 15 metres away. The antenna is connector to Q1 collwctor and will work with just a...

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