Sirens and Sound

K15 - 6 to 12V Piezo Screamer Price Photo Docs
Powerful 9V to 12V piezo alarm. Uses 556, auto-transformer and two piezo alarm elements. Circuit will deliver 108-110dB at 1M. Uses sweep circuit so there is no need to trim the circuit to match the cavity resonant frequency. We supply a plastic box with two piezo elements (35mm diameter) already mounted in their own resonant cavity. This is part of a commercial alarm unit but it uses our (better!) drive circuit. Ideal alarm unit for Kit 53.

K31 - 9V Siren Price Photo Docs
A surprisingly loud siren for such a simple circuit. Uses voltage controlled oscillator. 1/2 Watt, 8 ohm speaker supplied. 9V operation. Ideal to attach to an alarm system which needs an sound module.

K104 - Music Box Engine Price Docs
The electronic equivalent of a mechanical music box. Tunes are contained in an M3481 IC - click here for datasheet. It is activated by light falling on an LDR. It then plays a range of tunes. The kit can be placed anywhere you want to hear a tune when light shines on it; opening a cupboard or drawer, music box. Two music ICs and all components, including speaker, provided.

K126 - Mini-VOX and relay Price Photo Docs
VOX stands for "voice operated switch". Basically this kit picks up audio via a microphone input, amplifies it and uses it to operate a relay. Sensitivity can be adjusted by an onboard trimpot. Use it to give you hands-free control of things like tape recorders, lights, sirens, etc. Relay contacts rated ar 12/24VDC @ 1A. Based on a circuit published in Silicon Chip, Sep 1994, p31