In some cases, the electronic wrist watch, the alarm volume or voice warning about the current time may be insufficient. In this situation will help offer our readers a device that increases the volume of such signals.
Diagram of the device shown in the figure, its basis is USC on a specialized chip DA1. Mode constant current value is determined resistors R2 and R3, and the gain is the ratio of the resistors R5, R4 and is about 10. To the exit USC connected dynamic head of BA1, volume signal can be adjusted by the variable resistor R1.
To the wrist watch device is connected instead of or in parallel the piezoelectric sound emitter. If the case is metal, with him connect the common wire of the device.
The device incorporates resistors MLT or similar, variable resistor - SP-1, STRs JS4, capacitors C1, C4 - K10-17, oxide capacitors K50-35 or imported. IC TDA2030 interchangeable on TDA2040, dynamic head - any power 0,5...5 watts and voice coil impedance 4...8 Ohms, for example, 0.5 GDS-2, GDS-16. You can also use the speaker system with the appropriate resistance. Powering the device from a regulated source with an output voltage of 12 V, which provides load current up to 0.5 A.
All parts except heads, placed in the housing of a suitable size, using the hinged mounting. Correctly assembled device not establish requires.
Author: S. irgaliyev, Tashkent, Uzbekistan