Quartz timekeeping commercial music has two drawbacks: First, to point it as long as the night the music loud sound and RBI timekeeping sound affects people sleep, the second is the use of large batteries to power consumption. The quartz clock power supply circuit shown resolve this problem. How it works: power supply circuit as shown quartz timekeeping, 220V AC voltage by the step-down transformer T, the diode bridge rectifier VD1 ~ VD4, C1 obtained after filtering the DC voltage of about 3.6V, all the way through transistor VT1, consisting of light-emitting diode LED After the regulator output DC voltage of about 1.5V for quartz clock supply voltage within the travel time, and the other after passing switch IC TWH8778 for quartz clock circuits within the RBI's timekeeping to provide 3.6V power supply voltage. During the day when the light shines into the phototransistor when VT2, VT2 and showed low resistance conduction, so the integrated switching circuit TWH8778 potential higher than 5 feet 1.6V, TWH8778 conduction, 2,3 there is a voltage output pin, quartz clock circuits within the RBI's timekeeping power is on, or the slightest as long as the whole point, the speaker will be issued in the sound of loud music timekeeping and RBI sound. But in the evening, no light and cut-off due to VT1 was high resistance, TWH8778 potential of 5 feet below the 1.6V, TWH8778 deadline, 2,3 no voltage output pin, then even to the point, the speaker does not give any sound. Component selection: switch IC IC by TWH8778. Phototransistor VT2 use 3DU5, VT1 use 3BX31, tunneling current as possible. Diode VD1 ~ VD4 use 1N4001; use an ordinary red LED light-emitting diode LED round. 100kO resistor Rw use semi-variable resistor. Transformer T to be made, by GE12-type core, an area of 12mm × 18mm, the primary use of F0.12mm tightly wound 11,000 turns of enameled wire, enameled wire secondary with F0.47mm tightly wound 150 turns, if not the core, can also be power 3W , sub-3V power transformer maintenance of small tape recorders, then the volume and power consumption will increase.
