Production of wake-up device

The wake-up device is installed in the base of the toy bird and placed on the balcony at night. When the photosensitive device is exposed to light in the morning, the toy bird will make bursts of bird calls, calling people to get up quickly. VT1 is a photosensitive transistor, which together with resistor R1 forms a light-controlled circuit; VT2, oscillation transformer T and some resistor-capacitor components form an intermittent inductor three-point oscillator. The oscillator frequency is determined by the transformer primary coil inductance and capacitor C3, which is about 1000Hz; the intermittent frequency is determined by the R2, C2 charging and discharging circuit, which is about 1Hz5Hz. When there is no light, VT1 is cut off, VT2 is cut off due to the lack of base bias current, the circuit stops oscillating, and the speaker is silent. When light shines on the window of the photosensitive transistor VT1 after dawn, the leakage current (photocurrent) of VT1 increases sharply, that is, the base bias current of VT2 increases sharply, so the circuit starts to oscillate, generating intermittent audio oscillation signals, which are coupled to the speaker through transformer T, and emit intermittent bird-like sounds.

Component selection: VT1 is currently generally selected to be a 3DU type NPN phototransistor with a photocurrent greater than 1mA. VT2 is selected to be a 9014 (3DG6 can be used instead) transistor, β≥60. R1 is selected to be a RTX-0125/30kΩ carbon film resistor, and R2 is selected to be a RTX-0.125/3kΩ carbon film resistor. C1 is selected to be a CL, 0.22μF/63V coupling capacitor. T is selected to be a push output transformer for transistor radios; B is selected to be an 8Ω/0.5W speaker.