Use Y976 to make light-controlled flashing warning lights

The light-controlled flashing warning light circuit made with Y976 is shown in Figure 3-46. The circuit is mainly composed of novel alarm integrated circuit
Y976 and photoresistor RG and other components.
    Y976 is a CMOS alarm integrated circuit in a standard 8-pin dual-row plastic package. The function of each pin is shown in Figure
3-47. Pin 1 is the output terminal OUT, which can directly drive the speaker to produce sound without the need for an external power amplifier transistor; Pin 2 and pin 3 are
the alarm mode selection terminals, which can be grounded or left floating to obtain different alarm sounds: pin 4 is the ground terminal Vss; pin 5 is the function
control input terminal. When connected to a logic low level , the circuit does not When working, the circuit can work normally only when connected to a logic high level;
pins 6 and 7 are the external oscillation resistor terminals; pin 8 is the positive terminal of the power supply VDD. This warning light mainly uses its output terminal OUT to directly drive
the thyristor to work, and uses its 5-pin and photoresistor RG to form a light control circuit.
    In Figure 3-46, VD1, VD2, c] and C2 form a simple capacitor step-down half-transition rectification and voltage stabilizing circuit, which outputs
a DC voltage of about 6V for power supply to Y976. The potentiometer RPI, the photoresistor RG and the 5-pin of the integrated block form a light control circuit
. During the day, RG is exposed to light and has low resistance, so the function control input terminal EN of the integrated block is at a logic low level, the integrated block
does not work, and vs is off. off, the warning light H does not light up. When night comes, RO has high resistance when exposed to no light, and pin 5 of the integrated block is at
a logic high level . Pin l outputs a square wave pulse-shaped alarm sound signal and directly adds it to the control electrode of vs, so that the vs is
open and connected. cut off, so the lamp H flashes.
    Adjusting the potentiometer RPI can change the light control sensitivity of the circuit, making the circuit
H flash and glow under the illumination required to alarm. Adjusting the potentiometer
changes the resistance of the external oscillation resistor of the integrated block, so it can change
the frequency of the output pulses of the integrated block, that is, change the flashing frequency of the warning light H.