Vision health light meter three

Circuit Operation Principle The vision health photometer circuit consists of a photometric circuit, an ultra low frequency oscillator and an LED indicating circuit, as shown in Figure 9-67.

The photometric routing photoresistor RG, the resistor Rl, R2, the NAND gate integrated circuit IC (DI-D4), and the photometric/healthcare selection switch S2 are composed.
The ultra low frequency oscillator consists of the internal NAND gates D2, D3 (connected to the NOT gate), resistors R3, R4, potentiometer RP and capacitor C.
The LED indicating circuit is composed of the NAND gate D4, the resistors R5 and R6 and the light-emitting diodes VL1 and VL2 inside the IC.
Turn on the power switch S1, and the whole machine is energized. When S2 is placed in the "1" position, the circuit is in the metering state, and the ambient light is detected by RG. The resistance of RC varies with the intensity of the light.
When the ambient light is weak and the read/write requirements are not met, the resistance of RC is large, so that the input terminals of NAND gates D1 and D2 are low level, the output terminal is high level, and the output of NAND gate D3 is low. Ping, NAND gate D4 also outputs low level, red LED VLl lights up, indicating that the ambient light is too dark, should turn on the light to increase the light.
When the ambient light is suitable for reading and writing, the resistance of RG is small, so that the NAND gates D1 and D3 output low level (D2 output high level), the NAND gate D4 outputs a high level, and the green light emitting diode VL2 lights up. Indicates that ambient light is suitable for reading and writing.
If the ambient light is too strong, the resistance of RG becomes very small, so that the NAND gates D1 and D2 both output a low level, and D3 outputs a high level, so that D4 outputs a low level, and VLl lights up.
When S2 is placed in the "2" position, the ultra-low frequency oscillator oscillates, and the generated lHz oscillation signal is amplified and shaped by the non-wide D4, so that VL1 and VL2 alternately flash, "the user's eyeball follows VLl and VL2. Rotation of the luminescence and regular rotation can make the eye muscles rhythmically relax and contract, and achieve the effect of preventing myopia and correcting false myopia.
Adjusting the resistance of the RP can change the oscillation frequency of the ultra-low frequency oscillator.
Component selection
Rl-R6 uses 1/4W metal film resistor or carbon film resistor.
RG selects a photoresistor with a light resistance less than lkΩ and a 睹 resistance greater than 1MΩ.
The RP uses a small synthetic carbon film potentiometer or a variable resistor.
C selects an aluminum electrolytic capacitor with a withstand voltage of 16V.
Both VLl and VL2 use φ5mm ordinary light-emitting diodes (one for red and one for green).
IC selects CD401l or CC401l, MCl401l type NAND gate integrated circuit.
S1 uses a small single-pole toggle switch; S2 uses a bipolar dual-position band switch.
GB uses 4 AA batteries or a small DC regulated power supply.