Automatic hand dryer three

Circuit Operation Principle The automatic hand dryer circuit consists of a power supply circuit, a light control circuit, and a control execution circuit, as shown in Figure 9-126.

The power circuit is composed of a step-down capacitor C1, a bleeder resistor R1, a Zener diode VS, a rectifier diode VD1, and a filter capacitor C2.
The light control circuit is composed of an indicator light HL, a photoresistor RG, a resistor anal, a capacitor C3, a C4, a potentiometer RP, and a time base integrated circuit IC.
The control execution circuit is composed of a relay K, a diode VD2, a heating wire EH, and a fan motor M.
After the AC 220V voltage is stepped down by Cl, VS regulated, VDl rectified and C2 filtered, 6V DC voltage is provided for the light control circuit.
Normally, the RG is exposed to light from the HL and is in a low-resistance state. The 2 pin of the IC is high, the 3 pin outputs a low level, K is in a released state, and EH and M do not work. When the hand is extended to the air outlet below the hand dryer, the optical path between HL and RG is blocked by the hand, and RG changes from a low resistance state to a high impedance state, causing the IC 2 pin to become a low level, 3 feet. The output is high level, K is energized, EH is energized, M is energized, and the air outlet blows hot air. At the same time, C3 is charged by RP, so that the voltage of the 6 pin of the IC keeps rising. When the voltage of the 6-pin of the IC rises above 8V, the circuit in lC flips, the 3 pin becomes low level, K is released, and its normally open contact is disconnected, and the working power of EH and M is cut off.
Adjusting the resistance of the RP can change the time when the hand dryer is delayed.
Component selection
Rl and R2 use 1/4W metal film resistors or carbon film resistors.
The RP uses a small organic solid potentiometer or a variable resistor.
RG selects the MG42 series of photoresistors.
Cl selects a CBB capacitor with a withstand voltage of 450V; C2 and C are both aluminum electrolytic capacitors with a withstand voltage of 16V; C3 uses a polyester capacitor or a monolithic capacitor.
Both VDl and VD2 use 1N4007 silicon rectifier diodes.
VS selects lW, 6.8V silicon steady voltage diode, such as 1N4736 and other models.
The IC uses a time base integrated circuit such as NE555.
K selects JM-l3F type 6V DC relay.
EH uses about 5OOW of heating wire.
M uses a miniature AC 220V fan motor.
HL selects the indicator of 6V, O.lA