Automatic hand dryer four

Circuit Operation Principle The automatic hand dryer circuit consists of a power supply circuit, an infrared transmission circuit, an infrared signal processing circuit, an electric heater control circuit, and a fan control circuit, as shown in Figure 9-127.

The power circuit is composed of a fuse FU, a power switch S, a power transformer T, a rectifier diode VD1-VD4, a filter capacitor Cl, C5, C6, a resistor R13, a power indicating LED VL1, and a three-terminal voltage regulator integrated circuit IC3.
The infrared emitting circuit is composed of an infrared light emitting diode VU, resistors R7 and R8, a capacitor RP4, a capacitor C4, and a time base integrated circuit IC2.
The infrared signal processing circuit is composed of an infrared photodiode VD8, a resistor R9, a R10, a capacitor C7-C9 and an infrared signal processing integrated circuit.
The electric heater control circuit is composed of resistors R11, R12, a transistor V2, a thyristor VTl and an electric heater EH.
The fan control circuit is composed of a light control delay circuit and a fan motor control circuit. The light control delay circuit is composed of a resistor R1-R5, a photoresistor RG, a potentiometer RP1, a æ°– indicator HL, a diode VD5, a capacitor C2 and a transistor V1; the fan motor control circuit is composed of a potentiometer RP2, RP3, a diode VD6, VD7, capacitor C3, resistor R6, thyristor VT2, time base integrated circuit ICl and fan motor M are composed.
Turn on the power switch S, the AC 220V voltage is stepped down by T, VDl-VD4 is rectified, and C1 is filtered to generate +9V voltage, which is used as the DC working power of the infrared transmitting circuit and the fan control circuit. At the same time, the VLl is lit after R13 current limiting. . The +9V voltage is also subjected to secondary voltage regulation of IC3 to generate +5V voltage, which is supplied to the infrared signal processing circuit.
After the infrared transmitting circuit is energized, the output pulse frequency of 4OkHz is output from the 3 pin of IC2, and VL2 is driven to emit modulated infrared light. VD8 (installed opposite to VL2) receives the infrared light emitted by VL2 and converts it into a corresponding electrical signal. After the electrical signal is processed by IC4, it outputs a low level from pin 7, which turns off V2 and VTl. EH No heating, HL does not emit light, RG is in high resistance state without light, C2 is low potential at both ends, Vl is in the off state, ICl is not working, VT2 can not trigger conduction, fan motor M does not rotate.
When the hand is extended to the vicinity of the air outlet of the hand, the infrared light path between VL2 and VD8 is blocked by the hand, the 7 feet of the I call become the high level, and the infrared light path between V2 and VD8 is blocked by the hand, lC4 The 7 pin becomes high level, V2 is turned on, the high level of the emitter output is triggered by the VTl, and the EH is energized to start heating; at the same time, the HL is lit, and the RG is illuminated by the light to become a low resistance state, + 9V voltage is charged to C2 through RG and R3. When the voltage across C2 is charged to a certain value, Vl is turned on, ICl works, and the 3-pin output square wave pulse signal with adjustable duty cycle is added to VT2 via R6. The gate pole makes the VT2 intermittently conduct, and the M intermittent operation, blowing hot air from the air outlet of the hand dryer.
Adjusting the resistance of RPl can change the sensitivity of light control.
Adjusting the resistance of RP2 and RP3 can change the time during which M is energized or de-energized.
Adjusting the resistance of RP4 can change the frequency of the output signal of pin 3 of lC2.
Component selection
Rl-R13 uses 1/4W metal film resistor or carbon film resistor.
RPl and R are called ultra-small synthetic carbon film potentiometers or variable resistors; RP2 and RP3 use ultra-small organic solid potentiometers or variable resistors.
RG uses a photoresistor with a light resistance of less than 2kΩ and a dark resistance of more than 1OOkΩ. When used, it forms an optocoupler together with the HL package flower.
Cl-C3 selects aluminum electrolytic capacitors with a withstand voltage of l6V; C4 and C6 select monolithic capacitors or polyester capacitors; C5, C8 and C9 select aluminum electrolytic capacitors with a withstand voltage of lOV; C7 selects high frequency ceramic capacitors Or glass glaze capacitors.
VDl-VD4 selects 1N4004 or 1N4007 type silicon rectifier diode; VD5-VD7 selects 1N4148 type silicon switch diode for use; VD8 selects PH302 type infrared photodiode.
VLl selects φ3mm high-brightness light-emitting diode; VL2 selects SE303 type infrared light-emitting diode.
Vl and V2 select S9013 or S9014 type silicon NPN transistor.
Both ICl and IC2 use NE555 type time base integrated circuit; IC3 selects 78L05 type three-terminal voltage regulator integrated circuit for IC3; IC4 selects CX2O106 or KA2184 type infrared signal processing integrated circuit for IC4.
VT1 selects 3A, 600V bidirectional crystal tube; VT2 selects 1A, 600V bidirectional thyristor.
T selects 5W, the secondary voltage is gV power transformer.
EH uses 100-300W electric heating wire.
M uses a miniature fan of AC 220V.
HL selects the common æ°– indicator.