Olaite SBS-15 automatic hand dryer schematic

1.07E+15

The circuit principle of this type of automatic hand dryer is shown in the drawing. The circuit is mainly composed of a power circuit, a control circuit, and a hand dryer circuit.

Power supply circuit

The AC220V voltage is sent to the transformer T primary via the fuse FU, and the secondary output of the 16V AC is applied to the input of the rectifier bridge composed of D1~D4. After rectification, it is filtered by the capacitor C1 to obtain about 16V DC voltage. This voltage is then applied to a series-regulated voltage regulator circuit consisting of VT1, which outputs a DC voltage close to 14V from the VT1 emitter for the subsequent stage circuit. Because the voltage regulation of this voltage regulator circuit is realized by VD5, there is no voltage feedback, so the stability of this voltage regulator circuit is not very high. After the static (standby) measurement, the VT1 emitter is about 14V, and the rhyme In the state (dry hand work), the VT1 emitter is only 12.05V, and the output voltage varies greatly, which is not conducive to the stable operation of the latter circuit. Therefore, this part can be replaced with a three-terminal voltage regulator integrated block (AN7812) during actual maintenance. The specific operation is to first remove VT1, VD5, and Rl, and then adjust the voltage regulator integrated block appropriately. The (1), (2), and (3) feet can be connected to the three points A, B, and C respectively. This will output a stable +12V DC supply control circuit.

2. Control circuit

This part mainly includes infrared transmission circuit composed of transistors VT2~VT3 and SE303, infrared signal receiving and amplifying, frequency selection, shaping, filtering, comparison output circuit and switch composed of triode VT4 and relay J. Control circuit.

In the infrared transmitting circuit VT2~VT3, C3~C4, R3.

R6 constitutes a multi-resonant circuit. This circuit is a rectangular wave generating circuit that can generate a rectangular pulse continuously and periodically without the need of an external trigger signal. The pulse is composed of a fundamental wave and multiple harmonics. Its function is to drive the infrared emission tube SE303 to emit infrared rays, and the specific working process will not be described again. Its oscillation period is T=0.7 (R5xC4+R4xC3). It can be seen that the oscillation frequency is f=l/T=5kHz. When the circuit is normal, as long as the AC 220V mains is connected, the transmitting diode SE303 continuously emits infrared light at a frequency of nearly 5 kHz, just because no one is drying hands. Cannot be reflected to the receiving diode PH302, so that the hand dryer is in standby.

The infrared receiving diode (PH302), R7~R9 and RW form a receiving circuit. The RW is used to adjust the overall sensitivity of the automatic hand dryer. The infrared light emitting diode SE303 and the receiving diode pH302 are installed in the same direction of the air outlet and are isolated from each other, and are equipped with a blue filter on the front side. The IC1 internal op amp I is used as a comparator, and its output is used to drive the switching circuit; the op amp II is vacant: the op amp III and its peripheral components form an AC signal amplifying circuit; and the op amp IV and its peripheral components form a bandpass filter.

The specific working process is: when the hand approaches the air outlet, the infrared light emitted by the infrared light emitting diode SE303 is reflected by the hand to the receiving diode PH302. The PH302 receives the infrared light signal voltage and adds it to the (1) pin of the IC1 internal operational amplifier III. After it is amplified, it is output from the (8) pin and coupled to the (13) pin of the ICl internal operational amplifier IV through C7.

The (12) pin of ICl is divided by Rl5 and R16 to obtain a reference voltage of 1,2VCC. The frequency-selected and shaped high-frequency AC signal is coupled to the half-wave voltage doubler rectifier circuit composed of VD6 and VD9 through C4, c3 filter, and VDl2 is limited to become a DC signal and enters the internal IC of the comparator IC1. (3) Feet. The IC1(2) pin voltage is mainly obtained by voltage division of Rl9-R21, wherein VD8 uses its unidirectional conductivity to isolate. That is, when in static (standby), the power supply voltage +Vcc is applied to VD10 via relays J and R22, forcing it to breakdown, so that the (2) pin of comparator IC1 is guaranteed to be high. VD8 prevents this high level from forming a loop through R20 to the ground, avoiding the occurrence of malfunction of the interference signal.

Since the comparator (3) pin is higher than the (2) pin voltage at this time, its output terminal (1) pin changes from low level to high level, and the high level is applied to the base of VT4 via R23, then VT4 is saturated. When it is turned on, the relay J is energized, its control contact Jl-1 is closed, and the hand-drying circuit is energized, indicating that the hand dryer is in working state. Once the hand leaves the dryer air outlet, the PH302 receiving diode loses the infrared light voltage signal, and finally the IC1(1) pin output is low level, the triode VT4 is cut off, the relay coil is de-energized, and its normally open contact Jl-1 is broken. On, the main circuit power is cut off, the hand dryer stops working, and no hot air is discharged.

3. Hand dryer circuit

The hand drying circuit is mainly composed of the normally open contact Jl-1 of the relay J, the fan motor M, the over temperature protection resistor RT, the bimetal temperature control switch ST and the heating wire EH. When the coil of the relay J is energized, its normally open contact Jl-1 is closed, and the AC220V alternating current is simultaneously applied to the fan motor M and the heating wire EH, so that the hot air is continuously discharged.