A dishwasher circuit design schematic diagram using microprocessor control

　　The dishwasher adopts microprocessor control. Its operating voltage is 220V. The motor power of the cleaning pump is 120W, the motor power of the drainage pump is 60W, and the power of the heater is 800W. It adopts spray arm spray washing, and has four washing modes: pre-washing, washing, medium washing, and strong washing. The washing time is 20-25 minutes for washing mode, 35-70 minutes for medium washing and strong washing mode. The residual heat is used to dry the dishes.
Principle analysis:

　　(1) 220V mains power is added to the primary of the power transformer T, and after voltage reduction, the secondary outputs 16V AC voltage. After the voltage is rectified by the rectifier VD1-VD4 bridge and filtered by capacitors C1 and C2, a DC voltage is generated, which is then stabilized by the three-terminal voltage regulator IC4 to generate a 12V DC voltage for the power driver IC2 and control relays K1~K5. At the same time, the DC voltage is stabilized by the three-terminal voltage regulator IC5 to generate a 5V DC voltage as the working power supply for the microprocessor IC1, IC3 and the buzzer HA.

　　A high-frequency filter capacitor C and a varistor RV are connected in parallel at both ends of the input power supply. The high-frequency filter capacitor C can filter out the clutter signal of the AC power grid to prevent interference with the operation of the microprocessor; the varistor RV can prevent overvoltage and lightning from entering the circuit and play an overvoltage protection role.

　　(2) Pin 6 of the microprocessor IC1 is the 5V power input terminal, and pin 23 is the ground terminal. Pin 1 of IC1 and its external 65℃ temperature switch ST2, pin 2 and its external 55℃ temperature switch ST1, resistors R1 and R2, capacitors C10 and C11 and other components form a water temperature control switch circuit to control the water temperature. Pins 3 and 4 of IC1 and pins 7 to 12 and their external water level switch SL, gate switch SQ, water level detection switch S4, "start/pause" key S1, "program selection" key "S2, heating selection" key S3, cold gear selection switch S5, hot gear selection switch S6, resistors R3-R10, capacitors C12 to C19 and other components together form a program function switch circuit for program function selection.

　　(3) The buzzer control circuit is composed of the ICl@ pin and its external resistor Rll, transistor VT, buzzer HA and other components. When the dishwasher is drained, the ICl@ pin outputs a pulse signal, which is amplified by the transistor VT and drives the buzzer HA to make a buzzing sound, indicating that the dishwasher has finished washing. The reset circuit is composed of the IC124 pin and its external resistor R13, capacitors C22~C24 and diode VD5. Each time the power is turned on, the internal circuit of the ICl@ pin is reset.

　　(4) IC1 (18) to 22, 26 to 28 and its external 55°C indicator light, power indicator light, strong wash indicator light, 65°C indicator light, medium wash indicator light, cleaning indicator light, heating indicator light, pre-wash indicator light and other components together form a function display control circuit for program function display. Among them, indicator lights LED6 to LED9 are controlled by the output signals of IC3⑧, 11, ③, and ⑥ respectively. IC1 (13) to (17) pins are the output terminals of heating, stopping, water inlet, drainage, and cleaning functions, which are connected to the input terminals of power driver integrated circuit IC2④, ⑤, ① to ③ respectively. IC2's 12 to 16 pins are externally connected to control relays K1 to K5, whose attraction and disconnection are controlled by the output signal of IC1, so that the normally open contacts of the corresponding relays are actuated to realize the functions of water inlet, cleaning, heating, drainage, and stopping.