Commonly used relays, thyristors and high-frequency clocks, etc., may become the source of interference of the control board of small household appliances. For the above interference, its solution can be completed from the following aspects:

(1) Add a continuous current diode in the relay coil to eliminate the back electromotive force dry disturbance generated when the coil is disconnected.

(2) At both ends of the relay contact and connected to the spark suppression circuit (generally RC series circuit, resistance is generally selected from thousands of euros to tens of thousands of euros, capacitance is selected 0.01μ F) to reduce the impact of electrical spark.

(3) Connect a 0.01&mu to each IC on the circuit board; Eg. F High frequency capacitance to reduce the influence of IC on the power source. However, attention should be paid to the wiring of the high-frequency capacitor, and the connection should be close to the power end and as short as possible, otherwise, it is equal to increasing the equivalent series resistance of the capacitor, which will affect the filtering effect.

(4) Wiring should avoid 90 degree lines, and minimize high frequency noise emission.

(5) The RC suppression circuit is connected at both ends of the thyristor to reduce the noise generated by the thyristor (the noise may break down the thyristor when it is serious).

(6) Pay attention to crystal wiring. The crystal oscillator and the chip pin should be as close as possible, and the clock area should be isolated with the ground wire, and the crystal oscillator shell should be grounded and fixed. It is best to use low speed crystal oscillator as much as possible in the field where low speed crystal oscillator can be used.

(7) Reasonable partition of the circuit board (such as strong and weak signals, digital and analog signals). As far as possible, the source of interference (such as motors, relays) and sensitive components (such as single-chip computers) away.

(8) AC end with inductance capacitance filtering: remove high-frequency and low-frequency interference pulses, VCC and GND are connected to electrolytic capacitors and porcelain capacitors to remove high and low-frequency interference signals.