What are the common faults of hand dryers

Fault phenomenon 1: Put your hand into the hot air outlet, no hot air blows out, only cold air blows out.
Analysis and maintenance: Realizing relevant circuits is shown in Figure 1. There is cold air blowing out, indicating that the blower motor is powered on and working, and that the infrared detection and control circuit are normal. Only cold air indicates that the heater is open circuit or the wiring is loose. Upon inspection, the heater wiring is loose. After reconnecting, there is hot air blowing out, and the fault is eliminated.
Fault symptom 2: After being powered on, your hand has not yet been placed on the hot air outlet. The hot wind blew out of control.
Analysis and maintenance: Upon inspection, there is no breakdown phenomenon in the silicon controlled rectifier, and it is suspected that the photosensitive tubes inside the pins ③ and ④ of the photocoupler are subject to electric leakage and breakdown. After replacing the photocoupler, the operation returned to normal and the fault was eliminated.
Fault symptom 3: Put your hand into the hot air outlet and no hot air blows out.
Analysis and maintenance: Check that the fan and heater are normal, measure that there is no trigger voltage at the thyristor gate, and measure that there is a rectangular wave signal output at the c-pole of the control transistor VI. It is suspected that the photocoupler is defective. Use a multimeter Rxl0 to measure the forward and reverse resistances between the pins ③ and ④ of the photocoupler as infinity. Under normal conditions, the forward resistance should be several meters, and the reverse resistance should be infinite. It is determined that the internal photosensitive tube is open circuit, This causes the thyristor gate to not receive the trigger voltage and cannot conduct. After replacing the photocoupler, troubleshoot the problem.

The above content is organized by Superb heater Company, super heater. Mainly professional production: industrial heating elements, temperature measuring elements, production equipment, accessories, and raw materials such as tubular heaters, tubular heaters, belt heaters, ceramic heaters, silicone rubber heaters, thermocouples, etc.

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