8. Principles of operation
Descriptions of circuit operation
( 1 ) Notes for turning the power "ON / OFF"
1 When the power is turned "ON", the power lamp (LED1), the heater lamp (LED2) (JT-SB216JSH2-W/H/S-
NE only, with the heater switch ON), and blue indicators (LED10, 11) turn on after 1.5 seconds
hand dryer becomes ready for operation.
• Before the power lamp turns on, the hand dryer will not operate even if hands are inserted in the hand dry-
ing area. In the meantime, the microcomputer (IC20) of the main unit performs the initial settings, includ-
ing the setting of the hand detection sensor sensitivity.
• In order to set the sensitivity of the hand detection sensor correctly, do not insert hands in the hand drying
area until the power lamp is turned on.
• Even if the hand dryer has started immediately (within 15 seconds or less) after turning the power "ON", it
is normal though the motor input may become slightly lower because of the initial setting.
*1: If the power is turned ON again 30 to 120 seconds after turning the power OFF, it may take 3 seconds
before the operation is enabled.
2 When the power is turned "OFF", the power lamp and blue indicators turn off and operation stops.
• The circuitry takes about 40 seconds to discharge the voltage retained in it. Wait until the discharging time
elapses before plugging in or out the connectors, replacing the circuit boards, or doing other maintenance.
• Even when any error is occurred, the error display will go off if the power has been turned off. Only when a
microcomputer error is occurred, the error display persists till the voltage retained in the circuitry has been
discharged (till the microcomputer has been reset).
( 2 ) Hand detection and operation
1 The hand detection sensors are infrared sensors containing the light emitting sensor (infrared LED) and
light receiving sensor (photo-diode), etc. and consist of the upper sensor, the middle sensors, and the lower
2 Reflection type upper sensor:
This sensor detects the change in the reflected amount of infrared light when hands are inserted.
Transmission type middle and lower sensors:
These sensors detect that the infrared light is shielded when hands are inserted.
3 When the lower or middle sensors detect hands, the blower motor turns on and the hand dryer starts to
4 Once operation has started, it continues as long as any of the upper, middle, or lower sensors detects
5 If 1.5 to 3 seconds elapse without detecting hands by any of the sensors, the blower motor turns off and
6 The hand dryer continuously operates for up to 30 seconds.
• Once 30 seconds have elapsed, the hand dryer stops operating even if hands are detected.
• Since this is a function to assume the presence of a foreign object, the operation will resume if hands are
pulled out and reinserted.
( 3 ) Control of the heater (Applicable models: JT-SB216JSH2-W/H/S-NE)
1 The heater turns ON simultaneously with the blower motor turns ON. (The heater lamp turns on.)
2 The heater does not turn ON in the following occasions:
• When the heater switch is turned "OFF"
• When a temperature detected by the circuit thermostat on the control circuit board (JT-30M8A/JT-30M8)
is 32°C or higher
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, and the