Published:2011/9/9 8:00:00 Author:Vicky | Keyword: double contact-plate, resistance bridge touch switch | From:SeekIC
Resistance bridge touch switch in the picture 1 is composed of LM339. LM339 is a a quad voltage comparator (with 4 identical voltage comparator inside). The circuit only takes use of one of the four. Work voltage range reaches 2-32V. When hands are very close to the double metal plate but not touch them, pin2 of LM339 outputs low level signal, which makes the luminous diode LED1 conducted and lightened.
The difference of the resistance bridge touch switch in the picture 2 from picture 1 lies in that it adopts calculating amplifier LF353N instead of voltage comparator.
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