Grating circuit diagram of threshold switch

This circuit is suitable for applications with a wide supply voltage range (4.5~27V). The transistor T1, diodes D1 and D2, and resistors R1 and R2 form a constant current source. The two diodes form an approximately constant voltage on the base of the transistor regardless of the supply voltage. The constant current value of the transistor is adjusted by the resistor R2.

If the photocurrent of the phototransistor is more than 4 times the input threshold current of the integrated circuit, the influence of changes in component parameters due to temperature or aging can be reduced to a minimum. The threshold switch uses the integrated circuit TCA105, which can generate forward or reverse signals at its output terminals 4 and 5.

Main technical data: working voltage: 4.5~27V; total current consumption: 5.3~11.3mA; light-emitting diode current: 2~8mA; integrated circuit absorption current : 3.3mA.

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