Latching Schmitt trigger

153

01:12:23

Latching op-amp Schmitt trigger with 2 LEDs and Buzzer.

published 2 years ago

ElGatoG

2 years ago

Temperature alarm; The 20.3k resistor represents a 10k NTC type 2 thermistor. All resistor values are exact for what I have on hand. The left transistor latches when temp. gets higher than set point, the NO push button resets after temp. is lower than set point. The center transistor turns on the red LED and a small piezo buzzer, represented by the lamp. The right transistor turns on the green LED when temp. is below set point. Unit is powered from an old 1 amp iphone charger, maximum current 13.8 ma, maximum power 69 mw. Values shown give a temperature range of 32°F to 68°F, center of range is 50°F, I am using it as a refrigerator monitor set at 46°F.

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