Posted by Circuits Arena on Wednesday, 24 December 2014
Home Made Heat Sensor Circuit is the artlcle explaining Heat Sensor : Here is a simple circuit which can be used as a heat sensor. In the following circuit diagram thermistor and 100 Ohms ...
Heat Sensor :
- Here is a simple circuit which can be used as a heat sensor. In the
following circuit diagram thermistor and 100 Ohms resistance is
connected in series and makes a potential divider circuit . If
thermistor is of N.T.C (Negative temperature Coefficient ) type then
after heating the thermistor its resistance decreases so more current
flows through the thermistor and 100 Ohms resistance and we get more
voltage at junction of thermistor and resistance.
- This concept is so pervasive it has a name: voltage divider. The
input-output relationship for this system, found in this particular case
by voltage divider, takes the form of a ratio of the output voltage to
the input voltage.
- This output voltage is applied to a NPN transistor through a resistance.
Emitter voltage is maintain at 4.7 volt with a help of Zener diode.This
voltage we will use as compare voltage. Transistor conducts when base
voltage is greater than emitter voltage. Transistor conducts as it gets
more than 4.7 base Voltage and circuit is completed through buzzer and
it gives Sound.
