ELECTRONICSELECTRONICS

Frost AlarmFrost Alarm

ELECTRONICSELECTRONICS

When the thermistor When the thermistor temp is high the temp is high the resistance is low resistance is low

and the transistor is and the transistor is off.off.

ELECTRONICSELECTRONICS

Frost AlarmFrost Alarm

ELECTRONICSELECTRONICS

When the thermistor When the thermistor temp is low , the temp is low , the resistance is high resistance is high and the transistor and the transistor switches on.switches on.

ELECTRONICSELECTRONICS

Fire AlarmFire Alarm

ELECTRONICSELECTRONICS

When the temp is hot the When the temp is hot the thermistor resistance is thermistor resistance is

low so it takes little low so it takes little voltage and so the resistor voltage and so the resistor takes most of the voltage takes most of the voltage

and so the transistor and so the transistor switches on. switches on.

ELECTRONICSELECTRONICS

Fire AlarmFire Alarm

ELECTRONICSELECTRONICS

When the temp is cold When the temp is cold the thermistor takes the thermistor takes

most voltage and so the most voltage and so the resistor takes little and resistor takes little and

the transistor is off.the transistor is off.

ELECTRONICSELECTRONICS

Burglar AlarmBurglar Alarm

ELECTRONICSELECTRONICS

When the L.D.R. is in the When the L.D.R. is in the light ,the resistance is light ,the resistance is

low so the voltage is low low so the voltage is low and the transistor is offand the transistor is off

ELECTRONICSELECTRONICS

Burglar AlarmBurglar Alarm

ELECTRONICSELECTRONICS

When the L.D.R. is in the When the L.D.R. is in the dark its resistance is high dark its resistance is high

and the transistor switches and the transistor switches on.on.

ELECTRONICSELECTRONICS

Time Delay CircuitTime Delay Circuit

ELECTRONICSELECTRONICS

When the capacitor When the capacitor charges up to a certain charges up to a certain voltage after a certain voltage after a certain time , the transistor time , the transistor

switches on.switches on.

ELECTRONICSELECTRONICS

ELECTRONICSELECTRONICS

There are 3 process There are 3 process devices,devices,

The NOT gateThe NOT gate

The AND gateThe AND gate

The OR gateThe OR gate