Circuit detectors and sensors based electronics projects

An very simple and high efficiency pir motion detector circuit can be constructed using this diagram .
This pir motion detector circuit project use a PIR sensor , operational amplifiers a sound generator circuit and some others common electronic components .
The op-amp IC1D shapes the frequency response to amplify those frequencies produced when motion is detected and rejects all others, such as those due to noise or slow temperature changes.
As motion is detected, the voltage at the output will change and trigger either IC1C or IC1B.
The op-amps IC1A, IC1B and IC1C are configured as voltage comparators.
When IC1D outputs a voltage lower than 1.41V, it will force pin 2 of IC1 high.
When IC1D outputs a voltage higher than 1.67V, it forces pin 8 and pin 2 of IC1 to go high. A high in with one of these cases causes the output to go low and allows C9 to discharge through IC1A. The discharging of C9 will pull pin 6 of IC2 low and trigger the sound generator.
As sound generator you can use a HT2810 or HT2812 sound generator integrated circuit .
This motion detector alarm circuit requires two DC voltage 5 volts for almost all power connections and 9 volts for the sound generator circuit .
The Passive Infrared Sensor (PIR) used in this alarm circuit can be LHI-954 , KDS245 or other similar type .

If you want to make it portable you can use a 9 volts battery for 9 volts power supply and a LM7805 regulator to generate the 5 volts voltage that is required for almost all power connections .

This smoke detector circuit diagram is based on the SD2 CMOS Photo-Electric Smoke Detector Integrated Circuit manufactured by Supertex INC and include almost all needed components to build a very simple and high efficiency smoke detector project .As you can see , this smoke detector circuit diagram is very simple an require few external components .

The LED predriver output pulses an ex­ternal transistor which in turn, switches on the infrared light emitting diode at a very low duty cycle. The desired IR LED pulse period is determined by the value of the externai timing resistor. The Smoke Sensitivity is adjustable through a trimmer resistor which varies the IR LED puise width. The light sensing element is a silicon photovoltaic cell which is held at near zero bias to minimize leakage currents. The circuit can detect signals as low as 1 mV and generate an alarm. The IR LED pulse repetition rate increases when smoke is detected.
The IR diode can be RCA Type SG 1010A or Spectronics Type SE 5455-4 Clairex and the IR Photo detector can be Vactec VTS4085 .
Because the SD2 CMOS Photo-Electric Smoke Detector IC is designed for use in low power, battery operated, consumer applications it needs a 9 volts DC power supply (or a 9 volts battery ).

These metal detector circuit diagram is based on the TDA0161 monolithic integrated circuit , designed for metallic body detection by detecting the variations in high frequency Eddy current losses. For detecting metals , TDA0161 require an external LC tuned circuit .