Making a motion detector at home can have many practical purposes such as monitoring your pets, as well purely recreational purposes such as monitoring your friends and letting you know when people wander off the sidewalk and into your yard. In this example, an LED light is used as the signal to let you know when the sensor is tripped. However, you can use a small buzzer if you prefer an audible trip signal.
Instructions
1. Place the 741 Op Amp in the center of the bread board. The board is the object that looks like a circuit board, with holes in it. You will notice that these holes are grouped together. Collectively, they are called "nodes". Make sure that the pins on the amp are securely fitted through the board.
2. Locate pin number 1 on the amp (there are 8 pins). It will be the pin closest to the small circle imprinted on the amp in one of the corners. Moving counterclockwise, count and make note of pins 2, 3, 4, etc.. Place one pin on one of the CDS cells into the node where you put pin #2 of the op amp and the other pin on that same CDS cell into the #7 pin of the op amp.
3. Place one pin on the other CDS cell again into the node where you put pin #2 of the op amp, and the other pin on the CDS into the 4th pin on the op amp.
4. Connect the middle pin on the potentiometer to the 3rd pin on the op amp. Connect the right pin on the potentiometer to pin 7 on the op amp, and connect the left pin on the potentiometer to pin 4 on the op amp.
5. Connect the red 30 gauge wire to pin 7 on the op amp.
6. Connect the negative lead on the LED light to pin #6 on the op amp. There are two pins or leads on the LED light. The shorter is typically the negative lead. Connect the positive lead to one lead of the 1 kilo ohm resistor. Connect the other lead of the resistor to pin 7 on the op amp.
7. Connect the black 30 gauge wire to pin 4 on the op amp.
8. Connect the red and black wires to the battery terminals - red first to the positive terminal and black to the negative terminal. Always connect the positive terminal first and the negative terminal last.
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