In this project, I will show you how to make a wireless circuit using photoresistor, LM741 Op-Amp IC and 4017 decade counter. When you take your hand over the photoresistor while the switch is off, it will turn the appliance on. For the second time, when you take your hand over the photoresistor again, it will toggle the switch and switch off the appliance. A photoresistor is the same as other resistors but the difference is that their resistance change with the change in light falling on it.

Further About the Project...

In this project, I will show you how to make a wireless circuit using photoresistor, LM741 Op-Amp IC and 4017 decade counter. When you take your hand over the photoresistor while the switch is off, it will turn the appliance on. For the second time, when you take your hand over the photoresistor again, it will toggle the switch and switch off the appliance. A photoresistor is the same as other resistors but the difference is that their resistance change with the change in light falling on it. This change in voltage is sensed by LM741 Op-Amp and this will in turn control 4017 IC output which is connected to the AC light through relay module. So, each time we move our hand over the LDR, the intensity of light drops and it will either switch on or off the AC load.

Things You Need

Note: Photoresistors are often sold in the market as the light dependent resistor (LDR). They all are same. I am using the one with the cell resistance @ luminescence : (5~10)k Ohm @ 10 lux. The link below will lead you to the one I am using in the project.

List of materials:

• 1 x CD4017 Decade Counter: http://bit.ly/2SB4Ljc
• 1 x LM741CN IC: http://bit.ly/2QJXmkw
• 1 x 5V Relay: http://bit.ly/2QOJhSI
• 1 x Photoresistor: http://bit.ly/2QKEx0l
• 1 x LED Matrix: http://bit.ly/2C45Omz
• 1 x 22 uF Capacitor: http://bit.ly/2Gdpkkt
• 1 x BC546 Transistor: http://bit.ly/2UwK9KO
• 1 x 10k Ohms Potentiometer: http://bit.ly/2RRafXf
• 1 x 9V Battery Snap/Clip: http://bit.ly/2QnWket
• 1 x Breadboard: http://bit.ly/2AFJkpQ

I have been using electronic components from LCSC.com. LCSC has a strong commitment to offering a wide selection of genuine, high quality electronic components at best price. Sign up today and get $8 off on your first order.

What is Op-Amp LM741?

LM741 operational amplifier is a DC-coupled high gain electronic voltage amplifier. It's a small chip having 8 pins. It is used as a comparator which compares two signals. In Op-Amp IC 741, PIN2 is an inverting input terminal and PIN3 is non-inverting input terminal. The output pin of this IC is PIN6. The main function of this IC is to do the mathematical operation in various circuits.

While the voltage at non-inverting (+) is higher than the voltage at inverting input (-), then the output of the comparator is High. And if the voltage of inverting input (-) is Higher than the non-inverting end (+), then the output is LOW. In this Wireless Switch Circuit, LM741 is used to provide the Low to a high Clock pulse to IC 4017, for each time when one passes a hand over the LDR. Learn more about Op-amp 741 here.

Know More About the Decade Counter IC 4017

Most of us are more comfortable with 1, 2, 3, 4… rather than 001, 010, 011, 100. We mean to say that we will need a decimal coded output in many cases rather than a raw binary output. Let us now introduce you a new IC named IC 4017. It is a CMOS decade counter cum decoder circuit which can work out of the box for most of our low range counting applications. It can count from zero to ten and its outputs are decoded.

It can produce output at the 10 pins (Q0 – Q9) sequentially, means it produces output one by one at the 10 output pins. This...