Too cozy in bed or on the couch to get up and switch the lights? Or, maybe you also want to do the same with some other home appliances, including every kind of electrical device present in your home - hairdryers, coffee makers, laundry machines - any of it!
This can be effortlessly done with the mere click of a spare television remote. If you are a tech lover, or you are just knowledgeable and ambitious enough to enable future laziness, here is a guide to bringing an infrared-based wireless switch to operate appliances to life.
Most spare entertainment remotes (but not Wi-Fi remotes) or any other IR remote work to operate this switch. The circuit is shown in Figure 1. The infrared based wireless switch uses a decade counter CD4017, a TSOP1378 infrared receiver and some other minor components.
You can make this circuit schematic in any electronics simulation software, such as Altium Designer, Proteus Professional or Eagle. After making the schematic, you will need to produce a PCB layout design and generate some files. Understanding the circuit's operation is first up.
The design requires the following nine components to start constructing this wireless switch:
1. Infrared receiver TSOP1738
2. Decade counter CD4017
3. 7805 IC
4. 1N4007 diode
5. 100, 220k, 470 and 1k ohm resistors
6. BC558 and BC548 transistors
7. 33 μF, 100 μF and 0.1 μF capacitors
8. Two LEDs
9. Relay 5V, 100 Ω
These are relatively common components for electronics engineers, and might be on-hand already. If not, they are affordable in small quantities.
Turning the switch on
The wireless switch works on the principle that domestic remote controls emit infrared radiations when their buttons are pressed. Every button gives off a distinct pattern of infrared waves. Therefore, the remote control will generate infrared rays that will fall on the TSOP1738 infrared receiver in the circuit. This IC is active low, hence, its third pin (the output pin) will go low. Next, the transistor Q2 will boost the signal magnitude to send it to the clock input of decade counter CD4017.
Initially, the decade counter will be at its reset state, and all of its outputs will be low except for output Q0. Henceforth, the LED D2 will be illuminating at this point and demonstrating that the electrical appliance is switched off. Now, as soon as the transistor feeds it the clock signal, its output Q1 will go high and illuminate the LED D1. At the same time, the transistor Q2 will also switch on and the relay will energize. Also, the LED D1 will stop illuminating at this instance. And, your electronic device will turn on.
Turning it off
You will need to press the remote button again to switch off the appliance. The Q0 output of the decade counter will again go high and the LED D2 will start to illuminate. This is an indication that the device has been turned off. In this project, the CD4017 IC is functioning as a bistable multivibrator since the Reset MR (15th pin) and output Q2 (fourth pin) are connected. The 16th pin is the power pin (Vcc) and the eighth pin is the ground pin. This IC is active low, thus, the 13th enable pin is connected with the ground.
You may be wondering why we have connected resistors and capacitors. The 33 μF capacitor and 100 Ω resistor will mitigate any disturbances present in the power supply. Some other notable connections are the power (second) and ground (first) pins of TSOP1738 infrared receiver.
The final product
Hopefully, you know how to design circuit schematics. You will need to design a PCB layout of this wireless switch as shown in Figure 3. You can select custom PCB board size and properties such as through-hole components or surface mount devices. Furthermore, you can select auto-route or may route the connections yourself.
It is recommended that Gerber, drill and any related files be generated. A DIYer may visit any online reliable PCB supplier and place an order on their website. It is crucial that all the necessary files are generated and in the right format before uploading them on a supplier's website.
You are ready to assemble your electronic components as soon as you get the PCB delivered. Nevertheless, if you are not an expert at soldering the components then you may also the PCB manufacturers to also assemble and solder your components. But this would, of course, add to the cost of your final product.
You may also fabricate it manually. First of all, you will need to get a printout of your PCB layout on glossy/photo paper. Then, cut a circuit board from the copper plate and place the printout over it. Use iron heat to transfer the print onto the circuit board. To finish, peel off the paper after dissolving it in lukewarm water for about 10 minutes. The final steps would be to etch the copper plate and clean off the PCB.
(Editor's note: This article was edited on May 19, 2020 to resolve an error in the circuit diagram.)