Hi friends! I'm back with a new instructable where we can control home appliances such as lamp, fan, tv, etc. wirelessly depending on the type of relay used. I've designed it using a simple RF trans. & receiv. module at 433MHz. As we all know, this module can be used as a single channel communication but i've put a set of encoder and decoder ICs to make it support four channels. Encoder-Decoder ICs are very common now a days and its basic principle is logic gates which multiplexes multiple input channels and makes it one digital signal and then, is demultiplexed on the other side to four channels. The relay drivers used here are CL100 transistors and its equivalent is SL100. Both are same and are used here as current amplifiers for each channel. One more thing to consider here that you cannot just simply use encoder-decoder ICs b'coz as long as you'll press the button, there will be an output signal as '1' on the respective channel but when you release the button, there will be no output or '0' signal. So, for this i've used flip flop ICs for each channel; here 'CD4017'. CD4017 is a single flip flop IC, so you'll have to use four ICs for four channels. I've completed the project but i'll advice you guys to use '74HC175' which is a quad flip flop IC. It can be used instead of four 'CD4017' ICs and will pretty much reduce the congesting of wires making it more simple. The circuit diagram has been taken from circuitstoday.com and here we go... :-)

Step 1: Components Needed

1. Dotted PCB(Breakout board).
2. 433MHz. Rx Tx module(1 set).
3. Female header pins(not in diagram).
4. Indicator LEDs of desired colour(4 nos.).
5. 1k ohms(1/4watt) resistor(4nos.).
6. 100uF/25volt electrolytic capacitor(4 nos.).
7. 560ohms(1/4watt) resistor(4nos.).
8. 180k ohms(1/4watt) resistor(4nos.).
9. 100nF ceramic capacitor(4nos.).
10. BC558 transistor(4nos.).
11. CL100 metal cap transistor(equivalent is SL100)(4 nos.).
12. CD4017 IC(4nos.).
13. 16 pin DIP IC socket(4nos.).
14. HT12E IC(1nos.).
15. HT12D IC(1nos.).
16. 18 pin DIP IC socket(2nos.).
17. Electronic push button(4nos.).
18. SPST switch(1nos.).
19. 9 volt general purpose dry cell(1nos.).
20. Battery holder(1nos.).
21. 39k ohms(1/4watt) resistor(1nos.).
22. 1M ohms(1/4watt) resistor(1nos.).
23. 12inch long general purpose antenna or copper wire(2nos.).
24. 6volt relay of desired amperage(4nos.).
25. Some single strand wires.
26. Small plastic box for transmitter.
27. Access to soldering iron.
28. A telescopic antenna or 2 feet long 14SWG copper wire for making antenna.

Step 2: Make the Receiver

Guys, i won't freak you out giving lots of unnecessary steps. Just the important steps to consider, and if any problem, plz don't hesitate to ask!
So, here we're going to make receiver unit. Start with the PCB, plan and mark the places where to put ICs keeping the decoder IC separate from flip flops. I haven't used the voltage regulator(LM7805) viz. shown in the schematic coz i'll be using 5 volt regulated DC adapter. But guys plz do use the voltage regulator if you're powering the circuit by voltages above 7.5volt upto 12volt. Solder the IC sockets and the respective capacitors, transistors, resistors and LEDs of flip flop ICs close to them. Follow the image to clear out those metal cap transistor pin details if you're new to use them. Watch the schematic several times before soldering to avoid any mistake, but after all we're human beings, we can just try to be perfect. Haha. ;-)

Step 3: Make the Transmitter

I wanted to make transmitter circuit as simple as i can, so i didn't use PCB for it, instead i soldered all the components directly and thus, conserved the space. Put the ICs onto socket after completing all soldering work. Here, again i havn't used the voltage regulator and i'll advise you not to use it coz transmitter has the capability to handle voltages upto 12volt and its transmitting range too depends a lot on it. Use a direct 9volt battery and put an SPST switch for convenience. Then make its 4 channel button panel on a small PCB piece and drill holes on it to fix it on the plastic box(case) inside out. Now calculate the length of antenna required viz. very important. A slight mistake in antenna can result in huge range loss. In this project we're using a 433MHz transmitter frequency where the wavelength is .69 meters, or about 27.16inches. Strictly, the antenna size should be 1/2 or 1/4 the wavelength. The 1/4 of 27.16inches is about 6.82 inches and thus, we'll make it exactly of 6.82 inches. Our project is nearly complete..

Step 4: Relay Basics

There are many types of relays available in market. Generally, for these type projects, 6volt operated relays are used and they are of different amperages depending on the load. I'd suggest you to separate the relay board from receiver unit and connect their respective coil terminals using wires coz if by mistake the AC power gets in the circuit directly, it'll just blow off the whole receiver. Relay pinout is shown in the image. Connect one pin of coil terminal to +ve power supply and the other to the collector pin of CL100 transistor. Then connect the movable contact pin and N/O pin of relay in series with the desired appliance to the power supply mains.

WARNING:- Be careful when working with mains. Its too lethal. If you're not confident about it, please take help from experienced person!!!

Step 5: Assemble the Board and Get Started

All you've to do now is to find a suitable adapter for the receiver circuit. I used a normal cellphone charger. It gives 5.3volts and 500mA, enough to power the circuit and drive the relays. With this you're finished. Now go and have fun switching your home appliances wirelessly! ;-)