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SILICON CHIP Mini Projects #022 – by Tim Blythman RF Remote Receiver Jaycar’s MS6147 Remote Controlled Mains Outlet lets you control mainspowered devices without having to deal with mains wiring. It can be operated by the included RF remote control or another device equipped with a 433MHz transmitter (like we used in Mini Project #006, June 2024). That handy RF remote control can be used to control other devices too! T he MS6147 Remote Controlled Mains Outlet Controller bundle includes three switched outlet receivers and a handheld remote radio frequency (RF) transmitter. The transmitter has four channels, so there is an unused channel that could control something else. You can get extra mains outlet receivers, such as MS6149, to use with that extra channel. But that isn’t all you can do with it. For example, imagine a USB-powered lamp. While you could control it from one of these outlets by having a mains-powered USB power supply plugged into it, that would be unnecessarily complex. You could switch USB power to the lamp with a low-voltage relay or even a transistor, as we did in the Gesture-controlled Lamp Mini Project from January 2025 (siliconchip.au/ Article/17601). Or use this RF Remote Receiver to control the relay or transistor instead. It can receive signals from any of five different RF transmitters and then control something attached to the Arduino Uno board. Our project uses four LEDs to show the status of the four channels, making it easy to test the operation of these systems. The basic operation can be seen in our video at siliconchip.au/ Videos/RF+Remote We also wired up a relay module to demonstrate how to switch just about any low-voltage device. The Arduino ecosystem makes it very easy to customise the operation of the Receiver; you could add the USB-switching circuitry from the Gesture-controlled Lamp to add a switched USB outlet, for example. Alternatively, you could add some logic to the Arduino sketch to control some other low-voltage device. You could even program it to send a command (using a different medium, such as infrared) to another device, unifying control to a single transmitter. Circuit details Our circuit is quite simple, and we have laid it out on a prototyping shield attached to the Uno as per Fig.1. We expect many constructors will want to add their own hardware, so you might consider what else you want to control before commencing assembly. The 433MHz receiver module gets its power from the Uno via the shield to its Vcc and GND pins. A simple wire antenna is connected to the ANT pin of the receiver, while its DATA output goes to digital pin 2 (D2) of the Uno. Fig.1: the circuit is simple enough to wire up on a breadboard, but we laid it out on a prototyping board to make it more robust. Ensure that the necessary pads are connected underneath the board. To switch something with the relay, connect the C (centre, common) and NO (normally open) contacts as though they are a switch’s contacts. siliconchip.com.au Australia's electronics magazine March 2025  59 We are using this type of RF transmitter for this project. It can be purchased as part of a bundle (along with one or more Mains Outlets) from Jaycar with catalog codes MS6147 or MS6148. Kits like Jaycar MS6148 allow up to three mains devices to be controlled by a handheld remote, leaving a channel free on the transmitter for us to use. The Mains Outlets can be paired with up to three transmitters, but our Receiver can work with up to five! Four LEDs are driven by digital pins 7, 9, 11 and 13 (designated A, B, C and D, respectively). These have been chosen to allow a bit of space between them as they are laid out on the shield. Their anodes connect to the Uno’s pins via 470W resistors, while their cathodes are all connected to circuit ground. A 5V relay module is driven from digital pin 7 (connected directly to the relay module’s S pin). The module’s + and – pins are also wired to 5V and GND, respectively. About the only thing that should not be changed is the receiver’s DATA pin connecting to D2. The library we are using depends on the interrupt feature on this pin. Software We are using the RF433any library to decode the RF signals in this project. It can work with encodings from various protocols, including that used explore these a bit later, but each of the four LEDs behaves much the same as one of the four mains outlets would. For example, the ‘A’ LED will light up when either the A ON or ALL ON button is pressed. It will go out when either the A OFF or ALL OFF button is pressed. This keeps the operation straightforward and intuitive. The button codes are decoded independently, so there is no reason they can’t be allocated to ten independent and distinct functions by changing the way the software responds to the codes. In other words, there’s no reason the ON button has to switch an output on, or the OFF button switch it off. They are just buttons, including ALL ON and ALL OFF. This is left as an exercise for the reader! Construction by the Remote Controlled Mains Outlet Controller. More information can be found at https://github.com/sebmillet/­ RF433any As noted, this library uses the pin change interrupt feature of the ATmega328, so this project will only work with boards like the Uno or Nano and can only receive data on digital pins 2 or 3. It might work on other boards, but that has not been tested. The library waits for a transmission to be received and the 32-bit code is extracted. In the code used by the Outlet Controller, 20 bits are assigned to the address and four bits to the data or command, with another eight bits forming a checksum. The software compares the address to those stored and, if it matches, the output state is changed. There are mechanisms to learn an address and save it in EEPROM for later use. We’ll Have a look at our photos and Fig.1 to see how we assembled the parts for our prototype. The circuit is simple enough to be laid out on a breadboard, but we figured many constructors would want something robust. Fit the receiver module to the shield, watching the orientation. Solder it in place and then run insulated wires to the necessary pins on the shield. Note that some of the connections are made between adjacent pads on the underside of the shield. Next, fit the resistors and the LEDs. Make sure the LED anodes (the longer leads) connect to the resistors. Then connect all the LED cathodes together and to circuit ground. The relay module is wired up with plugsocket jumper wires; you could easily allocate it to a different button by connecting its S pin to a different digital pin on the shield. We also added a short length (~17cm) of coiled insulated wire to form the antenna; naturally, it connects to Parts List – RF Remote Receiver (JMP022) 1+ Transmitter from a Remote Controlled Mains Outlet Controller [Jaycar MS6147 or MS6148] 1 Arduino Uno R3 [Jaycar XC4410] 1 Prototyping shield [Jaycar XC4482] 1 5V single relay module [Jaycar XC4419] 1 433MHz wireless receiver module [Jaycar ZW3102] 4 yellow 3mm LEDs [Jaycar ZD0110] 4 470W ½W axial resistors [Jaycar RR0564] 1 USB cable to suit the Uno assorted hookup and jumper wires 60 Silicon Chip Australia's electronics magazine The 433MHz receiver module (Jaycar ZW3102; above) and 5V relay module (Jaycar XC4419, left). siliconchip.com.au the receiver module’s ANT pin. This length makes it a quarter-wave antenna at 433MHz, but we’ve generally found that these receivers work fine with just about any sort of antenna, or sometimes none at all! Programming Plug the shield into the Uno and connect it to your computer for programming. If you don’t already have the Arduino IDE installed, get it from www.arduino.cc/en/software Now install the RF433any library. Open the Library Manager in the IDE, search for “RF433any” and install the library with that name. We included a ZIP file of the version we used in the software download package (get it from siliconchip.au/Shop/6/1820). Assuming you have built the hardware as presented, select the Uno board and its serial port, then upload the RF_RECEIVER sketch. Open the serial monitor at 115,200 baud to interact with the Receiver. You should see something like Screen 1 appear when it starts up. The serial port is used for programming new codes and testing but it is not needed for normal operation (ie, receiving and responding to codes). The status report can also be triggered by sending a ‘~’ character (tilde) to the terminal. You will probably need to press Enter after that in the Serial Monitor, but other terminal programs may not require that. Pressing a button on a transmitter should result in a 32-bit code (eight hexadecimal nybbles) being printed to the serial monitor, like at the top of Screen 2. You can then enter “s” to save the address; it will be saved to the first free spot. The new code is seen in the updated status report. Subsequent presses of that button will also report that the Receiver is responding to that command, and you should see the corresponding LED switch on or off. Sending “0” on the serial monitor will delete the code allocated to the first slot; 1-4 will delete the others. So if you have multiple transmitters, you should press a button on each, then save it to the Receiver. After that, you can check the saved addresses with the “s” command. Each change to the address list is implemented immediately and also saved to EEPROM, so it will be available when the processor is restarted. Once it is all set up, it does not need to be connected to a computer and can be powered from a USB power supply instead. If you are interested in adding your own hardware to the Receiver, you can change the output pins near the start of the sketch with the likes of the RF_A_OUTPUT #define. The actions caused by each command can be customised further in the code­ Action() function. Summary The compact handheld transmitters of the Outlet Controller can now be used to control things other than mains outlets. With the Arduino IDE, you can add your own hardware and SC functions to our simple design. This is the finished RF Remote Receiver. You can change how the Arduino software responds to different commands. siliconchip.com.au Australia's electronics magazine SCREEN 1 ________________________________ A: OFF B: OFF C: OFF D: OFF 0 CODE: 0x----1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x0 ~ for debug data s to save last code to a slot 0-4 to clear a slot ∎ When first powered on, the Receiver will deliver the status report shown here to the serial port at 115,200 baud. You can also trigger the report by sending a tilde character (“~”). SCREEN 2 ________________________________ 903E0FAE Added to slot 0 Saved A: OFF B: OFF C: OFF D: OFF 0 CODE: 0x903E0 1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x903E0 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON Slot 0 cleared. A: ON B: OFF C: OFF D: OFF 0 CODE: 0x----1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x903E0 ∎ To add a code, press a button on your transmitter and see that the Receiver acknowledges it, then send “s” on the serial port. After that, you should see the Receiver respond to that transmitter. If you get an error that all the slots are full, free up a slot by sending a digit from 0 to 4. March 2025  61