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SILICON CHIP Mini Projects #012 – by Tim Blythman There are lots of IoT (Internet of Things) gadgets and widgets available, but many require a subscription to work. The WiFi Relay Remote Control could be considered one of the simplest IoT devices. You don’t need to sign up for anything, and you can build it yourself. WiFi Relay Remote Control W e covered Jaycar’s XC3804 WiFi Relay Module in January 2024 (siliconchip.au/Article/16088). As the name suggests, it is a small module containing a relay and a WiFi radio. The Relay Module can be controlled by sending commands over a WiFi network. It doesn’t even need an internet connection to work. While it’s a handy tool, another device is required to operate it. You could use an old mobile phone or similar WiFi-equipped device to control it, but we think there are better ways. So we’ve designed the WiFi Relay Remote Control. As the name suggests, it is a remote controller for the Relay Module. Since the Relay Module uses a dedicated WiFi network for its operation, it’s easy to set up a controller dedicated to that task. WiFi Relay Module There are more details on the WiFi Relay Module in our other article, but the principle of operation is as follows. The Relay Module sets up a WiFi access point, allowing WiFi clients to connect. When it receives particular web page requests, it operates the relay in response. So we just need to create a client that connects to the access point and then sends the appropriate requests depending on user input, like pushing a button. It would be good if it also indicated if the request has worked or not. That’s basically how the WiFi Relay Remote works. It has two pushbuttons connected to a WiFi Mini Main Board that connects to the access point provided by the Relay Module. When the buttons are pressed, it sends commands to open or close the relay. We’ve used illuminated pushbuttons, so the LEDs light up to show what is happening. You can see a video showing the WiFi Relay Remote in operation at siliconchip.au/link/abx4 Circuit details Fig.1 shows the circuit diagram. The pushbutton contacts are each connected between a digital I/O pin and ground. Internally, the processor on the WiFi Mini applies a weak pullup Fig.1: you could easily rig it up on a breadboard if you wanted to test it before building it. We recommend using the same pins on the D1 Mini as we did, as some other pins have special functions that might cause a conflict. Fig.2: how we placed parts on the underside of the shield (also refer to the adjacent photo). The shield’s top side is bare, apart from the switches. The wiring is hidden on the underside of the shield. We originally planned to use the D8 pin instead of D1, which would have made the layout neater. However, that is impractical, as D8 has a pulldown instead of a pullup. for those pins, so it can sense when the switch is closed and the I/O pin is pulled to ground. Two status LEDs are also provided that are internal to the illuminated pushbuttons. Each has a 220W series resistor to limit the current flow to an appropriate level for the LEDs. The WiFi Mini also has an onboard LED that lights up when pin D4 is driven low, so we can also use that as an indicator. Construction We intended the Remote to be a compact and self-contained unit, so the hardware has been assembled onto a small prototyping shield that can plug into a WiFi Mini. Fig.2 and the photos show how it has been laid out. Start by fitting the switches. Straighten the leads so that they will slot straight into the prototyping shield. To get the orientation correct, note the longer (LED anode) pins and place them as shown. Solder them after making sure the switches are flat against the shield. Solder the two resistors as shown, from the longer anode pin to the pads for D6 and D7. We use the inside row of pads so the outer rows are free for attaching the headers later. Keep the wire lead offcuts for the next steps. Next, solder a wire from the D5 pad to the corner lead of the switch as shown. All three leads on the other side of both switches connect to ground, so run a wire from each group of three back to the ground (G) pin. Then run a piece of insulated wire from the switch with the red LED back to D1. Slot the header pins onto the WiFi Mini (to align them) and then solder them to the prototyping shield. That’s it, the hardware is finished! Software operation The software consists of an Arduino sketch that uses the ESP8266 board profile. The sketch attempts to connect to the ‘Duinotech WiFi Relay’ access The assembled shield slots onto the top of the WiFi Mini, making for a compact unit. We used a small breadboard and jumper wires to power the WiFi Relay Module from the same supply for testing. The switch with the red ‘off’ LED is at the top, while the green ‘on’ LED is at the bottom. Unfortunately, there is no way to tell them apart when unlit, so our software lights both LEDs dimly so you can tell which is which. point created by the Relay Module, flashing the onboard (D4) LED until it does. Both switch LEDs are made to light dimly by driving them with a low duty cycle PWM (pulse width modulated) waveform so you can see which is on (green) and off (red). The software then waits until one of the buttons is pressed and sends the corresponding request to the Relay Module. Simultaneously, both LEDs switch off to indicate that a request is pending. If there is a successful response, the corresponding LED is switched on at full brightness, and the Relay Module will have its state set accordingly. If the request fails, both LEDs will return to a dim state after a while. The request can be tried again by pushing one of the buttons. Firmware installation Open the Arduino IDE and check that you have https://arduino.esp8266. com/stable/package_esp8266com_ index.json in your list of Board Manager URLs. Next, install the ESP8266 board profile from the Boards Manager Parts List – WiFi Relay Remote Control (JMP012) 1 Smart WiFi Relay Main Board [Jaycar XC3804] 1 WiFi Mini Main Board [Jaycar XC3802] 1 WiFi Mini Prototyping Shield [Jaycar XC3850] 1 PCB-mounting tactile switch with integrated red LED [Jaycar SP0620] 1 PCB-mounting tactile switch with integrated green LED [Jaycar SP0621] 2 220W ½W 1% axial resistors [Jaycar RR0556] 1 25mm length of insulated wire 2 5V DC power supplies siliconchip.com.au Australia's electronics magazine window. We used version 3.1.2 of the board profile, but later versions should work too. Download the software package for this project from siliconchip.com.au/ Shop/6/460 and then choose the ‘D1 R2 & Mini’ board type and its corresponding serial port in the IDE. Upload the sketch; no changes need to be made as the Relay Module uses a fixed WiFi network. Operation The LEDs on both buttons should light up dimly and the small blue LED on the WiFi Mini should start flashing. Power on the Relay Module. As you can see from our video and photo above, we just used a pair of jumper wires connected to the WiFi Mini’s 5V & GND (G) pins to get power for testing. After a few seconds, the blue LED will light solidly and you can control the Relay Module by pressing the buttons. If the blue LED goes out at any point, the Remote has lost its connection. In that case, check that the Relay Module is powered correctly. Note that other devices (such as a mobile phone or another Remote) can control the Relay Module. In this case, the LEDs might not show the correct status. There is no way to get the Relay Module’s status without triggering it, so there is no workaround for that without reprogramming the WiFi Relay Module with altered firmware. Now you can set up the Relay Module to run off its own power source and also control something. SC October 2024  67