I wanted to be able to remotely find out the status of the switch, so for this I will need to monitor the state of the outputs, hence I needed another 4 GPIOs to do this (or 8 additional GPIOs once I upgraded to 8 positions). The ESP8266 has 8 GPIOs, more than enough to drive 4 relays (will it suffice to drive the 8 positions switch?). I started with a 4 position switch (but eventually I would be upgrading to 8 positions), so I needed to drive 4 relays. There is plenty of time to improve the design and make it robust for high power transmitters. I looked at several relay types, and for this first version of the switch, I decided that going with something on the lower power side would be a wise choice, something that could handle 100-300 Watts. For example, if you have equipment that you can control with digital signals, like a tuner, you can easily build a remote switch that can do the job! With this brief introduction to the ESP8266, you can start having a lot of fun prototyping all kinds of interesting WIFI projects. You can find more information, programming code examples and detailed instructions about setting up and programming the ESP8266 here Also, when you start copying LUA code into the module, CoolTerm does a great job. Something like CoolTerm available here would do the job. Then you need to choose a serial terminal to send commands to the serial module that will send commands to the ESP8266. For USB to serial, any FTDI232 based module will pretty much work, but be careful as they are counterfeit FTDI232 that can render useless, make sure whatever you get is genuine. The key things to know is that you will need a USB to serial module to initially talk to the ESP8266, be familiar with serial communication and able to do some script programming. There is plenty of material out there to get anyone going with this little wonder. The module also features a serial interface so you can communicate with it to program or debug it. This is perfect to drive LEDs or relays and make them open or close according to some logic and control, either running on the module or instructed via a web or TCP server. The ‘stuff’ is simply digital signals, a 0 or a 1, or in volts, a few millivolts or 3.3 volts. 8 GPIOs means that we can program the module so it can read and write stuff on these GPIOs. It has 8 available GPIOs (input/output ports or general purpose input/output) available, which was not enough for this application, but that was all I had. Figure 1 shows the ESP8266 ESP-12 which is the one I’ve chosen for the project. The ESP8266 comes in many different packages, depending on the number of I/O ports you want to have access to. The ESP8266 acts as an access point and/or a WIFI station, so once it is configured it acquires an IP address and then you can communicate with it via a web browser or a TCP connection (phone, tablet, computer, etc). LUA is a scripting language used widely in the gaming industry and I picked it to program the ESP8266 because of being compact, very high level and allowing me rapid prototyping. But it can also be programmed in LUA using the NodeMCU SDK (open source, just Google it or go to GitHub). It can be programmed in C by flashing it with the manufacturer’s (Espressif) software development kit (SDK). The core control processor for the switch is a WiFi enabled microcontroller from Espressif with a very small footprint, the ESP8266. It is limited in its power handling and frequency bandwidth, but I believe it is of great use for most of ham radio operators. This article describes the design and construction of a remote WiFi Antenna Switch for HF that is an order of magnitude more economical than any wireless remote switch available today.
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