Here’s a week’s worth of temperature data from around my home. The blue, pink and red series are indoors. The orange and yellow series are outdoors - one inside a homemade Stevenson screen and the other under a pergola on the eastern side of the house.
I use a NodeMCU (ESP8266) device to drive B7971 nixie tubes using 8 x 74HC595 shift registers and 8 x SN75468 high voltage transistor arrays.
I talk about the code that makes this work, including using a Lua table to create a lookup table mapping characters to hex values that are sent to the shift registers to light the correct segments on the Nixie display.
I teardown a $10 motion activated solar garden light from Kmart in Australia.
I bought this product to solve the problem of not being able to locate my house key on the key chain at night. But I couldn’t resist tearing it down to discover the electronics that make it work.
Unlike most solar garden lights, that use Nickel Cadmium (NiCd) or Nickel Metal Hydride (NiMH) battery technology, this unit is powered by a single LiFePO4 (Lithium Iron Phosphate) cell. These cells produce a nominal 3.2V, which means that with a bit of hacking this unit could probably be used to power a microcontroller such as an Arduino at 8MHz.
I connect some rather nice fairy lights to an ESP-12 module based on the ESP8266 chip, running Nodemcu firmware and a simple Lua script. I describe how to connect a P-channel FDN340P MOSFET and a 2N3904 NPN transistor to form a high-side driver to switch big loads from this tiny wifi module and its 3.3V logic.
The result: I can control my fairy lights over wifi, potentially from anywhere in the world using MQTT. The possibilities are endless, but for now I’ll enjoy the cool glow and shimmering reflections of my “Moroccan” fairy lights…
The Lua code for controlling the fairylights using MQTT can be found here: