Dual Digital Thermometer
This is a thermometer kit that is fun to build, interesting to look at and above all very useful to keep track of indoor and outdoor temperatures.
The thermometer has 3 numeric displays that show the current temperature as well as minimum and maximum temperatures. Next to the numeric displays there is a 4-color bar graph display to simulate an old school mercury thermometer. You can choose to show the temperature in degrees Celsius or Fahrenheit. There is an external temperature probe included in the kit with a 1m cable that can be used to measure outside temperatures. The temperature range is from -50°C to 60℃ (-58℉ to 140℉) with a resolution of 0.1 degree.
You can set the thermometer to show the indoor or outdoor temperature only or both in and outdoor. When the thermometer is set to In-Out mode it will cycle between showing the indoor and outdoor temperature every 20 seconds.
From time to time the displays will be updated using a random animation. This makes this kit an interesting gadget to put on your desk. There are 9 different animations in total.
What is special about the electrical design of this kit is that all displays are driven using four 7400-series logic chips. Instead of a dedicated led driver the kit uses shift registers, counters and decoders as an alternative to drive the displays. A schematic can be found here.
Purchase a kit!
You can get the thermometer kit from my Tindie store. Each kit comes with all the components you need to put the thermometer togeher including the external themperature sensor with a cable length of 1m. For the finishing touches button caps and adhesive rubber feet are included. A micro USB cable to power the thermometer is not included with the kit.
Instructions on how to assemble the thermometer, operation notes and a schematic are included. No SMD soldering skills are required to assemble the kit. The micro USB socket that powers the thermometer is already soldered onto the board.