The power saving mode here is what sets this Instructable apart from other examples showing day of the week, month, day of the month, time, humidity, and temperature. It is this capability that allows this project to be run from a battery, without the requirement for a “wall wart”.
I had posted an earlier Instructable, Humidity and Temperature LCD Display with Power Saving Mode: Minimal parts, Fun, Quick, and Very Inexpensive, and at the end of that Instructable I presented a picture of an optional modification. That modification included the day of the week, calendar, and time also shown on the same display. I received a number of messages requesting information on that augmented display. Thus, I am posting this Instructable as a modification and extension to that earlier one.
To save readers the problem of having to find the earlier Instructable mentioned, I have duplicated some of the information presented in that Instructable here, and of course am including the augmented information to allow the Day of the Week, Calendar, and the Time to also be presented in addition to Relative Humidity and Temperature. However, some readers may not need the day of the week, calendar, and time, and only need the humidity and temperature displayed. For those readers, that earlier Instructable will work well.
As I mentioned in the earlier Instructable, my study was not always at the best temperature, so I decided it would be useful to display the ambient temperature on my desk. The cost of a sensor that provided humidity, in addition to temperature, was not prohibitive; therefore a humidity display was included in that project.
An additional requirement arose as my spouse frequently asked me for the day of the week and/or the day of the month, so I decided to include these in the display as well. I made two copies of the project shown here. One for my study, and one for the room in our house where my spouse is often found. I used both a (1) real time Clock (RTC) and (2) a humidity and temperature sensor.
Both the DHT11 and DHT22 humidity/temperature sensors I considered provide temperature results in Centigrade. Fortunately it is an easy conversion to Fahrenheit (the format used in the USA, which is my location). The sketch below provides code that can be easily modified to display temperature in Centigrade, if that’s what’s used where you’re located.
I considered both the DHT22 and the DTH11 sensors, and settled on the DHT22, although slightly more expensive. The DHT11 can often be purchased for less than $2, while the DHT22 is often found for less than $5. If purchased directly from China, the cost can be even less. If I only wanted to display temperature, I could have used a TMP36 sensor instead of the DHT22, and realized some savings, and indeed this is how I built an even earlier DIY project of mine. However, I decided to include the display of relative humidity among other items displayed in this project.
For more detail: Calendar- Time – Humidity and Temperature Arduino LCD display