# Large Pi-based Thermometer and Clock ## Overview This project combines a whole heap of modules to enable a Raspberry Pi to power a large 1.2 inch 4 digit 7 segment display. A small switch switches the display between showing the temperature and the current time. The project uses a real-time clock (RTC) to ensure that the Pi always has the correct time, even if it is not connected to the Internet. ![](https://cdn-learn.adafruit.com/assets/assets/000/006/396/medium800/raspberry_pi_overview.jpg?1396835749) # Large Pi-based Thermometer and Clock ## Hardware Info: ![](https://cdn-learn.adafruit.com/assets/assets/000/078/623/medium800/temperature___humidity_ds1307.jpg?1564094092) The RTC will allow a Raspberry Pi to know the time, even when not connected to the Internet. As such it is not essential to this project if your Raspberry Pi is going to have an Internet connection. The diagrams show GND connections in blue, +5V in red and +3.3V in purple. The I2C bus connections use orange wire for SDA and yellow for SCA.  ## 40-Pin (A, B, B+ and Zero) Cobbler Plus Schematic ![](https://cdn-learn.adafruit.com/assets/assets/000/078/625/medium800/temperature___humidity_Large_Pi_Based_Thermometer_Clock_bb.png?1564094808) ## 26-Pin (Raspberry Pi Rev 1 and Rev 2) Cobbler Schematic ![](https://cdn-learn.adafruit.com/assets/assets/000/006/463/medium800/raspberry_pi_fritzing4.png?1396836686) You may also like to look at separate tutorials for the RTC [http://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi](http://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi "Link: http://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi") and temperature sensor [http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing](http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing "Link: http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing") When everything is assembled, you can connect the ribbon cable to the GPIO connector. Remember to have the red or white band of the ribbon cable towards the SD card on the Raspberry Pi. # Large Pi-based Thermometer and Clock ## Pi Prep ## Update Your Pi to the Latest Raspbian Your Pi will need to be running the latest version of Raspbian. This tutorial was written using Raspbian Buster (July 2019). Checkout our guide for [Preparing an SD Card for your Raspberry Pi](https://learn.adafruit.com/adafruit-raspberry-pi-lesson-1-preparing-and-sd-card-for-your-raspberry-pi) if you have not done so already. After the installation is complete be sure and run the following commands to make confirm your installation packages are up to date.  ``` sudo apt-get update -y sudo apt-get upgrade -y sudo apt-get dist-upgrade -y ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/675/medium800/temperature___humidity_apt-get.jpeg?1564185432) ## Install adafruit-blinka Run the following command to install the adafruit\_blinka CircuitPython Libraries. ``` pip3 install adafruit-blinka ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/630/medium800/temperature___humidity_IMG_3015.jpg?1564101181) ## Enable 1-Wire Interface You'll need to start by enabling support for the DS18B20 1-Wire subsystem. [Visit this page for instructions on using raspi-config to enable 1-Wire support.](../../../../adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/ds18b20) ``` sudo raspi-config <Interfacing Options> <1-Wire> Enable/Disable <Back> <Finish> ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/626/medium800/temperature___humidity_1-wire-2.png?1564098471) ## Enable I2C Interface Our clock and 7-segment display work using I2C bus which the Raspberry Pi supports, but it needs to be enabled. This [page has step by step instructions](https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c). Enabling I2C is almost an identical process as enabling 1-Wire except that a reboot is required and we want to make sure to install the optional packages to scan the bus.  ``` sudo raspi-config <Interfacing Options> <I2C> Enable/Disable <Enable> <Back> <Finish> sudo reboot ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/673/medium800/temperature___humidity_i2c.png?1564184752) ## Test the I2C Bus ``` lsmod | grep -i i2c ``` Now that our Pi has rebooted we can confirm that the correct I2C modules have loaded with the following command. ![](https://cdn-learn.adafruit.com/assets/assets/000/078/628/medium800/temperature___humidity_IMG_3017.jpg?1564101154) ``` sudo i2cdetect -y 1 ``` This shows that two I2C addresses are in use – 0x68 and 0x70. Note that if you are using one of the very first Raspberry Pis (a 256MB Raspberry Pi Model B) then you will need to change the last digit of the command port 1 to port 0.  ![](https://cdn-learn.adafruit.com/assets/assets/000/078/629/medium800/temperature___humidity_IMG_3016.jpg?1564101169) # Install the HT16K33 Library The software for this project uses the Adafruit code for driving the 7 segment display.  ``` pip3 install adafruit-circuitpython-ht16k33 ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/841/medium800/temperature___humidity_ht16k33.png?1564521968) # Large Pi-based Thermometer and Clock ## Software ## CircuitPython Code The main loop simply checks the position of the switch and then either displays the temperature or the time. https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/Large-Pi-Based-Thermometer-Clock/thermo_clock.py We can easily copy this code onto our Pi's home directory using the 'wget' command and run it using the following python syntax. ## Download the Code ``` cd wget https://raw.githubusercontent.com/adafruit/Adafruit_Learning_System_Guides/master/Large-Pi-Based-Thermometer-Clock/thermo_clock.py ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/679/medium800/temperature___humidity_wget.png?1564186693) ## Run the Code The thermo\_clock.py script will not output anything when run, but what you should see is the time or temperature on the large 7-segment display. Using the slide switch should switch modes between time and temperature.  ``` python3 ./thermo_clock.py ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/078/682/medium800/temperature___humidity_thermo_clock.png?1564187042) ## Changing Temperature Units The temperature display can easily be changed from displaying degrees F to degrees C by swapping comment line in the code. ``` temp = int(read_temp()[1]) # F # temp = int(read_temp()[0]) # C ``` To swap, just move the # in front of the line that does not apply. ## Featured Products ### Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM [Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM](https://www.adafruit.com/product/3775) The Raspberry Pi 3 Model B is the most popular Raspberry Pi computer made, and the Pi Foundation knows you can always make a good thing _better_! And what could make the Pi 3 better? How about a _faster_ processor, 5 GHz WiFi, and updated Ethernet chip with PoE capability?... 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