After several months of "Out of Stock", DS1307 RTC module has experienced a huge upgrade. It comes with a Gravity I2C interface. Its size is also reduced to fit miniaturization applications. Gravity I2C DS1307 RTC module is an easy-to-use Real Time Clock module. It is cheap and affordable in most applications such as time clock, data logger, etc. The new version DS1307 RTC module adopts a high precision crystal oscillator which reduces time error dramatically. The test conducted shows the time error is only about 1 second in 24 hours (the average time error of Mechanical Watches is about 20s). The module is powered by single cell CR1220 (service life: 3~5 years). It is smaller and keeps EEPROM 4KB ROM to record information related to alarm clocks and events. Besides, you can set the I2C address by resistance adjustment. The Gravity DS1307 RTC module uses the Gravity I2C interface and you can plug it on the DFRobot Gravity IO expansion shield directly. Cooperate with the Arduino DS1307 library developed by DFRobot, it is easy to realize functions like setting time and time display. It can be widely used in DA (Data Acquisition).

Note: According to the latest Air Transport Regulations, the batteries, magnets, and liquids transport will be very stringent, so the cell battery CR1220 will not come with the module anymore. Please buy it from the local supermarket.

Project 1. Hyduino - Automated Hydroponics with an Arduino
hydroponics is growing plants without the use of a traditional dirt medium by using a nutrient rich water solution. This is especially great for those people that that have limited areas in their backyard to grow in.
Hardware list:

• Arduino Mega 2560
• Peristaltic Pumps (2)
• Regular Pump
• pH Electrode Probe and Connection to Arduino
pH Up/Down Solution
• 5V Relay Modules for Arduino
• 12V Solenoid Valve
• DHT11 or DHT21 or DHT22 Humidity/Temperature Sensor
• Photosensitive Sensor for Arduino
• Breadboard
• Various Wires
• Grow Lights (mine are LED)
• Sockets for Grow Lights
• 3.2" TFT LCD Shield + Touch Screen (usually has an SD card reader on the back of it)
• Water Level Sensor Float Switch (2)
• I2C RTC DS1307 AT24C32 Real Time Clock Module
• 9V and 12V Power Supplies
• Hydroponics Pots (I'm using 10 - 3" pots for this)
• 1" PVC Pipe and Fittings + Drain Pipe and Fittings

Project 2. How to Monitor the Home Temperature&Humidity with BME680

Design Idea: Take DFRduino UNO R3 as the controller and DS1307 as a clock. Then BME680 Environmental Sensor collects environment data and pass it to UNO. Finally, UNO input data to SD card that received from the sensor in every second.

Materials List:

• 1.DFRduino UNO R3 - Arduino Compatible x1
• 2.Gravity IO Expansion Shield for Arduino V7.1 x1
• 3.Gravity: I2C DS1307 RTC Module x1
• 4.Gravity: I2C BME680 Environmental Sensor x1
• 5.MicroSD card module for Arduino x1
• 6.SD/MicroSD Memory Card (8 GB Class10 SDHC) x1
• 7.7.4v Lithium Battery x1