DIY Data Logger for Signal Recording & Analysis

If you're interested in data loggers, you might want to check out this article.

This is a paperless data logger that can record two pulse signals and two custom electrical signals (current or voltage). It allows you to set the recording interval and comes with a 10,000mAh battery, which lasts for around 20 days (it's not low power, but sufficient). By using an SD card, data can be exported directly to Excel for processing. The screen is mainly used for settings and viewing real-time data, with no data processing capability.

You can use the DS1307 RTC chip and SSD1306 screen via I2C communication, and communicate with the SD card via SPI. The 328P microcontroller supports two external interrupts and one pin-level change interrupt (this function is not readily available in Arduino resources; you'll need to refer to the chip's datasheet to customize the registers).

The overall appearance is shown below. You can 3D print a sturdy case, and the clips should be very secure.

The screen will automatically turn off after 30 seconds, and there is an LED indicator inside. The LED blinks when recording data or when the battery voltage is low.

The SD card can be easily removed for data transfer. You can set the logging interval to every 5 seconds, but keep in mind that this will generate a large amount of data.

The internal wiring is shown below. If you don't plan to upgrade in the future, you can use hot glue directly.

This development board is quite large, so you can place it inside without needing to redesign the board.

If the encoder is difficult to secure, you can use hot glue, but this may break easily. So, leave a little room and don't glue it completely — it will still be possible to remove it with some effort.

After testing, if the connections are normal, you can attach the cover.

The case is shown below. You can use the Data_Master module, which has a relatively simple function. The program is now more portable, but the screen's menu interface takes up a lot of storage space. The 32K storage is completely used up.

So, what functionality does this offer? It can record current, voltage, and pulse signals. It's compact and mainly used for devices like pulse flowmeters, 4-20mA instruments, and 0-20V voltage meters. For example, you can connect a thermometer to record temperature changes, a flowmeter to record flow, or a pressure gauge for later data analysis.