In this DIY electronics project, we will design and build a custom data logger using the HM628512BLFP-5, a 512k x 8-bit Static RAM (SRAM) chip from Hitachi. The goal of this project is to create a simple, yet powerful, data logging system that can store sensor data for later retrieval and analysis, using the HM628512BLFP-5 SRAM as the central data storage component. This project can be adapted for various applications, such as logging temperature data, monitoring light levels, or recording analog sensor values.

The HM628512BLFP-5 is a 512Kbit (64KB) static RAM chip, which provides fast and reliable memory storage without the need for refresh cycles, making it ideal for data logging applications. The SRAM will serve as the memory storage for the data logger, allowing us to store sensor readings in real-time. The data will be read from the SRAM periodically and displayed on a digital display or stored on an external memory card for further analysis.

Components Needed

For this DIY data logger project, we will need the following components:

· HM628512BLFP-5 SRAM Chip (1 piece)

· Microcontroller (e.g., Arduino or STM32)

· Temperature Sensor (e.g., LM35 or DHT22) – or any other sensor depending on the application

· Real-Time Clock (RTC) Module (e.g., DS3231) for timestamping the data

· I2C or SPI interface module for communication between the microcontroller and memory chip

· LCD Display or LED 7-Segment Display for displaying the data

· Push Buttons for user input to start, stop, or reset the data logging

· Resistors and Capacitors for signal conditioning and noise filtering

· Power Supply (5V regulated)

· Breadboard and Jumper Wires for prototyping

· Storage: SD card module (optional for storing logged data externally)

· Switch to turn the system on and off

Understanding the HM628512BLFP-5 SRAM Chip

The HM628512BLFP-5 is a 512K x 8-bit SRAM chip, meaning it has a total of 512Kbits (or 64KB) of storage, organized as 512K x 8-bits. Here are some key features and specifications of the chip:

· Size: 512Kbits (64KB)

· Access Time: 55ns (for fast data retrieval)

· Voltage: Operates at 5V with low power consumption

· Interface: Uses a parallel interface, making it relatively straightforward to interface with microcontrollers, though it requires careful handling of data lines, address lines, and control signals.

· No Refresh Required: As a static RAM (SRAM), it does not require periodic refreshing like dynamic RAM (DRAM), which simplifies circuit design.

· Data Integrity: Offers fast and reliable read/write operations, which is crucial for real-time data logging.

The HM628512BLFP-5 SRAM is well-suited for applications that require quick and reliable data storage with minimal complexity. In this project, the SRAM will act as the main memory for storing sensor data, and its fast access time will allow the system to log data at regular intervals without significant delay.

Project Overview: Custom Data Logger

The aim of this project is to create a custom data logger capable of logging sensor data (e.g., temperature readings) at fixed intervals and storing this data in the HM628512BLFP-5 SRAM. The system will also include a real-time clock (RTC) to timestamp the data and an LCD display to show the logged data or the current status of the logger.

The microcontroller will handle the following tasks:

1. Sensor Data Acquisition: The microcontroller will periodically read data from a sensor (e.g., a temperature sensor).

2. Data Storage: The sensor data, along with a timestamp from the RTC, will be written to the HM628512BLFP-5 SRAM for storage.

3. Data Retrieval: The microcontroller can later retrieve the logged data from the SRAM for display or export.

4. User Interface: The system will include push buttons for starting and stopping data logging and an LCD to display real-time data or status messages.

The SRAM will store a predefined number of readings (depending on the available memory and the amount of data being logged) until the memory is full or the system is reset.

Step-by-Step Guide to Building the Data Logger

Step 1: Setting Up the Hardware

Microcontroller Selection:

o Choose a microcontroller with sufficient I/O pins and memory to interface with the HM628512BLFP-5 SRAM. For simplicity, we will use an Arduino Uno in this project. The Arduino Uno has enough GPIO pins to handle the parallel interface of the SRAM and is easy to program.

Connecting the SRAM:

o The HM628512BLFP-5 is a parallel SRAM, which means it requires multiple connections to the microcontroller. The main connections are:

§ Address Lines (A0 to A18): These are used to select the memory address location within the SRAM.

§ Data Lines (D0 to D7): These are used for reading and writing data to the SRAM.

§ Control Lines:

§ Chip Select (CS): This line enables or disables the SRAM chip.

§ Output Enable (OE): This line enables or disables the output of data from the SRAM.

§ Write Enable (WE): This line enables or disables writing data to the SRAM.

o Connect the address lines (A0-A18) to digital I/O pins on the Arduino.

o Connect the data lines (D0-D7) to digital I/O pins on the Arduino.

o Use a 5V power supply to power both the SRAM and the Arduino.

Sensor Interface:

o In this example, we'll use an LM35 temperature sensor, which has an analog output. Connect the VCC and GND pins of the LM35 to the 5V and GND pins on the Arduino, respectively.

o The analog output pin of the LM35 will be connected to an analog input pin on the Arduino for reading temperature data.

RTC Module:

o The DS3231 RTC module will be used to provide accurate time and date for timestamping each data point. Connect the SDA and SCL pins of the DS3231 to the corresponding SDA and SCL pins on the Arduino (for I2C communication).

User Interface:

o An LCD display (e.g., a 16x2 LCD) will be used to show the data logging status and sensor readings. Connect the SDA and SCL pins of the LCD to the same pins on the Arduino as the RTC module.

o Push buttons will allow the user to start, stop, and reset the data logging. Connect one pin of the button to the digital I/O pin on the Arduino and the other to GND.

Step 2: Implementing the Data Logging System

Sensor Data Collection:

o The Arduino will periodically read data from the LM35 temperature sensor.

o Convert the analog reading from the LM35 into a temperature value (in degrees Celsius).

Timestamping:

o Use the DS3231 RTC module to get the current time and date whenever a new sensor reading is taken. The timestamp will be stored along with the sensor data.

Data Storage in SRAM:

o When the Arduino reads the sensor data, it will store both the temperature value and the timestamp into the HM628512BLFP-5 SRAM.

o Use the address lines of the SRAM to store each reading at a unique memory location. Each entry will consist of:

§ 1 byte for the temperature value (e.g., a value from 0-255, representing a scaled temperature).

§ 4 bytes for the timestamp (e.g., the year, month, day, hour, minute, and second).

Data Retrieval:

o The user can press a button to display the most recent data entry on the LCD. The Arduino will retrieve the data from the HM628512BLFP-5 SRAM by selecting the appropriate memory address and reading the stored values.

Memory Management:

o Since the HM628512BLFP-5 SRAM has a total of 64KB of memory, and each data entry requires about 5 bytes (1 byte for temperature and 4 bytes for the timestamp), you can store up to 12,800 data entries in the SRAM.

o Once the SRAM is full, the system can either overwrite the oldest data or stop logging new data, depending on how you choose to handle this situation.

Step 3: Displaying the Data

LCD Output:

o The Arduino will display the most recent reading, along with its timestamp, on the LCD screen. This can be achieved by retrieving the most recent entry from the SRAM and displaying the values.

Data Logging Status:

o The LCD will also show the current status of the data logger, such as "Logging Data," "Stopped," or "Memory Full," based on user input and the current state of the system.

Step 4: Power Management

Power Supply:

o A 5V power supply is required for the Arduino, SRAM, RTC, and sensor. This can be provided by a USB cable or an external battery pack.

o The system should be low power to enable portable use in remote locations. Consider using a power-saving mode on the Arduino when not logging data.

Conclusion

In this DIY project, we have built a custom data logger using the HM628512BLFP-5 SRAM chip to store sensor data and display it on an LCD screen. The combination of a microcontroller, temperature sensor, real-time clock (RTC), and SRAM provides an effective and reliable solution for logging data at regular intervals. This project demonstrates the versatility of the HM628512BLFP-5 SRAM chip, as it is capable of quickly storing and retrieving data in a real-time system.

With this data logger, you can easily extend the system to log data from different types of sensors, such as humidity sensors, light sensors, or even accelerometers, making it a flexible tool for a variety of measurement and monitoring tasks. Additionally, the project serves as a foundation for more advanced systems that could include wireless data transmission, data storage on SD cards, or cloud-based logging solutions.