Introduction

In the world of electronics, data logging is an essential function in various fields, from monitoring environmental conditions to collecting data for scientific experiments. A data logger is a device used to record data over time, typically using sensors to capture physical parameters such as temperature, humidity, pressure, or light intensity. While data loggers can be complex, they often rely on components like memory chips to store the gathered data before being analyzed.

In this DIY project, we’ll build a simple data logger using the HM62256ALP-10 SRAM chip. The HM62256ALP-10 is a 32KB static random-access memory (SRAM) chip, which will serve as the data storage element in our logger. We'll create a basic system to record sensor data (e.g., temperature) and store it in the SRAM for later retrieval. The logger will not require complex code, as it will use simple analog sensors and a microcontroller to read data, store it in memory, and then output the stored data on a simple display.

By the end of the project, you will have a functional data logger that can collect and store data from a sensor, using the HM62256ALP-10 SRAM to temporarily hold the recorded information.

Materials and Tools

Components Needed:

· 1 x HM62256ALP-10 SRAM (32KB)

· 1 x Microcontroller (e.g., Arduino, PIC, or AVR)

· 1 x Analog Temperature Sensor (e.g., LM35 or TMP36)

· 1 x 16x2 LCD Display (for displaying the data or status)

· 1 x Real-Time Clock (RTC) Module (for time-stamping the data)

· 1 x Pushbutton (for manually triggering data recording)

· Resistors (various values)

· Capacitors (for stabilization and noise reduction)

· Breadboard or PCB (for assembling the circuit)

· Power Supply (5V DC)

· Jumper Wires (for making connections)

· Soldering Iron and Solder (for permanent assembly)

· Multimeter (for testing and troubleshooting)

Overview of the HM62256ALP-10 SRAM

The HM62256ALP-10 is a 32KB static RAM chip, commonly used for short-term data storage in embedded systems. This SRAM chip provides fast, low-latency read and write operations, making it an ideal choice for applications where high-speed data retrieval and storage are needed. Unlike dynamic RAM (DRAM), SRAM does not require periodic refreshing, making it simpler to interface with and use in smaller projects.

The HM62256ALP-10 operates on a 5V supply and has a 32KB memory capacity, organized in 8-bit words (i.e., it has 4,096 memory locations). It supports a fast access time of 100ns, meaning that the microcontroller can read from or write to it quickly, making it well-suited for logging data at relatively high speeds.

In this project, we will use the SRAM to store sensor readings and later retrieve the data for display. The system will also use a real-time clock (RTC) to record timestamps, allowing us to log when each reading was taken.

System Design Overview

The design of this data logger involves four main components:

1. Sensor: The system will use an analog sensor to collect data (in this case, temperature). The sensor will output an analog voltage that corresponds to the measured temperature.

2. Analog-to-Digital Converter (ADC): The microcontroller will read the analog voltage from the sensor using an internal or external ADC.

3. Memory: The HM62256ALP-10 SRAM chip will be used to store the data. Each data entry will include the sensor reading and a timestamp from the RTC.

4. Display and User Interface: A 16x2 LCD display will show either the current sensor reading or the stored data. A pushbutton will allow the user to manually trigger data recording.

The microcontroller will be responsible for managing the system, including reading sensor data, storing it in memory, and displaying the data on the LCD screen.

Circuit Diagram

The following components are involved in the circuit:

Analog Temperature Sensor (LM35 or TMP36): This will provide an analog voltage output that corresponds to the temperature.

o The Vout pin of the sensor will be connected to the ADC input of the microcontroller.

HM62256ALP-10 SRAM: The memory chip will store the temperature readings.

o The microcontroller will interface with the SRAM using the Address, Data, and Control pins. The chip will be connected using the address lines (A0 to A14) to access different memory locations. The data lines (D0 to D7) will be used for writing and reading data.

RTC Module (e.g., DS3231): This module provides real-time clock functionality to timestamp the data.

o The SCL and SDA pins of the RTC will communicate with the microcontroller using I2C protocol.

o The RTC will be powered by the same 5V supply.

16x2 LCD Display: This will display the current data or time.

o The LCD will be connected to the microcontroller using the I2C interface (for ease of connection) or the parallel interface (if required).

Pushbutton: The pushbutton will trigger the recording of data to SRAM.

o The button will be connected to a digital input pin on the microcontroller, which will trigger the microcontroller to read the sensor data and store it.

Building the Circuit

Step 1: Connecting the Temperature Sensor

Start by connecting the LM35 temperature sensor to the microcontroller. The LM35 provides a 1mV per degree Celsius output, so a 10°C temperature will result in a 10mV output from the sensor. The sensor’s Vout pin should be connected to the ADC input pin of the microcontroller.

· Connect the Vcc pin of the sensor to 5V, and the GND pin to ground.

· The Vout pin will connect to one of the ADC pins on the microcontroller (e.g., A0 on an Arduino).

Step 2: Wiring the HM62256ALP-10 SRAM

Next, wire the HM62256ALP-10 SRAM to the microcontroller. The SRAM chip has a set of address lines (A0-A14) that will be used to address memory locations, data lines (D0-D7) for reading and writing data, and control pins for the read/write operations.

· Connect the address lines (A0-A14) to the microcontroller's digital I/O pins. For a simple design, you can use a subset of available address lines to control memory access.

· The data lines (D0-D7) will also connect to the microcontroller's digital I/O pins for reading and writing the stored data.

· The CS (chip select), OE (output enable), and WE (write enable) control pins should be appropriately wired to the microcontroller to manage the read/write operations.

Step 3: Integrating the RTC Module

For time-stamping the data, use an RTC module like the DS3231, which communicates with the microcontroller via I2C.

· Connect the SCL and SDA pins of the RTC to the corresponding I2C pins on the microcontroller (typically A4 and A5 on an Arduino).

· Connect the Vcc and GND pins to the 5V and ground rails, respectively.

The microcontroller will periodically read the RTC to get the current timestamp (in hours, minutes, and seconds) and store it alongside the sensor data.

Step 4: Connecting the LCD Display

The 16x2 LCD display will provide a simple interface to view the current data. If using an I2C interface LCD, connect the SCL and SDA pins to the microcontroller’s I2C bus. If using a parallel LCD, connect the data and control lines accordingly.

· The LCD will display the current sensor reading and the timestamp retrieved from the RTC. You can choose to display the data in either a real-time format or after data logging is triggered.

Step 5: Connecting the Pushbutton

The pushbutton will allow the user to manually trigger data logging. Connect one pin of the button to the microcontroller’s digital input pin (e.g., D2), and the other pin to ground. When the button is pressed, the microcontroller will read the sensor data, retrieve the timestamp from the RTC, and store the data in SRAM.

Step 6: Power Supply

Ensure the entire circuit is powered by a 5V DC power supply. The 5V rail should power the microcontroller, the RTC, the SRAM, and the LCD.

Testing and Calibration

Once the circuit is assembled, it’s time to test the data logger. Perform the following steps:

1. Sensor Calibration: Verify that the temperature sensor gives the correct output and matches the expected values based on known reference temperatures.

2. Data Logging: Press the pushbutton to trigger data logging. Check that the microcontroller reads the sensor data, stores it in SRAM, and then displays it on the LCD.

3. Timestamping: Ensure that the RTC is providing the correct time and that each data entry includes the timestamp.

4. Retrieving Data: Check that the system can correctly read back the data from SRAM and display it on the LCD.

Conclusion

This DIY data logger project demonstrates the use of the HM62256ALP-10 SRAM for temporary data storage, interfacing with an analog temperature sensor, an RTC module, and a 16x2 LCD display to build a simple but effective data logging system. While this is a basic design, it forms the foundation for more advanced data loggers that can handle multiple sensors, larger memory capacities, and wireless data transmission.

By following the steps in this article, you will learn how to interface memory chips with microcontrollers, read sensor data, and store it for later use. The project also provides hands-on experience with various components and teaches how to design and implement a basic data logging system that can be expanded in the future.