DIY Electronics Project: Building a Memory-Based Digital Clock Using the HM6116ALP-3

Introduction

In the world of DIY electronics, creating a simple, functional project that combines various fundamental components can be both educational and rewarding. One such project involves the use of a dynamic random access memory (DRAM) chip, the HM6116ALP-3, in conjunction with a basic digital clock circuit. In this article, we’ll delve into how to design and build a Memory-Based Digital Clock, which will help you understand the versatility of the HM6116ALP-3 while giving you an enjoyable and practical electronic project to work on.

The HM6116ALP-3 is a 2K × 8-bit static RAM (SRAM) chip that provides ample storage for small-scale applications. Though SRAM is typically used in devices for temporary storage, in this project, we’ll use it to store time-related data. By leveraging the memory chip’s storage capabilities and combining it with a simple clock circuit, you can create a digital clock with custom time display features, all while learning about how memory works in electronic systems.

Let’s walk through the steps of this project, from components to construction, and see how we can build a fully functional memory-based digital clock.

Components Needed

Before starting your project, gather the following components:

1. HM6116ALP-3 SRAM Chip – The central component used to store the clock time data.
2. 555 Timer IC – For generating clock pulses at regular intervals.
3. Microcontroller (e.g., ATmega328P) – To control the operation of the clock and manage the SRAM.
4. 7-Segment Display – For displaying the current time in hours and minutes.
5. Resistors and Capacitors – For various signal conditioning and to ensure the proper functioning of the ICs.
6. Crystal Oscillator – To provide a stable clock signal for the 555 Timer.
7. Push Buttons – For setting the time or adjusting it manually.
8. Power Supply – To power the entire circuit.
9. Miscellaneous (wires, soldering iron, breadboard, etc.)

Project Overview

This digital clock is built around a central Microcontroller (MCU), which interfaces with both the HM6116ALP-3 SRAM chip and a 7-segment display to provide the current time. The main purpose of the SRAM is to store the time values and allow them to be updated regularly as the clock ticks forward. The 555 Timer will generate periodic clock pulses that keep the time updated.

The microcontroller will be programmed to manage the data stored in the SRAM, while also interpreting user input (e.g., setting the time using push buttons). The time will be displayed on a 7-segment display, showing hours and minutes in a standard digital format.

Step 1: Understanding the HM6116ALP-3 SRAM Chip

The HM6116ALP-3 is a 2K × 8-bit static RAM (SRAM) module. The 2K memory refers to 2048 bytes, and each byte is 8 bits wide. This is a small amount of memory, but for a digital clock, it’s more than enough to store the current time. Specifically, we will use two bytes to store the hours and minutes, one byte for the seconds, and possibly another byte for flags (indicating AM/PM or whether the clock is running).

• Address Bus: The address bus for this chip is 11 bits wide, meaning we can access any of the 2048 addresses by selecting appropriate address lines.
• Data Bus: The data bus is 8 bits wide, so each memory location can store an 8-bit value, which is ideal for storing numerical values like time in hours, minutes, and seconds.

Understanding how the memory is accessed will be crucial in programming the microcontroller to read and write time values to the SRAM.

Step 2: The Clock Pulse Generator

To keep track of time, we need a reliable source of periodic pulses that can increment the time data stored in the SRAM. For this purpose, we’ll use a 555 Timer IC configured in astable mode. The 555 Timer is capable of generating precise time intervals, and it is perfect for creating the clock signal that will trigger the microcontroller to increment the time.

The frequency of the 555 Timer needs to be set so that the pulse duration corresponds to a reasonable time increment. A common choice would be to set the timer to generate a pulse every second. This will give us the periodicity required to keep the time in sync with the real world.

Step 3: Microcontroller and SRAM Interface

The microcontroller is the heart of the clock. It controls the reading and writing of time data from the HM6116ALP-3 SRAM chip. The microcontroller will use the following key operations:

1. Write Time to SRAM: On initial power-up, or when the user sets the time, the microcontroller will write the time data (e.g., hours, minutes, seconds) to the appropriate memory locations on the SRAM chip.

2. Read Time from SRAM: Every time the clock ticks (every second, for instance), the microcontroller will read the time data from SRAM, increment the seconds, and update the values of minutes and hours when necessary.

3. Update Display: After reading the updated time from SRAM, the microcontroller will send the values to the 7-segment display to show the current time to the user.

4. Button Input: The microcontroller will also monitor the push buttons, allowing the user to manually adjust the time. When a button is pressed, the microcontroller will modify the appropriate value stored in SRAM and update the display accordingly.

Step 4: Wiring the 7-Segment Display

A 7-segment display will be used to show the current time. These displays are commonly used in digital clocks because they can clearly show numeric values. For this project, you’ll use two 7-segment displays to show the time in hours and minutes (e.g., 12:34).

To interface the display with the microcontroller, you’ll connect each of the 7 segments to one of the microcontroller’s output pins, through current-limiting resistors. The microcontroller will control the individual segments to display the digits corresponding to the current hour and minute.

Step 5: Setting Up the Push Buttons

In addition to displaying the time, you’ll also need to set the clock’s time manually. To do this, two push buttons will be used: one for increasing the hour and the other for increasing the minute. When the user presses a button, the corresponding value will increment, and the updated value will be stored in the SRAM.

Step 6: Powering the Circuit

A regulated 5V power supply is needed to power both the microcontroller and the other components. Since this circuit is quite low power, a simple USB connection or a 5V adapter will work fine for powering the project.

Step 7: Putting It All Together

With all the components gathered and understood, you can now begin assembling the circuit on a breadboard or a printed circuit board (PCB). Begin by wiring the 555 Timer to generate clock pulses, and then interface the microcontroller with both the HM6116ALP-3 SRAM and the 7-segment displays. Wire the push buttons to the microcontroller’s input pins for time setting, and finally, connect everything to your power supply.

Once the hardware is set up, you can begin programming the microcontroller to handle the clock functions. The program will need to:

1. Initialize the SRAM with a starting time value (e.g., 12:00).
2. Read the time values from SRAM every second.
3. Increment the seconds and, if necessary, update the minutes and hours.
4. Update the display with the new time.
5. Handle button presses to adjust the time.

Conclusion

This memory-based digital clock project is a fantastic way to explore both the practical and theoretical aspects of using memory chips like the HM6116ALP-3 in DIY electronics. It combines timekeeping, user input handling, and display management into a single, cohesive project.

By using the HM6116ALP-3 to store and manage time data, you not only gain hands-on experience with memory components but also develop a deeper understanding of how microcontrollers can interface with peripheral devices. Whether you are a beginner or an experienced hobbyist, this project offers a valuable opportunity to enhance your skills and build a useful, functional device for everyday use.