EPROM is a widely used memory type, commonly found in microcontroller applications as a program memory. In addition to its primary use for storing programs, it can also function as a programmable logic device (PLD). This allows EPROMs to implement not only basic logic functions but also more complex control and measurement systems. Below are two practical examples of how EPROMs can be utilized.
High-Precision Digital DC Voltmeter
Traditional digital voltmeters often use liquid crystal displays (LCDs), which may have limited brightness and small digits. This design introduces a large LED-based digital DC voltmeter that uses an A/D converter and EPROM as the core component. It is ideal for educational demonstrations or instrument panel setups where accurate voltage measurement and control are required.
The circuit includes IC1 (MAX174), which converts the analog input into a 12-bit digital signal. This signal serves as the address for the EPROM (IC2: 27512). The data stored in the EPROM corresponds to the display values for each voltage reading. IC3–IC6 act as BCD-to-seven-segment decoders, while IC7 (556) generates timing pulses and IC8 (CD4584) conditions the signals. The four-digit LED display is driven sequentially, with the EPROM addressing different sections for upper and lower digits, ensuring smooth and flicker-free operation.
The resolution of the system is 4.88 mV per LSB, but since only two decimal places are displayed, the EPROM only needs to store data accurate to 0.01 V. To expand the range, a switch can be added to select between 0–20 V and 0–200 V, with appropriate attenuation for the higher range. Additional ranges can be managed by using higher address bits in the EPROM, allowing for multiple configurations without reprogramming the entire chip.
Lantern Controller
To enhance festive environments, a lantern controller using an EPROM can generate various lighting patterns. The circuit uses a ripple counter (e.g., CD4040) to cycle through addresses in the EPROM, which stores lighting sequences. Each bit in the EPROM data determines whether a specific light is on or off. By adjusting the DIP switches, users can change the lighting patterns easily.
The EPROM can store up to 256 different lighting programs, each lasting about 4 minutes at 1 Hz. For more channels, additional latches (like 74HC373) can be used, expanding the system to control 64 or more lights. This approach ensures flexibility and scalability for various applications, from simple displays to complex multi-channel lighting systems.
By leveraging the versatility of EPROMs, engineers can create efficient and customizable solutions for both measurement and control tasks, making them valuable components in a wide range of electronic designs.
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