Counter Circuit DiagramsLCD-LED Display

Knitting Counter Schematic Circuit Diagram

Knitting always involves a lot of counting as you have to keep track how many rows you’ve knitted and how many should follow. This can, of course, be done with pen and paper, but it’s more fun with an electronic variant using a microcontroller.

Knitting Counter Schematic Circuit Diagram

This counter has the following functions:

  • Switch S1 increases the counter by one.
  • Switch S2 saves the current count in the EPROM memory of the microcontroller
  • Switch S3 resets both the counter and internal memory to zero.

Managing Power and Display Functions

Switch S4 serves as the device’s power toggle, activating or deactivating it. Upon activation, the display reveals the value stored in the internal memory. To conserve battery life, the display and counter functions automatically deactivate after 5-10 seconds. Pressing S1 reactivates the display and functions. Additionally, an LED indicator signals the device’s status, even when the display is off. To maximize the 9 V battery usage, a low dropout voltage regulator (LP2950) is employed. The core component of the circuit is the PIC 16F628A microcontroller, which multiplexes the three digits of the common cathode LED display. The software, written in PICbasic from Proton, can be easily modified if needed. Despite the absence of timers or interrupts, the software efficiently manages the display, turning it off based solely on programmed instructions.

Circuit Construction and Layout

The circuit is constructed on a standard experimenter’s board, with the component layout designed using the Lochmaster program from Abacom. This layout optimization ensures the circuit’s efficient functioning and organization of components.

Understanding Erasable Programmable Read-Only Memory (EPROM)

EPROM, short for Erasable Programmable Read-Only Memory, is a data circuit that retains its memory even when power is turned off. This unique characteristic allows EPROMs to store essential data, such as the operating system and program for access control panels in security systems. Erasure of EPROM data is achieved by exposing the memory chip to intense ultraviolet light through a designated window, enabling the memory to be reset and reprogrammed for reuse.

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