Sunday, March 28, 2010

Electronic Number Panel

In this design we present an electronic number display panel using low cost and low power electronic components. This proposed design is mainly based on CD4510 - CMOS up/down counter and SN74LS47 - BCD-to-Seven-Segment Decoder/Driver. With the existing configuration, this counter may be able to count (up/down) from 00 to 99 and it can easily extend to more digits by setting up additional CD4510 and SN74LS47 chip pairs.

Current system is also equipped with the beeper (which based around NE555 timer IC) to indicate the increment or decrement of the count.


This system is design to work with DC 9V – 12V (500mA) power supply and at the time of testing we use 10V (2.5A) DC power source to check this system. This proposed system contain 7805 regulator and it is necessary to apply suitable heat-sink to this regulator.

In this project, we design PCB using double sided PCB and make dimensions and shapes according to the existing enclosure of old electronic number panel system. It is not necessary to follow it, as it is.

The complete schematic diagram and PCB pattern is available to download at http://elect.wikispaces.com

Tuesday, March 23, 2010

Virtual MCU Base Programmable Timer

In this article we implement virtual (computer simulation base) microcontroller driven programmable timer using Proteus VSM. This proposed system is design using Microchip PIC16F877A – 8bit microcontroller and its system software is developed using MikroC PRO 3.2 for PIC. Most of the components in this proposed design are based on Proteus VSM - simulation models and we assign standard component names to them to assist in actual prototyping.

In this simulation we use PIC16F877A as main system controller and 4 row monochrome LCD display unit with HD44780 compliant controller (in 4bit mode). This proposed simulation model is design to work with +5V supply voltage, but it can also operate using battery power (3 × 1.5V).

When implementing this system for the real-life use, it is highly recommended to integrate battery backup facility to this system. It helps to drive this system continuously with minimum amount of disturbances.

According to the supplied source code, end user may be able to program start time and end time of the timer or specify only the start time. Once the timer get started user may be able to terminate the timer by pressing “OK/Timer Disable” key.

Please note that this system is provided only for demonstration purposes and end user need to calibrate MCU crystal and other associated components to obtain exact 1Hz clock trigger. The Lamp (L1) shown in the simulation model is for the demonstration purposes only. Ignore this component at the prototyping stages. All the source codes and Proteus ISIS simulation files of this project is available to download at elect.wikispaces.com.

Thursday, March 4, 2010

8 pin 2 digit seven segment display driver

This is a simple microcontroller base implementation to drive 2 digit 8 pin seven segment display (SSD) unit. For this implementation we use Microchip’s PIC16F84A – 8bit microcontroller unit and Proton+ PICBASIC compiler. Compared with other SSD units this SSD unit needs special algorithm to drive it. Some of the logical procedures to drive this SSD unit are illustrated in below,



This illustration is valid only for single digit of target SSD unit and it can easily expand to 2 digits by activating pin no 5 and 6 with appropriate inputs.

In attached design we use PIC16F84A MCU with 4 × 2SC945 general purpose NPN transistors to drive this TOD-4201LR SSD unit. This proposed system is design to work with +5V DC power supply and may not need any additional data source.

Supplied software for this project is for demonstration purposes only and it perform counting from 0 to 99 and then reset back to 0. To generate the output user need to assign required number to the value variable and make jump to the show_num section of code. According to the given lookup table this software may be able to generate digits from 0 to 9 and “E”, “-“ and “.” symbols.

All the source codes and schematic diagram of this project is available to download at http://elect.wikispaces.com