Electronic Combination Lock Using PIC16F628A

This electronic combination lock can be use with an outdoor gate. The functionality is implemented in software. It turns on a relay (usually to open a door) for a few seconds if someone enters the valid code. The relay can operate a power to open type electric strike with a shorting contact or a power-to-hold type electromagnetic lock with a breaking contact (we need the relay because these locks usually work with AC, not DC). The code can be changed any time after entering the current code.

Water Level Controller and motor Protector v2

This is the v2 by using PIC16F877A with minimum components. The most left circuitry is the same as in mains monitor; used to check to variation in ac voltage (operating range is between 200v ac - 240v ac). Five pull-up resistor circuitry is used to measure the water level in the desired water tank. Note that the push buttons are used here is only for illustration purpose, basically they are representing the probes (6 probes made of 28 gauge wire; one is of ground (reference) level). The left most probe indicates 20% of water in tank, next indicates 40% and so on till 100% or full level.

Stepper Motor Programming

Full Step Sequence:
I am using PIC16F628A with uln2003 to drive unipolar stepper motor. Adjusting the delay will increase or decrease the speed of the motor. Here just for demonstration i have taken some delay, you can change it as you want. If you want to change the direction of stepper motor, just reverse the step sequence (means 9,3,6, and C etc). 

Unipolar Stepper Motor Drivers

There are actually many ways you can interface a stepper motor to your controller, out of them the most used interfaces are:

• Interface using L293D - H-Bridge Motor Drive
• Interface using ULN2003/2004 - Darlington Arrays

Stepper Motor Stepping Modes

Stepper Motor Connections:
Unipolar motor should have five or six connections depending on the model. If the motor has six connections like the one pictured above, you have to join pins 1 and 2 (red) together and connect them to a (+) 12-24V voltage supply. The remaining pins; a1 (yellow), b1 (black), a2 (orange), b2 (brown) should be connected to a driver (ULN2003 etc).

Stepper Motor Introduction

Introduction:
This section of tutorial will explain you everything that you need to know about stepper motors. Stepper motors can be used in various areas of your microcontroller projects such as making robots, robotic arm, automatic door lock system etc. This tutorial will explain you construction of stepper motors (unipolar and bipolar stepper motors ), basic pricipal, different controlling types (Half step and Full step), Interfacing Techniques (using ULN2003) and programming your microcontroller in C to control stepper motor. 

Mains Monitor

Mains Monitor or Manager is the circuit; i used to measure or check the ac voltage and frequency. Its accuracy is about 90-97% and quite handy for hobbyist. The ac voltage limit is 500v ac and 99Hz for frequency. There are two different ideas combine, to achieve this goal. 

Glow Plug Controller

In diesel engines, the air in the cylinders is not hot enough to ignite the fuel under cold conditions. Therefore each cylinder of these engines is fitted with an electric heater known as ‘glow plug.’ A control circuit is necessary to optimise the functioning of glow plugs. It raises the air temperature inside the engine cylinder for quick and reliable starting, extended battery life and reduced diesel consumption.

Mini UPS System

This circuit provides an un-interrupted power supply (UPS) to operate 12V, 9V and 5V DC-powered instruments at up to 1A current. The backup battery takes up the load without spikes or delay when the mains power gets interrupted. It can also be used as a workbench power supply that provides 12V, 9V and 5V operating voltages. The circuit immediately disconnects the load when the battery voltage reduces to 10.5V to prevent deep discharge of the battery. LED1 indication is provided to show the full charge voltage level of the battery. miniature white LEDs (LED2 and LED3) are used as emergency lamps during power failure at night.