Automatic 12V Lead Acid Battery Charger

Part	Total Qty.	Description
R1, R3	2	330 Ohm 1/4W Resistor
R2	1	100 Ohm 1/4W Pot
R4, R8 ,R5, R7	4	82 Ohm 2W Resistor
R6	1	100 Ohm 1/4W Resistor
R9	1	1K 1/4W Resistor
C1	1	220uF 25V Electrolytic Capacitor
D1	1	P600 Diode	Any 50V 5A or greater rectifier diode
D2	1	1N4004 Diode	1N4002, 1N4007
D3	1	5.6V Zener Diode
D4	1	LED (Red, Green or Yellow)
Q1	1	BT136 TRIAC
Q2	1	BRX49 SCR
T1	1	12V 4A Transformer	See Notes
F1	1	3A Fuse
S1	1	SPST Switch, 120VAC 5A
MISC	Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output, Fuse Holder

Notes

1. R2 will have to be adjusted to set the proper finish charge voltage. Flooded and gel batteries are         generally charged to 13.8V. If you are cycling the battery (AGM or gel) then 14.5V to 14.9V is generally recommended by battery manufacturers. To set up the charger, set the pot to midway, turn on the charger and then connect a battery to it's output. Monitor the charge with a voltmeter until the battery reaches the proper end voltage and then adjust the pot until the LED glows steadily. The charger has now been set. To charge multiple battery types you can mount the pot on the front of the case and have each position marked for the appropriate voltage.

2. Q1 will need a heatsink. If the circuit is mounted in a case then a small fan might be necessary and can generally be powered right off the output of D1.

3. T1 is a transformer with a primary voltage appropriate to your location (120V, 220V, etc.) and a secondary around 12V. Using a higher voltage secondary (16V-18V) will allow you to charge 16V batteries sometimes used in racing applications.

4. If the circuit is powered off, the battery should be disconnected from it's output otherwise the circuit will drain the battery slowly.

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Control electrical appliances using PC UPDATED

 Introduction

In this article I will first tell you about how to build the LED interface circuit for the Parallel Port and then how to control the circuit using software. With this very basic prototype you will be able to learn a lot how the parallel port works. So, I'll start with the circuit first.



                                              




Circuit Description

Components Used:-
Eight RED colored LEDs
DB-25 Male Connector
Zero PCB
Ribbon WireAll you need to do is to connect each data pin from the parallel port (pins 2 to 9) to positive terminal of a LED and one ground pin (any one from 18 to 25) to the negative terminal of all the LEDs.
Since LEDs have polarity, you should pay attention to correctly locate its positive and negative terminals. If you pay close attention, you will see that LEDs are not completely rounded, the cathode side is a little bit flat. Also the longer leg of LED is anode or positive terminal and the shorter leg is cathode or negative terminal.

                                          




How the circuit works?

Working of this circuit is pretty simple. When data at any pin 2 - 9 is '1' , that particular LED will glow, else if data is '0', the LED will stop glowing.

When data at any pin from 2 - 9 is '1',then it means that 5 volts is coming out of that pin and is going towards +ve terminal of LED. Circuit gets completed through ground pin (any from 18 to 25) and the LED glows until data at that particular pin is not '0'.

This data flow is controlled using software discussed below.

Software

To control any port we need a kernel mode driver software. Softwares generally run in USER mode. But to control theParallel Port we need a software running in kernel mode. I have used C#.Net for developing this software.
Download and install Microsoft .NET Framework Version 2.0.
Now download and install My Parallel Port Control Setup.
Download the source code in C#.Net.

In The End

This article was just an building block to the parallel port interfacing.

Color Sensor

Color Sensor

Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only �AND� gates and �NOT� gates. When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corres- ponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is. When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted : 1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs. 2. Common ends of the LDRs should be connected to positive supply. 3. Use good quality light filters. The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions

Basic Electronics   

    
The goal of this chapter is to provide some basic information about electronic circuits. We make the assumption that you have no prior knowledge of electronics, electricity, or circuits, and start from the basics. This is an unconventional approach, so it may be interesting, or at least amusing, even if you do have some experience. So, the first question is ``What is an electronic circuit?'' A circuit is a structure that directs and controls electric currents, presumably to perform some useful function. The very name "circuit" implies that the structure is closed, something like a loop. That is all very well, but this answer immediately raises a new question: "What is an electric current?" Again, the name "current" indicates that it refers to some type of flow, and in this case we mean a flow of electric charge, which is usually just called charge because electric charge is really the only kind there is. Finally we come to the basic question:

What is Charge?

No one knows what charge really is anymore than anyone knows what gravity is. Both are models, constructions, fabrications if you like, to describe and represent something that can be measured in the real world, specifically a force. Gravity is the name for a force between masses that we can feel and measure. Early workers observed that bodies in "certain electrical condition" also exerted forces on one another that they could measure, and they invented charge to explain their observations. Amazingly, only three simple postulates or assumptions, plus some experimental observations, are necessary to explain all electrical phenomena. Everything: currents, electronics, radio waves, and light. Not many things are so simple, so it is worth stating the three postulates clearly.

Charge exists.   

We just invent the name to represent the source of the physical force that can be observed. The assumption is that the more charge something has, the more force will be exerted. Charge is measured in units of Coulombs, abbreviated C. The unit was named to honor Charles Augustin Coulomb (1736-1806) the French aristocrat and engineer who first measured the force between charged objects using a sensitive torsion balance he invented. Coulomb lived in a time of political unrest and new ideas, the age of Voltaire and Rousseau. Fortunately, Coulomb completed most of his work before the revolution and prudently left Paris with the storming of the Bastille.

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