How to Read Schematic Diagram

Schematic diagram are drawings that shows all significant components, parts, or tasks (and their interconnections) of a circuit by means of standard symbols. Use these tips in order for you to learn how to read schematics.


Steps:

(1.) Familiarize yourself with the standard symbols

here is a little guide that shows you the basic symbols for all sorts of components. its handy to keep a little guide like this around in case you forgot some.

(2.) Look at the connections

physically parts are connected by wires, in the diagrams you will see black lines going from one part to the next. this means that you connect them with a wire

when the black lines cross in a diagram there are ways of telling whether or not the wires should be connected to each other.

(3.) Don't forget the polarity

some components to a circuit board are polarized, meaning one side is positive and the other is negative. this means you have to attach it in a certain way. for most symbols polarity is included in the symbol. in the the photos below you will find a guide to distinguishing polarity for various symbols.

*** TRY TO READ THIS SCHEMATIC ***

Okay, so now that we've gone through the basics, lets try to read a real world schematic of a circuit. so lets dissect this circuit!

the first symbol you see is the one with two horizontal lines, one smaller than the other. do you remember what is this? you can always look back at the guide, its a battery. 
Next you can see that there is a line connecting the positive side of the battery to the second part which if you look back at the guide you will find is a switch with two positions: closed (on), and open (off). seems backwards? its not because if you think of that little door like thing on the symbol closing than it would complete the circuit, thus being "on".
So when we flick the switch closed where does the electricity go next? that squiggly line is a resistor. this is a symbol you REALLY want to memorize. they are in almost every circuit. Basically in just makes sure that the not too much power from the battery is sucked up by the next part by resisting the flow of electricity.
So the final part is the triangle thing. that is a diode (as you can see on that handy chart in this ible). in this case a light emitting diode, or LED. remember LEDs are polarized so when you actually go to make this circuit make sure you put it in right. 
finally you can see that the negative side of the LED connects back to the negative battery terminal and the circuit is complete! And after this, you can now make your own FLASH LIGHT. 

you can now continue on to building the actual thing!

Reference: http://www.instructables.com

Kirchhoffs Circuit Law

   with one of Kirchhoffs laws dealing with the current flowing around a closed circuit, Kirchhoffs Current Law, (KCL)while the other law deals with the voltage sources present in a closed circuit, Kirchhoffs Voltage Law, (KVL).

Kirchhoffs First Law – The Current Law, (KCL)                 

      states that the “total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node“.

• The 1 ^st law or the junction rule: for a given junction or node in a circuit, the sum of the currents entering equals the sum of the currents leaving. This law is a statement of charge conservation.The junction rule tells us I₁ = I₂ + I₃ .

Kirchhoffs Second Law – The Voltage Law, (KVL)

    states that “in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop” which is also equal to zero. 

• The 2 nd law or the loop rule: around any closed loop in a circuit, the sum of the potential differences across all elements is zero. This law is a statement of energy conservation, in that any charge that starts and ends up at the same point with the same velocity must have gained as much energy as it lost. where the boxes denote a circuit element, the loop rule tells us 0 = (V_b - V_a) + (V_c - V_b) + (V_d - V_c) + (V_d - V_a) .

Understanding the Basics

Understanding the metric system is easy if you know what base units means and what the prefixes are and how they are used. The metric system was designed to make measuring things easier and universal.

1

Know how the base units work. In the metric system, each form of measurement has one base unit. The most common base units are:

• length - meter (m)
• volume - liter (l)
• mass - gram (g)

2

Understand multiples of ten. The metric system is a decimal system, meaning every unit gets bigger or smaller by multiples of ten: Smaller measurements are divided by ten; larger measurements are multiplied by ten.

3

Learn the common prefixes. The common prefixes are milli-,centi-, deci-, deka-, hecto-, and kilo-. In the metric system, you look at the prefix to see the size of the unit, while the base unit tells you what is being measured. For instance, if you are measuring mass, the base is grams. If you want to know the size, then you look at the prefix. When the prefix kilo- is used, it means that the size is 1,000 time larger than the base. A kilogram is 1,000 times larger than the base of 1 gram.

4

Use the sentence “King Henry Doesn’t (Usually) Drink Chocolate Milk” to remember these prefixes. In this sentence, the first letter of each word represents a prefix while “Usually” represents unit or the base unit you are using. This sentence represents the prefixes in this order: kilo-, hecto-, deka-, unit, deci-, centi-, and milli-.

5

Draw a diagram to help you remember. Drawing a diagram will not only help you remember, but will help you to understand the relationships between prefixes and base units. Draw a horizontal line. Then, draw seven vertical lines across the horizontal line. Write the first letter of the prefixes above each vertical line: K, H, D, U, D, C, and M. Beneath the vertical line with “U,” write the first letter for the most common units: meters, liters, and grams.

Reference: http://www.wikihow.com

Soldering

Soldering is defined as "the joining of metals by a fusion of alloys which have relatively low melting points". In other words, you use a metal that has a low melting point to adhere the surfaces to be soldered together.

Part 1: Prepare the materials

Use a soldering iron with the appropriate heat control.

Use solder wire of an appropriate alloy.

Try to get flux-cored wire if possible.

Get the necessary board and components.

Get a clamp to hold the components.

Part 2: Soldering Process

1. Prepare the components for soldering. Select the correct component by checking it's type and value carefully.
2. Be extremely careful and solder in an appropriate location. Always solder in a well-ventilated area, using breathing and eye protection
3. "Tin" the solder. Melt a small blob of solder on end of the soldering iron. This process is called tinning and it helps to improve heat flow from the iron to the lead and pad, keeping the board safe from the heat.
4. Feed the solder onto the interface between the pad and lead. Flux from the solder wire is only active for about one second maximum after melting onto the joint as it is slowly burned off by heat.
5. Stop feeding the solder interface is filled. No more than a drop or two of solder should be necessary for each joint, though it will vary slightly for different components.