Resistors are electronic components which have a specific electrical resistance that oppose the flow of current through the circuit .Resistance is the value of resistor which measures how much electric current is limited with 1 volt voltage . They are made out of either carbon, metal, or metal-oxide film wrapped in a helix around and covered by an insulating material .
Types of Resistor
There are two types of resistor available in market
Type -1 Through-hole These resistors come with long, pliable leads which can be stuck into a breadboard or hand-soldered into a prototyping board or printed circuit board (PCB). These resistors are usually more useful in DIY projects , breadboarding, prototyping, or in any case where you’d find difficult to solder small SMD type resistor to your PCB . The long leads usually require trimming, and these resistors are bound to take up much more space than their surface-mount counterparts. You can buy a resistor as low as 0.1$ per resistor piece
The most common through-hole resistors come in an axial package as shown in picture . The size of an axial resistor is relative to its power rating. A common ½W resistor measures about 9.2mm across, while a smaller ¼W resistor is about 6.3mm long.
Type-2 Surface-mount These resistors are usually tiny black rectangles, terminated on either side with even smaller, shiny, silver, conductive edges. These resistors are intended to sit on top of PCBs, where they’re soldered onto pads or foot-prints . Because these resistors are so small, they’re usually set into place by a pick and place machine in the PCB factory and , and sent through an oven where solder melts and holds them in place. These types of resistor are very hard to assemble by hand . We need special tools to assemble it by hand precisely and accurately .
SMD resistors come in standardized sizes; usually either 0805 (0.8mm long by 0.5mm wide), 0603, or 0402. They comes along with a wheel where thousands of resistor are aligned in such a way that pick and place machine detect them and place automatically to the board They’re great for mass circuit-board-production, or in designs where space is a precious commodity.
Resistor color code
There is hard to mark the resistor with exact value of resistance in some case so international standard color code are followed by everyone in the world . To find the resistance with color code multiply these color followed by multiplier and add them with some error/tolerance value as shown in chart below .
Alternatively there are color calculator available on internet you can just google if you find difficult doing math to calculate resistance value or color value from resistor . Here i have embeded a color code calculator for through hole type resistor you can just enter the value and press calculate button to display the result .
note:if you do not have exact value of resistance you need , you should combine two or more resistor to match the value . you can comibine two or more resistance either parallel or series format . If you connect resistors in series the total value of resistor is sum of individual resistors and if you connect resistors in parallel the value of total resistance is multiplication of all value divide them with sum of all resistor value
Beside these There are many types of resistor with different package . Some resistor comes with IC package with a lots of resistors are available to a single ic , some resistors are variable types which have variable resistive property we can find there type of resistor in old radios and TV where brightness and volume is controlled menually . So you do not need to learn more about Resistor for now go further reading other things in this website that might be useful to you .