02
Resistors
In lesson 01 you learned about how electricity is the foundation of all moving machines, which is what robots are.
You learned how that electricity can be stored and tapped into.
In this lesson, you will learn the importance and application of resistors.
These are those beige or blue tubes with colorful bands you can find on any electronics board and even in some toys.
Types
There are 2 types you will come across, blue and beige colored.
The blue are:
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thicker
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contain metal oxide film
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more accurate because their tolerance for inaccuracy is only +/- 1%
The beige are:
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smaller
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contain carbon film
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have a tolerance for inaccuracy of +/- 5%
In other words, blue is bigger and better, beige is smaller and cheaper.
Both are great.
What am I seeing?
What do the colors mean?
Where am I?
"WHAT YEAR IS IT?"
Simply put, resistors throttle current which you learned was the flow of electricity, which we measure in amps(A).
Inside a resistor there is a poor electrical conducting material in the middle of two wire ends.
This resistance to conduct electricity from one end to the other is measured in ohms, the sign used is the Greek Omega, Ω.
Here is the symbol you will see on schematics for a resistor...
I kid, I kid!
Here is the real schematic symbol, a scrunched up piece of wire desperately trying to resist the current passing through itself.
Imagine a hose with water flowing through it. That current is too fast and will break our nozzle, so we jam some cotton into the hose effectively slowing down that flow. This is similar to what a resistor does.
Resistors can also get hot because they are RESISTING that flow, so there is a build up of electrical friction, but nothing to worry about at this point.
A cool thing is if we connect two resistors in series it divides the voltage!
Series just means they are connected in a line head to toe from the power source A to the target B (see below).
This will be a cheap and useful quick fix when our battery power is too much and we need to drop it so we don't burn out any components or the microcontroller itself.
Here is how to decode those color bands easily:
From left to right think number, number, decimal multiplier, % tolerance.
Take a minute to review this color scheme.
Practice writing it out.
It will make things much easier later!
Common Uses of Resistors
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protect LEDs
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Limit excessive current to protect components
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Pulling pins up (on) or down (off) on microcontrollers
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Limit charge rate of capacitors
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Provide appropriate voltage to transistors
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2 or more used in series as voltage divider
This is all alot of new information and can seem confusing at first.
I promise if you reread this page a few times and relax, giving yourself time to digest it, you WILL understand it faster than I did!
Pop Quiz
1. What does a resistor do?
2. What are the differences between the 2 common types?
3. What is the rating for a resistor that has color bands Red Black Black Gold?
4. What is the rating for a resistor that has color bands Red Purple Green Silver?
5. Name 2 common uses of resistors.
Make sure you have a basic kit. Arduino is fine, it contains the removable AVR 328p chip we will use.
I started with something very similar.
Summary
You know now the importance and uses of resistors.
You know how they function and the difference between the two commonly used types.
You also learned how to identify their resistance in ohms by reading the colored bands
You even learned that you can connect 2 resistors in series to decrease voltage.
This knowledge will come in handy when we start using LEDs.
See you in the next lesson!
