Basic Electronics and Robotics Training Course: Part 2 (Page 1 of 3)
In this chapter, we will continue learning about resistors and how they are used in the following settings and laws:
- Resistors in Series
- Resistors in Parallel
- How resistors are used
- Capacitor Basic
Before proceeding, please remember that working with electronics can be dangerous. Make sure to be careful and follow all safety precautions when working on your project.
Before we get started, let’s look at how the resistors are coded with color bands and what it means.
Print out this chart for your bench for a quick reference when calculating resistor values.
Try to remember these colors and their color value; this will help you identify the ratings of any standard carbon resistor more quickly.
If you look at a resistor, you will see 4 bands of color. The first 2 colors are the numeric number for the value and the 3rd is a multiplier of the first 2 numbers and then the 4th color is it's tolerance. Meaning that the measured value of the resistors ohm will be in-between this percentage.
RED BLACK YELLOW GOLD
2 0 4 5%
204 = 20 x 10,000 = 200,000 ohm or 200K ohm
Note: You see that all I did was added four zeros to the end of the first two numbers--so don’t let the multiplying throw you off.
Tolerance = 200,000 x .05 = 10,000 +- the total resistance
So now this resistor can be anywhere between 210K and 190K
200,000 + 10,000 = 210,000 or 210K ohms
200,000 – 10,000 = 190,000 or 190K ohms
The letter K stands for 1,000 ohm so 210K = 210 x 1,000 = 210,000 ohms
Note: Most resistors are between 1 to 1 ½% tolerances of the manufacturing noted value, but can be as high or as low as its given tolerance.
Go ahead and try some other colors on your own to get a better understanding of how the color coding works.
Resistors in Series
When you place resistors in series, their ohmic values simply add together to get the total resistance. This is easy to see intuitively, and it’s quite simple to remember.
Suppose the following resistances are hooked up in series with each other: 112Ω, 470Ω, and 680Ω. What is the total resistance of the series combination?
Just add the values or each resistor, getting a total of 112 + 470 + 680 = 1262 Ω. You might round this off to R = 1260 Ω. It depends on the tolerances of the components how precise their actual values are to the ones specified by the manufacturer you use.
Now, it's time to prove what we just learned. You’ll need some resistors of any value and as many as you want to try to calculate in series, A calculator to add the values, a multi-meter and a breadboard.
These are the resistors that I had just picked out at random in my stock.
47K = 47,000 Ohms [ Yellow, Purple, Orange, Gold ]
27K = 27,000 Ohms [ Red, Purple, Orange, Gold ]
2.2K = 2,200 Ohms [ Red, Red, Red, Gold ]
1K = 1,000 Ohms [ Brown, Black, Red, Gold ]
If we put these in serial to each other on the breadboard and take a reading using our meter, then the resistance should be as follows:
47000 + 27000 + 2200 + 1000 = 77,200 Ohms or 77.2K for short
Now, let’s make that reading. My meter reads 75.6K.
But wait!! You say, “ I thought it was going to be 77.2K Ohms? What happened?”
Remember that Gold band on the resistors? Well if you remember that it means that there is a 5% tolerance on those resistors, so the reading can be between 5% up or down on the reading of each resistor. So let’s take a look at it in full at a 5% tolerance of our added resistance and see if our reading is in-between these values.
77,200 * 5% = 77,200 * .05 = 3,860 ohms +-
77,200 – 3,860 = 73,340 ohms
77,200 + 3,860 – 81,060 ohms
So the reading I got from my meter is correct and so the resistors are within the 5% tolerance.
Do as many of these as you like to make sure you understand how series work with resistors.