Basic Electronics and Robotics Training Course Part 1Posted by GWJax on Tuesday, 11 May 2010
Basic Electronics and Robotics Training Course
Welcome again to another one of my articles. This article is part 1 of many and I will be teaching you basic electronics for robotics and hacks, plus mods for your own robots.
There will be projects to do in almost every article to help you understand the material that is provided. Please rank these articles so we can see how you like them and also leave comments or questions about the related material that you are having trouble with and I’ll do my best to help you understand the information.
PLEASE NOTE: Please feel free to share any information that you think would help out other members as long as the information you provide is on topic and any other article pertaining to the Basic Electronics and Robotics Training Course articles.
For all of you that are new to robotics and electronics, I truly hope you enjoy these lessons. As with anything it takes time and practice to build, mod or make your own circuits and robots. There will be a lot of math involved for those who want to design circuits but in general basic algebra and basic math is all what is needed such as OHMs Law: E = IR where E = Voltage, I = Current, and R = Resistance. With any 2 of these you can find the answer to the other one. We will go into detail on this later on and what it is used for. Now enough of the intro, let’s dig in and start learning.
Figure 1-1 is a short version of schematic symbols; try to memorize these symbols because you will need to know what these are when reading a circuit diagram. As we continue with this training I’ll be adding more to this list. It might be a great idea to enter into the Gallery at the top of this article and download the picture and print it out for a reference until you learn what they are just by looking at them.
1-1 Photo was taken from the Forrest Mims III, RadioShack Electronics Learning Lab and the book can be downloaded for FREE at the RadioShack web site. to download it. This kit is also a GREAT for those who are just getting started and it has a great power source that you can do some of your testing and circuit building with.
Let’s get started with the Tools that you will come across when doing electronics, hacks and mods.
First thing is to get your hands on a solder-less breadboard, these are great for building prototypes of a circuit that you are testing out or designing before you waste your time in soldering the components in place and finding out that the circuit does not work at all or you need to swap out another resistor to bring down or up the voltage. These boards can be bought in different sizes. They also are included on most electronics “trainers“ as described in the above link at RadioShack. In figure 1-2 is a photo of a breadboard. The breadboard consists of a matrix of holes in which rows or columns of them are interconnected. To wire a circuit, you have to place a component’s pin or wire into one of the holes in the breadboard and then either put in a wire or another component into a hole that is connected with that one.
Fig 1-2 This is just one size of many breadboards available and this one can be found here at this link and I’ll be using this one in the project we will be doing in this article.
The other tools are just listed here rather than showing pictures:
- Phillips head screwdriver #1 and #2
- Small Flathead screwdriver like what you find in a watch repair kit.
- Soldering Iron no more that 25 to 45 Watts
- Solder 60/40 Rosin-Core
- De-soldering Braid found at RadioShack or on-line.
- Razor blades
- Side cutters or another name is flush cutters to cut your wire
- Wire stripers
- DMM “Digital Multi-Meter” and probes
This is just a quick list and as you go, you will increase your tools as you need them.
OK, let’s get some math over with so we can start your first project. This part I’ll be introducing to you OHM’s Law. We all know building things are fun to do else you would not be reading this lesson. But you cannot just throw parts together and expect them to work unless you want to see the “magic smoke” come out of the chips and smell that electronic burnt smell; once you smell it you’ll never forget what it is. Ohms Law is a very basic algebra equation but in its true form it is nothing more than basic math. So don’t let this bother you.
Ohm’s Law was named after G.S. Ohm, the German scientist who formulated it. Ohm’s Law states that in an electrical circuit, the voltage drop is equal to the value of the current multiplied by the resistance of that circuit.
An analogy of Ohm’s Law that is used widely today is the flow of electricity through a wire or circuit is like the flow of water through a pipe. The volume of the water is the same as Current while the pressure of the water is to say it’s the Volts, and the diameter of the pipe is the Resistance.
A wide pipe that offers little resistance to the flow of water and can handle a high volume of water (I=Current) at low pressure (E=Volts) thus this same pipe will have the same output if the Current, or rate of flow, increases, while the pressure (Voltage) is reduced. If the pressure (Voltage) is increased while the diameter of the pipe remains the same, the amount of water flowing through the pipe (Current) will also increase. Now changing the Resistance buy cutting the diameter of the pipe down or up, will have an effect on the other two.
Did you get that? If not, read it again and again till you do.
Now mathematically, Ohm’s Law is expressed as:
E=I*R or short E=IR
Where E=Volts, I=Current and R=Resistance
With any two of these you can find the answer of the third. Below are the break downs for each letter that you are trying to find.
Finding the Voltage: E=IR
Finding the Current: I=E/R
Finding the Resistance: R=E/I
Another simple way to remember the combinations is this:
By putting your finger over what you want to know will give you the formula. Try it out to see if my formulas are correct..
Now let’s do a quick pop quiz - head to the next page!
Hint: mA = milli Amps. 1 milli-Amp is equal to 1 one thousandth of an Amp or stated as 0.001 or 10-3
uA = micro Amp = 1 one millionth of an Amp or stated as 0.000001 or 10-6
K = One thousand
M = One million
1 Find the current if you have a voltage of 15v and the resistance of 240 ohms
1 Find the Voltage if you have the current of 100mA with the resistance of 1.5K Ohms
2 Now find the resistance of a circuit that is using 12v at 500uA
Now, head to the next page to see the answers.
Pop Quiz Answers:
- I = 15 / 240 I = 0.0625 Amps
- E = 0.1 * 1500 E = 150 Volts
- R = 12 / 0.0005 R = 24K Ohms or 24000 Ohms
If three questions were not enough for you, go ahead and make up more to practice on.
PROJECT TIME !!
Let’s make our first project just to keep you interested in what’s being taught. First, acquire the parts that are needed for this simple circuit.
- 1K resistor (Brown, Black, Red, Gold will be on the color band of the resistor. I’ll get to this in the next chapter)
- Push Switch or Toggle Switch (SPST or STDP)
- 1ea LED of any color
- Solid strain Wire of 20 or 22 gauge
- 9 Volt battery
- 9V battery clip.
- Meter with probes
- Or you can download the MultiSIM software (the link is below in this article)
NOTE: All these parts can be found at your local electronics dealer such as Radio Shack or from scrap electronic boards.
Now let’s look at the schematic that we will build. I’m designing this circuit using Electronics Work Bench 8 Professional or also as known as EWB8 or MultiSIM 8. You can get a FREE 30 trial of this software and I think the student version is free as well but not sure. The student version is great for small circuits yet, I think you only have about 100 points to work with but this is more than enough for you right now in these articles I’m writing. Follow this link to read more about the program and download the software so you don’t have to buy anything for these projects.
If you built the project on the breadboard then it should look like this or close to it.
Let me tell you one thing about the LEDs. If you have a new LED, the Cathode “negative side” will have the shorter leg and the Anode “Positive side” will have the longer leg also if you look at the base of the LED the Cathode side will have a flat spot on it. Now look at the schematics for this circuit and find the LED. The triangle with a line at the top is the Cathode and of course the other lead is the Anode. If you can not see the flat spot look at the photo below and you’ll see inside the LED. The lead that has a bowl on it is the Cathode, this is where the silicone chip is placed that lights up when power is applied. Knowing this always helps when you have a LED that is hard to see the flat spot.
Now that we know how to set the LED in the correct position and built our circuit, let’s try it out. Press the switch and the LED should light, if it does not re-check your wiring and check that the LED is placed correctly. When you release the button the electricity is cut off from the circuit “Load” hence the circuit is described as being open. If you do not have a switch for this project then just use a wire to emulate the switch by plugging it in and out.
Now let’s do some measuring and math with this circuit. First let’s measure the voltage across the battery. Set you meter to the 20 volt range DC. Place your black lead “ Negative or ground ” on the – side of the battery and place the Red lead “ Positive ” on the + side of the battery and write down this voltage. Mine is 9.01 volts so E = 9.01. Now with the circuit turned off measure the resistors OHMs. Turn your meter to measure resistance and on my meter I’ll set it to 20K. My resistance of the 1K resistor is 0.99K so R = 990 OHMs. Since we cannot measure resistance through the LED we can measure the Voltage drop. To do this measurement place the Black lead on the Cathode leg and the Red lead on the Anode leg of the LED. Press the switch to turn on the circuit. You should get around 2 volts. Mine reads 2.01 volts. So with these readings our total voltage going through our circuit is: 9.01v - 2.01v = 7 volts and the resistance = 990 OHMs. So what’s our current through the circuit?
I = E/R : I = 7 / 990
I = .007 Amps or 7 mA
Ok, time to prove this! If you are using the MultiSIM program then remove the line from the ground and the LED connection and for those who built the circuit do the same. Now connect your meters Black lead to Ground (-) and the RED lead to the LED’s Cathode. Set your meter up to read Current. You will need to remove the RED lead from the meter and connect it to the 10ADC jack. Now turn your meter to the 10A setting. Turn on the switch or press down on it, your meter should now read around 7 mA. See photo below using the MultiSIM program.
You’ll notice that I changed the Switch J1 to a SPST switch instead of a NO” Normally Open “ Push Button switch. In the Simulator it reads 7.34 mA this is because in the program it uses precise readings from all components. The components that we use have a tolerance percentage such as our resistor with the Gold band on it which means 5% tolerance up or down from the given value. Our 1K resistor can read from 950 OHMs on the low end and 1.05K OHMs on the top end.
In the next article we will continue learning about resistors and how they work.
Topics are as followed in the next chapter:
- Resistors in Series
- Resistors in Parallel
- Kirchoff’s Voltage Law
- Kirchoff’s Current Law
- Thevinin’s Equivalency
I know this sounds hard and most of you do not even know what these laws are in electronics... but, hang in there and all will be explained in the next chapter. Thanks for reading this article and I hope all of you had learned something. If you have any questions about the material in this first chapter, please leave a comment and I’ll explain it to you. Have fun learning electronics and do experiments on your own to help better understand this material.