MJLorton Solar Power and Electronic Measurement Equipment Forum
Tutorials, lessons and courses => Tutorials, lessons and courses => Topic started by: MJLorton on June 07, 2012, 06:07:30 AM
-
Hi All,
I've posted the first video in this series:
Electronics Tutorial #1 - Electricity - Voltage, Current, Power, AC and DC:
http://www.youtube.com/watch?v=-qMcHSb2WMs
Feel free to discuss this series here...post suggestions of what you would like to see covered in future videos.
Cheers,
Martin.
-
Martin,
Had to nip out earlier so I didn't finish the video so you may have already covered this but I'd next cover the basic components like resistors and caps with perhaps a few ohms law examples. Just some simple stuff to ease people in to thinking about circuits and whats doing what.
From the 15, 20ish mins I did watch though it's seemed very good, should be easy enough to digest as a beginner.
Cheers
Kris.
-
Hello!
Very good tutorial indeed. 8)
Please allow me to explain what I miss from most of the tutorials that explain the basics of electricity: I'd like to hear more about the relationship between Voltage and Amperage through a few examples. The reason for this would be to better understand how these two components work together to operate electronic devices. I understand the analogies (e.g. water flowing through a pipe or hose) that people use to explain electricity, but for some reason I cannot differentiate enough the two, or with other words I don't understand exactly how they work together to make electronic devices work.
Let me describe a few situations to illustrate what I mean:
1) Let's say we have a 24 Volt/100 Watt light bulb that I would like to use. Given the two figures we can calculate that the bulb will drain 4.16 Amps from a particular power source. Now let's compare it to a 220 Volt/100 Watt light bulb. This one would drain only 0.45 Amps. How's that and why?
2) Let's say we would like to operate a laptop with solar power. Let's pretend that all we have is two types of solar panels (both capable of about 65 Watts of power, but having different Voltages and Amps) and a laptop that is rated at 19 Volts. There's no inverter, no charge controller, no battery in the story. One of the solar panels is rated at 2.70 Amps at 24 Volts and the other at 3.42 Amps at 19 Volts. Both produce the same power (65 Watts), but what will happen to the laptop if we try to operate it with these solar panels? Will it work with the 19V/3.42A panel? Will the 24V/2.70A panel fry it? How and why?
What I'm trying to find out is how important it is to take into consideration the Voltage and Amperage needs of a device when designing a power source for it? And to make things even a bit more complicated: what does power factor and power factor correction mean?
I don't know if these two situations or my questions make any sense to you, but anyway, I said I'll give it a go. :)
-
A great book:
"Getting Started in Electronics" by Forrest M. Mins, III.
http://goo.gl/vXz7x (http://goo.gl/vXz7x)
-
@angelico, to whoever had time do "design" book this way should be awarded. Those kind of fun looking and simple explained topics should be used in schools. I am shure many students would have picked up Electronics at much faster paste with that kind of book.
Thanks for pdf for shure.
-
@birrbert
Every circuit, a water-pipe too, has a resistance, otherwise you never need a pump and you have a perpetuum mobile ;)
Calculate it:
U^2 / P = R
so
24V^2 / 100W = 5,76 Ohm
For the 230V I calculate with 240V, so it's easier to understand. (24V are 10% of 240V)
240V^2 / 100W = 576 Ohm
Check this out:
100W / 240V = 0,42A
100W / 24 = 4,2A
So we have a current of 10% from the 4,2A
Is one part stable, the other both must be balancing. That's it what Martin try to teach in his video.
First rule is to understand, what this formula means: U = R * I That's the basic of all kind in electronics.
2) In your Notebook the resistance is not stable and it wants 19V. Now how you want calculate it with 24V ?
2nd. A Notebook is not a Resistor, but a complex circuit. If you "put" 24V in it, what you think what happens ?! Yepp, you have expensive junk on your table and a nice smell of burning in your room.
You ask: what does power factor and power factor correction mean?
Maybe it is better you lean the first rule ;) http://en.wikipedia.org/wiki/Power_factor_correction#Power_factor_correction_in_non-linear_loads
-
Hello!
Very good tutorial indeed. 8)
Please allow me to explain what I miss from most of the tutorials that explain the basics of electricity: I'd like to hear more about the relationship between Voltage and Amperage through a few examples. The reason for this would be to better understand how these two components work together to operate electronic devices. I understand the analogies (e.g. water flowing through a pipe or hose) that people use to explain electricity, but for some reason I cannot differentiate enough the two, or with other words I don't understand exactly how they work together to make electronic devices work.
Let me describe a few situations to illustrate what I mean:
1) Let's say we have a 24 Volt/100 Watt light bulb that I would like to use. Given the two figures we can calculate that the bulb will drain 4.16 Amps from a particular power source. Now let's compare it to a 220 Volt/100 Watt light bulb. This one would drain only 0.45 Amps. How's that and why?
2) Let's say we would like to operate a laptop with solar power. Let's pretend that all we have is two types of solar panels (both capable of about 65 Watts of power, but having different Voltages and Amps) and a laptop that is rated at 19 Volts. There's no inverter, no charge controller, no battery in the story. One of the solar panels is rated at 2.70 Amps at 24 Volts and the other at 3.42 Amps at 19 Volts. Both produce the same power (65 Watts), but what will happen to the laptop if we try to operate it with these solar panels? Will it work with the 19V/3.42A panel? Will the 24V/2.70A panel fry it? How and why?
What I'm trying to find out is how important it is to take into consideration the Voltage and Amperage needs of a device when designing a power source for it? And to make things even a bit more complicated: what does power factor and power factor correction mean?
I don't know if these two situations or my questions make any sense to you, but anyway, I said I'll give it a go. :)
Thanks for the feedback.
I'm going to try put a nice analogy / illustration together in the next video (will post in the next day or two) that I hope will explain this.
I also have an old video where I explain power factor:
http://www.youtube.com/watch?v=VU7aYKSDRrE&feature=plcp
Cheers,
Martin.
-
Hi. Thank you so much Martin!
So YouTube Service sent me an e-mail this morning that a new video has been uploaded with the title Electronics Tutorial #2 - Power - the relationship with Voltage and Current, but unfortunately when I click the link YouTube says This video is private. Sorry about that. Something went wrong?
edit: I just saw the note video. Thank you.
-
Hi. Thank you so much Martin!
So YouTube Service sent me an e-mail this morning that a new video has been uploaded with the title Electronics Tutorial #2 - Power - the relationship with Voltage and Current, but unfortunately when I click the link YouTube says This video is private. Sorry about that. Something went wrong?
edit: I just saw the note video. Thank you.
Yes....my humble apologies. I have just posted another video explaining that I did not get the analogy correct when trying to explain power....I hope to do a better job and have it posted again later this week.
Cheers,
Martin.
-
Hi Martin.
In one of your older videos I've seen you expect P = V * I. Happened. But in the description of the new video (private) you wrote again P = V * I.
That's false. V is the unit of U. Properly it means P = U * I. Its the same like "We have 23 temperature here; or we drive last night with 260 speed on the highway" ;)
I mean, it is a tutorial, and a tutorial should be correct...
-
Hi Martin.
In one of your older videos I've seen you expect P = V * I. Happened. But in the description of the new video (private) you wrote again P = V * I.
That's false. V is the unit of U. Properly it means P = U * I. Its the same like "We have 23 temperature here; or we drive last night with 260 speed on the highway" ;)
I mean, it is a tutorial, and a tutorial should be correct...
So voltage is always U?
If so, I've never heard of that. I think the only place I have seen U used is in a few text books. I have always considered them interchangeable.
This interchangeability does have the advantage though that if I hand write a V and it looks like a U, they will mean the same thing 8).
-
It is "The International System of Units" but the Americans are interested in themselves only and therefore such nonsense comes out of. The IS is U and not V, E, J or whatever.
By the way - because the Americans do not want to get used the SI system, are smooth one or two Mars probes the target passed by.
So it is quite useful to the world wide standard, for systems, to develop international work ...
>This interchangeability does have the advantage though that if I hand write a V and it looks like a U, they will mean the same thing
No, it is not the same. Temperature (T) can't be °F, °C, K ... or speed (V) can't be mph or kmph. The unit of speed is mph and the unit of temperature is °F,°C, K and the unit of voltage (U) is V. Very Simple
If you mean, it's the same, remove the °F sign of your clinical thermometer, write °C on it and lets see what happens if you ask your Doc.
-
Here's another newbie situation I ran into. :)
I wanted to figure out how resistance worked in practice by driving a red LED from 12 Volts. Of course, in order to do this I needed resistors otherwise the LED would burn out. So I said I'd like to drive the LED with 3 Volts from a 12 Volt source, which means that I needed to dissipate 9 Volts. I assumed that the LED would consume about 0.02 Amps (20 mA).
Now, to calculate the resistance needed I used the formula R = U : I, which in my case would translate to R = (12-3) : 0.02 = 9 Volts : 0.02 Amps = 450 Ohms. I linked a 100 Ohm, a 150 Ohm and a 220 Ohm resistor in series, meaning a total of 470 Ohms, pretty close to what I needed. But, surprise surprise when I measured the Volts on the LED's legs my multimeter was showing around 4.8 Volts instead of 3 Volts I wished for.
So what did I do wrong? :-\
PS: Maybe you can incorporate something similar in the next electronics tutorial, Martin. Thanks!
-
Chinese LED. The forward drop is only approximate, and depends on how the die was made and how it was done. Forward drop can be anything from 1.7V for a red LED, to around 3V for a white/blue LED. If you connect it backwards it may light a little, but will fail rapidly.
-
Look into the Datasheet. You need the forward Voltage Uf and the forward current If.
(12V - Uf) / If = R
For a 20mA LED is 4,5V to much. If you don't have the forward voltage, calc with 2V and 20mA and use the next higher Resistor
so
10V / 20mA = 500Ω > 560Ω ^ ~18mA << works.
If you have a white one, maybe 3,6V..
8,4V / 560Ω = 15mA << all fine..
Take it easy, you are not a design engineer...
-
PS: Maybe you can incorporate something similar in the next electronics tutorial, Martin. Thanks!
I did...I hope the theory works for you...
Electronics Tutorial #5 - Ohm's Law Pt 2 - Application:LED Resistor, Voltage Divider, Current Shunt
https://www.youtube.com/watch?v=AWLJADJTWHU
-
OK. Let this be a rhetorical: how on earth did I miss part 2? :o
Let me make that up to you with a Like after I watched it. ::)
-
No prob....thanks! ;)
-
Hi Martin,
(sorry my english...)
I like very much the electronics tutorial #8 about diodes.
I dont have a waveform generator to reproduce the experiments.
But i know that is possible to do with Arduino (see attach).
Thanks very much.
-
Ahh
Why you don't use a transformer ? And for other waveforms the good old XR2206.
Or look at ebay. For under 50.- I am sure you find a useable function generator for your first steps.
-
Hi Martin,
(sorry my english...)
I like very much the electronics tutorial #8 about diodes.
I dont have a waveform generator to reproduce the experiments.
But i know that is possible to do with Arduino (see attach).
Thanks very much.
Hi Angelico
Thanks very much for the feedback and a great post. Using Arduino had crossed my mind but ultimately I wanted a reasonably good function generator for the bench. Great to know that there are options for folks to build.
Cheers,
Martin.
-
Hi,
I have some questions after watching Electronics Tutorial #1:
- What determines that a power source will produce AC or DC?
- If AC is more efficient than DC, why is DC used in automobiles?
- On the oscilloscope, when the wave goes past zero, is electricity being produced?
- In the analogy of the pipes and water it's mentioned that the power source doesn't produce the water/electricity. What does produce it?
- In the pipe analogy, it's stated that if the valve is closed there will be no flow but there will be still pressure. Would that pressure exceed the 12 volts because it has nowhere else to go and the pressure just keeps building at the valve?
- The 110v doesn't produce enough amps to operate a kettle, so a greater voltage is needed. Why then in a car is a larger battery that will produce more amps but keeps the same voltage? Shouldn't a greater voltage be needed to produce more amps? How do two different sized batteries produce different amperages even though they have the same voltage? Sometimes even the same sized batteries produce different amps.
Thanks,
bc10
-
Okay, I've been following the series closely and I've run into some problems I can't seem to get my head around.
When we're working out R2 in the Voltage Divider, your formulas seem to make sense. I arrived at 829.4 Ohms just like you, however I didn't really "get" the relevance of bringing in a parallel circuit but I carried on with the formulas.
What I didn't get was how 829.4 Ohms became Rt when working out R2 when R1 = 4.7K Ohms. I thought Rt = the some of all the resistance in your circuit, including all resistors.
I hope you see where I am coming from.
Cheers, Dan.
-
What determines that a power source will produce AC or DC?
Ac is produced by rotating machinery in most cases, used because you can easily transform the voltage to different levels and trasnsmit over a long distance with little loss. DC is mostly produced by batteries and generally is useful as it does not go to zero with each cycle but has both constant polarity and voltage. For a resisive load the source is not important, but many loads will stop working with AC as the polarity reverses.
- If AC is more efficient than DC, why is DC used in automobiles?
In a car DC is stored by the battery in a chemical reaction, and this enables you to store power for later use, like to start the car later.
- On the oscilloscope, when the wave goes past zero, is electricity being produced?
Yes, power is the product of voltage and current, and with AC into a resistive load it is always going to be positive.
- In the analogy of the pipes and water it's mentioned that the power source doesn't produce the water/electricity. What does produce it?
A pump does, like in voltage the electrons do not produce voltage but this is generated by either an external force increasing the energy of the electrons or a chemical reaction doing the same.
- In the pipe analogy, it's stated that if the valve is closed there will be no flow but there will be still pressure. Would that pressure exceed the 12 volts because it has nowhere else to go and the pressure just keeps building at the valve?
No, the anology is not exact because the pump builds up to a pressure where the flow passes back through the pump for a centrifugal pump and for a piston pump till the force driving the pump is equal to the back pressure. This is analogous to the open circuit voltage as no current or water flows, this is the open circuit voltage or the closed pressure.
- The 110v doesn't produce enough amps to operate a kettle, so a greater voltage is needed. Why then in a car is a larger battery that will produce more amps but keeps the same voltage? Shouldn't a greater voltage be needed to produce more amps? How do two different sized batteries produce different amperages even though they have the same voltage? Sometimes even the same sized batteries produce different amps.
A kettle can be built to work on 110V, it just draws more current, and the max current is limited by the wiring. The relationship between current and voltage is resistance. A resistor can have a high value, and thus you need a high voltage to get a defined current to flow through it. A lower value resistor needs a lower voltage to get the same current. Voltage and current multiplied together gives power. You can have a low voltage and high current, or a high voltage and low current, but have the same power in a resistor. In a car battery you have the ability to deliver a lot of current, and the batteries may be rated for how much current they can deliver, this is generally given as cranking current, so that you can draw up to this current safely for a few seconds to start the car.
-
Hello Martin,
I just saw your first video on electronics tutorial, I immediately liked, subscribed and came to your forum.
I have got some doubts.
How electrons flow in an AC supply. As electrons experiences push and pull how can it flow from one point to another.
It has a logic that in DC supply electrons are flowing as it is just a flow of electrons.
But in AC how is it possible. I hope you understand my doubt.
I also have some other doubts.
How many electrons flow in an ampere and how it is defined?
How voltage is defined and how the pressure of electrons are calculated?
How resistance is defined and how many electrons are blocked in an ohm?
Waiting for your reply. Thank You