Electronics tutorial

[MJLorton]

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.

[TTL]

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.

[birrbert]

Hello!

Very good tutorial indeed.

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.

[angelico]

A great book:
"Getting Started in Electronics" by Forrest M. Mins, III.
http://goo.gl/vXz7x

[Elvis O.]

@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.

[Fennec]

@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

[MJLorton]

Hello!

Very good tutorial indeed.

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.

[birrbert]

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.

[MJLorton]

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.

[Fennec]

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...

[steve30]

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  .

[Fennec]

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. 

[birrbert]

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!

[SeanB]

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.

[Fennec]

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...