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Tech Talk with Gus 20 - Pre-pre Embedded Systems - Part 2


#1

In this episode, we continue the talk about the very basics you need to know to get started using electronics and embedded systems.


#2

I’m a software guy, but I have been doing basic hardware stuff for years. I want to say that I am enjoying this “prep-pre” stuff. Yeah, I know this stuff, but Gus is explaining it really well.

I had never heard, “what a resistor does is convert voltage to heat”. Somehow that was clearer than any explanations about resisting current flow. If a resistor is converting voltage to heat, then obviously the voltage on one side will be different than the voltage on the other side - because some of that voltage was converted to heat.

Why do we need a resistor? Because the LED only wants one volt and only so much current. So, I need to lose 2.3 volts before I feed the LED. Somehow, I have gotten by with simple circuit design for a long time without ever understanding it quite that way. Thanks.


#3

@ Blue Hair Bob - a small correction, it is better to say it converts the electrical energy (not voltage) to heat.

In the early days, it was very hard for me to understand the difference between current and voltage! But thinking of a voltage add a bag of charge and the current as the how many bags are getting across was what made sense for me.

Another one is why an unconnected pin is not zero volts, and why it is “floating”. This is for another tech talk :slight_smile:

I am glad you are enjoying the talks.


#4

@ Gus - I wonder how long till you talk about signal propagation delays and transmission lines :smiley:


#5

That is why voltage measures potential!


#6

I still dont get it :slight_smile:

A bag of charge? I.e. the sum of the charge of the electrons? 1 electron in the bag = charge of -1, 1million electrons in the bag = -1million charge?

So what is the difference between 1 bag of 1 electron, and 1 million bags with 1 electron? Wouldnt the sum be the same? The voltage?


#7

@ mtylerjr - it is not a bag of electrons. The one electron is holding a one bad full of charge.


#8

But every electron has the same charge, no?

So every if bag is the same, just the voltage of 1 electron, then every voltage is the same, and the analogy makes no sense in my head :frowning:

Voltage is always the voltage/bag of one electron?


#9

@ mtylerjr - Yes every electron has 3.3V of charge. More electrons is not more voltage, it is more current.


#10

Ah, ok. I did not know that individual electrons each had a charge of 3.3 volts. I thought they had a negative charge, actually, and that positrons had positive charge. Or that you needed two things to measure voltage. But my physics teacher was a bit loopy. He probably made all that stuff up.


#11

And current flows from - to + but I am trying to explain the very basics in the simplest possible way.


#12

(dad was a physics prof, so I am pedantic about this stuff, because … science) So, technically, an electron does not have a charge of 3.3V. It has a charge of 1.602e-19 coulombs, or energy of 1.602e-19 joules when moved through a potential of 1V. The numbers are actually not interesting - the bit that matters is that voltage is a difference in potential (electrical ‘pressure’) and current is a flow of electric charge. And yes, this is way more than one needs to know to light LEDs, but I didn’t want to leave the misconception that an electron has a voltage of 3.3V.


#13

Who am I going to believe? You or Gus? He’s a GHI employee!


#14

Awesome! More science please :slight_smile:


#15

Like water in a pipe pressure that is exerted upon the water filled pipe at one end, appears at the other end of the pipe far far far faster then the actual water moves through the pipe. Electrons drift along slowly in a conductor. The drift velocity is on the order of millimeters per hour, but increases with voltage.