uber newb

[audioguru]

If you don't want a low-dropout regulator then give the 7805 enough input voltage for it to meet its specs, some which are stated with an 8V input.
Its dropout voltage is typically 2V at 1A. Then it is dropped-out and is no longer regulating.

 

[kchriste]

If a power source can "source" so much current and an electrical component like a pic uses only , say, 10% of that current. What does this mean for the life of the power source (being a battery) verses the same circuit consuming 20% of the current?

In an ideal circuit, the one with 10% consumption will let the battery live twice as long as the one using 20% of capacity.

or does this mean that the 10% or 20% is really all that is being used?

Exactly!

 

[Clonus]

Ok,if (in this example) 10% is all that is being used, how is this happening?

What properties of the circuit only draw this much energy?

This is what I am thinking.

1) i take a battery and close th circuit
2) current flows at optimum strength unless there is some resistance.
3) this resistance is being wasted as heat.

so, why would some circuits, such as a pic, act differently on this?

assuming that shorting a battery releases much of it's potential energy.


This is hard for me to ask because io am not sure how to ask it.

it seems to me that some circuitry resists while others "draw". This drawing of energy seems more efficient that resistance.

do i have it wrong ?

 

[eblc1388]

A battery is an energy store. It stores chemical which reacts to give energy. After the chemical used up or the reaction stops, no more energy.

It is like a bank saving account. Initially you have a large deposit in it. If you draw only little at a time(like $1) then the account balance can stay positive for a long time.

If you draw ($100 or $1000 /per day) then the account deposit will soon be used up. It is the same case for a battery. Drawing lower current will enable the battery to last a longer time. A such, low value resistor draw large current and high value resistor draws little current.

The "thing" (or in proper electrical terminology, the "load") that you connects to the battery terminals determines the current value and thus power consumption and nothing else. The battery cannot limit the power consumption if it is below its maximum output current(owing to internal resistance but that's another story).

You're saying "the resistance is wasted as heat" is not correct. The resistance does not change but the "electrical power" is wasted as heat in the resistor, not before the resistor.

 

[Clonus]

A battery is an energy store. It stores chemical which reacts to give energy. After the chemical used up or the reaction stops, no more energy.

Ok, understood.

It is like a bank saving account. Initially you have a large deposit in it. If you draw only little at a time(like $1) then the account balance can stay positive for a long time.

Ok, understod.

If you draw ($100 or $1000 /per day) then the account deposit will soon be used up. It is the same case for a battery. Drawing lower current will enable the battery to last a longer time. A such, low value resistor draw large current and high value resistor draws little current.

Ok, I understand this in theory. What I am trying to understand is "what" is this "draw" of energy. Why does something draw the energy and why do others resist? Or do these things happen at the same time?

The "thing" (or in proper electrical terminology, the "load") that you connects to the battery terminals determines the current value and thus power consumption and nothing else. The battery cannot limit the power consumption if it is below its maximum output current(owing to internal resistance but that's another story).

If the battery cannot limit it's output current then I don't understand where this current goes if the power consumption in the "load" is less than what the battery supplies.

You're saying "the resistance is wasted as heat" is not correct. The resistance does not change but the "electrical power" is wasted as heat in the resistor, not before the resistor.

Well, grammer error. I really meant the resisted power, the power that is being wasted as heat is this resisted power while the remainder is the actual result of the rest of the power getting through.



When I think back to pics and leds, i think this.

Pic is a small micro device that uses clock cyces. Perhaps the low current "Draw" has something to do with the clock cycles and how it uses energy consumption, whereas leds are a constant burning of energy mostly as light.


This basic electricy thing feels like it's right on the tip of my tongue but i need that one example that pushes me over to see the big picture.

I have a computer background, I am a profressional application developer for a large financial firm. When it comes to understanding the basic understanding of electricity and it's laws, there is just something that I am not getting here.

I have a good understanding that, basically, we have a power "source" that is consumed by the "load". There are a variety of electrical components that allow storing, resisting, inducing etc of this energy. What I am trying to figure out right now is why there is this draw of energy over the voltage?

Someone ick me in the head!

 

[eblc1388]

Ok, I understand this in theory. What I am trying to understand is "what" is this "draw" of energy. Why does something draw the energy and why do others resist? Or do these things happen at the same time?

I'm glad you have at least grasped some of the ideas in previous post.

A battery has two terminals and have a potential difference between them. This "difference" is the same as other physical differences in the real world like different pressure, or different temperature. When there is a bridge between the two sides, then something will flow so that the difference balanced out.

In case of a battery, a wire or resistor provides a "bridge" between difference potentials so a current will flow naturely. The magnitude of this current is govern by ohm's law.

The resistor is a passive element and does not have to "actively" involved in order to "draw" the current. The current flows by law of physic. Think of a connecting pipe between two water tanks with different levels. The water flow automatically in the pipe.

If the battery cannot limit it's output current then I don't understand where this current goes if the power consumption in the "load" is less than what the battery supplies.

Battery supplied power = power consumed by load + power wasted as heat in resistor

Does this make sense to you?

 

[Clonus]

Yes, this makes sense to me. I did read and understand potential difference, which we call voltage. Voltage is the force that causes this currenty of electrons. Oh btw, do the electrons travel from negative to positive?

1) Can you give me an example of what a typical 9 volt battery sources? Is that the correct way of asking what the optimal power output is?


Lets see if I can understand this.

If battery sources X and load consumes Y.

X=100 and Y = 90, does this mean that (Z=X-Y) Z is wasted as heat?

In the case of a microchip, it consumes so many microamps but the battery sources much more than the pic consumes. This current is used partially in the pic, what happens to the rest of the current?

 

[eblc1388]

In the case of a microchip, it consumes so many microamps but the battery sources much more than the pic consumes. This current is used partially in the pic, what happens to the rest of the current?

Do not think of current, think of energy. The battery has a lot of energy, but a microchip only takes a little energy at a time. Therefore, the battery can supply the microchip for a very long time(weeks/months). If you connect a 10 Ohm resistor to the battery, it will takes a lot of energy and the battery will run down quickly(minutes or hours) .

A battery can source a large current, e.g. a 12V car battery can source over 500A if required, but if a microchip is connected, the chip only take a tiny current (a few mA) and the battery cannot force more current through the microchip. Just like you have 5 millions in the bank and go to withdraw just $5 for a breakfast. Do you waste any money in doing so?

 

[Clonus]

ahhhh, ok!

So, this is new to me.

I did not understand that the microchip actualy has some properties that will allow only so much current to flow out of the battery...

why does this microchip only consume so little, when the battery sources so much more?

 

[eblc1388]

awhy does this microchip only consume so little, when the battery sources so much more?

The microchip and other modern microcontrollers are purposely designed to use as little energy as possible so that they can be battery powered. There is more trick in them where the chip can go to sleep and consumes even less current in doing so.

 

[Clonus]

I think it's geat that microchips use little power however, this still doesn't answer my question.

you said...

"The battery cannot limit the power consumption if it is below its maximum output current"

The microchip is below the maximum output current.

How does this micro-circuitry only pull a small amount of current when the battery should be sourcing more?

 

[Nigel Goodwin]

How does this micro-circuitry only pull a small amount of current when the battery should be sourcing more?

The battery doesn't "source more", it has the capability to provide a certain amount of current - but that value depends on what the load requires.

For example:

You buy a large bottle of whiskey - does that mean you're going to get dead drunk if you open it? - no (hopefully), because you drink it a small glass at a time, and don't pour the entire bottle down your throat.

Exactly the same for your PIC - the battery is a large bottle, and the PIC is only taking tiny sips!.

 

[Clonus]

ok, that is interesting and i understand it.

So, if i have a resistor and put it between the potential, does this mean there is a full sourcing of power but some of it is burned as heat the rest just passes through the resistor and combines with the positive charge?

But, a microchip does't have this same property?

Instead of creating a short circuit with resistance the microchip somehow is able to "sip" the power somehow?

Do you know how is occurs?

Is it microchips that have this capability only (compared to resistors and other basic components)?

i think my problem is that i can't grasp either why and how current is controlled, what keeps it from flowing or what causes it to flow as well, how do these parts react with the current?

if you fully understand the physics here, can you determine where i am getting something wrong?

 

[Hero999]

It looks like you need to read up a little on ohms law.

The current in a circuit is directly proportional to the voltgage and resistance.

Take a perfect voltage source of 10V. If you place a 10 ohm load across it 10V/10ohms = 1A will flow. If you a 5 ohm load 10/5 = 2A will flow. If short circuit it with a perfect conductor and infinite current will flow.

Note, the voltage source is perfect, it can supply an indefinite current but the the actual current in the circuit is restricted by the resistance. In reality there's no such thing as a perfect voltage source, there's always a limit to the amound of current that will flow. This is normally caused by the resistance of the wiring. In practice you always make sure that the load will draw a much a much lower current than the power supply's limit.

In DC circuits, power = V*I, so if you lower the current then the power consumption will be reduced. There are two ways of doing this, one is to increase the resistance, the other is to reduce the voltage. This is why your PIC uses less power at lower voltages.

**broken link removed**
https://www.iguanalabs.com/ohmslaw.htm
https://www.electronics-tutorials.com/basics/ohms-law.htm

 

[eblc1388]

So, if i have a resistor and put it between the potential, does this mean there is a full sourcing of power but some of it is burned as heat the rest just passes through the resistor and combines with the positive charge?

The word "resist" means something that opposes and a resistor do just that. The current flowing in the resistor heats up(I*I*R) and convert all the power into heat. There is nothing else passing through or get bypassed except that very current. So all of it get converted into heat, assuming there is nothing else other than the resistor is connected.

Is it microchips that have this capability only (compared to resistors and other basic components)?

No. A 10 Megaohm or higher resistor will "sip" less current than a microchip.

i think my problem is that i can't grasp either why and how current is controlled,

It is determined by the battery voltage, resistance or impedance of the load. Higher voltage, higher current. Lower resistance, higher current. That's Ohm's Law.

what keeps it from flowing or what causes it to flow as well,

Potential difference between the ends of a resistive component causes the current to flow. No current flow if the two points are at the same potential. No current flow if it is a capacitor.(approximation applicable in this context to the OP only).

how do these parts react with the current?

Turn it into heat(a resistor), gives off light(a LED), becomes magnetic(an electromagnet), moves ions to opposite electrodes, or do some useful work(a motor). The list goes on....

if you fully understand the physics here, can you determine where i am getting something wrong?

Yes, we are trying, desperately. I'm now going to fetch the whiskey bottle Nigel has mention.

 

[Clonus]

lol, sorry everyone, thanks for taking the time to help me understand.

I think i "understand" the basics ... basically, i just need to think about it for a little while and hope it sinks in.

No more questions, Ill read from the beginning to end a few times and let it settle in my head.

Again, I appreciate your patients!

kind regards,
Clonus

 

[Clonus]

Oh, here's a great line from Hero999

"The current in a circuit is directly proportional to the voltgage and resistance."

This is something that I needed to hear!

thanks
clonus