Very very elementary electronics questions

Thu Jan 05, 2012 12:29 pm   

"fungus = retarded fuckhead


Your conclusion is right but the reasoning is wrong.


** His reasoning is 100% spot on - you asinine POS.

Fuck OFF !!!

LUNATIC !!!!!

Thu Jan 05, 2012 1:18 pm   

On Jan 5, 11:10 am, "Phil Allison" <phi...@tpg.com.au> wrote:

When you drink through a straw are you pulling
the liquid upwards or is the atmosphere pushing
it towards your mouth?

I learned the answer to that in first year physics,
maybe you were asleep...?

Thu Jan 05, 2012 3:45 pm   

My post didn't show up, so here it is again.





This requires you to know and understand "Ohms Law". The voltage is the
pressure that pushes the current through your
load (device). If you drop the voltage in half it will not push enough
current through your device to make it work properly.



Why wouldn't the 9V fry the circuit board?

There could be a regulator in the speaker that drops the voltage down
to 6 volts. Or the amplifier could just work from 6 to 9 volts, the
power output would be higher with higher voltage.




lets say a 12v car battery and a much smaller 12v battery. More / Less
amps? (i assume obviously there are greater capacities)

Assuming the same chemistry, a larger battery would be able to deliver
the same amperage for a longer time and/or more current without having
it's voltage drop below it normal voltage. The larger battery would also
have a lower "Internal Resistance".


less or more (DC) voltage?

Many factors, a tv remote control has to turn on an LED with maybe
15ma of current and needs to fit in your hand, so 3 volts, 2 AAA
batteries will work great. Although for a longer life I like AA.
If you have an amplifier supplying 10 Watts instead of 3 volts you
might want 12 volts or even 15 volts as a supply voltage, this higher
voltage allows you to push enough current through the speaker to get
10 watts. If you only had 3 volts it would take additional circuitry to
get 10 watts. The current from the 3 volts would also be 5 to 10 times
higher also.
Devices are designed around a specific voltage, if you exceed that,
something will probably get hot.


how do i know whether a higher voltage / higher amp charge will ruin
my device?

You don't want to exceed the voltage that a device is designed for,
you can have a power supply that will deliver higher current than the
device is rated for. The device will only use the current it needs when
supplied the proper voltage.

Note: a wallwart will measure a higher than rated voltage until the
current output is at it's rated current.
Example: A specific 12 Volt wallwart measures 16.5 volts until it has
a 1.5 amp load applied, then the voltage measures 12 volts.
This goes back to question 3 and "internal resistance"



Your welcome.
Mikek

Thu Jan 05, 2012 6:18 pm   

On Wed, 04 Jan 2012 16:33:31 -0800, nuevallorker wrote:


Well, mostly yes.

In general, if a supply says "3V, 500mA" that means that it is _rated_ to
supply 500mA at 3V -- it doesn't mean that it will push 500mA out of its
terminals while delivering 3V. In fact, it can't -- to get 3V at 500mA
requires a load that will consume 500mA when it has 3V on it.

If you had a source that would deliver 3V no matter what, and a load that
wants to take 500mA at 3V, then 500mA will flow regardless of whether
that source is capable of delivering barely 500mA, or 500A.

Life is complicated by wall warts. If you have an older wall wart that
says "3V at 500mA", it might deliver 4V at no current, and more than 500mA
at less than 3V. So unplugging from a "3V, 500mA" wall wart and plugging
into a "3V, 5A" wall wart might get you more voltage, although usually
things would still work.

Newer wall warts (the slim, light weight ones) have switching supplies in
them, and are better regulated (although I'm sure that not all of them
are perfectly regulated). So you can at least hope that if it says 5V,
it'll be 5V over a large range of currents.

My advice is to -- for the most part -- treat the voltage on a wall wart
as gospel, and treat the current rating as a "do not exceed". So if you
have ten 12V, 100mA devices, then feel free to connect one or all of them
to a 12V, 1A wall wart. But if you have a 12V, 1A device, expect it to
make your 12V, 100mA wall wart fall to its knees.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

Sat Jan 07, 2012 1:21 pm   

"fungus = retarded fuckhead


** His reasoning is 100% spot on - you asinine POS.

Fuck OFF !!!

FUCKING LUNATIC !!!!!

Sat Jan 07, 2012 2:01 pm   

On Jan 5, 12:29 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

I hope this is just a communication problem
because you seem to be telling us his widget
is actively pulling electrons from the power
supply.

It isn't. An electrical device is just a pathway
for electrons to travel from a place of higher
potential to a place of lower potential. It plays
no role in moving those electrons (quite the
opposite in fact - it resists their movement).

The original statement about a device "drawing
amps" is ass-backwards.

A better way to think about it is that a device
allows a certain amount of current to pass though it.

It doesn't matter whether a 1 amp device is connected
to a 1 amp power supply or a 1 million amp power
supply. Only a certain amount of current can pass.

The amount of current that can pass depends on the
electrical resistance of the device and the power
supply's voltage. It obeys Ohm's Law.

Sat Jan 07, 2012 2:54 pm   

On Jan 7, 1:21 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

Your resistors are actively pulling electrons
out of things? Our energy problems are over,
and it's all thanks to Phil!

Sun Jan 08, 2012 1:42 am   

"Ecnerwal" wrote in message
news:MyNameForward-1AE84E.13414804012012_at_news.eternal-september.org...


Another fairly good source of basic information is:
http://www.allaboutcircuits.com/

And also:
http://openbookproject.net/electricCircuits/
(which I think preceded the allaboutcircuits site and "borrowed" material
from it)

If your interests tend toward radio, TV, and other RF devices, here is an
ancient favorite:
http://www.arrl.org/news/the-i-2010-arrl-handbook-i-our-biggest-and-best-ever

I found it most helpful to actually build and test circuits. There are still
some kits and trainer modules that provide this, such as:
http://www.amazon.com/Snap-Circuits-SC-750R-Student-Training/dp/B000IXMP6Q

You can also learn a lot by developing and playing with circuits using
LTSpice, which is a free application with which you can make schematics and
run simulations and see circuit performance graphically:
http://www.linear.com/designtools/software/

Another free simulator package is TINA, which you can get through
www.ti.com, or www.tina.com

Here's a video:
http://www.youtube.com/watch?v=7j5QLQ0yzn0

It has user interactive components such as switches, pots, and LED displays,
plus test instruments like scopes and multimeters. It also has a PCB design
module.

The simulator approach is safer than building actual circuits, but it is
sometimes more fun and memorable to build and test actual hardware. Just be
careful with voltages about about 24V, and wear eye protection in case a
capacitor explodes (which can happen even on low voltage battery projects.

Have fun!

Paul

Paul