LED Resistor one more question
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Posts: 46,084
Hi,
Thanks a lot you guys answered really fast and now I understand. So I
guess I will ask one more question. Ok whats bothering me now is the
placement of the resistor. I see the placement at
Stamp--LED--Resistor--ground. I think of the electic going from the stamp
and needing to go through the resistor before the LED. Well really I would
not think it would mattor which side of the LED its on because ether side its
going to limit the amount of electicity in the circute. Then to confuse me
more I asked my dad and he said that the power flows from negitive to
positive. So if you guys could just set me strait on this I will feel really
good. Thanks a lot.
Jim
Thanks a lot you guys answered really fast and now I understand. So I
guess I will ask one more question. Ok whats bothering me now is the
placement of the resistor. I see the placement at
Stamp--LED--Resistor--ground. I think of the electic going from the stamp
and needing to go through the resistor before the LED. Well really I would
not think it would mattor which side of the LED its on because ether side its
going to limit the amount of electicity in the circute. Then to confuse me
more I asked my dad and he said that the power flows from negitive to
positive. So if you guys could just set me strait on this I will feel really
good. Thanks a lot.
Jim
Comments
Well, there is a lot of confusion on this point. Engineers imagine
electricity flowing from + to -. However, electrons actually go from -
to + but it doesn't matter as long as you pick one and stick to it.
Don't think of the resistor as controlling the circuit. In a series
circuit, the current is the same throughout. Each piece of the circuit
has to "eat" a little voltage and the total amount will add up to the
total voltage.
So you can put the resistor on either side of the LED. Suppose your
creditors lined up every month at your door (that'd be a long line for
me). You give all your money to the first guy, he takes what you owe him
and passes the rest behind him. One month, you come home late, and the
line is already at your door. So you give your money to the last person
and they pass it up the line. Either way, you have to start with all the
money. At the end of the line there is no money left.
How's that for an analogy?
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: jay [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=RZ3PmdbKUfgAfsL15ENejj-OJI67rr1ofofLP7N4mpiMdWhkN04UnwfcOn_d9Bcv1mk]ygg@g...[/url
> Sent: Tuesday, February 19, 2002 11:32 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] LED Resistor one more question
>
>
> Hi,
> Thanks a lot you guys answered really fast and now I
> understand. So I
> guess I will ask one more question. Ok whats bothering me now is the
> placement of the resistor. I see the placement at
> Stamp--LED--Resistor--ground. I think of the electic going
> from the stamp
> and needing to go through the resistor before the LED. Well
> really I would
> not think it would mattor which side of the LED its on
> because ether side its
> going to limit the amount of electicity in the circute. Then
> to confuse me
> more I asked my dad and he said that the power flows from negitive to
> positive. So if you guys could just set me strait on this I
> will feel really
> good. Thanks a lot.
> Jim
>
> To UNSUBSCRIBE, just send mail to:
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> http://docs.yahoo.com/info/terms/
>
Don't worry about where the resistor is, it can be between the STAMP pin
and the LED, or between the LED and ground. Think of the LED and
resistor as two separate water pipes attached together, with water
flowing instead of electrical current. The water/current has to flow
between the STAMP pin and ground and it doesn't matter which order the
two "pipes" are connected in.
Your dad is sorta correct, depends on whether you are talking "electron"
flow or "hole" flow. This gets real technical and beyond the scope of
your question. All you need to know is that you must have a complete
circuit between the STAMP pin (positive) and ground (negative) in order
to get current (electrons) to flow.
There is one important thing to know, you must have the polarity of the
LED correct or the LED won't light up. The LED is a device called a
diode and only allows current to flow in one direction so the negative
lead of the LED must be attached to ground (either directly or thru the
resistor) and the positive lead of the LED attached to the STAMP pin,
(either directly or thru the resistor). How do you tell which LED lead
is which? If you look close at the LED you will see that it is round
with one side having a little flat part. The LED wire leg closest to the
flat side is the negative side of the LED so will be attached to ground.
Ray
jay wrote:
>
> Hi,
> Thanks a lot you guys answered really fast and now I understand. So I
> guess I will ask one more question. Ok whats bothering me now is the
> placement of the resistor. I see the placement at
> Stamp--LED--Resistor--ground. I think of the electic going from the stamp
> and needing to go through the resistor before the LED. Well really I would
> not think it would mattor which side of the LED its on because ether side its
> going to limit the amount of electicity in the circute. Then to confuse me
> more I asked my dad and he said that the power flows from negitive to
> positive. So if you guys could just set me strait on this I will feel really
> good. Thanks a lot.
> Jim
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/