Newbie BS2 user w/ Newbie Question
I just hooked up my BS2 for the first time, and tested it by
connecting this simple circuit (the cimplest one I could find) from
the manual:
+5v
LED
220 Ohm Res.
I/O Pin 0
The circuit works, and I am really excited about getting into
STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
also connected the circuit without it, and it still works just as
well. The voltage across the LED w/o the resistor is 5v, and with it
is 3.7v. Is the sole purpose of the resistor to lower the voltage a
little, dimming the LED a little? Or does it serve some other
purpose?
Thanks in advance. Any info on good online resources would be
appreciated.
connecting this simple circuit (the cimplest one I could find) from
the manual:
+5v
LED
220 Ohm Res.
I/O Pin 0
The circuit works, and I am really excited about getting into
STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
also connected the circuit without it, and it still works just as
well. The voltage across the LED w/o the resistor is 5v, and with it
is 3.7v. Is the sole purpose of the resistor to lower the voltage a
little, dimming the LED a little? Or does it serve some other
purpose?
Thanks in advance. Any info on good online resources would be
appreciated.
Comments
http://www.al-williams.com/wd5gnr/stampfaq.htm#s2.4
http://www.al-williams.com/wd5gnr/basiccir.htm
Al Williams
AWC
* NEW KIT: Need a 5V Power Supply?
http://www.al-williams.com/awce/ps1.htm
>
Original Message
> From: apecitydotcom [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=PMWsAotT7aXbEsyM-Ji_wtduWgPHglcgB59buUlYxd21CoBg4y4u7if4OSKp_HdPhsPKvTBitFD65Ve8aQ]fines@m...[/url
> Sent: Monday, December 24, 2001 10:06 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Newbie BS2 user w/ Newbie Question
>
>
> I just hooked up my BS2 for the first time, and tested it by
> connecting this simple circuit (the cimplest one I could find) from
> the manual:
>
> +5v
LED
220 Ohm Res.
I/O Pin 0
>
> The circuit works, and I am really excited about getting into
> STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
> also connected the circuit without it, and it still works just as
> well. The voltage across the LED w/o the resistor is 5v, and with it
> is 3.7v. Is the sole purpose of the resistor to lower the voltage a
> little, dimming the LED a little? Or does it serve some other
> purpose?
>
> Thanks in advance. Any info on good online resources would be
> appreciated.
>
>
> 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/
>
protects the LED and the Stamp. As you get more involved in electronics,
you'll learn to calculate proper resistor values for your unique circuits.
LEDs have a specified forward voltage that is usually in the range of 1.2 to
1.7 volts. The resistor, if you will, soaks up the rest (since the circuit
voltage is 5 volts). Lets say, for example that your LED had a forward
voltage of 1.4 volts (very typical). That would leave 3.6 volts across the
resistor. Using Ohm's Law, we can determine that the current flow through
the circuit is about 16 milliamps.
Since you can't light too many LEDs at 16 mA, you might consider changing
your resistor value to 470 ohms or 1 kOhm. That will let the Stamp light
more at the same time.
You might consider Scott Edwards' book "Programming And Customizing The BASIC
Stamp Microcontroller." It will help you get started in Stamps and give you
some fundamentals in electronics as well.
-- Jon Williams
-- Parallax
In a message dated 12/24/01 10:06:32 AM Central Standard Time,
fines@m... writes:
> I just hooked up my BS2 for the first time, and tested it by
> connecting this simple circuit (the cimplest one I could find) from
> the manual:
>
> +5v
LED
220 Ohm Res.
I/O Pin 0
>
> The circuit works, and I am really excited about getting into
> STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
> also connected the circuit without it, and it still works just as
> well. The voltage across the LED w/o the resistor is 5v, and with it
> is 3.7v. Is the sole purpose of the resistor to lower the voltage a
> little, dimming the LED a little? Or does it serve some other
> purpose?
>
> Thanks in advance. Any info on good online resources would be
>
[noparse][[/noparse]Non-text portions of this message have been removed]
Typically LED's require 1.7 to 2.1 volts to operate and any higher voltage
will cause it to burn out. It sounds like you lucked out not smoking the LED
or Stamp. In the future I would follow the directions so won't damage
anything.
As far as the resistor value, knowing how much power the LED consumes and
what voltage it requires, along with a simple formula allows you to
determine what resistor to use.
Original Message
> I just hooked up my BS2 for the first time, and tested it by
> connecting this simple circuit (the cimplest one I could find) from
> the manual:
>
> +5v
LED
220 Ohm Res.
I/O Pin 0
>
> The circuit works, and I am really excited about getting into
> STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
> also connected the circuit without it, and it still works just as
> well. The voltage across the LED w/o the resistor is 5v, and with it
> is 3.7v. Is the sole purpose of the resistor to lower the voltage a
> little, dimming the LED a little? Or does it serve some other
> purpose?
resistor you exceed the power dissipation of the LED.
Original Message
From: "apecitydotcom" <fines@m...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, December 24, 2001 8:05 AM
Subject: [noparse][[/noparse]basicstamps] Newbie BS2 user w/ Newbie Question
> I just hooked up my BS2 for the first time, and tested it by
> connecting this simple circuit (the cimplest one I could find) from
> the manual:
>
> +5v
LED
220 Ohm Res.
I/O Pin 0
>
> The circuit works, and I am really excited about getting into
> STAMPs. What I don't get is, why is the 220 Ohm resistor there? I
> also connected the circuit without it, and it still works just as
> well. The voltage across the LED w/o the resistor is 5v, and with it
> is 3.7v. Is the sole purpose of the resistor to lower the voltage a
> little, dimming the LED a little? Or does it serve some other
> purpose?
>
> Thanks in advance. Any info on good online resources would be
> appreciated.
>
>
> 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/
>
>
>
(you can pump amps thru the LED for short perios of time) but what is
more important the current out of the stamp, you could fried it.
--- In basicstamps@y..., "Stephen H Chapman" <chapman@t...> wrote:
> The 220 ohm resistor is to limit the current thru the LED. Without
this
> resistor you exceed the power dissipation of the LED.
>
Original Message
> From: "apecitydotcom" <fines@m...>
> To: <basicstamps@y...>
> Sent: Monday, December 24, 2001 8:05 AM
> Subject: [noparse][[/noparse]basicstamps] Newbie BS2 user w/ Newbie Question
>
>
> > I just hooked up my BS2 for the first time, and tested it by
> > connecting this simple circuit (the cimplest one I could find)
from
> > the manual:
> >
> > +5v
LED
220 Ohm Res.
I/O Pin 0
> >
> > The circuit works, and I am really excited about getting into
> > STAMPs. What I don't get is, why is the 220 Ohm resistor there?
I
> > also connected the circuit without it, and it still works just as
> > well. The voltage across the LED w/o the resistor is 5v, and
with it
> > is 3.7v. Is the sole purpose of the resistor to lower the
voltage a
> > little, dimming the LED a little? Or does it serve some other
> > purpose?
> >
> > Thanks in advance. Any info on good online resources would be
> > appreciated.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@y...
> > 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/
> >
> >
> >
flow in all other branches.
Original Message
From: "acatano2002" <acatano2002@y...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, December 24, 2001 12:44 PM
Subject: [noparse][[/noparse]basicstamps] Re: Newbie BS2 user w/ Newbie Question
> The 220 ohms resistor is to limit not only the current thru the LED
> (you can pump amps thru the LED for short perios of time) but what is
> more important the current out of the stamp, you could fried it.
>
>
> --- In basicstamps@y..., "Stephen H Chapman" <chapman@t...> wrote:
> > The 220 ohm resistor is to limit the current thru the LED. Without
> this
> > resistor you exceed the power dissipation of the LED.
> >
Original Message
> > From: "apecitydotcom" <fines@m...>
> > To: <basicstamps@y...>
> > Sent: Monday, December 24, 2001 8:05 AM
> > Subject: [noparse][[/noparse]basicstamps] Newbie BS2 user w/ Newbie Question
> >
> >
> > > I just hooked up my BS2 for the first time, and tested it by
> > > connecting this simple circuit (the cimplest one I could find)
> from
> > > the manual:
> > >
> > > +5v
LED
220 Ohm Res.
I/O Pin 0
> > >
> > > The circuit works, and I am really excited about getting into
> > > STAMPs. What I don't get is, why is the 220 Ohm resistor there?
> I
> > > also connected the circuit without it, and it still works just as
> > > well. The voltage across the LED w/o the resistor is 5v, and
> with it
> > > is 3.7v. Is the sole purpose of the resistor to lower the
> voltage a
> > > little, dimming the LED a little? Or does it serve some other
> > > purpose?
> > >
> > > Thanks in advance. Any info on good online resources would be
> > > appreciated.
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@y...
> > > 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/
> > >
> > >
> > >
>
>
> 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/
>
>
>
My point is that the LED can take amps, the stamp does not.
--- In basicstamps@y..., "Stephen H Chapman" <chapman@t...> wrote:
> In a series ckt the current in any one branch is the same amount of
current
> flow in all other branches.
>
Original Message
> From: "acatano2002" <acatano2002@y...>
> To: <basicstamps@y...>
> Sent: Monday, December 24, 2001 12:44 PM
> Subject: [noparse][[/noparse]basicstamps] Re: Newbie BS2 user w/ Newbie Question
>
>
> > The 220 ohms resistor is to limit not only the current thru the
LED
> > (you can pump amps thru the LED for short perios of time) but
what is
> > more important the current out of the stamp, you could fried it.
> >
> >
> > --- In basicstamps@y..., "Stephen H Chapman" <chapman@t...> wrote:
> > > The 220 ohm resistor is to limit the current thru the LED.
Without
> > this
> > > resistor you exceed the power dissipation of the LED.
> > >
Original Message
> > > From: "apecitydotcom" <fines@m...>
> > > To: <basicstamps@y...>
> > > Sent: Monday, December 24, 2001 8:05 AM
> > > Subject: [noparse][[/noparse]basicstamps] Newbie BS2 user w/ Newbie Question
> > >
> > >
> > > > I just hooked up my BS2 for the first time, and tested it by
> > > > connecting this simple circuit (the cimplest one I could find)
> > from
> > > > the manual:
> > > >
> > > > +5v
LED
220 Ohm Res.
I/O Pin 0
> > > >
> > > > The circuit works, and I am really excited about getting into
> > > > STAMPs. What I don't get is, why is the 220 Ohm resistor
there?
> > I
> > > > also connected the circuit without it, and it still works
just as
> > > > well. The voltage across the LED w/o the resistor is 5v, and
> > with it
> > > > is 3.7v. Is the sole purpose of the resistor to lower the
> > voltage a
> > > > little, dimming the LED a little? Or does it serve some other
> > > > purpose?
> > > >
> > > > Thanks in advance. Any info on good online resources would be
> > > > appreciated.
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@y...
> > > > 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/
> > > >
> > > >
> > > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@y...
> > 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/
> >
> >
> >