controlling LEDs
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I want to control a lot of LEDs (the kind that come with the parallax robot
curriculum, not display terminals). I want to be able to have about 10 of
hopefully up to 200 LEDs be on at once and I'd like to be able to select
those 10 using the Stamp. Do I need a special board to control those LEDs?
If so, does anyone know of one?
thanks
bob
curriculum, not display terminals). I want to be able to have about 10 of
hopefully up to 200 LEDs be on at once and I'd like to be able to select
those 10 using the Stamp. Do I need a special board to control those LEDs?
If so, does anyone know of one?
thanks
bob
Comments
search for "bs2 led", you'll likely find several examples. The hard part is
power. Each LED will take around 10ma, adds up real fast!
Original Message
From: <eclecticrr@A...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, December 26, 2002 10:35 PM
Subject: [noparse][[/noparse]basicstamps] controlling LEDs
> I want to control a lot of LEDs (the kind that come with the parallax
robot
> curriculum, not display terminals). I want to be able to have about 10 of
> hopefully up to 200 LEDs be on at once and I'd like to be able to select
> those 10 using the Stamp. Do I need a special board to control those
LEDs?
> If so, does anyone know of one?
>
> thanks
>
> bob
>
> 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/
>
>
No special board needed, just properly connected transistors between the
Stamp and the LEDs. Are you planning to run the LEDs from 5V or perhaps a
9V or 12V supply? If using 5V you can connect groups of 2 common LEDs in
series with a current limiting resistor. With 9V or 12V supplies, you can
connect several LEDs in series (along with the current limiting resistor)
and control several of these "chains" with an inexpensive PN2222 NPN
transistor. Or use a IRL520N MOSFET and control a zillion LEDs with one
Stamp pin!
When you say "10 of... 200 LEDs" does that mean you will have 20 independent
groups of 10 LEDs? If so, do you plan to use an IC to expand the number of
I/O pins available from the Stamp?
Randy
www.glitchbuster.com
Original Message
From: <eclecticrr@A...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, December 26, 2002 10:35 PM
Subject: [noparse][[/noparse]basicstamps] controlling LEDs
> I want to control a lot of LEDs (the kind that come with the parallax
robot
> curriculum, not display terminals). I want to be able to have about 10 of
> hopefully up to 200 LEDs be on at once and I'd like to be able to select
> those 10 using the Stamp. Do I need a special board to control those
LEDs?
> If so, does anyone know of one?
>
> thanks
>
> bob
>
> 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 just need power. use a trasnsitor. A pn2222 will yeild 200 ma
so at 10mA per led, that is lots of lights. TO-92, and it will work
directly from a Stamp Pin.
Assume your pn2222 has an hfe of 50, and you want 200ma.
you are powering with 12 volts ? with this much power, I assume you
are not using batteries ? 500 led's at 10mA each = 1/2 amp.
To look at the current draw,
10mA for the led, 20 LED's per transistor.
200ma/hfe50=4ma to drive the transistor into saturation. The Stamp
can put that into 10 transistors.
You could put the pn2222 into a Darlingto pair with a something more
powerful, but that is much more work.
One ULN2003 Darlington chip will control 7 channels at 500mA per
channel.
DIP14 or the ULN2803 with 8 channels. both under a buck.
for the ULN200x the hfe is 1,000 so you can drive 7 channels with
50led's/channel with less power from the stamp than one pn2222 needs
to control 50 led's
IF you want individual chips, you can use the single TIP120's but the
cost is up to like over 80 cents each. For that money, Randy at
Glitchbuster.com can offer MOSFET's.
I didn't look at the numbers for the MOSFET, but outpt power goes way
up and input power is still really low.
Controlling 10 circuits with 500 LED's on a circuit is simple with
the Stamp. Controlling 500 seperate LED's such as a moving sign is
considderably more complicated.
If you are thinking that route, you need to considder speed as the
serial connection will slow things down.
Dave
--- In basicstamps@yahoogroups.com, "Randy Jones" <randyjones@w...>
wrote:
> Bob...
>
> No special board needed, just properly connected transistors
between the
> Stamp and the LEDs. Are you planning to run the LEDs from 5V or
perhaps a
> 9V or 12V supply? If using 5V you can connect groups of 2 common
LEDs in
> series with a current limiting resistor. With 9V or 12V supplies,
you can
> connect several LEDs in series (along with the current limiting
resistor)
> and control several of these "chains" with an inexpensive PN2222 NPN
> transistor. Or use a IRL520N MOSFET and control a zillion LEDs
with one
> Stamp pin!
>
> When you say "10 of... 200 LEDs" does that mean you will have 20
independent
> groups of 10 LEDs? If so, do you plan to use an IC to expand the
number of
> I/O pins available from the Stamp?
>
> Randy
> www.glitchbuster.com
>
>
>
Original Message
> From: <eclecticrr@A...>
> To: <basicstamps@yahoogroups.com>
> Sent: Thursday, December 26, 2002 10:35 PM
> Subject: [noparse][[/noparse]basicstamps] controlling LEDs
>
>
> > I want to control a lot of LEDs (the kind that come with the
parallax
> robot
> > curriculum, not display terminals). I want to be able to have
about 10 of
> > hopefully up to 200 LEDs be on at once and I'd like to be able to
select
> > those 10 using the Stamp. Do I need a special board to control
those
> LEDs?
> > If so, does anyone know of one?
> >
> > thanks
> >
> > bob
> >
> > 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/
> >
> >
> >
pmeloy@s... writes:
> You don't need a special board, just chips and power. Go to google and
> search for "bs2 led", you'll likely find several examples. The hard part is
> power. Each LED will take around 10ma, adds up real fast!
>
>
In fact, 10 LEDs at once @ 10 ma each (100 ma) is too much for the stamp to
handle. To drastically reduce the current needed by the stamp, make the stamp
turn on a transistor, (like a 2n3904) and have the transistor in turn ground
the stamp.
If you need assitance on the transistor hook up (emitter follower is
simplest), write back.
[noparse][[/noparse]Non-text portions of this message have been removed]
http://www.allegromicro.com/sf/5832/