BS and LEDS

Archiver

Hi,

I would like to drive some leds from my BS2 from Christmas.
How many leds (typical red ones) can a Basic Stamp 2 drive?
I suppose this is a small number. What can I do to extand this number?
(I don't need a BS output for each led, several leds can be turned on/off at the
same time)

Thanks,

Nicolas

Archiver

My thought would be that each output can handle a max of two LEDs
assumming 10 mA per LED. Be sure to use an external 330 Ohm resistor
or use a 5V LED which provides an internal series limiting resistor.

This could be simply expanded by adding an octal driver such as the
ULN2803 which is about a $1.00. This would allow you to sink current
for 20 or more LEDs for each Stamp IO.

Peter H. Anderson, http://www.phanderson.com
Homebrew BS2, BS2 Starter Packages

--- In basicstamps@egroups.com, "Nicolas Fournel"
<Nicolas.Fournel@f...> wrote:
> Hi,
>
> I would like to drive some leds from my BS2 from Christmas.
> How many leds (typical red ones) can a Basic Stamp 2 drive?
> I suppose this is a small number. What can I do to extand this
number?
> (I don't need a BS output for each led, several leds can be turned
on/off at the same time)
>
> Thanks,
>
> Nicolas

Archiver

Maxim makes a great IC for this purpose, the MAX7221 can drive up to 64
LEDs while only requiring 3 pins

-
Ian Bobbitt

---

When an error occures:
A novice user blames himself,
a normal user blames the computer,
a power user sighs and gets another cup of coffee.

KB9VEX

ICQ: 14106680

It said requires windows 95 or better, so I installed Linux.

On Wed, 15 Nov 2000, Nicolas Fournel wrote:

> Hi,
>
> I would like to drive some leds from my BS2 from Christmas.
> How many leds (typical red ones) can a Basic Stamp 2 drive?
> I suppose this is a small number. What can I do to extand this number?
> (I don't need a BS output for each led, several leds can be turned on/off at
the same time)
>
> Thanks,
>
> Nicolas
>
>
>
>
>

Archiver

>
> My thought would be that each output can handle a max of two LEDs
> assumming 10 mA per LED. Be sure to use an external 330 Ohm resistor or
> use a 5V LED which provides an internal series limiting resistor.
The specs are (sink/source)25/20mA per pin max, but 50/40mA total per
I/O port. So (on seperate pins)5 LEDs at 10mA or 2 at 20mA etc.

Archiver

<><><
I would like to drive some leds from my BS2 from Christmas.
How many leds (typical red ones) can a Basic Stamp 2 drive?
I suppose this is a small number. What can I do to extand this number?
(I don't need a BS output for each led, several leds can be turned
on/off at the same time)
<><><
Date: Thu, 16 Nov 2000 06:40:41 -0000
From: "Peter H. Anderson" <pha@p...>
....
This could be simply expanded by adding an octal driver such as the
ULN2803 which is about a $1.00. This would allow you to sink current
for 20 or more LEDs for each Stamp IO.
<><><

Don't forget you'll need lots more current for all the LEDs so
you'll need a power supply which will handle the number of LEDs
times current per LED if in parallel or higher voltage with
LEDs in series.... and add up all the branch currents.... don't
try to let the STAMP regulator handle all the current if you've
got a lot of lamps.... With various on/off schemes it may be
hard to predict peak currents but if you have the LED power
isolated from the STAMP power likely nothing more serious than
dimming will happen - or the power supply regulator overheat
or its fuse blow...

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Archiver

Hi,
I don't know if this will be of any help or not, but Radio Shack has low
current (2mA)
diffused LED's. I purchased several for a project, so I wouldn't have to
worry about damaging my stamp. Of course there are other ways to use regular
LEDs, but I was looking for the easy way. I know that they come in Red and
Green (perfect for Christmas). They were relatively inexpensive, I think
about 27 or 29 cents each. I put a 1600 ohm resistor in line with them.
I'm not sure if they are listed in the regular catalog, but they were listed
in a catalog they had in the store, I guess it was a catalog aimed more at
commercial accounts, but anyone can order from it.
The Part number is TA-9006107 (Red). I don't have the number for the Green
ones in front of me now, but if you need any more info, let me know.
Happy Holidays
Kay

Archiver

sent:
>>Hi,
>>I don't know if this will be of any help or not, but Radio Shack has low
>>current (2mA) diffused LED's.

FYI, the part numbers are:
Green -- p/n 276-303
Red -- p/n 276-310

Archiver

:
> >>Hi,
> >>I don't know if this will be of any help or not, but Radio Shack has
> >>low current (2mA) diffused LED's.
>
> FYI, the part numbers are:
> Green -- p/n 276-303
> Red -- p/n 276-310
>
>
I wonder if these are Quality Technologies units like I used to get
from Digi-Key(they had yellow also). I used them in an r/c battery
monitor. They were a second source of an HP LED.

Mike DeMetz sect. Michiana R/C Choppers
miked@t...
http://sites.netscape.net/mdemetz