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Electronegativity
06-11-2005, 09:55 AM
Hi guys (gals?), I am new to the Basic Stamp and my first one is in the mail (BS2-1C).

I want to use it to drive a 2 digit numerical LED display (Lumex LDD-C516RI).

My current idea is to feed output from the BS2 I/O pins through OP-AMPs to each of the pins on the display.

This seems a bit clunky, and I would rather not tie up all those I/O pins on the BS2 if I don't have to.

Any help would be appreciated.

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I wonder if this wire is hot...

Chris Savage
06-11-2005, 10:17 AM
Hello,

·· The MAX7219 is one possible option for this application.· Widely used for this, and plenty of example source code.· You could also use 74HC595 shift registers...Don't forget resistors for each LED.· If you don't mind me asking...Op-Amps for LED drivers?· I had never heard of anyone doing that short of a simple comparator.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

Electronegativity
06-11-2005, 10:44 AM
Hi Chris:

My knowlege of electronics is extremely limited.
I know an LED needs more voltage than the BS2 can put out, So I figured I would step it up.
I also realized that my idea was obviously bad, which is why I posted the question.

Do I need to buy 1 or 2 MAX7219 chips to operate a 2 digit display?

What resistors do I need to make it work with BS21C and a display that requires ~2V and 10mA?

As long as I have you here, what is the best method of providing small (< 1MB) nonvolatile memory that the BS2 can use?

Thanks for the help,

-Alexander

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I wonder if this wire is hot...

Chris Savage
06-11-2005, 11:16 AM
Alexander,

·· Actually the typical LED drops about 1.2 volts, whereas the Stamp Module puts out 5 Volts.· Current is the issue.· However, the MAX7219 can drive 8 7-segment displays or 64 individual LEDs.· I've only used it for 7-segment displays, and I've only used 6 at once, but it will handle 8.·Below is a link to the product on our web page.· You can view the datasheet from http://www.maxim-ic.com just search that part #.

http://www.parallax.com/detail.asp?product_id=603-00001

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

Electronegativity
06-11-2005, 11:29 AM
Thank you Chris, the MAX7219 is well suited to my purpose, but you alluded to resistors in your first reply; what number and type of resistors do I need?

-Alexander

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I wonder if this wire is hot...

Chris Savage
06-11-2005, 11:33 AM
Alexander,

·· You don't need resistors with the MAX7219.· Well, you need two, but they're both listed in the docs.· There's also a sample in the StampWorks Manual, a free download in PDF format from our website.· It can show you an example of using the MAX7219.· Good luck!

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

Electronegativity
06-11-2005, 12:12 PM
Thanks again Chris, I'll give it my best shot.

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I wonder if this wire is hot...