Older LED ... any uses?? How to connect to Prop-1???

[mhein68]

I had several LED's that someone sent me a long time ago... they are "NSN382 multiplexed 2 digit 7 seg led display"  Are they useful? Data sheet should be attached... I am not a genius, just playing around with different stuff so try to make explanation simple!  ;) Thanks!

P.S.. Or if someone wants them let me know and I can send them out to you? Maybe trade?

[menehune]

You didn't mention if you had the common cathode or common anode versions (do you know?), but the 7 segment displays are just 7 rectangular LEDs arranged like a number 8 with either the Anode or cathodes tied together (or common). 

Since they require 1.7 volts and 10mA to illuminate, you could use them like regular LEDs.  Hook the six outer segments to six output pins on the stamp, connect a proper current limiting resistor and you could make a wagon wheel effect. 
To create numbers on them, you would need additional ICs to decode/drive the 7seg displays.

330 ohms (1/8W) is needed to safely drive your display at 5 volts.
1.2kohms (1/2W) is needed to safely drive your display at 12 volts.

You could either perform the Ohms Law calculations yourself or use an online LED resistor calculator.

It's always fun to get a grab bag of LEDs or take apart an old piece or gear and see what you can salvage off it. 
Just be careful, if the LED is too far out of color (the red looks yellow-orange or the green looks yellow-green), you may be overdriving it-increase the value of the current limiting resistor.  It may overheat (burning your fingers if you are holding it ;)) and release the magic smoke.  Then it's no good for anything.

[mhein68]

You didn't mention if you had the common cathode or common anode versions (do you know?), but the 7 segment displays are just 7 rectangular LEDs arranged like a number 8 with either the Anode or cathodes tied together (or common). 

I would have no idea, but I will try hooking it up and playing around... I have about 5 of them so I can go through a few!

[JonnyMac]

You should be able to read the part # from the side of the LED module and from that determine whether it's a common cathode or common anode device.  With seven pins from your Prop-1 you can make any digit and a few alpha characters as well, and even do little animations (rotating bug, etc.) on the display.  This uses up a lot of I/O, though.

This article may be a bit helpful: http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/vol4/col/nv104.pdf

[menehune]

If you can determine the common pin and the leds don't light with one polarity, try the other way.

Yes, you could use 7 pins on the prop, or you could use a BCD to 7 seg driver chip and only use three pins, but it is more complicated to connect and program.  I think I used a BCD decoder in one of my BS2 experiments.  It's probably easier to just directly connect the pins to the I/O on the prop.

[mhein68]

Hi all,
    I have been experimenting and heres what I found.. I hope this is clear as mud!  ;D  #7 and #10 are +positives. Here are the other combinations:

4+7=A
5+7=B
13+7=C
2+7=D
9+7=E
11+7=F
6+7=G
4+10=H
5+10=I
13+10=J
2+10=K
9+10=L
11+10=M
6+10=N
12+7=O
12+10=P

Of course O and P are decimal points. I am going to solder up some wires and try it out. Any program suggestions?
Also I am willing to share two of these to any 2 that want to mess with it! :) First two get one... Thanks!

[mhein68]

After a sleepless night (flu or cold!?)  :P I have thought about it.. I dont think using both digits is possible with a prop-1? You would need more outputs like a prop-2...  Am I wrong?

[JonnyMac]

You'll need some interfacing circuitry to use both.  I would suggest experimenting with one digit first, then move on to the second as your programming skills improve.

[mhein68]

Hi all,
      I have wired it up and it seems like alot for a prop1 to do.. It works but as more segments go on the dimmer they all seem to get. I am experimenting with different ways of turning them on and off!! Thanks all for the help with getting it to light up! I am not doing any high pressure project just playing around learning how it all works.. I hope to be as good as all of you someday! Thanks again! :)