display

MacGeek117

Instead of using 7 1-kilo-ohm resistors connected to all the segments like in the WAM
book, chapter 6, page 172, why don't you use 1 resistor connecting common to
ground? -bugg

Martin Hebel

One good reason is because LED's drop a certain amount of voltage across them, and LED's have varying·tolerances, connecting all the LED's in parallel·with a common current limiter gives varying levels of brightness affecting the quality of the display.

Feel free to experiment with a common resistor though!




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Martin Hebel

Electronic Systems Technologies
Southern Illinois University Carbondale
Personal Links - ·Lot of BASIC Stamp info
and
SelmaWare Solutions
StampPlot Pro Version 3 Release 4
Graphical Data Acquisition for your Micro and Imagination!
Now allows additional controls to be added, or developed.
·

allanlane5

Also, if you turned on ONE LED, it would draw a certain current (5 Volts - 1.4 volts) / 1000 == 3.6 mA

Now, if you turned on a second LED, the 3.6 mA would be divided in half -- each would get half (depending on the manufacturing tolerances of the LED's). Thus, they would be half as bright -- if they lit at all. With the third LED, it gets even less.

Now, if each one has its own resistor, then each one gets its own 3.6 mA.

Now, if you had a faster processor, concievably you could 'strobe' each LED segment so only one at a time was on.· If you cycled through all LED's fast enough (20 times a second or more), your eye would 'average' out the pulses so they would all seem to be on.· I'm not sure the BS2 is fast enough for this -- but even if it was, you wouldn't want to spend all of its time refreshing an LED display.

MacGeek117

Thanks guys! is there any way of strobing the display with a BS2?
-bugg

Chris Savage

I don't know what made me think of it, but years ago when I was first building with a lot of LEDs on a board, I remember reading an article for a Constant Current Regulator...Seems like it used a standard LM78xx/LM340 regulator, configured in a strange manner...Ah, okay, here it is, right in the datasheet!

http://www.national.com/ds/LM/LM340.pdf

If memory serves, we used this in a Digital Dashboard project some years ago to maintain brightness on the dash display.



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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·

MacGeek117

Thanks guys. Thanks Chris. I'll try to figure that out. -bugg

MacGeek117

Oh, by the way, is there any way to program a BS2, e, sx, p, pe, to have a 12-bit
variable? -bugg

MacGeek117

Also, guys, check the program and please tell me if it would work. -bugg

Andy Lindsay (Parallax)

That's pretty cool, and it looks like it should work so long as the result is less than 65536.

It's also possible to plot the rectangle in the Debug Terminal. If you're interested, check out Activities 1 and 2 in this post:

How to - Accelerometer (2) Tilt, Display Graphics, and Video Games

... actually, it turned out to be a little bit of a head-scratcher, so here is a code snippet you can add to your program between the last DEBUG command and the LOOP:

[color=blue][color=#000000][color=green][color=green]  ' Plot perimeter with length and width.[/color]
[color=green]  ' Add to PERIMITER_FINDER.bs2 - insert between the [/color]
[color=green]  ' last DEBUG and the LOOP command.[/color]
     [color=blue]DEBUG[/color] [color=purple]CRSRXY[/color][color=black], 0, 7[/color]
  [color=blue]FOR[/color][color=black] perimeter = 0 [/color][color=blue]TO[/color][color=black] ((width * 2) - 1) [/color][color=blue]STEP[/color][color=black] 2[/color]
    [color=blue]DEBUG[/color] [color=purple]CRSRX[/color][color=black], perimeter, [/color][color=red]"* "[/color]
  [color=blue]NEXT[/color]
  [color=blue]FOR[/color][color=black] perimeter = 1 [/color][color=blue]TO[/color][color=black] (length - 1)[/color]
    [color=blue]DEBUG[/color] [color=purple]CR[/color][color=black], [/color][color=red]"*"[/color][color=black], [/color][color=navy]REP[/color] [color=red]" "[/color][color=black] \((width * 2) - 3), [/color][color=red]"*"[/color]
  [color=blue]NEXT[/color]
  [color=blue]FOR[/color][color=black] perimeter = 0 [/color][color=blue]TO[/color][color=black] ((width * 2) - 1) [/color][color=blue]STEP[/color][color=black] 2[/color]
    [color=blue]DEBUG[/color] [color=purple]CRSRX[/color][color=black], perimeter, [/color][color=red]"* "[/color]
  [color=blue]NEXT[/color]
 
  [color=blue]DEBUG[/color] [color=purple]CR[/color][color=black], [/color][color=purple]CR[/color][color=black], [/color][color=red]"Press any key: "[/color]
  [color=blue]DEBUGIN[/color][color=black] perimeter[/color]
  [color=blue]DEBUG[/color] [color=purple]CLS[/color]
 
[/color][/color][/color]

Post Edited (Andy Lindsay) : 1/5/2005 10:11:26 PM GMT

MacGeek117

Here is another program for someone to check. -bugg

MacGeek117

Oh, by the way, if you didn't uderstand the program, look at page 172 of the WAM book
-bugg

Andy Lindsay (Parallax)

Hmmm, yes, I was hoping somebody would do that. It's a nice combination of a couple of different elements from What's a Microcontroller, right?

You can probably replace all the PAUSE 1000 commands in the CASE statements with just one after the ENDSELECT.

Although the program will work without the PAUSE, it probably helps prompt the user to have a delay before the next digit request.

MacGeek117

thanks again Andy. I didn't think of that . Also I've made an area finding program. -bugg