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6 Digit 7 Segment LED Display Panel — Parallax Forums

6 Digit 7 Segment LED Display Panel

SELSEL Posts: 80
edited 2010-08-16 19:14 in Propeller 1
I have already interface a LCD display to the DS1302 RTC.
Now I wish to modify my objects and interface a 6 digit 7 segment LED display.
I want to save time and a lot of effort by not having to build a circuit board for the LEDs.

I would like to find a panel of six 7 segment LED that has all the resistors and other components built in
and all I need do is connect the segments and digits select pins from the propeller to the panel.

I very much prefer the 7 segment LED over the LCD display.

Has anyone seen such a panel that I may purchase?

Comments

  • Invent-O-DocInvent-O-Doc Posts: 768
    edited 2010-08-02 21:36
    Hmmm. I make 'em from scratch with an SX/B sample application, but there are a couple other opteions:

    -Parallax has a serial 4 digit 7s LED that can have two units stacked together for 8 digits
    -sparkfun has a 4 digit serial 7seg LED display with 4 digits (also non-serial versions) though the LED displays are a bit smaller,but it is cheaper than the parallax ones. They are about $15, come in 4 colors and are a snap to use.

    Also,
    -I got a good deal on 4 digit and 3digit LED displays at futurlec and they have a reduced pin count (still need resistors, etc)

    Either way they are a bit pricey, but will do what you want. Hope this helps, good luck.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tom Talbot
    New Market, MD, USA
  • SELSEL Posts: 80
    edited 2010-08-02 22:30
    Invent-O-Doc:

    Thank you for your input!

    I really need an already built six digit display that I can connect to the propeller chip. I looked at Sparkfun and Parallax, but they are only four digits.
    I will admit that most LED displays only have four digits. I guess that is the reason I am having trouble finding one with six. Most commercial clocks, using LED display, only
    show 4 digits.

    I purchased six digital LEDs from Parallax and soon realized just how many lines would have to be run on the bread board to get all six up and running!
    I want to use the Propeller Proto Board to interface an already built LED PANEL as I did with a LCD display.

    So, I am seeking a six digit LED panel that I connect the a..g segment and digit select lines.

    Any further thoughts would be appreciated!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2010-08-03 02:36
    SEL,

    I just finished making my own six digit display.· I doubt it's what you're looking for but it is pretty darn cool.

    I used SparkFun's 6.5" seven-segment displays.· There are aspects of my project that could help you.· An important part of having six digits was the ability to use shift registers.

    I used Dennis Ferron's object 74HC595_MultiPWM.· This object lets you control the brightness of each segment.· The object will control up to four shift registers.· The shift registers (up to four) use three pins.· The clock lines are run in parallel and the data line is daisy chained.· (This set up saves a lot of pins).· I use high power shift registers (TPIC6B595)·that can only sink current but the normal power ones can both source and sink.· I didn't want to multiplex my digits so I used one chip per digit.· Each chip can control eight segments which is how many each digit·has (including decimal point).· I use two groups of three chips to control the display.· I've only programmed it to display time so far (hours, minutes, seconds) but I also plan to have it display data from various instruments.

    My program also controls a LED array but I could probably cut it down to just the time keeping parts, if you're interested.

    I'm pretty sure you could use this code to control a six digit display with six pins.

    Duane
  • turbosupraturbosupra Posts: 1,088
    edited 2010-08-03 13:14
    Hi Tom,

    How many pins are you dedicating to control a 4 segment LED?

    I have 4 pins right now communicating with a BCD and controlling a single 7 segment LED, which is a lot of pins. Do you have to use 8 pins or is there a way to use 5 or 6 pins that controlled four 7 segment LEDs? A 5 pin would give me 32 binary combos and a 6 pin, 64, correct?





    Invent-O-Doc said...
    Hmmm. I make 'em from scratch with an SX/B sample application, but there are a couple other opteions:

    -Parallax has a serial 4 digit 7s LED that can have two units stacked together for 8 digits
    -sparkfun has a 4 digit serial 7seg LED display with 4 digits (also non-serial versions) though the LED displays are a bit smaller,but it is cheaper than the parallax ones. They are about $15, come in 4 colors and are a snap to use.

    Also,
    -I got a good deal on 4 digit and 3digit LED displays at futurlec and they have a reduced pin count (still need resistors, etc)

    Either way they are a bit pricey, but will do what you want. Hope this helps, good luck.
  • SELSEL Posts: 80
    edited 2010-08-03 16:37
    Duane,

    Thanks for your input. But this really does not solve my problem as stated below.

    Once again Thank you for taking the time to give other avenues to pursue.

    SEL
  • Invent-O-DocInvent-O-Doc Posts: 768
    edited 2010-08-04 00:38
    @turbosupra: I use one pin per segment and one pin per digit select (or a shift register). I know you can reduce this with charlieplexing but thought it easier to use more lines than to go with the complexity of that. They way I'm using it is having the LEDs on the same board with an SX DIP chip (have lots) as a dedicated serial device. I use those with the prop or the sparkfun serial ones (they are really compact and use one line per 4 digits) and can mound side/side for an 8-digit display pretty easily.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tom Talbot
    New Market, MD, USA
  • turbosupraturbosupra Posts: 1,088
    edited 2010-08-04 16:41
    Hi Doc,


    Does it look like this? Or are you actually using 1 pin for each segment of the LED (a-f) and then a shift register on top of that?

    I drew this up and tried/built this last night and it worked. The refresh rate was fast enough to where my eye could not tell.

    sevensegmentschematic1.png


    Invent-O-Doc said...
    @turbosupra: I use one pin per segment and one pin per digit select (or a shift register). I know you can reduce this with charlieplexing but thought it easier to use more lines than to go with the complexity of that. They way I'm using it is having the LEDs on the same board with an SX DIP chip (have lots) as a dedicated serial device. I use those with the prop or the sparkfun serial ones (they are really compact and use one line per 4 digits) and can mound side/side for an 8-digit display pretty easily.
  • dgatelydgately Posts: 1,633
    edited 2010-08-04 17:25
    http://www.blueroomelectronics.com/Dragonfly.?



    -dgately
  • turbosupraturbosupra Posts: 1,088
    edited 2010-08-05 13:26
    ^ I swapped to PNP's and coded for lows and got better results with LED brightness. I believe the high impedance of the LED wasn't allowing the transistor to turn on fully.
  • Invent-O-DocInvent-O-Doc Posts: 768
    edited 2010-08-05 23:43
    I tried it that way and it worked, but I put wired each segment up individually because for me it wasn't worth the few io lines saved to put another into the schematic. I used PNPs too.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tom Talbot
    New Market, MD, USA
  • turbosupraturbosupra Posts: 1,088
    edited 2010-08-06 00:59
    If I have 6 LED's, that'd be 24 pins, but with this method I'll use 10 pins instead so if it works I'm going to stick with it!

    Invent-O-Doc said...
    I tried it that way and it worked, but I put wired each segment up individually because for me it wasn't worth the few io lines saved to put another into the schematic. I used PNPs too.
  • yarisboyyarisboy Posts: 245
    edited 2010-08-16 19:14
    There is a driver object in OBEX for the MAX6956 chip. I looked up Jon Williams article from the November 2005 issue of NutsVolts magazine. In it the now obsolete MC14489 chip was used. That was pre-Prop but good info none the less. I've got a bunch of these chips left over so I did a board with three of these chips daisy-chained on a serial bus to give me a maximum possible 15 digit display. There isn't anything in the OBEX for the MC14489 so, with luck, I soon may be the first to provide it. September 4th. It works on my breadboard. Should have it on OBEX in a couple of days.
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