Hi, Scott. If you're looking for minimum cost/high reliability, you might want to consider manufacturing some small flip cards with numerals on them (card stock works well for this), and affix them to some rings mounted on the upper part of the display. If you use a printer to make your numbers, it can look pretty good, and is about as reliable as you can get. Flip cards over to get to the right numbers, and you're there. I've seen it done effectively for church fundraisers.
But, if you've just got to have an electronic display, I'd go with some of the 3" 7-segment LED displays from Jameco, along with a 6VDC 800 mA wall wart, a bag of 220 ohm resistors, and four $0.89 DIP switches to manually set the segments. If you combine that with an 8" wide protoboard, you can do the whole electronics part for about $46 bucks plus shipping. Whoever is changing the numbers will have to use a pencil to manually turn on each segment, but that's doable by a non-technical person, because they can see the segments light up. A small instruction sheet with pictures of the segments and what DIP switches to turn on for which numerals will work OK for minimum cost. Each digit will be wired something like this (view in fixed font or M$ Notepad):
- o-----o-----o-----o-----o-----o-----o-----o | | | | | | | | | | | | | | | o o o o o o o o '\ '\ '\ '\ '\ '\ '\ '\ \ \ \ \ \ \ \ \ o \ o \ o \ o \ o \ o \ o \ o \ | | | | | | |
6VDC .-. .-. .-. .-. .-. .-. .-. | | | | | | | | | | | | | |
220 ohm| | | | | | | | | | | | | | X 7 '-' '-' '-' '-' '-' '-' '-' | | | | | | | V ~ V ~ V ~ V ~ V ~ V ~ V ~
- ~ - ~ - ~ - ~ - ~ - ~ - ~ |a |b |c |d |e |f |g | | | | | | | o-----o-----o-----o-----o-----o-----o-----'
- created by Andy´s ASCII-Circuit v1.24.140803 Beta
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You'll still need an enclosure, some standoffs to mount the protoboard to the front of the enclosure, and some red plexiglass to put in front of the LEDs to improve contrast and get them their display without seeing the rest. That's your pidgin.
Here's a parts list:
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DISPLAY 3", 7-SEG, C.C.RED, 1 DIGIT Jameco #: 202542 MFG:LIGITEK MFG#:LSD30155-20/A
1+ $5.49 USD
TRANS,WALL,6VDC/800mA,F2
2.1mm X 5.5mm,UL,BLACK Jameco #: 147707 MFG:JAMECO RELIAPRO MFG#:DCU060080C6961
1+ $4.95
SWITCH,DIP,SPST,8SWTH,
16PIN,50VDC/100mA,SKT:37372 Jameco #: 38842 MFG:JAMECO VALUEPRO MFG#:DS-08-G-01-BL
1+ 0.89
@ CARBON FILM RESISTOR, 1/4W 5%, 220 OHM, (SOLD IN BAGS OF 100) Jameco #: 30470 MFG:HONJU MFG#:R220/100
1+ 0.99
PROTOTYPE BUILDER,5.5"X8.0" PCB,PRE-ETCHED,DRILLED, GOLDSUN Jameco #: 206594 MFG:JAMECO VALUEPRO MFG#:PCB-594
1+ 14.99
If you can scrounge the wall wart and the perfboard, the price goes down to $27 plus shipping.
Some times these things happen. I guess it comes from wearing the "nice guy" sandwich sign ("nice guy" on the front -- the back of the sign says "kick me"). Even so, I still wear the sign, too. ;-) Good luck Chris