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Electronics 7-segment LED Clock

Discussion in 'Modding' started by Explicit, 27 Sep 2004.

  1. Turbokeu

    Turbokeu Member

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    My 57x51cm (22.5x20.0") Bungard photosensitive PCB sheet finally arrived:
    [​IMG]

    Therefore I was able to make a second 2.3" display board in one piece, and the 4.0" display board in only two parts.
    The back of the 4.0" display:
    [​IMG]

    Right:
    [​IMG]

    Middle: I used brass profiles that I soldered to the PCB as reinforcements.
    [​IMG]

    Left: The Clock PCB is mounted on 4 standoffs that are soldered to pads on the display PCB. This Clock PCB is the simple one. A second Clock PCB with RF433-receiver and hourly gong is waiting to be soldered.
    [​IMG]

    Front: The PCB, the sides of the displays and the 10mm colon LEDs have been black spray-painted. The 5x5mm status LEDs are not yet mounted (waiting for delivery from Lumex). Remark, the PCB is 68cm wide and 14cm high (26.8"x5.5").
    [​IMG]

    And finally working: (the clock starts at 12:00:00 because the DCF module is not connected). The protective sheet is still on the digits to protect them from scratches.
    [​IMG]

    The copper side of the new 2.3" display board in one piece:
    [​IMG]

    New and 'old' 2.3" board:
    [​IMG]

    Front: The protective sheet (covered with some black paint from the spray) is still present on the left 2.3" displays.
    [​IMG]

    Only two Clock PCB's with gong and RF-receiver, and nine more Clock PCB's without to make...:)

    The PCB layout for the RF-transmitter keyfob is finished too:
    [​IMG]

    I found a cheap 2-button keyfob case at Farnell to house the transmitter.
    Pics will follow in the next few days.

    CD :D
     
    Last edited: 18 Oct 2005
  2. Turbokeu

    Turbokeu Member

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    Just finished the display board with the 0.8" white displays, they are beautiful!
    The colour goes from soft warmwhite to blinding bluewhite with the automatic PWM brightness regulation of the LED clock board.
    This is somewhere between the two brightnesses:
    [​IMG]

    CD :)
     
  3. star882

    star882 New Member

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    Idea: Add a cheap MP3 player ( http://www.compusa.com/products/product_info.asp?product_code=285177&pfp=BROWSE ) and start it playing using a free GPIO for a musical alarm! The MP3 player I linked to is actually the one that I used for a similar project, except that it's modifying an existing alarm clock. I have even designed it to run off the existing batteries by using a power pin of the memory slot to control the bias to a simple 2 transistor amp. The MP3 player automatically turns off a while after the music stops so I didn't need to design a circuit to turn it off. Since your clock runs from AC, power management shouldn't be too much of an issue. My design only draws about 150mA (at 3v) while playing and only a few uA when not playing. It's pretty loud (using a small 1" 8 ohm speaker) and quality is a little better than AM radio. I also jumpered a line to ground to disable the Flash writing power supply to save a few mA or so of power.
     
  4. Wolfe

    Wolfe New Member

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    Just out of curiosity, how much did that PCB cost?



    I'm back!! It's only been something like 6 months.
     
  5. Turbokeu

    Turbokeu Member

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    This one cost me 61.00 Euro (about £45.50 - $73.00).
    The previous one (a couple of months ago) was 56.00 Euro.

    CD :)
     
  6. Turbokeu

    Turbokeu Member

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    Hey, seems like a good idea!
    I always wanted the Big Ben chime sound for the hourly gong...

    You did find out where to connect it to a GPIO I presume?

    CD :)

    PS: Just sent an inquiry to CompUSA about delivery to Belgium...
     
  7. Wolfe

    Wolfe New Member

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  8. Turbokeu

    Turbokeu Member

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    Hey that Rogue MP3 player seems great!
    But too expensive for just a Big Ben chime on my clock...

    I could use this one for another project.
    Thanks for the link.

    CD :)
     
  9. bigal

    bigal Fetch n Execute

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    pah, just get one of them £10 mp3 players (128meg or even just 64meg) and hack the button to it. two presses of play to run file and another long one to switch off (or auto off)
     
  10. Turbokeu

    Turbokeu Member

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    No updates on the LED clocks actually, all (0.36", 0.8", 1", 2.3" and 4.0", except the 0.56") display boards are finished and functional.
    Now looking for the right colour of Perspex to put in front of the displays, and looking for adequate aluminium profiles to build the cases.

    Richard from this forum already finished his 4.0" LED clock, including the housing. Beautiful job Richard!
    The clock is actually showed in Tina's (Richard's wife) clock shop (Richard, I hope you don't mind publishing your 4.0" clock):
    Remember: this clock is more than 30" wide!
    [​IMG]

    On the other hand I found some time to make more nixieclocks with the spare tubes that I own:
    I found the 14x NEC CD66A tubes (16mm digit size) through eBay in Germany, the 12x Rodan GR-112 tubes (12mm digit size) through marktplaats.nl in the Netherlands.

    [​IMG]

    [​IMG]

    The GR-112 tubes were still soldered onto a big display board (following the info that I found they were used in some Sony measuring equipment).
    While desoldering I unfortunately broke one of the 12 tubes (they were also attached with velcro tape). Therefore I'm missing one tube to make a second GR-112 clock...:(
    The tubes are now all soldered onto 1.08a tube boards from Claus Urbach (www.nixieclocks.de):

    [​IMG]

    The GR-112 tubes in action:
    [​IMG]

    The finished clock with K8 housing, CD66A tubes and "phenolic" spacers:
    [​IMG]

    I need some more clock boards and K8 housings but I will wait till my finances get better...

    This is why I like the NEC or Rodan nixietubes so much:
    The anode grill isn't made from a coarse honeycomb mesh like most other tubes, but from very thin horizontal wires making the digits much more visible.

    [​IMG]

    CD :)

    Edit: Name changes of some pictures.
     
    Last edited: 19 Oct 2006
  11. SteveyG

    SteveyG Electromodder

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    Thought I'd add to your clock thread with one line of the new display I'm building...

    [​IMG]




    [​IMG]




    [​IMG]

    I've still got to finish off building the other four sets of boards.
     
  12. Turbokeu

    Turbokeu Member

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    Hi Stevey!
    Nice job there!
    Are you using discrete LEDs for the display?
    Not that easy to make such big PCB's (how many parts is yours made from?)
    Are the chips above the display ULN2x03 drivers and 74xx595 8-bit shift registers?

    I'm busy too with my blue 2.1" 5x7 dot display schematic (have actually 6 pieces, need 3 more because I forgot to take into account a 'space' column between characters...).

    I'm thinking about how to achieve the very nice 'rain drop' effect as you can see on some commercial LED message signs: the dots are randomly falling and form the characters.

    I also acquired a couple of Allegro A6812 20-bit VFD drivers for use with my IV-11 VFD tubes, and a couple of ST M5451 35-bit LED drivers that I plan to use (if possible) with the dot matrix display.

    CD :)
     
  13. SteveyG

    SteveyG Electromodder

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    Yeah, I'm using shift regs and darlington drivers. And those are discrete LEDs - Almost 1000 per row of text. - Peak current per row of LED's is ~23A!! (LEDs are pulsed at 160mA).

    The PCBs are made in four sections, roughly 280mm per section.


    The effect you're after is relatively easy to produce. Just apply a mask to the characters (AND them with your character detail) and randomly fill the masks with 1's until they're all 1's.
    If you're after an actual raining effect, then just apply the mask to the top line, and progressively move the mask down until it reaches the bottom line.
     
  14. Turbokeu

    Turbokeu Member

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    Wow...7000 LEDs! :jawdrop:
    Better have a good PSU to feed all these...

    Thanks for the hint on the 'raining' effects, good start for developing the routines.

    Since a couple of years I'm watching this link for RGB dot matrix displays:
    [​IMG]
    Prices dropped from the initial $90.00 to the actual $36.00/piece, but it's still quite pricy...

    These RGB displays would make an amazing clock, I'm thinking on cycling rainbow colours through the digits. :naughty:

    CD :)
     
  15. Mike K8LH

    Mike K8LH New Member

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    Hi Guys:

    Just stumbled onto this thread a few days ago and wanted to say thanks for the very fine and stimulating example projects...

    May I share a minimalist (some might say "cheap skate") single chip design concept for the smaller 7-segment displays? It uses 8 pins and N(N-1) multiplexing, sometimes referred to as Charlieplexing (a Maxim term), to drive up to eight 7-segment displays...

    [​IMG]

    I have a prototype with a 4-digit 0.56-inch 'stick' display running off of a 16F628A now (for several days) and brightness seems very good... I thought about leaving out the PWM brightness circuitry but then thought it might be kind of neat to fade out and fade in the colons and perhaps use a morphing type of 100-msec fade-out and 100-msec fade-in on the individual digits that are changing, or on all the digits(?)... Can't wait to add the circuitry/code and try it...

    I use a mechanical Rotary Encoder with 18 detents per revolution and built-in push button switch on the shaft to provide for a single clean control... The interrupt code that 'scans' the switch matrix provides a soft 'click' through the speaker when the Encoder is rotated to a detent position and produces a 'beep' for a short push button press or a double 'beep' for a long push button press...

    For those who may be interested, the N(N-1) multiplexing scheme relies on the ability of a PIC pin to output a high (source current), output a low (sink current), or become a high impedance input (which neither sources nor sinks current)... The "down side" is that it's wired a bit differently from other multiplexed displays... Here's how you'd connect eight CC or CA displays;

    [​IMG]


    Thanks again for the inspiration Gentlemen...

    Regards, Mike
     
    Last edited: 20 Nov 2005
  16. mattthegamer463

    mattthegamer463 New Member

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    quick question. if i have display of 10mA LEDS that totals to 16 leds and 160mA of current being drawn, is that too much for the parallel port to handle? it would be 20mA per pin and 160mA total. can someone tell me if im ok or risk blowing my paralell port? thanks.
     
  17. FourDee

    FourDee New Member

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    don't you already have a topic about this question?
     
  18. mattthegamer463

    mattthegamer463 New Member

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    i know, but i dont get very many answers. i figured posting here would maybe help get a answer quicker because this is a fairly popular thread.
     
  19. Turbokeu

    Turbokeu Member

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    You're welcome Mike!

    Your concept seems well thought, it gives me some idea's too...
    You could use hardware PWM through the PIC's CCP1 pin for the brightness regulation, works great.

    Keep up the good work :thumb:

    CD :)
     
  20. Mike K8LH

    Mike K8LH New Member

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    Hi CD,

    Yes, I was planning on using the CCP1 output with the PWM period equal to the 'digit' scan period... And you could change the PWM rate for each individual digit or column which I suspect would allow for some pretty interesting effects besides just dimming the entire display for dark room settings...

    I am running into brightness problems scanning eight columns at a 12.5% duty cycle though... This worked well on a past eight digit Frequency Counter project but I was using Agilent low current (5-ma) displays... I found I can get adaquate brightness by reducing the segment current limiting resistors to 10-ohms on the Clock design but the additional voltage drop through an N-channel MOSFET for the brightness control would be intolerable... Soooo, it seems I may be ording some common anode display samples and feeding the NPN column drivers with some voltage higher than 5 volts and placing the PWM driver MOSFET up there too...

    Thanks again... Please take care... Best regards, Mike

    <added>

    BTW, scanning the display is incredibly simple using just a couple variables (BITPOS and BUFPTR) and an eight byte digit segment buffer array (LEDBUF)... Here's an excerpt from my ISR... Have fun...


    Code:
    ;
    ; The eight LED displays or columns are 'scanned' one at a time
    ; for a 12.5% LED duty cycle.  Each Port B pin may be sourcing
    ; current to segments up to 87.5% of the time...
    ;
    ISR_LED	bsf	STATUS,RP0	; bank 1 (RP1 already clear)	  |B1
    	movlw	b'11111111'	;				  |B1
    	movwf	TRISB		; turn off LED display		  |B1
    	bcf	STATUS,RP0	; bank 0 (RP1 already clear)	  |B0
    	xorwf	BITPOS,W	; invert column/float bit	  |B0
    	movwf	PORTB		; new output pattern		  |B0
    ;
    	movf	BUFPTR,W	;				  |B0
    	movwf	FSR		; setup indirect address	  |B0
    	movf	INDF,W		; get digit segment data	  |B0
    	andwf	BITPOS,W	; AND the float/column bit	  |B0
    	btfss	STATUS,Z	; turn 'float' segment on?	  |B0
    	iorlw	b'10000000'	; yes				  |B0
    	iorwf	BITPOS,W	; pick up the float/column bit	  |B0
    	iorwf	INDF,W		; pick up digit segment bits	  |B0
    	xorlw	b'11111111'	; invert all bits		  |B0
    	bsf	STATUS,RP0	; bank 1 (RP1 already clear)	  |B1
    	movwf	TRISB		; display new digit		  |B1
    ;
    	bcf	STATUS,RP0	; bank 0 (RP1 already clear)	  |B0
    	incf	BUFPTR,f	; increment buffer pointer	  |B0
    	bcf	STATUS,C	; clear the carry bit		  |B0
    	rlf	BITPOS,f	; shift the float/column bit	  |B0
    	btfss	STATUS,C	; all 8 digits scanned?		  |B0
    	goto	ISR_CTR		; no, branch			  |B0
    	rlf	BITPOS,f	; yes, reset to b'00000001'	  |B0
    	movlw	LEDBUF		; get digit buffer address	  |B0
    	movwf	BUFPTR		; reset buffer pointer variable	  |B0
    ;
     
    Last edited: 23 Nov 2005

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