Scoreboard Project Cont;

Discussion in 'The Projects Forum' started by Oxbo Rene, Apr 17, 2009.

  1. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Good morning Sarge, Bernard and forum folks.
    This is Friday and I'm back looking for your knowledge once again.
    This week I have been doing mostly hardware work.
    Went to Skycraft and found this ideal little box to make the "console" out of.
    Have installed the N.O. push button switches on it (see attached).
    The two buttons on the far left side will be the up/dwn count for the "Home" team score, the two buttons on the far right side will be the up/dwn count for the "Guests" team score.
    The four buttons in the middle will be for the "Countdown" clock, which are found in the Kit (see attached schematic diagram). Still haven't installed the "Period" button yet.
    The two black buttons on the very front are the "reset" buttons for the individual team scores, etc.
    As you can see in the attached schematic diagram of the kit LED driving circuit, I plan on tapping in right where the red lines are and running those lines also to the big board where I will configure to work the big LEDs (with your help, hopefully).
    Also there will be lines (not shown) for the power/resets/four buttons/Period, etc.
    Will eventually install a socket/plug to run all wires necessary through a 10 ft cable up to Big Board, etc.
    ---------------------------------------------------------------------------------
    I did not have any 14 pin sockets to hook up the dual 556 circuits for the up/dwn pulses to the CD40110B's on "Team Scores", so scavanged on old one off an old board. Installed it and tried circuit, one side worked as planned, one side didn't, just stayed high regardless of which button I pushed (up/dwn).
    Got to checking and found no continuity from back of board to pin #8 on top of socket. Don't know if that would've caused condition or not. Re-checked all components layout, seems to be OK.
    Just awhile ago the mail arrived with my new 14 pin sockets, so, will be out there in a few minutes installing them and see if I can get that puppy put to bed, etc..
    Please advise if you see me going in the wrong direction, etc.
    Have a nice day.
    Oxbo
     
  2. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    OK, success!
    Installed new 14 pin socket, everything works great!
    These new sockets are heavy duty and I like em alot, not like those little pushed in pins, etc.
    The old socket was rather corroded, I brushed it up a bit but couldn't really clean down inside.
    Lesson learned = don't use old/used sockets, etc......
     
  3. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Alright;
    Got other half of board (components) soldered in and, so,
    have two 556 circuits running four push buttons, and everything seems to work good,
    Am happy.
    Tx's so much for your support ........
    Bye.......
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Hey Oxbo,
    Good to hear that things are coming together nicely!
    Nice console that you managed to find. Skycraft is an incredible source of stuff.

    Caution though, their IC prices have gotten too high; you can get better deals through Digikey; and Digikey's stock is "all new" direct from the manufacturers; while Skycraft's IC's are "new old stock"; many have bent pins, corrosion, and have been subjected to who-knows-what kind of abuses.

    Started a new job a couple weeks ago, so don't have much time to be on AAC lately. However, keep us posted on your progress, and if you run into a jam, give as many relevant details as you can, and we'll try to help you.

    Note that you'll have to re-post the relevant schematics in this thread, as otherwise responses may be very significantly delayed.

    Keep on keepin' on ;)

    [off topic]
    BTW - do you have your own welding gear? Our Vietnam War Museum really could use some help to re-configure our PBR's boat trailer (PBR = Patrol Boat, Riverine) so that we can tow it with our 5-ton truck. No funds to pay you with, unfortunately - we're only funded by donations from members and the public, which is almost enough to keep the lights and phone on. But if you'll help with the welding, I'll donate some of my own electronics "stash" to ya.

    The trailer was built from 8" steel I-beams. I think it could be re-configured by cutting the tongue near the "box" frame using either a cutting torch or abrasive cutting disks from the top, raising the tongue upwards, and re-welding it.

    If you're going to be heading to Skycraft tomorrow, stop by the Museum.

    Address:
    3400 N Tanner Rd, Orlando, FL 32826
    Google Maps will get you close to that location. It's just a mile or so off SR-50. Wish I could say I'll be there tomorrow, but duty calls. Even if you have no interest in helping out with the PBR trailer, it's an amazing place to visit - that grows on you, the more that you visit.
    Website: http://nwmvocf.org
     
  5. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Sarge;
    PM sent.
    Yeah, I love it, every time I go over to Skycraft and get back home, then I remember something I forgot, have to return, etc.
    These guys kill me with their prices, spent over $80.00 in two days just buying little bitty things.
    Am ordering more and more from Digi-Key, always costs $7.50 for shipping, etc.
    P.S.-> Have tried to get them to send me a catalog= no results....
    Found a nice company (where I purchased the 14 pin sockets) over in Tarpon Springs, called "West Florida Components", they shipped my stuff (resistors/capacitors/sockets) in a little padded shipping envelope rather than a big ole box....Shipping still costs $5.50 though....
    Will try and check out the Museum next trip over, etc....
    Oxbo
     
    Last edited: Apr 18, 2009
  6. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Alrighty now......
    Have been busy fabricating the "period" PC board.
    Last update I had finished fabing the twin 556 circuit board, which was controlled by four N.O. push buttons, two for the up/dwn count for the "home" team, and, two for the up/dwn count for the "Guests" team.
    Then, had to back up and fab the "Period" board. We had finally figured out the circuit to function as proposed, and, needed to now do the board.
    Before I committed to fabing the board I needed to reconstruct the circuit one final time to
    be absolutely sure it's firm and solid in it's design, etc.
    Well, I did, and using just the diodes, it did not work properly. I messed with it quite awhile and finally decided that perhaps the "AND" gate design might offer a more solid design. I recall Sarge mentioning that the diode circuit would be "close" as to working or not, not sure what that meant exactly but it stuck with me, and, wanting something solid I elected to go with the "AND" gate circuit.
    Reconstructed the "AND" circuit and it worked flawlessly, so, commited to put it on PCB.
    Attached are the photos of the board layout and the board in operation.
    FYI =
    Voltage across LEDs = 1.8v
    Voltage across the resistors = 9.5v
    9.5v/470 ohm resistors = 20.2 ma
    20.2 ma (x) 9.5v = 192mw (x) 2 (safety factor) = 384mw = 1/2 watt resistors used.
    Sorry Sarge, got the resistors on wrong side.......
    Have a nice day
    Oxbo
     
  7. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    A couple more pics;
    Things progressing smoothly, however, am out of "dry Transfers" and the only fellow I can find that sells em is out till Datec (whatever their name is), gets more mfg'd, etc. He says call him back in June LOL.
    Finally going to work in the morning on the new Mobile Launch Platform for the moon rocket, hopefully can last a couple years.
    Got one more board to make for the team scores (CD40110B's and resistors), then the "challenge", doing the Kit and tapping off the data lines to go to the big board, etc...
    OK, I never could've gotten this far without this forum and the folks found here.
    Tx's so much,
    Oxbo
     
    Last edited: May 7, 2009
  8. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Good morning.
    I have been waiting for the world to re-discover "dry Transfers".
    Talked to a fellow (Retailer) who said he talked to the company (DateK) official who said their machine was broken and they were deciding to NOT fix it and discontinue the "Dry Tansfers" line of products. Whether that includes ALL or just the electronics part I don't know. However, he states the company is searching China for someone there who might be able
    to offer the line to all of us that like em, etc....
    So, as reluctant as I am to change over to computer generated PC board layout, guess it's going to be inevitable sooner or later. I just hate to have to purchase a Laser printer, my old HP inkjet works just fine, then ya gotta learn a PCB layout program, that's the part I don't like, just tooooo complex for my needs.

    OK, have been dwelling on my circuit design for driving the big LEDs, taking data from the Velleman kit in the console portion of the system.
    I was reading a thread on that "other" electronics forum where a fellow (djv2008) is trying to do the very same thing as I am.
    And, toward the last of the thread a mister (ericgibbs) offers a great looking drawing, and I have taken the liberty to purloin that drawing and see if I can get a suitable circuit for myself out of it, etc....
    Rather than using 5V buffers, I choose 12V cmos stuff.
    My design incorporates his suggested Switching transistors "ZTX751" as I think they are well suited for this (I think).
    And rather than use his resistor values, I consulted a document for designing switching transistors (see Attached) for my guide.

    The following is what I've come up with:
    hfe for the ZTX751 = 230 (SEE ATTACHED).
    Figuring from there to obtain Ib =
    Ic load Max = 160ma (this I arrive at from figuring if the 7-segment LEd were fully lit, say with an "8" plus a DP = 8 (X) 20ma = 160ma.
    (Big LEDs = all segments, plus DP, require 20ma each)
    According to the doc, Ib = Ic/hfe = 160ma/230 = 696ua
    Adding in 30% for saturation insurance = 696ua (X).3 = 209ua = 209ua (+)696ua = 905ua.
    So, Ib = 905ua.
    (I know this is incorrect, probably wrong hfe, but, that's what I see on the attached graph).
    And playing along with the doc,
    Calculate for R1.....
    Vcc = 12V
    Ic = 160ma
    Ib = 905ua
    hfe = 230
    ----------------
    R1 = 12V/Ic/hfe (X) Ib =
    R1 = 12V/160ma/230(X)905 =
    R1 = 12V/160ma/208150 =
    R1 = 12V/.000001 =
    R1 = ERROR = Ha !
    See attached diagram where the fellow converts Ic ma to A, but doesn't do it to Ib (circled in red).
    So here I am, lost again.
    I feel the hfe is where the problem lies.
    Could someone just give me good value for hfe for this setup ?
    Also attached is my schematic for driving just "one" 7-segment LED utilizing the ZTX751.
    Tx's so much
    Oxbo

    -----------------------------------------------------------
    MM74C904 Datasheet =
    http://www.ic-on-line.cn/IOL/viewpdf/MM74C904_103169.htm
    ULN2804AN Datasheet =
    http://www.ic-on-line.cn/IOL/viewpdf/ULN2803AN_192599.htm
     
  9. Wendy

    Moderator

    Mar 24, 2008
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  10. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Hi Bill;
    Interesting read in the PC board fab section.
    I have dnl'd the Express PCB software, guess that's where I'll start.
    The Stadium ckts stuff I did see before, but, am afraid, is quite a ways over my head, would've liked to see it in action.
    I was looking at this stuff ->
    http://www.techniks.com/
    What do you think about it ?
    Is expensive, but, for as much as I mess with this stuff (making electronic projects) I could stand it once, etc....

    (Yep, just read about the Staples paper, guess it's got to be worth a try, whenever I get a circuit figured out with the PCB layout software), ugh !
     
    Last edited: May 31, 2009
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Well, the newer technology really isn't that bad. Tools like Cadsoft's Eagle take some time to learn them well, but you can actually get going pretty quickly. Once you get used to it, you can lay things out a lot more quickly than trying to do things all by hand. Besides, there are "rule checks" to help ensure that you haven't bollixed things up too badly.

    Here's a pretty good tutorial for Eagle:
    http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=108
    The current version is 5.something. I have V4.16r2, so if you want me to help you with something later on, you better download the older version, as I can't load files created with the newer version.

    OK, just for starters I tracked down the ZTX751. They're a nice PNP transistor if you need that much horsepower, but I'm thinking you'd be much better off with a simple Darlington that's about 1/3 the price, widely available, and you really don't have to worry about gain since an MPSA64 PNP Darlington has a minimum gain of around 10,000. Your CMOS IC's could drive those using a 10k resistor and not even break a sweat. ;) The other nice thing about using a Darlington is that you may not need to use a pull-up resistor to turn the thing off.
    Digikey has the MPSA64's in stock:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MPSA64GOS-ND
    10 for $1.88.

    At this point, I don't remember anymore if your displays are common cathode or common anode?

    Try using http://www.Octopart.com to locate suppliers. That site was designed by three bright college students who got tired of looking for parts everywhere.

    -----------------------------------------------------------
    MM74C904 Datasheet =
    http://www.ic-on-line.cn/IOL/viewpdf/MM74C904_103169.htm
    ULN2804AN Datasheet =
    http://www.ic-on-line.cn/IOL/viewpdf/ULN2803AN_192599.htm[/QUOTE]
     
    Last edited: May 31, 2009
  12. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Tx's Sarge;
    Was hoping you'd help out.
    The LEDs are common anode.
    From reading the other forum's thread, I got the feeling that the kit is multiplexing the LEDs, will that have any affect on my configuration?
    If I use a 10K resistor for R1, according to the doc for designing switching transistors, it says R2 should be 10 times the value of R1, can you concur on that ? (pull-up resistor to turn off = I'm lost)
    Have installed the female db-25 pin socket in the console and run all the wires to the terminal strip inside. Wires looked to be approx size #24 (pretty small).
    I elected to install a separate plug for the power, suspecting that the #24 wire might not be large enough to carry the required current for powering the console circuits (power supply will be located in the Big Board).
    Thanks so much
    Oxbo
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    OK.
    Well, you need to enable just one of the digits at a time. That's the point in using the PNP transistors to source current to the common anode.
    Yep, that'll work. :) PNP transistors are somewhat like NPN transistors, but opposite. They're usually shown with the emitters up and the bases to the left.

    Hmm, something I didn't think about was the saturation voltage of the MPSA64. It should be around 0.8-0.9v at the current current you're dealing with (20 to 140mA). Figure that in with your current limiting resistor requirements.
    OK, sounds good.
     
  14. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Oh yeah,
    Here's some progress pics.
    Looks like it's going to be fairly crowded in there, might have to attach a fan on the outside, etc....
     
  15. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    Chit man ! ! ! !
    That went pretty good !
    Yes, I can't really present any argument against this program !
    Now I got to go out and buy a Laserjet printer.....
     
  16. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    OK Sarge;
    Here's my figuring for the MPSA64 configuration (attached).
    I went with the voltage divider circuit because I just can't figure the series resistor on the base, coming from the buffer.
    Don't know what Ib base will draw, etc.....
    Could get away with 1/4 watt resistors, 1/2 watt for DP, just decided to go with all 1/2 watt, etc...
    Bill;
    Went down to Staples, got a little mono $100 Laserjet P1006 printer.
    Will be trying to fab the circuit board, hopefully today, etc....
    Oxbo
     
    Last edited: Jun 7, 2009
  17. SgtWookie

    Expert

    Jul 17, 2007
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    OK, I'm forgetting again - what's the point of using the MM74C904?

    Something tells me this isn't going to work. The MM74C904 is a noninverting buffer designed to interface between different logic types (PMOS, CMOS and TTL) but it's Vcc is the same for input and output.

    You're really going to have to use open-collector or open-drain outputs to change between the different voltages. This will work fine, because the MPSA64 will source the current from the base. You can use a resistor of between 7.5k to 10.5k from the base to the open-collector output, and another 100k resistor from the base to Vcc/Vdd to keep it turned off when the open-collector output isn't sinking current.

    The ULN2804 inverts the signal; when the input is high, the output sinks current.
    The MPSA64 doesn't invert the signal, so you need to use inverting buffers.

    Keep in mind that the ULN2804 was designed to be used with CMOS operating with Vdd from 6v to 15v, while the ULN2803 was designed for TTL or CMOS operating at 5v. The difference is the intrinsic base resistors; the 2803's base resistors are around 3k, where the 2804's are around 10.5k.
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    Well, geeze - it just hit me; you could use another ULN2803/ULN2003 as the open-collector inverter to drive the MPSA64's. Just use a 1.2k to 3.3k or so resistor between the driver's output and the MPSA64's base, and 12k to 33k resistor from the base to Vcc.
     
  19. Oxbo Rene

    Thread Starter Active Member

    Feb 20, 2009
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    OK;
    Take a look at this.....
    According to Mr Gibbs drawing (attached), he's using a 74LS07 (non inverting) buffer to drive the ZTX751.
    And, he's using 74LS04 (inverting) buffers to feed a 2803A, which feeds the segments via the resistors, etc....
    I gathered that the drive transistors did not need to be inverted, etc, Whereas the segments did.
    I just didn't show the inverters in the drawing, but have now (attached).
    I just happened to choose the MM74C904, and had already changed my mind but hadn't changed drawing yet. I changed to CD4050BCN-ND's.....
    See attached drawing....
    I read somewhere that the Darlington Vb should be above 1.4V to achieve saturation, so I chose resistor values to get 1.5V.
    Your resistor values only give me 1.14V for Vb.
    I am involved in getting this "Ironing" a PCB figured out (now that I have a Laserjet, and the PCB software figured out, so, while I was waiting to make the decision to move to software/laserjet stuff, and exhausting my search for dry transfers, I got to playing with this "kit" conversion thing.
    So, the crux of the matter is that I can't/haven't gotten to experimenting with the circuit on the breadboard, a big drawback.....


    Just posted this, then see your most recent post, let me know what you think of my latest, while I digest yours, etc....
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    OK.
    If I remember correctly, the kit uses common cathode LEDs.

    Your large 7-seg displays are common anode.

    Therefore, to use the signals from the common-cathode kit to drive common-anode LEDs, you must invert the logic for both the digit select, the segments a-g, and the dp.

    Note that the ULN2x03/ULN2x04 driver ICs invert the input logic. If you bring the input high, the output goes low. If you bring the input low, the output gets pulled towards Vcc by the load.

    The MPSA64 is a horse of another color. ;) If the base is pulled near Vcc, the transistor will be turned off (won't conduct). If the base is pulled more than about 1.3v less than Vcc, it'll start conducting (sourcing current).
     
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