HELP please: add a pause switch to countdown timer

Discussion in 'The Projects Forum' started by Alex Morfe, Jan 18, 2015.

  1. Alex Morfe

    Thread Starter New Member

    Oct 5, 2014
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    20150119_120800x.jpg 20150119_120909x.jpg

    this is a coin-operated countdown timer... basically, you drop coins into a coin slot, and preset minutes are added to the timer...
    questions:
    1. how to add a pause switch -- on/off switch to suspend/resume the countdown
    2. how to add a push switch to add minutes to the time (bypassing the coin slot)
    3. how to add a push switch to remove minutes from the time
    4. how to speed up the countdown (2x or 5x)

    thanks.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Without a schematic adding those functions would be difficult except perhaps adding time.
    For that you could just add a switch in parallel with the coin slot switch.
     
  3. spinnaker

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    It would be easier to scrape the whole thing, salvage the parts you want like the display, relays, enclosure and coin slot. Build your own. Can't be too hard.
     
  4. Alex Morfe

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    Oct 5, 2014
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    hi crutschow! thanks for giving me your time :)
    how should I do that?
    the coin slot is connected to a 3-prong connector labeled "12V-coin-ground"... "coin" prong goes to cathode of 817c optocoupler, while "ground" goes to emitter of the 817c... will it be as simple as connecting "coin" to "12v", or "coin" to "ground"?

    thanks again :)
     
  5. Alex Morfe

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    Oct 5, 2014
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    hi spinnaker! thanks for your time also :)
    at first, my plan was to build one from scratch, but I already have this so, I thought, I don't have to reinvent the wheel or something -- just make it better :)
    plus that this module is technically cheaper bought as a whole rather than getting it piece by piece and assembling it :)
    btw, I am just a hobbyist/enthusiast who likes to build things from other things -- while not understanding too much of electronics, just the basics :)

    thanks again :)
     
  6. elec_mech

    Senior Member

    Nov 12, 2008
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    A quick look-up of the IC reveals it is a microcontroller. Since there are no other IC's present, I assume everything is done on the IC including reading the coin acceptor, timing, and controlling the display. Without re-writing the code to the microcontroller, there is no way to add the functions you're asking for.

    It sounds like you're trying to use this for something well outside its intended purpose, not simply make modifications to an existing device. So let's step back. What is it, ultimately, you're trying to do?

    Do you need to use the coin acceptor?

    What range of time are you looking for, e.g., 00-99, 000-999, etc.?

    Do you need to display seconds as well as minutes, e.g., MM:SS?

    Why the need to speed up the countdown?

    Do you need relays to do something at the end of the time?

    Do you need a buzzer?
     
  7. Alex Morfe

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    Oct 5, 2014
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    hi elec_mech, thanks for your time... answers above in hicaps :)
     
  8. spinnaker

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    Exactly what is "hicaps" ?? Not sure where elec_mech was going there anyway since you will probably need to rebuild the box like I said anyway.

    Don't embed your answers within the comments. Makes it very hard to read. Instead break up the comments into separate blocks.
     
  9. crutschow

    Expert

    Mar 14, 2008
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    Not sure.
    The best way to determine what happens is to monitor the voltage between the coin terminal and ground to see what it does when you input a coin.
    Does it give different times for different coins? If so you would likely have to monitor the signal with an oscilloscope since the signal may be a series of pulses.
     
  10. elec_mech

    Senior Member

    Nov 12, 2008
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    In a long way I was agreeing with you. I just wanted to point out to the OP why he'll need to build up his own unit or at least look at a different device. If the coin acceptor was needed, we'd need to know more about it. Since it's not, we can forget about it.

    Alex,

    I'm a little confused. It sounds like you already have a partial circuit somewhere. Is that correct? Can you post a schematic of what you have? Or, if I understand your first CAPS comment, are you trying to modify this board and put it back into whatever it is designed to go into? If the latter, what is it? A video arcade cabinet? Skee ball?

    It sounds like you want the following:
    1. Countdown from as much as 3 hours to as little as 15 minutes.
    2. Increase or decrease the count via push buttons.
    3. Display minutes and seconds. For 3 hours, do you want H:MM:SS or a MMM:SS where MMM is 180 minutes at 3 hours? Can't really display minutes and seconds with 4 digits if you're counting down from 3 hours.
    4. Speed up the countdown if somebody does something? Like what? What would trigger the change in countdown speed?
    5. You mention already having a relay and buzzer hooked up? Is this on another circuit or are you referring to the board pictured above? If the former, please post a schematic.
    As spinnaker mentioned, to do what you want will require a new circuit altogether. The board uses a single microcontroller (uC) to handle everything, so there is no way to modify it as-is with all the functions you want. If you've got programming experience, you could potentially program another uC and replace the existing one, but you'd also need a board for the new uC since you're unlikely to find one with the exact same pinouts as the existing one. With all the time and work involved in that, it would about the same as designing your own complete board from scratch and doing exactly what you want.

    You could look for another product that meets your needs better or design your own circuit. Designing your own in hardware wouldn't be terribly hard, but it would be involved and require several IC's. An alternative is a hardware design with a uC which you program - this will require less parts, but more time in programming. However, you could then change the function on the fly as needed.

    As crutschow mentioned, you may be able increase the time alone if that is enough. Where does the coin acceptor plug into on the board? I think it is the 3-pin connector on the right labeled 12V/ON/GND, but I want to be sure.
     
  11. Alex Morfe

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    Oct 5, 2014
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    sorry about the hicaps and embedded reply :(
     
  12. Alex Morfe

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    Oct 5, 2014
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    I don't have an oscilloscope and I don't know how to use one :)
     
  13. Brevor

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  14. Alex Morfe

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    Oct 5, 2014
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    hi elec_mech,
    That board is used as the timer for a computer in an internet café... You drop coins to buy minutes of usage -- minutes is preset using the DIP switch.
    When timer activates, the 2 relays will turn ON anything plugged into it (usually the power of the lcd monitor, and the usb hub where keyboard and mouse is plugged in)... When countdown ends, relays goes off.
    The 4-digit display will show the remaining minutes only if it is over 100... If remaining is less than 100 it will show minutes and seconds (i.e. if remaining is 120 minutes then it will show 120; if remaining is 93 minutes and 57 seconds then it will display 93.57).

    I am planning to use this as a timer for a "mock b omb" to be used in our airsoft games (counterstrike scenarios):
    -- replacing the coin slot with a numeric keypad circuit (or pushbutton) to start the countdown (and the relays are switched on)
    -- when time runs out, the normally-closed of the relays are turned on thereby activating a very loud horn

    The PAUSE switch will be used to suspend the countdown when it is diffused -- more time left means a higher score. Can this be done by disconnecting the crystal or something? :)
    The SPEEDUP will be used for when they cut the wrong wire when trying diffuse.

    correct, that's the connector for the coin slot... it is labeled 12V/COIN/GND... "coin" pin goes to cathode of 817c optocoupler, while "ground" goes to emitter of the 817c... will it be as simple as connecting "coin" to "12v", or "coin" to "ground"?

    sorry but I don't have the schematics for this. :(
    I don't know anything about microcontrollers, sorry. :(



    thanks!
     
  15. Alex Morfe

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    Oct 5, 2014
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    Hi Brevor! thanks for this. Now I know what to Google -- "8052"... not much results for "sm8952ac25p". :)
     
  16. spinnaker

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    Oct 29, 2009
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    Not having the schematic nor the source code, that would still be an enormous task.
     
  17. elec_mech

    Senior Member

    Nov 12, 2008
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    In that case, you could try adding a switch as shown below. I'm making several assumptions, so there is a chance this could damage your board. If you're not willing to chance it then don't. I assume the coin acceptor sends a signal through an opto-isolator which is then fed to the uC. We're simply adding a switch to simulate the coin acceptor signal. There is a chance the coin acceptor must send several signals (like data) in which case this won't work. There is also a chance (that I'm assuming here) the coin acceptor only sends a single signal with each coin. This is probably a clean signal and most switches have bounce, so you may see the time jump much higher than expected. If so, we're on the right track and you can add a debounce circuit.

    I don't think making a schematic from the pictures would be hard - this is a single-sided board and everything appears fairly straightforward. However, I have to agree with spinnaker that without the original code, rewriting the 8052 will be an immense task, especially if you haven't written code before. If you're not in a hurry, I can put together a design using a PICAXE uC and write the code to do what you want, but I'm tied up until late March.

    Out of curiosity, how much did you pay for the board?
     
  18. Alex Morfe

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    Oct 5, 2014
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    I'll try that maybe next week -- I don't want to chance it just yet. :)
    Yes please, and do take your time, am not in a hurry... I also want to learn this PICAXE uC.
    The board is approx $7... the coin slot is $3.

    Thanks for all the help guys! :)
     
  19. elec_mech

    Senior Member

    Nov 12, 2008
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    Well do. The PICAXE is a great starter platform. May I ask where you bought these, particularly the coin slot (link if possible)? I have an upcoming project where I'll need one and $3 would be awesome.
     
  20. Alex Morfe

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    Oct 5, 2014
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    I bought it here in Manila... at a store named Deeco (Dee Hwa Liongco) -- I don't think they have an online shop :(
    I can disassemble mine and send you pictures, measurements, and schematics if you like. It's fairly easy to DIY. :)
    If you like to view videos of this, search for "pisonet" in youtube.

    I have one final question regarding this timer: if I physically disconnect XTALn from the uC (or from ground), will that stop the countdown?

    thanks!
     
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