60 second lcd countdown

Discussion in 'The Projects Forum' started by electric_man, Aug 11, 2011.

  1. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    I'm looking for the simplest solution to accomplish this. Not necessarily the cheapest.

    I need a large 2 digit lcd display. 2 - 4 inches tall. That will count down from 60 seconds to 0. The countdown needs to be started / restarted with the push of a button. If I could have the countdown stop that would be nice, but not needed. It will always be a 60 second countdown.

    I haven't had much luck finding something that does this out of the box.
     
  2. Wendy

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    Mar 24, 2008
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    My kitchen timer meets your timing requirements. It fails on the LCD display, which is ¾" tall. So (to me) the hard part is the display. We'll see what some of the other folks here say.
     
  3. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    The problem with kitchen timers is if the power is turned off you probably have to reset the countdown time. I want something that I can setup as a 60 second count down and it will always be that even after a power loss.
     
  4. Wendy

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    Mar 24, 2008
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    http://www.globalindustrial.com/p/f...mpaignId=T9F&gclid=CKnSoojZx6oCFYfD7QodyzfMzg

    http://www.google.com/products/cata...=X&ei=GwhETrW0FrTisQKB5sXWCQ&ved=0CMIBEPMCMAk

    http://www.google.com/products/cata...=X&ei=GwhETrW0FrTisQKB5sXWCQ&ved=0CKIBEPMCMAM



    Google is your friend.

    Power turned off? You do realize kitchen timers use batteries, and do not have power switches.

    What part of the world are you? It will help locating parts.

    If you want to build this yourself LEDs are probably a lot easier, I could find LCD displays but in general hobbiest types are pretty small. The basic function is simple enough, it is the display that is the trick.

    What is your application?
     
    Last edited: Aug 11, 2011
  5. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    Last edited: Aug 11, 2011
  6. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    It will be part of a larger 12 volt system that will be plugged in so I don't want to go battery powered.

    The application is literately just large clock that counts down from 60 seconds to 0. Activated by pushing a button on a control box that will be attached to the device by a long cable.

    It is for a sporting event where an athlete has 60 seconds to complete a task.

    LEDs would work fine too.

    Something like this
    http://www.microframecorp.com/product/D6320.html

    but without the remote control and easily locked to 60 seconds. I would like to do it for less that $50.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I have designed stadium timers before, didn't build it, but made complete prints on the project. I would put a battery backup in your design, but that is me.

    There are lot of ways to go about this project, especially DIY. I just answered a thread where a guy wanted to do something extremely similar for 10 minutes (I think).

    You are about to get lots of reply's where people recommend PIC (AKA, µC or micro controllers). This is a good solution, it doesn't use many parts and can be simple to build. The catch is you have to write software, which is harder than it sounds, and you have to program a little chip. The learning curve for both is pretty drastic, which is something the other folks have trouble wrapping their heads around. But the end product is deceptively simple.

    The other way is to use discrete parts. I would place this as an intermediate level electronics project, with about 6 or so chips. It is simple (for me) to design, and also works.

    At the moment I'm working on a digital clock for the AAC book. I can draw up something in between, but if you are a total beginner at electronics this is not a simple project.

    I guess it boils down to your level of expertise with electronics?
     
  8. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    I can assemble a circuit board for this if I had to. Designing it might be a bit out of my current abilities.

    I might need to make a lot of these and saving my time is worth more than saving 20 bucks, so I was hoping someone might know of a simple setup that can control the display.
     
  9. elec_mech

    Senior Member

    Nov 12, 2008
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    Hi Electric_man,

    So to recap:
    2 digits
    Count from 60 to 0 in seconds
    Digits to be 2-4" tall

    By always be that, you mean:
    a) it continues to run and display the time if you lose power.
    b) it stops when you lose power but it is frozen and visible, e.g., if power was lost at 42 seconds, the timer would stop but you'd see 42 seconds on the display.
    c) if power is lost the timer stops but continues whenever power is restored (display on or off?).

    As Bill mentioned, you can probably get your hands on bigger LCDs, but they aren't common and therefore pricey. You can have a 12" LCD, but it will won't be any "brighter" than what you saw, unless you get a backlight, but even then . . . If you need it brighter, LEDs are the way to go. You can easily make it any size you want with LEDs. Labor a bigger concern than cost? Buy large, premade 7-segment displays:

    http://www.futurlec.com/LEDDisp.shtml

    Again, as Bill mentioned, this can be done without a microcontroller, but whatever you do will require some assembly onto a board. If you're only going to build a few, you can get away with soldering parts to a prototyping board such as:

    http://www.radioshack.com/product/index.jsp?productId=2102846

    If you're going to be building a lot more, then you should have someone design a PCB for you and have a bunch made to save you time once you've tested a circuit that will work for you.

    This isn't exactly what you need (way overkill), but it should help to give you an idea on how the circuit will look.

    http://forum.allaboutcircuits.com/attachment.php?attachmentid=31563&d=1308768439

    You can replace the count down IC with a 1 second counter connected to your ON switch.

    Wire the second digit so that it stops at 6 and perhaps sends a stop/disable signal to the counter.

    Just some ideas . . .
     
  10. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    By power loss I just mean that when someone unplugs the device and puts it away. The next time it is used no programming needs to be done like set the countdown length.

    I'm not worried about the system loosing power in the middle of the event.

    I will probably go with something like this. http://www.futurlec.com/LED/7SR30011AS.shtml for the display and just put the control stuff on a prototyping board like you suggested.

    I'm still going to try and find something a bit more premade, or maybe find someone to make it for me for a price. I don't see how companies get by with charging $400 for a simple 2 - 4 digit countdown timer. Just doesn't seem like there is that much in materials for such a device.
     
  11. elec_mech

    Senior Member

    Nov 12, 2008
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    Hi Electric_man,

    Ahh, gotcha on the power loss. Simple but no presetting - just power up and go.

    Yeah, that link with the remote device - I made something similar years ago as my first electronics project for fun. Now, all mine did was increment up one digit at a time with a button press on the remote. Theirs has a timer and probably a micocontroller and some outputs, but I built mine for ~$35. Most of that was the case, the electronics are almost nothing.

    Anyways, the digit you selected will work, but one question: will this be indoors or outdoors? This display is perfect for indoors. If the display will be outdoors, you'll want a brighter display.

    How many of these do you want? I'd be happy to design and test a circuit and build a few for the cost of the parts and something for labor. This would be a lot of fun as long as you don't need them too soon.

    Also, what kind of enclosure do you need the display in? Would a simple wood or shadowbox picture frame work or do you need something more polished?

    Do you just want a simple button press to start the timer? Do you need the pause or reset the timer once it's been started or would just turning the power off and on to reset it work? What do you need it to do when it reaches 00?

    Display:
    1) Leave the 00 displayed?
    2) Turn off the display?
    3) Flash the display?

    Else:
    1) Turn on an LED?
    2) Sound a buzzer?
    3) Else?
     
  12. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    This will be indoors.

    Right now I need 2 of them.

    When the time runs out I want it to just leave "00" up there. It would be best if there was just a single button that started time over at 60 when pushed. It could be pushed while still counting down, or while sitting at 00. I suppose this button could simple cut power to the device and reset it that way.

    It doesn't need an enclosure, just needs to be able to flush mount in another larger box.
     
  13. Wendy

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    Mar 24, 2008
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    I can draw a schematic, like I said, but it will take a little while.
     
  14. elec_mech

    Senior Member

    Nov 12, 2008
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    Hey Bill,

    I can begin a schematic over the weekend to cover the "body" of the circuit. Could I post it and ask you to review it? I'll start looking, but do you know of a simple 1 Hz clock circuit?

    Electric_man,

    Once a schematic is made, I can test it on a breadboard and come up with a parts and approximate price list. At that point you can look at it and see if you'd like to build it yourself or have me build it depending on your preference. Sound good?
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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  16. elec_mech

    Senior Member

    Nov 12, 2008
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    Thanks Sgt. Wookie! That looks like it will work nicely.
     
  17. Wendy

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  18. elec_mech

    Senior Member

    Nov 12, 2008
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    Bill,

    Wow, that is simpler. Thank you!
     
  19. electric_man

    Thread Starter New Member

    Aug 10, 2011
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    Sounds great.
     
  20. elec_mech

    Senior Member

    Nov 12, 2008
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    Electric_man,

    When do you need a (well two) completed units? Is it something you can put to use as soon as you get it or is it for a future event?
     
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