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  • 60 second mechanical timer

    Hi,

    I have been tasked to make a timer for learning disabled students. I need to create a timer that runs for 1 minute, (we ain't doing celestial timing here - hand grenade accuracy is all that is required), and will use a linear moving 3D printed "toy" to show the "time" passed. The biggest issue is cost. It must be cheap, yet sturdy enough to survive teachers and the occasional student.

    I would prefer a windup 60 second mechanical timer because of simplicity of the rest of design and the ding! sound and auto stop at the end, but those seem to be difficult to find from my duckduckgo searches. 60 minute timers are a dime a dozen - 60 second timers, not so much.

    A tiny battery powered DC motor might be the best I can do, but the added cost of a battery pack, limit switch, and buzzer might be more costly than desired. Plastic springs could be printed along with gears, but I have no experience with horology to do that kind of design work......

    Any and all advice appreciated!
    If you think you understand what is going on, you haven't been paying attention.

  • #2
    I had a a old school timer used in developing film. I don't think I still have it.

    Hal
    Last edited by Hal; 03-31-2021, 06:52 PM.

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    • #3
      Not sure exactly what you're looking for here. Would something like what's pictured here (image borrowed from internet) modified so when the ball drops down to change direction a flag is tripped showing a number (amount of time) has passed? Maybe it could be expanded, or the ramp angle changed, so that it takes close to a minute to cycle. Or maybe a minute to drop a specific number of balls?

      Click image for larger version  Name:	ball-drop.jpg Views:	51 Size:	76.1 KB ID:	1936805

      Another option might be a small plastic hourglass. Those are available for cheap that measure one minute.
      Last edited by tom_d; 03-31-2021, 10:07 PM.

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      • #4
        Does it have to be mechanical?
        This is a trivial project with an arduino clone, two LEDs and a momentary button.

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        • #5
          A 60k ohm resistor and a 1000uf cap would approximate sixty seconds.

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          • #6
            Not mechanical, only thing I can think of that uses that kind of time is a motion light. Maybe a timer out of one of those quarter op binoculars at overlooks.

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            • #7
              Some old board games had a 1 min wind up timer. Can’t rember what, maybe hungry hippos.

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              • #8
                https://www.amazon.com/Koplow-Games-...84186351&psc=1

                Where's OldTiffie when you need him?

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                • #9
                  I believe there are timers that are intended to mount in a standard light switch box that are mechanical in nature and do not require any power to run. They have a simple knob that is turned to the desired time period and then they just run down to zero. Check out McMaster stock # 7014K45.

                  https://www.mcmaster.com/timers/?Src...t_InpBox=timer

                  They are intended for everyday use so should be fairly hardy. You could probably get one for a lower price if you look around. Perhaps at a local hardware or home supply store.
                  Paul A.
                  SE Texas

                  And if you look REAL close at an analog signal,
                  You will find that it has discrete steps.

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                  • #10
                    I'm thinking simple hourglass.... er... minute glass. The glass itself could be made from two small clear plastic bottles of some sort as long as they taper to a small'ish neck. make up an adapter that connects them and play with the opening at the middle and amount of sand to produce a 1 minute drop of the sand.

                    Another option if you want it to go DING at the end would be to get one of the mechanical hour timers. Dig into it and lighten up or otherwise modify the escapement so it "ticks" 60 times faster. Although in that case I'm thinking that the fairly noisy buzzing will be distracting..... so no, ditch that idea....

                    I just checked and 1rev/min motors are available on Amazon for under $10. If a friction fit but slippable cam disc was attached to the arm so it could safely be stalled a slot in the disc could allow a clapper arm to drop into the slot and "ding" a bell. At the same time the clapper arm would stop the disc from turning. Then to start it up again just lift the clapper arm and it rides against the OD of the cam disc until it falls into the slot and dings the bell at the end of the minute. it would be quiet in use but a line of some sort would act like a rotating hand on the face of the disc.

                    Should be buildable for around $20 if you don't charge for your time. Less if you can score the stuff for the cam disc, box and power cord for cheap or free. I'll bet that if you told the folks at the local hardware store what you're doing that they'd likely donate what you need.
                    Chilliwack BC, Canada

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                    • #11
                      You want an EGG timer ala ebay

                      https://www.ebay.com/itm/Mechanical-...wAAOSwyEhfg-dr

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                      • #12
                        Originally posted by BCRider View Post
                        I'm thinking simple hourglass.... er... minute glass. The glass itself could be made from two small clear plastic bottles of some sort as long as they taper to a small'ish neck. make up an adapter that connects them and play with the opening at the middle and amount of sand to produce a 1 minute drop of the sand.
                        See post #8 😁 Lots of 1 minute "hourglasses" on Amazon.

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                        • #13
                          Originally posted by bob_s View Post
                          Those things have exceptionally poor accuracy at their minimum time.
                          That being said, the cheapest digital kitchen timer at walmart would do the job perfectly.

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                          • #14
                            This is the sort of challenge I loved when I was working with disabled students.

                            Though I understand your preference for a mechanical mechanism, there are high-torque quartz clock movements available quite cheaply, with a second hand. If a light-weight disc was mounted in place of the second hand it could stop the clock once every 60 seconds by operating a microswitch with a peg or notch, or preferably by actuating an optical slot-switch with a slot or hole, on the same principle as self-parking car wipers.

                            If it only needs to be seen by one student at a time , the disc could have animations or increasing bars or what-you-fancy painted on it, viewable through a window or a slit. Cut-outs, back lighting... If it needs to be visible from all round, put the clock on its back to make the disc horizontal and let your imagination run wild. If the electronics will stand it, it might be possible to increase torque by running it on, say, 3 volts instead of 1.5.

                            If you can source a movement from an old centrally controlled clock system (Synchronome or similar)) you would have loads of torque to play with, though you would need to invent your own seconds timer.

                            You should be able to have loads of fun doing this!

                            George B.

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                            • #15
                              Could you cannibalize an old micro-wave?

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