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Stopwatch modification?

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  • Stopwatch modification?

    Hi all; heres something i was thinking of rigging up:

    $7 dollar kitchen timer from evilBay with LED display
    Some wire, solder, soldering iron
    other assorted electronic parts...

    (cooking analogy ends here)

    anyway, i was thinking - somehow wiring the DPDT? brew switch to activate the LED stopwatch - ie. when you press the switch to brew coffee, the timer starts, hence displaying shot time, and stopping when you press the switch to stop the shot.

    ...Im going to be really incoherent here because Im still trying to figure it out in my mind. Im thinking there are some possible problems that my limited electrical knowhow has no solutions for:

    - not enough poles on the switch - easily solved with a 4PDT switch or something. i hope.
    - the switch mechanism on the brew switch is a simple open/closed thing...activating a stopwatch requires an open/closed/open instantaneous button press kinda connection (well...thats how i see it in my head). how do you convert the simple on/off action into a button press kind of action?
    - the timer will have to be powered and reset manually. oh big deal.

    Anyway...hoping you knowledgable coffeesnobs (Mal? Sparky? Anyone???) will be able to tell me if this project is:
    a) feasible
    b) a good idea in the first place
    c) none of the above

    sorry...i just love tinkering. i really should have done engineering.


  • #2
    Re: Stopwatch modification?

    You can get "Push On/Off" switches.


    • #3
      Re: Stopwatch modification?

      Hi TG,

      yup, i know about the instantaneous on/off buttons, but im after some kind of circuit which would activate both the stopwatch & the brewing circuit with a single switch.
      using a separate switch wouldnt be much help - unless i was mounting the stopwatch somewhere where i was unable to press the button on its housing.

      i hope that clarified the idea (more like mess in my head)



      • #4
        Re: Stopwatch modification?

        You would just wire both the stopwatch and the brew connections to the one switch.


        • #5
          Re: Stopwatch modification?

          Oh, i dont understand how to get both circuits (brew & timer) operating from the same switch; i thought the two switching systems they used were incompatible. Maybe ill explain how i see it and everyone can show me the error of my ways

          a) Coffee machine brew switch is like this (SPST for arguments sake...i think its a DPST but same idea)

          (one end of circuit)------/ o----------(other end of circuit)

          hence when you press the on/off switch to brew coffee, the circuit stays closed hence current flow due to completed circuit for however long the switch stays on.

          b) The kitchen timer (or other stopwatches that i can think of) is more instantaneous (i dont know if theres a technical term for it):

          (one end of circuit)------o ___ o----------(other end of circuit)

          thus pressing the button closes the switch, releasing it opens switch. Circuit is only complete when button is depressed - first press turns on timer, second press turns off timer.

          What i cant understand is how to run both of these different circuits from the same switch...
          a) use the existing brew switch, using a different set of poles to operate the timer. switch closed - coffee extraction starts, timer starts. switch opened - extraction stops, timer continues (as another close is required to stop the timer?) it would work...but youd have to close/open the switch again to stop the timer.

          b) use a push on/off switch - push and hold down the switch for the extraction to initiate and continue; id rather not press the button for 25 seconds when i could be steaming milk instead. also starts the timer...but once again, would have to press the switch again to turn off the timer.

          i guess a third solution would just to be to find a timer which operated using an on/off switch as a trigger...but i have no clue where to find one or how to build one.

          anyway, im very open to criticism atm; point out my flaws!



          • #6
            Re: Stopwatch modification?

            Learn to count in your head with relative precision. No need for a fancy switch or stopwatch.

            Wiring a DC circuit via the brew switch, that uses a 555 timer might be a solution, but requires more effort than seems feasible.


            • #7
              Re: Stopwatch modification?


              Most stop watches these days are digital meaning they have some inherant software algorithm.
              The way it has been designed/programmed will determine how the watch responds to the switch.

              Usually the switches in timers [and most digital devices] are momentary [thats the technical term for it] and this allows for the switch to have multifunctionality which saves on hardware costs.

              In most timers, the algorithm is looking for a "close" of the switch to start the timer, and it will probably want to see it closed for 0.5 sec to eliminate bounce.
              Once the timer is going and the button has been released, the algorithm will then look for another "close" to stop the timer.
              Therefore the required behaviour of the swith is determined by the software which you cannot access or change.
              As you correctly identified, the brew switch has a different behaviour: "Latched" ie it stays on until switched off]
              This makes your idea difficult but not impossible.

              Some kneejerk suggestions:

              Some DPDT switches are momentary on one throw and latching on the other. So you could activate the timer with a pulse and then flick the switch the other way for the shot.

              Or, you could build a simple logic circuit that has a momentary push button that activates the timer and also latches a SR [set reset] FlipFlop, the output of the flip flop would then drive a relay [or SSR] with 240VAC rating AND at least 10 amp rated contacts.

              But in reality, related to the cost of an ubiquitous $7.00 timer, a
              suitably rated DPDT Momentary/Latched switch will be very difficult to find and probably quite expensive.
              Furthermore, any logic circuit you bulid [whilst in itself cheap] will require an expensive output relay, transformer and rectifier for the DC supply and furthermore youll have to drill/machine holes in your machine to mount all this somewhere.

              It is a good idea, but overall, I agree with Nunu that its hardly worth the effort.

              Really, given you have spent hours sourcing your beans on coffee snobs, then having roasted them to perfection, youve diligently dialed in your grinder and ground the beans to a specific predetermined dose, then carefully filled the PF, tapped it down, leveled and tamped to a well practised exact pressure,
              and all this prior to pulling the shot.....One must ask:

              How inconvenient is it to activate the brew switch and then hit the timer button?


              • #8
                Re: Stopwatch modification?


                Dumb question here.... but why would you want to do it?

                The best pours are stopped manually at the first sign of blonding..... so why "pre-set" a time for the brew... unless you are interested in timing the shot to see if you need to grind finer/coarser.

                IMHO a "timed pour" is one step worse than a "volume pour" like my La Cimbali does.... and I dont use/like that either....

                After a while you get pretty familiar with the time it should take for the pour- to the point where blonding starts.... just in your head..... and then adjust the grind to correct any slight changes due to ageing, humidity etc.

                Yes, you could get something like that to work, yes it would be tricky but I cant (personally) see any real benefit from the effort required.


                • #9
                  Re: Stopwatch modification?

                  A "push on/off" switch means push once for on and push again for off.


                  • #10
                    Re: Stopwatch modification?

                    whoops, looks like Ive confused everyone on what Ive been trying to achieve.

                    Reubster is on the money; im basically trying to eliminate the inconvenience of pressing the start button of the stopwatch and the brew switch simultaneously, nothing more. Sorry to everyone who thought I was trying to integrate a timed pour into the machine or anything else, I do understand the downfalls of this and agree with you entirely.

                    I know this is kind of silly when I could just count in my head, but Im a silly kind of guy. But yes, it appears that it just might be a lot of effort for a very minor thing.

                    Will probably have a brief look around for a momentary/latched DPDT switch, but if nothing reasonable pops up, Ill probably leave it as that. Maybe this is why there are so many more useless inventions than useful ones



                    • #11
                      Re: Stopwatch modification?

             idea to stir the pot.

                      I think my idea is now purely theoretical since it seems like too much effort; google found me no switches like the ones Reubster was talking about. However, it did get me thinking...

                      An ugly solution could be to replace the existing switch with a 3 position switch where:
                      position 0 - unconnected (pump off, stopwatch circuit open)
                      position 1 - stopwatch circuit closed, pump still off (no connection to pump)
                      position 2 - stopwatch circuit open, pump circuit closed/on

                      thus from the off position (0), flip the switch through position 1 (hence activating the stopwatch) to position 2, activating the brew circuit. reverse to turn off.

                      But yes...I still agree with you all, it is much ado about nothing. But so are many other things...



                      • #12
                        Re: Stopwatch modification?

                        Heres a thought.
                        Start the stopwatch with one hand and the brew switch with the other.


                        • #13
                          Re: Stopwatch modification?


                          Yup that idea of yours [ie pos 1, pos 2, pos 3] could work.
                          What you need is a three pole switch.
                          Thisll be hard to come by as "rocker" switches are virtually never more than DPDT.

                          a ROTARY switch can have more than two poles, and this would be kind-off cool to use.............flick it around until the brew position, along the way youd have triggered your timer, then when the shot is done, flick it back.
                          Im picturing some kind of big bakelite/deco style knob or what is known in the music industry as a "chicken head knob"

                          I love the old electronics, esp the valve stuff!

                          The only problem is that rotary switches [especially those that are rated for 240VAV & 10amps and are "ganged" meaning multi-poled are rather expensive, new industrial rated variants would probably be in the order of $100+ because they are made to order.

                          Youd probably need at least two poles, since the three way valve would also need to be switched.

                          Youd be best to scour the electronic junk/dump shops, such as "Rockby" in Melbourne .


                          • #14
                            Re: Stopwatch modification?

                            Im picturing those guitar pickup selector switches (i know theyre not rated for ) a la Les Paul or Stratocaster. Come to think of it...itd be interesting to see what it looked like if you changed all the switches to that style, then switched out the steam knob for a tone/volume knob looking thing & changed the steam tip to the end of a 1/4" jack...

                            ...on the other hand, maybe not.



                            • #15
                              Re: Stopwatch modification?

                              Originally posted by Thundergod link=1189600593/0#11 date=1189680495
                              Heres a thought.
                              Start the stopwatch with one hand and the brew switch with the other.

                              If the watch has a countdown function, set it to 30 seconds then start and when it hits 25 seconds, hit the brew switch..... when it beeps, turn the switch off and Voilà!