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  • Timed Grinder dose

    Before I embark on yet-another-modification to my coffee gear I thought I'd seek some opinions on how good timed grinding actually is for dosing.

    I have a Macap MC4 (the deli bag version) which is a delightful grinder, in terms of noise and quality of grind etc. I've slightly modified it to be a bit better - so it retains almost no grinds. In the past I've not filled the bean hopper - I tend to put beans in on demand. So my dosing has been done with either scales or a scoop - measure the beans in, get the ground beans out.

    But just lately I've tried filling the hopper and timing (with my watch). I've found 20 seconds is exactly right for the big VST basket and 12 seconds for the 15g basket. In so far as I can tell, this seems 100% repeatable. So I have been toying with putting in a small microcontroller to run the grinder for timed dosage. With a tiny knob to adjust in 1/10 (because it is easy) second units. I've been planning on replacing the big aluminium casting with the snout on it anyway - so before I start milling some Aluminium for that, I figured I might try to figure out if it is worth building in a dosage mechanism.

    So: anyone care to pass on thoughts about timing your grind?

    /Kevin

  • #2
    Hi Kevin,

    You may prefer to sell and upgrade to a Macap M4D? The inbuilt timer and associated dose are both very accurate.

    I have it on good authority that a CS'er will list his in the next few days (along with an Duetto Alex Duetto II). The grinder has probably done <100 shots

    Sadly, he's been seduced by the convenience of the Nespresso POD....

    Chris

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    • #3
      Ahhh - I forgot about the M4D..

      But this is not because I *have* to, it is because I *can* My problem is that in addition to teaching engineers to be engineers, I actually *like* being an engineer and making stuff... (Much to Mrs. KJM's annoyance at times...)

      I've done a small amount of the CAD work for replacing the front of the grinder, and I've been re-thinking the aluminium. I suspect I'll make a nice wood front with an ally delivery tube for the grinds..

      Like I said, I *have* to tinker

      /Kevin

      PS: Back on track - I take it you approve of the M4D timing mechanism?

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      • #4
        Originally posted by KJM View Post
        PS: Back on track - I take it you approve of the M4D timing mechanism?
        Sure do

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        • #5
          Hmmm... Timed dose *works*

          I've been laid up at home with shingles for the past week, and have spent some time working on my prototype timed grinder widget.

          The prototype is built using standard Arduino components. Should anyone want to give it a go with their grinder, the code is attached.

          While Arduino is cheap and cheery platform to use, it is also fairly painful when you want to do spiffy efficient time critical things. Fortunately the grinder timer isn't one of those things The hardware involved is actually made with Freetronics hardware (Hi Jon!) - which is available from their website or Jaycar, and an incremental rotary encoder. The only custom thing I have is a box with an SSR (Solid State Relay) in it to do the mains switching. If you don't know what an SSR is or how you might switch mains via a microcontroller - this isn't for you Seriously.

          I purchased my encoder from a well known auction site, but (almost) all encoders of the cheap sort (mine cost $0.30 - I bought 25 I seem to recall...) - are the same.

          A standard UB1 Jiffy box is sufficient to hold the 10A SSR, the Arduino and the PSU for the Arduino, but I already had a box with the LCD and encoder and Arduino in it, and an SSR-in-a-box so mine is a 2 box solution.

          Since this is mains switching, I don't feel I should be posting detailed how-to's on this, the above is more than sufficient if you have the background.

          Code is self explanatory and seems to work.

          The final solution will use a tiny 0.91" OLED display integrated into the replacement front to the grinder. With a nice shiny knob on the top There will be no external boxes etc - everything actually fits inside the Macap grinder quite nicely

          Cheers
          /Kevin
          Attached Files

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          • #6
            You are too clever for me.

            I hope you found the challenge enjoyable.

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            • #7
              Well, it was a distraction...

              I actually have the OLED display now, and it is very spiffy. It is actually double-sided taped to the box, but it just looks lovely!

              Having a timer is a great thing - I'm totally convinced! Thank you Chris - your comment forced the issue for me.

              It'd be a pretty simple little box to build - a thing your grinder plugs into with a knob and a display. Very simple to make any grinder work on a timed basis. In so far as I've been able to measure, the dose is completely repeatable - which is really nice. I'll have to get the new front for the grinder made up now and integrate it all!

              /Kevin

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              • #8
                Does this mean we will now see a gadget that plugs into the wall that can time for very short periods?

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                • #9
                  Well, I have that now. The timed thingy is basically exactly that. The only small foible with the thing is that the SSR I have put in the box is a 10amp one. Because it is small enough to fit into the shell of the Macap Since the usage of the grinder is not lots of really short cycles - like 100mSec on, 100 off and so on - the heatsinking requirements for the SSR are fine.

                  If you want really short on/off times and you're switching something like a motor (any inductive load) - then the heatsinking and current handling requirements will go up rather a lot (or the lifetime of the device goes down!). At work I have a diecast aluminium box with a 40amp SSR in it that a team of students have been using to switch loads on and off with. The load they've been switching is not that big (2kW) and in normal use it is absolutely fine. When they did screw up and switched it on and off at an exact 100mSec rate, there was a horrible smell and touching the box left your skin on it Instructive

                  /Kevin

                  Comment


                  • #10
                    Hi Kevin,

                    I can appreciate you can get little grind retention when you're hopper dosing and the burrs and sweeper channel empty, but if you're cutting off the power after a certain time, won't you see more grounds retained along with partially ground beans stuck in the burrs? Or would you go back to wasting a few grams at beginning each time in the home situation?

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                    • #11
                      Next project dosing by weight?

                      Digital kitchen weighing scale interface for Arduino

                      Comment


                      • #12
                        Originally posted by KJM View Post

                        So: anyone care to pass on thoughts about timing your grind?

                        /Kevin

                        Yep. The geekiness appeals to me. I'm thinking about buying a couple of these:
                        eBay link removed per http://coffeesnobs.com.au/general-ne...icy-rules.html1S 3M Adjustable Delay Timer Module for Entrance Access Control Amplifier PLC
                        I'd desolder the pots and make up a case with two of these in it, plus two SSR, plus I'd deconstruct a 7 day timer to fit in the case, plus 12V PSU. I'd mount new pots wired back into the timer boards, and stick nice knobs on them, but this unit would be out of sight - it would have 230v in, and two 230V out, one for grinder, one for coffee machine.
                        On the bench would be a little control box (with only 12v control circuits going to it) made of stainless, with two push button switches, and two nice toggle switches.
                        One push button would be timed single dose, one double dose. One toggle switch would be timer bypass/manual on for the grinder, the other would be 7 day/24 hour timer on, the other would be a bypass for that timer (to turn power on to the coffee machine bypassing the timer).
                        Last edited by Javaphile; 17 May 2013, 07:11 PM. Reason: eBay link removed

                        Comment


                        • #13
                          Kevin

                          some pictures of your new front fitting to the macap would be interesting.

                          Thanks



                          Originally posted by KJM View Post
                          Well, I have that now. The timed thingy is basically exactly that. The only small foible with the thing is that the SSR I have put in the box is a 10amp one. Because it is small enough to fit into the shell of the Macap Since the usage of the grinder is not lots of really short cycles - like 100mSec on, 100 off and so on - the heatsinking requirements for the SSR are fine.

                          If you want really short on/off times and you're switching something like a motor (any inductive load) - then the heatsinking and current handling requirements will go up rather a lot (or the lifetime of the device goes down!). At work I have a diecast aluminium box with a 40amp SSR in it that a team of students have been using to switch loads on and off with. The load they've been switching is not that big (2kW) and in normal use it is absolutely fine. When they did screw up and switched it on and off at an exact 100mSec rate, there was a horrible smell and touching the box left your skin on it Instructive

                          /Kevin

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