Sorry to raise such an old thread but I am wanting to mod my BNZ md74 grinder with a timer mod. I had heard of the David Makin modded grinders and found the reference in the above old post.
Anybody know anything about the mod wiring designs parts lists etc. or who Wushoes is ? (maybe beanflying from ccf)
Some of the mods out there you connect into your grinders wiring, but the best one I have seen you just plug your grinder into the timer unit (as above)
If anybody has any info it would be appreciated.
Chester
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Re: Grinder Timer
Early days yet psaigh, still trying to see if it does what it was intended to do, with some consistency. The led in the on/off switch flashes a couple of times a second for some reason - havent checked out why yet, but when I was putting it together, the battery was the length of an alligator lead away (30cm), now it is nearly 2 metres away, so maybe a voltage drop is causing that. Who knows?Originally posted by psaigh link=1215167303/0#4 date=1215331841Looking forward to hearing more about your unit philmak, any thoughts on selling one? happy to pay for parts, labour and shipping.
The particular relay I used is only good for 3 amps, my Sunbeam grinder uses only 150W, so no where near the 15 amps you mentioned. Something that can handle that current (@240 volts ac) would be quite expensive in itself.
The way it works is by generating simple square/sawtooth timing signal with a variable frequency, within limits. This signal is connected to the input of a circuit which counts the number of the waves. I have set the count to 8192. Hence, if you want a time of 6 seconds, you need to have the frequency set at 8192/6=1365Hz. The led in the on/off switch is actually connected to the output of the timer, and should technically be flashing at 1.365kHz (which you shouldnt notice). I put 2 terminals across this led so I can measure the frequency on the DMM so Ill have to see if this is still the case.
All in all, it seems ok, and certainly filling the basket with one push of a button is easier than having to hold the pf against a momentary button etc, but wouldnt be able to switch the 15 amps you need.
Cheers
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Guest repliedRe: Grinder Timer
.001s, thats nuts!! but from what I hear David it was damn pricey. Looking forward to hearing more about your unit philmak, any thoughts on selling one? happy to pay for parts, labour and shipping.
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Re: Grinder Timer
pretty cool. Let us all know how it goes PhilMac.
A while ago, I made a digital timer which any electrical appliance can plug in to. It can be set to 0.001 s resolution. My intent was to use it on any manual grinder for Barista Competitions.
Depending on blend/origin, my K10 will be set from around 4.3 seconds to 5.3 seconds.
I had two of these units integrated in to David Makins twin BNZ grinder set up for the 2008 World Barista Championship.

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Re: Grinder Timer
So far so good, from limited testing on beans getting to the end of their shelf life I have managed fairly consistent results. My grinder is a Sunbeam, which throws out around 1 gram per second. I subscribe to the dose/tap, dose/tap, dose -tamp theory, so I have set the timer to give somewhere around 6 seconds of grind before switching off. I dont know the actual time, just adjusted the timer to give 6 grams.
Ill try and post some pictures.....

The red button is the on/off switch with a red led (that flashes, should be solid - havent worked that out yet?), there is a green led that stays on to remind that the power is still on, the lurid pink knob is the time adjust and I put a fuse on the side in case my soldering is dodgy.

The inside of the little black box.


The clock/counter circuit is housed in an AC junction box along with the solid state relay, that hides under the benchtop (our powerpoints are under the bench) connected to the little black box next to the grinder by cable.
Probably all up about $50. More tesing required as I only drink 2-3 cups per day, until I get around to roasting some of my decaf beans!
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Guest repliedRe: Grinder Timer
Let us know how it goes! Ive been looking for a relatively cheap timer that can handel 15amps and be altered in intervals of 0.1 of a second. So far the best units (either built units or hobbie kits) are darkroom timers, but Im yet to find a reliable unit for less than $100
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Grinder Timer
All this talk about digital grinders (M4D etc) got me thinking - it cant be that hard to come up with a circuit to switch on and switch off a grinder for a certain amount of time. Found a few circuits on the net that might do - a 555 clock timer, 4020 ripple counter and a relay adjustable within certain parameters, made from cheap bits available from Jaycar etc.
Anyway, I bread-boarded the components, and so far the so good, a variable on/off timer switching the AC power supply to the grinder (testing was done on a light bulb), all powered by a 9 volt battery. I am hoping this will add a consistency to dosing. Yet to do the actual tests and weigh the results but. See how we go
CheersTags: None
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