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DIY grinder timer with 0.1 sec resolution
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dwRK
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Joined: 14 Sep 2013
Posts: 92
Location: Houston
Expertise: Just starting

Posted Wed Jan 15, 2014, 9:35am
Subject: Re: DIY grinder timer with 0.1 sec resolution
 

a rotary switch with the spindle through the gap will make adjustment easier...you can still add that in...
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witoldb
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Joined: 15 Aug 2013
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Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
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Roaster: DIY 250g drum roaster
Posted Wed Jan 15, 2014, 12:02pm
Subject: Re: DIY grinder timer with 0.1 sec resolution
 

My circuit is using binary code to set the time but "inverted".
Timing resistors are active/connected into the circuit when particular dip switch is open.
With non-binary rotary switches, you will need at least 2 (for seconds and decimals) + separate resistors for each position on both switches.
You could limit seconds from 5 to 15 and use two 10-position switches.
I'm not sure if coded hexadecimal or binary rotary switches will work in this circuit.
I agree that timing should be easily adjustable without tilting the grinder and will mod it in the future (currently I have too many projects to complete).
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dwRK
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Joined: 14 Sep 2013
Posts: 92
Location: Houston
Expertise: Just starting

Posted Wed Jan 15, 2014, 2:14pm
Subject: Re: DIY grinder timer with 0.1 sec resolution
 

Sorry...didn't pay attention to your circuit earlier...

I think this "binary" business is in terms of dip operations only...i don't see the circuit as binary at all in the digital sense of 0 and 1

Its been a long time since I looked at a 555...the dip switches changes the resistance of the string...so there's probably a voltage reference and comparator somewhere...your circuit is probably quite unique...

rotary encoders won't work without further ic to decode

i'd keep the dip switches...but perhaps do this to give you +/- 0.5s...i would find a small vr, stick the shaft out through the hole you did for the portafilter switch, stick the switch behind the vr...but you'll have to build a rig behind assuming you have space...this way you can do two things though that hole and keep it tidy

dwRK: circuit.jpg
(Click for larger image)
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 118
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Thu Jan 16, 2014, 9:59am
Subject: Re: DIY grinder timer with 0.1 sec resolution
 

Idea with a pot and switch is excellent.
After checking my spares I found 2 suitable pots with push-on switches, enough for my home and work grinders.
I will keep dip switch under the grinder for seconds and replace decimals switch with pot/switch combination.
One pot reads 23k5 and another 24k66 so I have to calculate accordingly values for timing capacitor and resistors to get around 1 sec adjustment from the pot.

witoldb: pot switch for grinder.JPG
(Click for larger image)
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dwRK
Senior Member


Joined: 14 Sep 2013
Posts: 92
Location: Houston
Expertise: Just starting

Posted Thu Jan 16, 2014, 10:52am
Subject: Re: DIY grinder timer with 0.1 sec resolution
 

that is great! just make sure you have space...i've had my fair share of "oh ohs" :)

also it doesn't have to be 1s...i just sketch it there and 1s range looks like something i'd would choose...

good luck and thanks... i may just build one for my grinder :)
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