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Coding a universal Arduino Coffee Control unit with pid
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tinyenormous
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Joined: 22 Mar 2013
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Posted Tue Apr 30, 2013, 8:28am
Subject: Re: Coding a universal Arduino Coffee Control unit with pid
 

Ouch!
Pressure sensors are pricey!
http://www.digikey.com/product-search/en?FV=ffec5663

That's going to be on the "wait until I can find a surplus sensor" list for now. I bet it could still easily be controlled (blindly) by pwm/modulating the pump pressure.

Ross
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DanoM
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Posted Tue Apr 30, 2013, 10:17am
Subject: Re: Coding a universal Arduino Coffee Control unit with pid
 

There's a Korean poster on YouTube that has a PWM for his vibe pump that seems to have good control.  You'd likely have to test it in various environments, but I would guess you can dial in the pressure with this and have it be relatively stable for pressure?  Of course an analog meter to keep an eye on things wouldn't hurt either.
http://www.youtube.com/watch?v=2Ugl5pp5zaQ

What I would like to do is convert his PWM controller into using either a spring loaded slide rheostat or a 1/4 turn rheostat so that you could put a mini manual electro-lever on the machine for pulling shots.  Pull down harder against a spring for more pressure, ease up for less, etc...  Put in an analog pressure meter next to the lever and you'd have a very nice manual addon to that PWM system.

I did read somewhere that the Ulka pumps do tend to loose some flow as they age, so you might have to tune your PWM settings from time to time.

Ah... To have an endless supply of cash to spend on such mods!  LOL
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billc
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Joined: 15 Jan 2009
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Posted Tue May 7, 2013, 9:33pm
Subject: Re: Coding a universal Arduino Coffee Control unit with pid
 

Ross,
You can control the pump vis the controller.  It is similar to PWM but not called PWM.  Look up Phase control (phase fired control, signal chopping etc).  Essentially to control the ac coil you still need to have something that is similar to an AC signal (60 hz that is).  The way you control it is to delay the turn on time from when the voltage is at zero.  To do this you must have something that senses the zero crossing of the AC voltage.  Google it for more info.

You also need to have a type of relay that is a random fire type, meaning that it can turn on anywhere in the AC Wave.  It is more typical to find a zero crossing SSR, meaning that it always turns on only when the voltage is zero.


BillC
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Everman
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Everman
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Posted Tue May 14, 2013, 4:51pm
Subject: Re: Coding a universal Arduino Coffee Control unit with pid
 

Looks like a fun project, I look forward to seeing how it turns out. I "eventually" want to do some modding to my Elektra project machine and a data logger would be useful.
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joshblake
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Joined: 6 Jun 2013
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Location: Toronto
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Posted Thu Jun 6, 2013, 9:44pm
Subject: Re: Coding a universal Arduino Coffee Control unit with pid
 

]Just came across this topic! I love the idea's here! I've actually already completed a lot of the feature-set that everyone is looking for including the AC-phase chopping to allow pressure control at the pump. Check it out: http://josh.to/crema. I'll be dropping the source code and hardware files under the Creative Commons Share-Alike Attribution license for anyone that's interested!

Regarding pressure transducers - I believe Auber Instruments sells them for a reasonable price that provides a ratiometric voltage output dependent upon the pressure Click Here (www.auberins.com).

I've been considering adding a 16-bit DAC to allow for a voltage dependent output to allow for Linear-Voltage-Dependent-SSRs as well as geared pumps (from Fluid-o-tech etc.). Although I have no immediate need for these features myself.

Cheers!

Josh.
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