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pressure profiling with vibe pump
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Bgosselin
Senior Member


Joined: 26 Jul 2012
Posts: 51
Location: Canada,quebec
Expertise: I love coffee

Posted Thu Oct 25, 2012, 7:26pm
Subject: Re: pressure profiling with vibe pump
 

Craigman Said:

What about looking at the plumbing side of things and using a adjustable needle valve or something simular?

Posted October 25, 2012 link

I plan to plumb this my R58 and see what type of pressure I'm going to get.  I would know then what can be done.  The dimmer switch seem like an easy solution.  I was puzzeled why it wasn't implemented on commercial machine.  Now I know that adjusting speed on a AC motor is not that easy.

I do question why it's so revolutionnary.  The Slayer seem to be base on this principle where you should slow the extraction at one point during your shot to get better flavor.  Why is 9 bar the norm for espresso?  Why not 7 or 6?

I've been reading daily  about coffee gears, beans etc for the last few months and I feel like I just scratch the surface.

Thanks everyone for educating me.  :)
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Craigman
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Joined: 13 Oct 2012
Posts: 11
Location: Sunshine coast Australia
Expertise: I love coffee

Posted Wed Oct 31, 2012, 1:13pm
Subject: Re: pressure profiling with vibe pump
 

because my dimmer only slightly works, I can only regulate about 1 bar with it, must not have a compatible dimmer or something.

I tried another dimmer and it did not work either, in fact when I was disconnecting it I got one hell of a shock! and it was not even plugged in!

It had a little black box with it that must have had some sort of capacitor or something because it stored a charge and nailed me.

Now I am thinking to work more on the plumbing side

I have already installed a OPV and a gauge, so I was thinking to add a needle valve lever type mounted on the outside of the machine.

It would be plumbed in after the OPV and before the brew head and would just bleed off water back to the tank the same as the excess now does from the OPV only I could control it manually.

here is a sketch if you can follow that.

Craigman: Presure control (Large).jpg
(Click for larger image)
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Craigman
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Joined: 13 Oct 2012
Posts: 11
Location: Sunshine coast Australia
Expertise: I love coffee

Posted Thu Nov 1, 2012, 7:22pm
Subject: Re: pressure profiling with vibe pump
 

It has been proven without a doubt by Slayer that a slow per-infusion first,  then Full pressure for a short time

then back down the pressure to adjust the flow rate and it works well.

My theory is they just picked 9 bar as a happy medium because it was easy and it does work.

when we don't really know what is the ideal pressure during the full pressure phase?

it may be something like 2-12-4

seems to me even 15 bar for a short time might extract the more deeper oils depending on the beans
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Craigman
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Joined: 13 Oct 2012
Posts: 11
Location: Sunshine coast Australia
Expertise: I love coffee

Posted Tue Dec 25, 2012, 7:56pm
Subject: Re: pressure profiling with vibe pump
 

latest video

http://www.youtube.com/watch?v=BvFv2jess3M
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jonr
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Joined: 25 Jun 2013
Posts: 300
Location: Americas
Expertise: I like coffee
Posted Sun Aug 11, 2013, 7:17pm
Subject: Re: pressure profiling with vibe pump
 

Is there any merit to using flow feedback?  Ie, install a flow meter and have a computer control pressure to achieve a certain flow profile?  It almost sounds like that is really what is being described here.
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billc
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Joined: 15 Jan 2009
Posts: 133
Location: Seattle, Washington
Expertise: Professional

Espresso: CC1 - GS - GS3 - GB5
Grinder: Baratza - Mazzer-Marzocco
Drip: My own Creation
Posted Tue Aug 13, 2013, 6:17pm
Subject: Re: pressure profiling with vibe pump
 

jonr,
Is is difficult to measure the flow rate accurately during the brew phase because of the low flow rate.  It can be done just not economically.  A standard flow meter may be used but it does not give enough resolution to give an accurate flow rate.  In the case of the vibe pump, during the brew phase pressure is directly proportional to the flow rate.  Change on and you change the other.  

BillC
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jonr
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Joined: 25 Jun 2013
Posts: 300
Location: Americas
Expertise: I like coffee
Posted Wed Aug 14, 2013, 7:28am
Subject: Re: pressure profiling with vibe pump
 

I supposedly hold a steady 9 bars and it looks like the flow rate through the coffee varies a little throughout the shot.  Maybe the coffee is changing as it absorbs water?  Or crema is influencing the apparent volume but not the actual water flow rate?

How important is pressure (or flow) feedback?  Is open loop control of vibe pump power (say a table of % power vs time) enough or does one need a pressure or flow sensor?

> It has been proven without a doubt by Slayer that a slow per-infusion first,  then Full pressure for a short time then back down the pressure

Is there any consensus on the taste value of pressure profiling?   I'm considering adding it.  Putting a DC SSR on the pump is very easy, adding a pressure sensor would take some minor plumbing work.
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billc
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Joined: 15 Jan 2009
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Location: Seattle, Washington
Expertise: Professional

Espresso: CC1 - GS - GS3 - GB5
Grinder: Baratza - Mazzer-Marzocco
Drip: My own Creation
Posted Wed Aug 14, 2013, 8:56pm
Subject: Re: pressure profiling with vibe pump
 

I have been testing a variable vibe pump and a pressure sensor for some time now.   Pressure profiling is a bit of a challenge with a vibe pump.   The flow rate of water through the coffee is somewhat dependent upon the pressure on the coffee cake.   so, when you reduce power to the pump to lower the flow rate it also reduces the pressure on the coffee causing a larger flow rate thus reducing the pressure even further.  currently there is a lot of prediction in my control theory (yuck!).  This problem is very specific to the vibe pump since it is very flow dependent.  

If you do add a SSR to the pump for control make sure it is a random fire SSR and not the standard zero cross SSR.


BillC
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DeanOK
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DeanOK
Joined: 24 Sep 2012
Posts: 696
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Wed Aug 14, 2013, 9:31pm
Subject: Re: pressure profiling with vibe pump
 

billc Said:

I have been testing a variable vibe pump and a pressure sensor for some time now.   Pressure profiling is a bit of a challenge with a vibe pump.   The flow rate of water through the coffee is somewhat dependent upon the pressure on the coffee cake.   so, when you reduce power to the pump to lower the flow rate it also reduces the pressure on the coffee causing a larger flow rate thus reducing the pressure even further.  currently there is a lot of prediction in my control theory (yuck!).  This problem is very specific to the vibe pump since it is very flow dependent.  

If you do add a SSR to the pump for control make sure it is a random fire SSR and not the standard zero cross SSR.


BillC

Posted August 14, 2013 link

Bill:

Has anyone experimented with an ECM motor (brushless DC motor that speed can be controlled by a PWM signal) to drive a rotary pump? I have always thought this would be something to try, however I am not sure the ECM motors that are currently in production can change speed rapidly. This may be a requirement to be able to track and adjust pressure by using a transducer and processor to send PWM signals to the motor and change speeds fast enough to actually control pressure in a usable way.
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billc
Senior Member


Joined: 15 Jan 2009
Posts: 133
Location: Seattle, Washington
Expertise: Professional

Espresso: CC1 - GS - GS3 - GB5
Grinder: Baratza - Mazzer-Marzocco
Drip: My own Creation
Posted Thu Aug 15, 2013, 7:51am
Subject: Re: pressure profiling with vibe pump
 

Yes, I have a new procon mini pump with a brushless motor attached.  This is the best I have used thus far but it is expensive.   The fluid-o-tech TMFR also is a brushless motor with speed control.  You can change speed pretty fast and with good control (just too expensive for production use).

I have also tested a Gear pump with a brushless motor that was pretty good.  I also had the opportunity to test a gear pump that was attached to a stepper motor.  A bit expensive but you can not only control speed but you can control volume by turning the pump a specific number of rotations.

Sorry this is a bit off topic.

BillC
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