Pressure Perfect with Vibe Pump

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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#1: Post by cafeIKE »

First, I brew mostly medium roast coffees and don't overdose the basket. Seldom is there a shower screen imprint on the puck. My current Honduras/Yrg 60/40 blend is 21.7g in a Synesso triple basket for about 33g/66% shot. So YMMV.

The pressure can drop when the heater element kicks in. Depending on coffee and shot parameters, a perfect pour can go sideways when the pressure falls. ≈15 years ago I added a PID to my Vibiemme Domobar HX and shortly thereafter I added a PID cutout to prevent this pressure drop on the PID cycles, trading a slight temperature drop for constant pressure.

Post gicleur, on the puck pressure pulsing with PID. A single, but similar drop occurs if the pressure stat kicks in whilst steaming.

Whilst rebuilding one of my PID Vibiemme espresso machines, I noticed the diode symbol on one Ulka pump terminal.

:idea: Of course! The pump only works on the negative half cycle :idea:
The piston is pulled back and water is expelled by the spring on the positive ½ wave.

Simple to add a diode bypass to keep the heater element off during the negative half cycle, preventing the pressure pulse and temperature drop.

Relay: Zettler Power Relay SPDT 30A 120VAC AZ2280-1C-120A @ Amazon
Control wired across pump. NC terminal wired across Diode Bridge.

Bridge: BR3510 Bridge Rectifier Full Wave 35A 1000V @ Amazon
Bolted to chassis for cooling. NOTE Polarity.

Full PID Schematic PDF

Full Pstat Schematic PDF

With Pressure Perfect mod, pressure remains rock solid regardless of PID or pressure stat.
This is pre-gicleur which varies much more than post gicleur shown earlier.


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#2: Post by Jake_G »


That is brilliant!

I see you are in Florence! I was there on Tuesday spending a day with the family before heading back to muggy Wisconsin.

I could have gone for some pressure perfect espresso... :D


- Jake
LMWDP #704

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#3: Post by HB »

That is such a smart idea! We noticed the same vibe pump pulses long ago in the Quickmill Alexia Review and suggested they add a SSR that cut off the heating when the pump was on -- with the assumption it wouldn't impact brew temperature. Your solution is much more sophisticated. 8)
Dan Kehn