Tom, I don't have such an elaborate rig like you guys.. but just for kicks I manually pressure profiled a few shots.

My water inlet is on a T with a water faucet (like for filtered water for drinking):

mains------|--------FILTER ------- rotary pump inlet
...............|........................|
.....kitchen faucet.................|
.........................................|
..........................drinking water faucet


So if I use the drinking water faucet (will abreviate DF) I can change the pressure the pump inlet sees

Since my Brewtus II is an e-61, If i put the lever half-way I get line preinfusion

so for the test shots, I turn DF on full, then lift lever half way [pressure is near 0], slowly close DF.. pressure nears 4 bar (my mains pressure), then when DF is fully closed, lift lever fully to activate pump

If I do this, the shot seems to strangely blonde a lot sooner than if i don't use DF at all and just go from 4 bar straight to 9

I know that I can't run the pump with DF open and of course I don't do that - I'm just talking about during the line-level preinfusion stage

so my results are consistent with yours (which is strange to me as I thought a slow ramp up would yield a longer shot)

here is my version of some "cheapo preinfusion" not saying it really actually does anything but here it is.

i noticed that the boiler pressure is lower when 2 groups run at the same time. gr1 brewing then gr2 started without any resistance will lower the pressure about 2 bar.

the following is for entertainment purposes only.
----------------------------
build shot.

put PF into gr1.

start gr2 with nothing there.

leave gr2 running start gr1 brewing, the pressure will level off about 2 bar lower than normal.

at about 8 seconds when drops appear, stop gr2, the pressure goes up to full pressure.

towards the last 10 or seconds you can then start gr2 to drop the brew pressure again.

then stop gr1 brewing.
---------------------------
i dont do this everytime but sometimes i will do it for fun mostly.

i am not saying its revolutionary but its an observation of the behavior of my machine and it is another way to manipulate the brew pressure without modifying the machine.

thanks for the time.

It's kind of funny that you call it "cheapo" preinfusion. There's nothing cheapo about a 2 group GB5...

uhh its a 3 group.. .you betta recognize!!! hehehe

i need to sell this beast but i love it so much. my wife thinks it looks great in the living room.

jon

Hi guys,

for those who thought this thread went dead here's a quick resurrection:

- a shot with a DIYed Scace-like device:

http://www.flickr.com/photos/tompjagiello/4304470943/

- an actual espresso shot

http://www.flickr.com/photos/tompjagiello/4304505139/

I was surprised with the low pressure shot, fruity and even though it was too long still quite tasty.

As you can see on the second clip the controller is far from perfect and there's a major overshot at the beginning of the shot, but keep in mind this is a simple k=1 proportional controller, so I'm actually surprised it works so well. I'm planning to add an integral and derivative elements in the following days and will update with some more vids.

Regards,
dsc.

Hi again,

another update, slowly getting there, I just have to implement SPI to allow setpoint reads/writes to an external SRAM and we're good to go.

http://vimeo.com/9218344

I've added a simple timer to the LCD so now you can see how long the last shot was which is actually quite handy sometimes.



Regards,
dsc.

Just in case any of you [prospective] pressure profilers missed it, LM USA wrote an excellent blog post about what pressure profiling is, and more importantly, what it isn't. I thought it was really well-thought-out, and while I didn't learn anything new, I thought it was a very balanced representation of the prospective value of pressure profiling.

Being an engineer I find this a very interesting thread. I added electronically controlled preinfusion to my Bezzera BZ35, with the details posted at Adding preinfusion to a rotary pump machine. My controller is much less sophisticated than described here but the pressure control technique may be a lower cost alternative to a variable speed pump.

Hi guys,

I finally managed to get the SRAM chip working (yay!!!) and here's how it all works:

http://vimeo.com/9653943

Shows manual mode and replay function, so if you find something that works well you can save it and replay it how many times you want.

Regards,
dsc.

Hi everyone,

resurrecting an oldie simply to show how it's all coming along. This will be mounted in a custom made machine that I'm planning to put together in the coming months:



Hopefully the next video will actually feature an extraction.

Regards,
dsc.