In this thread a pressure gauge for the strega was discussed. It seems however that there is not enough space to fit the gauge inside the machine.
The Super Strega: Modifying preinfusion pressures and other functional improvements

Another option I have been thinking of would be to use a Pressure transducer, in combination with an Arduino, and have the pressure shown on an LCD.
http://stores.ebay.com/Industrial-stuff ... 2911276017

Ideally it would even be possible to use the same arduino board to regulate the voltage to the ulka pump to hold a certain pressure during pre-infusion. And to go even further, a thermocouple could be used to measure the temperature of the water going to the group.

I don't have a lot of experience with the arduino however, does anyone see any issue with this idea?

Also, if I would place the Pressure transducer on the tee, as indicated in the picture below by erics, would that enable me to measure the pressure only at pre-infusion, or would it also show the pressure when the lever is released?

An arduino can do that, although you should also consider other micro-controllers (tradeoffs depend on the details). Also consider using a RTD or digital sensor instead of a thermocouple. And a flow sensor (IMO, flow control is more important than pressure).

Unfortunately, I don't know of off the shelf solutions - so it can be a lot of work.

There is space to add a gauge in the front cover but you would have to cut a new hole. I have the aux. gauge sitting on top of the machine in a stand where it is very easy to keep track of the pressure but you could install both the gauge & $6 dimmer controller in a box next to the machine. A lot less work & $$ then what you are talking about.

The only way to read pressure in the group after the lever is released is to tap into the group. Breaking into the line before the group will only give you fill pressure but that's all you really need to know.

Just picked up a different lever so my Strega with all mods will be listed for sale soon.

Just picked up a cheap strega myself ! I was planning eventually on popping in a brew pressure gauge using Erics' tips on the Super Strega Thread. The boiler pressure gauge isn't very relevant because you know when the machine is not up to pressure by tapping the steam wand. It would be nice to have both a boiler/brew gauge obviously to check if something is wrong with your boiler element or pstat, but it's not necessary.

I was going to keep the boiler pressure gauge and just have it tied to something inside the machine, and use the existing hole for the brew pressure gauge. This seems like a good strategy before modifying the pump to change pressure.

For the pump I was thinking of doing 1 of three things in ascending order of difficulty:

1) Dimmer Switch like Tom. This is a good option that i will probably go with, but I would want a slick installation that I could clearly see the marks for accurately moving the knob back and forth for flushing/pulling shots.

2) T in a needle valve on the HX pipe (next to the new pressure gauge T) and basically be like a super slayer. The problem is that flushing the machine will be slow, and you would want some way to bypass it. T-ing in the needle valve, the pressure gauge fitting AND a little loop around the the needle valve with a solenoid would allow you to skip the low flow when you want to flush or something like that. The needle wouldn't be adjustable without taking off the top, but slayers don't seem to mind.

3) Most complicated - add another pump. Ulka makes 3 bar pumps that have low flow and are almost silent. This would be similar to the needle valve. Then add an easily accessible hidden switch under the body to flip it from the new brew pump to the old pump.

Arduino is cool, but I don't know how to code (((

bostonbuzz wrote:
1) Dimmer Switch like Tom. This is a good option that i will probably go with, but I would want a slick installation that I could clearly see the marks for accurately moving the knob back and forth for flushing/pulling shots.

You can make all the marks you want but the only settings that will be accurate from day to day will be Off & full on. You won't get the exact pressure from the vibe pump at a specific setting each time. It's best to start low & dial it up to the pressure you want while watching the gauge.

3) Most complicated - add another pump. Ulka makes 3 bar pumps that have low flow and are almost silent. This would be similar to the needle valve. Then add an easily accessible hidden switch under the body to flip it from the new brew pump to the old pump.

The stock pump will pull from 1.5 bar to 11 bar so why bother with a second pump?

A relatively easy "improvement" for the Strega and other electrically heated groupheads would be to apply a PID to the installation. I do know of one such application but would want the person who did the implementation to discuss same.

In my opinion, grouphead temperature "rules the roost" but only to the extent that one can differentiate brew temperatures between "A" and "B" for a given bean.

With the Strega, I've been so happy with it's inherent ability to preinfuse (counting or listening for pump quieting sound) as well as it's inherent temperature profile...that I would have a hard time changing it.

I use an Arduino now for my roasting, but in the past I used one for a PID on a caravel, and a few other projects. In my opinion they are very versatile, but I would skip using a single Arduino for so many things (multiple PIDs, controlling multiple devices...etc), just because they are really hobby class devices and not as reliable as other electronics. I can see how it would be very tempting given they have so many I/Os...and for what they cost and their ability they are fantastic fun...I'm just not sure I would put my Strega's ability to work or not solely dependant on an Arduino.

If you could do it where the Arduino and it's controls were optional, with basic controls still working as normal, I would consider that as a good option and a fun project, but ultimately if it was me personally I would do it on a different machine. Just my opinion.

Erics, I'm with you on this. I have a pid sitting in a box that would work great for the grouphead heaters. I think I'll give it a whirl maybe after the holidays. Thing is I'd probably want to do the boiler as well, that means getting a dual PID controller and a bigger ssr.

Unless...I do recall some inexpensive pressure controller for boilers with a very small dead band being discussed here briefly, but I can't find it.

I don't find the deadband on my pressurestat to be that big of a deal in operation, what annoys me more than that is the noise it makes. But I suppose always having it the same pressure might make brew water temp a tiny bit more reliable. But in the end, as Eric mentioned, you'd get more milage out of PIDing the grouphead heaters.

erics wrote:A relatively easy "improvement" for the Strega and other electrically heated groupheads would be to apply a PID to the installation. I do know of one such application but would want the person who did the implementation to discuss same.

In my opinion, grouphead temperature "rules the roost" but only to the extent that one can differentiate brew temperatures between "A" and "B" for a given bean.

Hi Eric. Do you have any more information about this mod? Where would you place the thermocouple?



Number 12 is a "Thermic safety device 95deg" which I guess switches the group heaters on and off?




I guess that heating element only can switch on or off? Or would it also work with pwm?