PID'ing the Olympia Cremina

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starry

Postby starry » Jun 30, 2007, 3:11 am

PID'ing Olympia Cremina
a new idea...I think.

For some time now I've been pondering the challenges of using a PID on lever machines. The most obvious and troublesome is the lack of boiler pressure needed to prime the cylinder.

I was encouraged to see Raj's version in "Positive pressure, PID Pavoni: world domination begins", but I wanted to do something a little different. The main issues that I wanted to resolve were thermal instability caused by the introduction of unheated water, and lever resistance.

The idea for my system is to use air pressure instead of water pressure. I've seen some folks toy with the idea of using a bicycle pump, but I was looking for a more "elegant" solution. That caused me to begin a quest to find the appropriate miniature pump or compressor that might do the job. I quickly found that there are many choices for such a pump available for differing industrial needs and selecting the appropriate type and size of such a pump was a bit beyond my abilities. What I did then was to try to think of a more common type of pump that I may have seen before in my day-to-day experience. There were several that came to mind, but the most promising was the type of pump that is usually found in an automatic blood pressure machine, the type that typically sells for about $40 at the local pharmacy. I didn't want to actually pay for it since there was a possibility that it may not work at all so I asked a friend who is closely associated with the medical community if he might know of a source. It turned out he had a "barely used" machine that gave very inaccurate results for monitoring blood pressure. The store wouldn't refund his money so he gave it to me.

Here is a picture of the box:

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I pulled the thing apart and it yielded a very small pump (or is it a compressor?....I don't know). It runs on 4 AA batteries or 6 volts.

This is a photo of the pump:

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The first thing I needed to do was to determine if it would be capable of at least 1 bar to pressurize the boiler. 1 bar is roughly 15 psi so I went to the garage and scrounged some small fittings that came with a vacuum pump that I purchased for bleeding the brake lines on my car and a pressure gauge. I made an adapter from two cone shaped fittings put together with a small peice of tubing to hold them together and plugged the output of the pump into the pressure gauge via the adapter I made.

Here's what the setup looked like:

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I hooked up the batteries to the pump and read the gauge. I was ecstatic! It read 19.5 psi!

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Now I wanted to see what would happen when I pressurize the boiler using the pump. Another fortunate circumstance allowed me to do this with ease. My lowly Olympia Cremina is not in possession of it's original phenolic knob affixed to the boiler cap, but only has the brass cap which contains a one-way valve designed to allow air into the boiler after use when the machine cools down. It's a check-valve installed in a VERY convenient place. The missing phenolic works to my advantage here... and the little cone shaped adapter I used for my pump test fitted beautifully into the tiny hole. I inserted it, and with the Cremina turned-off, I pumped up the boiler and waited for the familiar click of the pressure-stat. It only took a few seconds!

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This means that with the right modifications to the wiring, I could have a two position switch which would work in position one to provide the factory intended wiring path (for steam) and position two for PID control and most-importantly, compressed air from the pump with the pressure-stat acting as it's on-off control!
My next step from here is to package it in an elegant manner. Photos coming when as I make progress, maybe in a few weeks, as time permits.
Ralph Walter

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matadero210

Postby matadero210 » Jun 30, 2007, 12:44 pm

Hi Ralph,

This is a very interesting development--good spot on the mini-pump. I too thought about it for my second system, but stuck with the water pressure approach. The only real advantage to connecting to mains is that you can pull cleaning shots as often as you want. I typically pull 2-3 empty shots in between each real one--I'm constantly amazed at how many fines find their way up into the system. We now also use the system for green tea or other hot-water dispensing. Parenthetically, I have a dream of making an espresso machine out of one of those sink-mounted hot water dispensers--a sink mounted espresso machine with only the head showing--no mess, no cleanup, everything in the sink. It could be a lever, natch, or even hydraulic, with waste water going into the sink. Since most houses have 40psi or more, a 3:1 piston/cylinder is all it would take.

If you use a check valve, you need some air in the system to provide compliance for the displaced water when the piston is raised in the Pavoni. Other levers, maybe the Elektra MCAL, have vented air behind the piston (ie, the space behind the piston is not part of the boiler system). These are poor candidates for water pressure, since water is inlet during the piston fill (which does NOT happen on the Pavoni).

For steaming, I rigged the PID to be always on, but bypassed the heater directly with a 'steam' switch. The PID doesn't seem to mind too much the little 'excursions' to steaming land.

Look forward to seeing how this works out--I would have bet that the pump was only capable of .2-.4 bar--happy to see otherwise.

raj
LMWDP 117

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starry

Postby starry » Jun 30, 2007, 12:51 pm

Raj,
Thanks for your interest. I've worked out the wiring for my system, and it will also leave the PID on during the steaming excursion. More to come.....
Ralph Walter

mturkel99

Postby mturkel99 » Nov 08, 2007, 4:43 pm

Sorry for the bump but is this dead? How you given up?

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starry

Postby starry » Nov 14, 2007, 10:04 am

NO! I haven't given up! I'm near completion. I've been using it for a while now and I think it's a great improvement. I've invested considerable time and energy on this with little actual time in my schedule for the project. It is functionally usable but cosmetically it has a little more that needs to be completed. As of now, it looks like this:

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Ralph Walter

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espressme

Postby espressme » Nov 14, 2007, 12:16 pm

Nice package!
Richard
richard penney LMWDP #090,

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starry

Postby starry » Nov 14, 2007, 1:23 pm

Thanks! It was my hope that it would look like it was manufactured that way. The top part above the PID and buttons is what will change. I am still hunting for another boiler cap which will enable me to begin the final challenge of extending the boiler fill tube by about 2 inches. I will be using the old cap to help accomplish this. If anyone has a cap or knows where I might find one, please send me a PM. Thanks.
Ralph Walter

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TUS172

Postby TUS172 » Nov 14, 2007, 10:47 pm

Very nice indeed! Care to show us under the 'hood'? :)
Bob C.
(No longer a lever purist!)
LMWDP #012

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espressme

Postby espressme » Nov 14, 2007, 11:40 pm

Being a homely shop masochist, I would recommend taking the cap to a local small machine shop along with a fresh pound of Pourover Grind Roast for their MR C%^&*, and asking them if they could machine a tube to what you need on the sketch you made before going there. :) Should be about $50 for one or less. My cremina seems to have a 25mm Diameter x 1.5 pitch thread on the boiler tube. That could translate to a sloppy 63/64 x 17 threads per inch. :twisted: You will probably have to have it lathe cut so make a few to silver braze to other things later. Silver solder is now Cadmium free in this country. You might contact "fullsack" about a cap with the plastic broken. I know someone around here had one!
Nice project!
sincerely
Richard

starry wrote:Thanks! It was my hope that it would look like it was manufactured that way. The top part above the PID and buttons is what will change. I am still hunting for another boiler cap which will enable me to begin the final challenge of extending the boiler fill tube by about 2 inches. I will be using the old cap to help accomplish this. If anyone has a cap or knows where I might find one, please send me a PM. Thanks.
richard penney LMWDP #090,

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starry

Postby starry » Nov 15, 2007, 12:51 am

OK. Here are some pics. As you can see, this is still a work in progress.

PID is on the left, switch in the center provides on-off for the pump. Up is "pump automatic" (on-off provided by the p-stat) and down is "pump off", switch on right provides "factory operation" or "steam" in up position and "PID" in down position. The air pump is seen in the upper left.....still not permanently hooked to the boiler. The brass fitting is a 10/32 check valve with Viton seals to withstand any possible temperature challenges. The fitting on the end provides me with the ability to manually pressurize the boiler through the one-way valve in the top of the boiler cap. The SSR is on the upper right.

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"Instrument Panel"

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Shows a layer of Styrofoam under the instrument enclosure that keeps things a bit cooler. Also the platinum RTD sensor for the PID lives under the small chunk of foam which insulates it from ambient temp and holds it in intimate contact with the boiler. The black thing in the lower left is a regulated power supply that supplies 10 volts to the pump. On the right side of the boiler is an area where I tried to use some polyethylene foam which melted. I haven't bothered to clean it up just yet.....

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Ralph Walter