Controller part 10 - GICARs of the world unite

A collection of GICAR controller circuits.

CIV`s Cimbali Junior 





Dynamos' Gaggia lever 














Circuit from 1998 RL30 GICAR from an Aurora

Controller part 9 - autofill, electrolysis and GICARs

After an interesting discussion on the Home Barista forum about the possibility of a constant DC voltage causing electrolysis of the autofill probe I thought it would be a good idea to revisit the auto-fill circuitry. 

When I repaired the GICAR in my machine, I looked fairly closely at the circuit. I took a few notes, but I didn't draw it completely. Looking back at the notes, what I did see was an AC transformer with two taps, marked as 15V and the other for 20V (these measured 19 and 27 VAC (with no load)). I'm pretty sure that the probe was connected after a rectifier and that a capacitor was used to provide hysteresis. I therefore assumed that there was a constant DC voltage going to the probe. However, I just took the cover off my machine at home and put a multi-meter on the probe. The readings are not conclusive. I see roughly +160mV which seems to drop occasionally, possibly below zero. I don't see AC, but this is on a 200V scale with a cheap digital meter... I'll bring home a better meter this evening. It seems pretty unlikely that there is 19V or 27V AC present though.

Here are the photos of the GICAR controller that I took way back when:

Controller part 8 - eagle fight

Canada is a great place: trees, more trees, beer that doesn't taste like water, Montreal. We even have a puppy for prime minister. Getting things to Canada from the US on the other hand, is like chewing pebbles. I've been waiting since the end of July for paint samples to come by USPS. Lost in the mail. Resent. Still waiting. 

In the interim, I've been in a grim death-struggle with Eagle CAD, candidate for "World's Most Un-intuitive CAD Package". I also wired up the prototype controller. All the AC and signals to the lower board (the bull-dog clips are holding a piece of rubber over the exposed AC connections on the bottom) :

Then I made a break-out for the IO to the micro-controller from a piece of protoboard and some jumper wires. It plugs into un-used analog pins on the Arduino.

Overall it's a bit messy, but not too bad given that it is frankensteined together from various different projects. The only real problem is that the USB port is at the opposite end from all of the other connections. This is inconvenient for positioning the box in the base of the frame. The other mild annoyance is that the LCD screen is just too wide to fit across the short side of the box. So, at least for now, the interface will have to read from the side of the machine. 

The next step is to make custom boards for the keypad/screen and the power distribution/sensors/relays because protoboard just ain't gonna cut it. Ultimately, it would be better to incorporate all three boards into a single one, but that is a lengthy task which requires a much higher volume to make it worthwhile. Here is a first bash at the keypad shield. 

This is a pretty simple board: just the connections between the LCD and the microcontroller to make, plus an IDC connector to hook up a few flavors of power, ground and a bunch of pins to the lower board. The keypad design is clever - all the buttons are on a single analog pin, pressing one of them engages one of five different resistors. The pin reads the resistance and thus can distinguish which button has been pressed. 

There is, however, a mistake in the original design which has been blindly duplicated hundreds of thousands of times. The transistor that controls the LCD back-light is missing a diode (or minimally a resistor) to prevent current flowing back to the IO pin on the microcontroller and burning it out.

Suffice it to say that this shall be remedied.

Controller part 7 - proto case

Ok, I've been lax with the my posts and a few weeks have gone by. However, even though we are experiencing our brief period of non-inclement weather we refer to as 'summer', I have not been entirely idle.

I ordered a bunch of electronic parts for the controller box.

Including these LEDs from Bivar, which came in a fancy box and are somehow suggestive of marriage proposals.

(With this LED, I thee wed?)

I've not done enough PCB design work to be confident enough to order a board without building a prototype first. Normally I would just test the circuit on bread board, but this one has to handle AC distribution, so I decided to put one together on proto-board. After a lot of faffing around in Eagle CAD (candidate for the world's most un-intuitive CAD package) and time spent dragging the net for 3D models of the components, I settled on an enclosure size and cut the blank board to size. 

A first go at the layout of the lower and upper levels. AC-DC supply, 5V relay and opto-isolator board.

The Arduino fits over the top. 

And the LCD and keypad shield sit on top.

The models of the keypad shield PCB that I found on the internet don't quite match the one that I have. This meant that I spent a looooong time measuring the layout with calipers to figure out where the holes have to be cut in the enclosure box. This will be easier next time as I will design my own shield.

Four hours of setup for two minutes of cutting? Too late now if I got this wrong!

Thankfully, it fits.

The button hole cut-outs are a little on the large size. I think that the CAD model I used must be incorrect. Still, more than good enough for the prototype.

Frame part 4 - rust paint

The pressure gauge is mounted to the top of the level gauge in the original which means that it has to be 'outside' the case. This is an expedient method but personally I find it a little too "steam engine" in an otherwise minimalist design. The advantage of exterior mounting it is that it is much easier to take off as the part that it mates with is fixed. With my mounting method, attaching the copper line directly to the gauge is more of a hassle. OTOH it isn't like you have to take the case off once a day...

I installed the SSR and slapped a coat of rust paint on the frame. This was also a case of expediency as the frame will be powdercoated. I just lost my patience with the rust. Amazing stuff that paint, you could almost put it on with a spoon and it will still level itself out...

Sheeeeeeet metal part 3 - test fit

A quick update on the progress of the sheet metal.

Months ago, when I ordered the cold-rolled steel for the frame, I neglected to actually measure it when it was delivered. I therefore missed the fact that the supposed 1/8" x 2" was in fact 1/8" by 2 1/4". As a result, the base of the frame was a 1/4" too high meaning that the hole in the backsplash for the group didn't line up with the flange on the boiler. I cutout and remade the cross bars, cleaned up the (now rather beaten-up) frame uprights and put everything back in its place.

While doing so, I welded on a couple of tabs to keep the backsplash in place. The tabs, together with the last interior flanges of the cover create a track for the backsplash to slide into. 

The tab clamped in place before welding.

The cross bars must be set back by at least same distance as the tabs. A scrap of 3/8" bar plus a brass shim create the necessary thickness.

Back to where we started!

Now for the fun part! I made a change to the design because I was unhappy with the placement of the pressure gauge. There is just enough room to fit the gauge and a u-bracket between the upright and the exterior of the cover. 

This gauge is both easier to read in this position and is now flush to the exterior surface. Far more satisfying all around. 

I knew there was a reason to put a coil in the line to the manometer! It was an easy job to reshape the existing part and to re-orient the coil so that the condensate runs back into the boiler.

AND... just because I like to feel like I've achieved something today, a test fit of the case parts with (yet another) valve. 

Hmm. This thing is starting to look vaguely like a coffee machine.

Sheeeeeeet metal part 2 - unboxing

All of the sheet metal parts showed up in a nicely packed box yesterday.

The drip tray insert is just laser cut for the moment. I wanted to check it for the fit before paying for the custom tooling required to stamp the holes.

The drip tray itself is pretty much good to go like this. There is a slight difference in the finish at the corners where the discoloration from the welding was buffed out, but this is actually more visible in the photo than it is in reality. 

The warming shelf - ready to go except for the system for retaining it in place.

The cup warmer rails.

The backsplash, ready to be installed.

... and the cover. This is the most difficult part of the lot because of the radiused corners at the back. Those have given me much pain both to model in cad and in finding a supplier able to make them. 

A test fit of the cover and the drip tray...

... and, following a complete disassembly of the machine, a test fit of the the backsplash and cover.