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.