Electrical Modifications For Phidget 1012

  Sometimes last year, when I was about to order the remaining boards for input detection (for detectors & points status) I realized that the manufacturer of the board I was about to buy had a new product, capable of twice as many inputs. Namely - the new Phidget 1012 had 16 digital inputs as compared to the old Phidget 1018 board containing only 8. However there's a catch with the new board - it requires an external DC power supply.

  Even though I've previously believed that separate input boards are needed for optical detectors and for the switches' feedback, it turns out they can be handled by the same board. The key is using a ground level selected at the potential of 'brown' (of the Viessmann 5200 transformer). Going back to how the 1012 works - this will show an input as ON if the power supply has its circuit closed by the 1012's ground pin and that specific input (eg for input 0, this will be ON when the MRD1's relay is closed, namely when G and D1 are shorted on the figure below). Note that the DC power supply's polarity DOES matter. All in all, pretty straightforward for the optical detectors. Now for the feedback of switches, there's 'grey' and 'green' which get alternatively connected to the 'yellow' and 'pink' respectively, depending which way the switch is toggled. Since 'yellow' and 'pink' are actually outputs of the Phidget output board (1017), these are simply commanded by the input board's relays, which simply connect the "brown" of the Viesmann 5200 transformer to either 'yellow' or 'pink', respectively. So the key in getting the feedbacks to work with the 1012 as well is to have ground always connected to the same potential of "brown", which is made through a simple connection, as indicated in the picture below.

  Initially I had trouble understanding how this works, simply because both DC and AC notions apparently got together in the same figure. However the "brown" (BN) is a simple connection, there's no alternative current flowing through this diagram. It's simply that one can choose his arbitrary ground for the direct current.

  Special thanks go to John Parsons of Azatrax - the manufacturer of the optical detectors used on this layout - who was kind enough to point me in the right direction with the Phidget 1012.

More "Earth" Boards

In the end, 3 boards, each containing 8 squares, were built to get a sense of the resulting color during the tests described here. The last square of the 3rd board was rather dark, and - given blue pigment was added incrementally to each - I was confident each of the shades could be replicated. Then the day came when I actually wanted to produce a specific color, in order to patch some of the earth already fixed on the layout. I chose the most similar shade on the test boards, which meant a concentration of 4.2% blue ultramarine pigment in the standard base formula I've been using. However applying it in just one coat resulted in a color more similar to a 2.8% square.

Given things were totally different from what I was expecting, 2 more test boards were built. This time however, the increment percent of blue ultramarine pigment was increased from around 0.3% (in the first 3 boards) to an average of 0.7%. Still 2 coats were used. The sifting would be done until the new specs of formula barely get "wet". However this time the upper portion of each square was left soaked on purpose. It turns out that these soaked spots actually will dry sensibly lighter than the rest of sifted formula, which has an important contribution to the outcome.

  Thinking about what could have gone wrong in the first boards, it might have been some already prepared base formula, which could have been done without the electronic weighing scale. Also, given the final percentage of the last test patch went up to 10% ultramarine blue, I've also considered how this percentage is calculated. So far in the test boards done, formula was already mixed for the previously completed square. This had a known percentage of blue pigment, which has been gradually increased. In my calculations for the next square, the percent of added pigment will only be computed given the total weight of the existing formula. Adding the blue pigment's weight to the equation wasn't necessary since the difference in orders was quite important (30mg for 15g). However given that bigger and bigger percentages were being used - now reaching 10% - this had to be revisited. Simply think of having 10 grams of the formula already available; we need to get the final percentage to 10% blue pigment. The simplest way would be to consider adding blue pigment in an amount equivalent to 10% of the formula's weight. In our example - 1 gram blue pigment. However the resulting formula now weighs 11 grams. Hence the pigment's correct percentage is 9.09% - becoming quite far off from what we had in mind.

  So doing a little math, we'll first consider C the existing's formula weight, X the weight of blue pigment that needs to be added to get to the desired p percentage of blue ultramarine pigment. The equation thus becomes X / (C + X) = p. This becomes 1 / (C/X + 1) = 1/p. Which eventually becomes X = C / (1/p - 1).

  Turning to our example, the needed weight of blue pigment to be added to reach a percentage of 10% is in fact C/9, which amounts to 1.11g. Computing the resulting percentage yields 1.11g / (10 + 1.11g) which comes really close to 10 (9,999%).

Even More Electrics

Again there's been some work done exclusively on the wiring part. The original connecting board now has both its D-Sub connectors soldered to the corresponding wires (photo 1 showing work in progress). These wires consist mainly of individual signal LEDs and track / power / optical detector current. For the second connecting board, built a month back, the connector with the optical detector wires had about half of these soldered (photo 2 from when this was done). The short-term goal has become setting up 3 signals and the already connected optical detector in such a way that each signal "thinks" and reacts according to the various detectors located in front and after it.

This will most likely be a stepping stone towards the final computer-controlled code, yet should be simple enough to get some visible results fairly quick.

  Since the connector with the wires for optical detectors has been fixed to the connecting board, the control panel board had a corresponding connector installed, and wires placed for linking it to the Phidget 1018 interface. A second cable was assembled in order to link these 2 (photos 3 and 4).

  Finally the wiring plan for the layout itself has been entered in a Visio document (preview in photo 5). Holes cut in the foam underlying board are also present. The whole idea is to be able to successfully track a wire, since now there's information about its endpoints, its color and the tooltip entered (ShapeSheet->Comment). As for the control panel (preview in photo 6) - the wires that will be done in the future still have a black color, to differentiate from the ones already installed, that have been colored according to their real counter-parts.

  Tonight I've also connected the various power supplies and checked that everything works well. Last photo shows the temporary setup employed, complete with an USB hub, which was connected through 2 USB extender cables - just to be sure that the hub can be physically placed behind the layout - actually the spot where the control panel will be sitting, in a vertical position.

  What was unexpected was the sheer amount of time needed to complete this wiring part. Just tracking each and every cable on the layout itself and drawing the corresponding diagram took easily 30 work hours. Each 32-pin connector cable took more than 5 hours to build. What started as a very simple job ended taking much more that I would have ever expected - which makes me seriously think about DCC decoders for each signal, switch and other accessory in the future, given the wiring should mainly consist of 2 wires carrying the signals across. But for now - and this layout - things will stay the same. There are still a couple of  items to be purchased - namely some Phidget boards that will take care of additional optical detectors, switch feedback and switch operation; some D-Sub connectors; a small power supply for the optical detectors in order to stop using the current bulky one; and a few others.

More Electrics

Realized at one point that since there's no map of how each wire goes where, not to mention that some of the wires lost their purpose during the time since not all of them were marked - that it's gonna get complicated soon if this isn't rectified. So there have been quite a few hours over this months of mapping out what goes where. A Visio diagram was also employed, and each wire colored as it is on the layout, complete with tool-tip comments that show a wire's function when hovering over it.

Work was done to the electrical panel that will contain all the modules (Viessmann, Phidget, etc.) so I can finally move away from the wiring-in-a-box approach. 

Last but not least, since it turned out that quite a few wires will be required in the end, no less than 4 D-Sub connectors would be needed (37 pins/ connector, however because I'm using some 32-wire legacy cable, 5 of those pins will go unused). The required connectors, brackets and various other items were purchased;  so far a connecting cable was built, the original connecting board got modified so that it holds 2 connectors, and a new enclosure for a similar cassette plus the corresponding board were just finished today.

Precision Earth Test Patches

As stated previously, the precision scale recently bought was instrumental in creating a test board, with 8 patches of earth formula. This is simply a 1-cm thick foam board, on top of which one sheet of plaster cloth was applied - both to provide better grip for the zip texturing to come, and to replicate exactly the layout structure. The starting formula was the now classic 5 parts plaster, 1/5 parts burnt sienna dry pigment, 4/5 orange dry pigment. Each patch has a known ratio of blue ultramarine pigment, which was increased  in small doses against each one. For each patch, the procedure was similar - wet the spot with white glue, apply the corresponding formula with a tea strainer, leave to dry for 1 hour, then repeat again in the same location, then move on.

  After adding the determined weight of blue ultramarine dry pigment - usually around 0.04 grams - the whole formula would be thoroughly mixed in a "shaker" for 4 minutes, as to ensure a uniform outcome (the days when I would use a spoon to mix things are long since gone - since applying the resulting mix resulted in particles of the stronger pigment - then black - "shining" through the whole formula).

  As the last patch on the first test board was still not matching the medium earth color on the layout, I decided to extend the batch of tests on another test board. Photos 2 and 3 show the first test board and second one, respectively. The white spots on the edges of the patches represent white glue, migrating from the patch under work to the previous one(s), already finished. Not a big drawback since the colors can be matched like this with no problem. The 2nd board still needs to have one application over the 7th patch, and the last one completed.

  For both boards, the order of the patches if left to right on the top row, then right to left on the bottom row - so that the 1st one is on top left, while the 8th one always on the bottom left. 

  The percentages of blue ultramarine dry pigment is as follows: 1st test board - patch 1: 0%, patch 2: 0.1%, patch 3: 0.22%, patch 4: 0.43%, patch 5: 0.61%, patch 6: 0.9%, patch 7: 1.2%, patch 8: 1.6%. 2nd test board -patch 1: 1.8%, patch 2: 2.0%, patch 3: 2.2%, patch 4: 2.5%, patch 5: 2.8%, patch 6: 3.1%, patch 7: 3.3%, patch 8: 3.5% (patch 8 not visible in the photo at this time).

The last photo shows both boards alongside, just to get an idea of the color ranges in both.

Precision Scale

Even though I've revisited the earth formula here, I never really managed to make a true "formula" - one that could be replicated time after time, using precise measurement. As a result the various earth patches done so far on the layout vary in various degrees. Since I've been having a hard time matching colors with different batches lately, I've decided it's time to take things further and bought a precision scale. It can measure in increments as small as 1 milligram, so hopefully this will be good enough to replicate various dry pigment formulas over and over again. At 20 pounds, it's actually a good price - considering it actually has that 1 mg granularity observed after some testing. The photo shows this little device at work, while I was adding small amounts of ultramarine blue to the old earth formula (5 parts plaster, 1/5 parts burnt sienna, 4/5 orange). This has to do with a small test board made from a piece of foam and a sheet of plaster cloth applied on top - its role being that of sampling various combinations and writing down the various ratios involved. 

Why blue pigment instead of pure black one to make the formula slightly darker ? 2 reasons: the complementary color of the light brown-ish color that my earth formula has is actually blue, as seen here (a hue plus its complementary color will yield black in color theory when applied to pigments as stated here), secondly, I've never experienced this combination before (I've been adding only black pigment until now).