Sunday, May 31, 2015

Crazy Clock: Reverse engineering the Quartex movement

The Crazy Clock is a pretty good product, but what it needs to take it to the next level is a manufacturing partner to actually make movements with the crazy clock built in in place of the boring controllers that are normally used.

So far, I have been taking Quartex Q-80 movements apart, cutting the traces on the board, and wiring the crazy clock into place. That works acceptably, but the retrofit operation is very fiddly. There has to be a better way.

So I sat down and attempted this evening to reverse engineer their enclosure and board.

The gear assembly with the original controller attached

The space in the chassis where the assembly sits

Here's what we have to work with. The metal contacts from the battery holder at the top (in this picture) of the chassis mate with the contact patches at the bottom of the board. The large "hump" at the bottom right mates with the large square cutout in the board. The hole at the bottom left mates with the pin that comes through the board at the top left. The other holes and slots in the board accommodate pins and protrusions from the gear case, and the single screw that holds the assembly together. In the upper right corner of the chassis and to the left of the board space at center, there are two small spacing pins that are meant to rest against the gear case assembly.

The board

The board can be removed from the gear train simply by removing the single screw at the bottom between the contact patches and desoldering the two coil pins. The board simply lifts off the gear case. Note that the screw holds the two halves of the gear case together. I made no attempt to open the gear case, as it's entirely likely that the gears would be difficult to reassemble if they fall out of place. Since there's no need to access the gears, there's only a downside to attempting to get in there.

Carefully measuring the location of the features of the original board led to this design (seen here as rendered by OSHPark):

Note that the space at the bottom left is dead space to accommodate the spacing pin that's in the upper right corner (as shown) of the chassis. Immediately to the right of the ISP header is the cut-out. One of the goals of the design is to make sure that the ISP header is available for programming even with the board assembled in the movement. That will make reprogramming it easy (or at least easier).

There are, at this point, still some important unknowns around the physical tolerances - particularly in terms of depth. The original board is thinner than the boards from OSHPark, and the original board had only the bonded and potted chip rather than a collection of traditional surface mount parts. I did, however, hold an original crazy clock board in place in the bottom of the chassis and it did appear to be flush with the spacing pins, which suggests that it will work. No way to know for sure until the prototypes come back in a week.

If this works, then it will make the process of retrofitting the Quartex movements much easier. The risk, however, is that if I order a ton of them and then Quartex redesigns their movements, I'll have a completely worthless inventory.

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