Electric Beginning

It’s a bit funny. I’ve welded professionally for 4 years; I’m pretty good at brazing and
fabrication in general. I’ve also soldered and repaired various electrical things from appliances
to automobiles. With that experience I entered into making the TouchDRO with a few assumptions.

  • My various skills would make board level soldering easy (partially true)
  • Because I bought the premade board from Yuri, hooking it up to my linear encoders would be
    easy. (partially true)
  • I would not have to buy the specialty crimpers and such because I am skilled with needle nose
    pliers (totally false)

I decided to buy the premade board from Yuri for the first Touch DRO install. Part of the
reasoning for that was to make the install easier but part of it was that it came with a faster
processor than the MSP430 Launchpad. I couldn’t use the Arduino board because it doesn’t support
Quadrature Encoders and one of my encoders has 1 micron resolution.

A 1 micron encoder counts 25,400 times per inch. It is possible that a slower processor might not
be able to keep up with the scale during rapid traversal. It is also quite possible that the slower
processor would have been fine but for the $40 price difference, I decided to go with the faster
processor and cooler looking board because I’m just that kind of a geek.

So I set about hooking up the TouchDRO board to the encoders on my mill. In general that means connecting power to the board and the board to the scales. Overall a pretty simple process but as usual there were a few complications. The DRO that I am replacing is an old Acu-Rite II  DRO. It uses military grade connectors that, while, not hard to find are quite expensive. I decided to standardize on DSub-9 connectors as they are common, inexpensive and come standard on many encoders. I also decided to solder headers to the DRO board and make wiring harnesses to connect the DSub-9 connectors to the board. This would allow me to easily adapt the DRO to fit a variety of scales which should be useful as this is kind of my “development rig”. So, at a high level, the process is:

  1. Modify encoders to use DSub-9 connectors instead of milspec
  2. Make DSub9->milspec adapters so that I can still use the old DRO
  3. Solder headers to TouchDRO board
  4. Make wiring harnesses to connect DSub9 sockets to board headers

I’ll cover the details of these and more in a following post.



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