v.0.1.5: rebuild and bug fixes

I just finished building the version 0.1.5 machine.

Here’s what I’ve been working on during the past month and a half:

Electronics:

  • Fixed EAGLE routing flaws (thanks Dorkbot Chicago for a very timely EAGLE CAD class!)
  • Fixed part specification flaws (it turns out that the digital pots I originally used can’t handle much more than 8V, I was giving them 18V – oops!)
  • Built a completely new test machine from scratch, by hand (not as bad as I originally feared)
  • Started an arduino shield based design (using adafruit’s excellent protoshield as a starting point)
  • Started testing the MCP4912 DAC as a replacement for the dual 4911s, I’m currently using.
  • Switched from arduino duemilanove to freeduino/boarduino for physical design improvements (I’d like to use the UNO, but I’m waiting/hoping for improvements in the USB functionality of that board before switching).
  • Added a fast prototyping area for experiments.

Physical:

  • Stopped using magnets as fasteners for the scanning head – those were awful.
  • Built a completely new physical support with improved tripd geometry and stability.

Next up:

  • Redesign the X/Y signal pathway to use the full +/- 9V range and be flexible enough to handle +/- 18V via switch and/or gain adjust (I’m only using +/- 5V now, and it’s not flexible at all).
  • Redesign the transimpedance amp pathway to improve signal/noise ratio and gain.
  • Investigate alternative approach mechanism designs.

Reminder: I’ll be showing the ChemHackerSTM version 0.1.5 at the Armand Hammer Museum in LA on Saturday afternoon/evening as part of CRITTER Salon’s Enormous Microscopic Evening.

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Pining for the fjords

HELLLLOOOO POLLY!This project is not dead, it’s just pining for the fjords!

Actually, I’ve been up to my neck in:

  • rebuilding the circuit from scratch
  • debugging software
  • debugging hardware
  • redesigning circuitry

This is all stuff that is slow and relatively unglamorous.

I’ve been working frantically because I’ll be in LA next weekend showing the microscope at the Enormous Microscopic Evening at the Armand Hammer Museum in UCLA on November  6th at 4pm, and I’d really like to have version 0.2 ready for the exhibit.

I’ve learned a lot in the past month – notably that I had made a few poor design assumptions (now thankfully corrected).

Many thanks to everyone for being patient, everyone who has helped me with debugging and redesign, and to CRITTER salon for inviting me to the Enormous Microscopic Evening!

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STMs on a Plane: Prototype Electronics and Security Checkpoints

Before: in a cigar box

When I first mentioned I was going to demo the early prototype of the STM at the Open Science Summit, everyone who had actually seen the thing asked me (worriedly) how I was going to get it through the security checkpoints at the airport.

Looking for advice, I brought the prototype to Steve Y., the experienced head of security at my office, and asked what he thought I should do. “Well, what you have here doesn’t look great, but it’s not bad. Here’s what I’d do: put it in a nice box, put some official labels on there, put some kind of identifying label on there, and then send it through the X-ray machine alone. You’ll be fine.” With this pattern to follow, here’s what I did:

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