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Posts from — May 2011

The Connector Addict?

I love the Pen Addict’s slogan: There are worse addictions…..right?

I’m not a connector addict, although I do like trying out new connectors.  Partly it’s because I haven’t found the ideal connector system (or systems; I often want some variety so that the same connector type isn’t used for a variety of incompatible uses, and thus you have to be careful where you plug a connector in).

But I still enjoy receiving the occasional Mouser order with some new connectors.  So along with an order for some MDR connectors for my Copley Accelnets, I included connectors I haven’t tried such as:

  • Kycon USB B high retention force connector.  The big feature: minimum removal force is increased from 10N (standard USB) to 15N.  I like them; USB plugs come out too easily, but this connector makes it a lot harder for a USB cable to become accidentally unplugged.
  • Amphenol USB A locking connector.  The big feature: the connector has a locking tab that grabs onto the little square holes on a USB A-type plug.  That’s even better than the Kycon: it takes over 95N to separate the plug from the jack without unlocking.
  • TE/AMP MTE connector.  Nice, affordable IDC connectors, except you need really expensive tooling to use them easily.
  • Molex Micro-Fit Jr 3.0mm BMI.  I wanted to check out the blind mate version of the Micro-Fit; I’m still not a Micro-Fit fan.
  • Phoenix PST 1.3/8-LV-5.0 header with shroud.  The shroud provides polarization.  The Phoenix PST headers and PT terminal block plugs are a very affordable removable terminal block system.
    • One gotcha: you have to use the shrouded headers with the PT 2.5 series (e.g. PT 2.5/8-PVH-5.0) not the 1.5 series (e.g. PT 1.5/8-PVH-5.0).
  • Phoenix ST-Combi connector and ST-Twin terminal block.  I’m looking at using these for DC power distribution.

May 23, 2011   No Comments

Autodesk 123D MCAD and PCB Models

Autodesk just released the beta version of the 123D 3D mechanical CAD program.  It’s meant for hobbyists, but Autodesk surprised me by including both STEP file import and export.  (Free or low cost commercial CAD programs almost always don’t include free STEP file export).

123D is the standalone version of Inventor Fusion, so it is a direct modeler (not a history based like SolidWorks or Alibre).  So put together free, easier to use (direct modeling), and STEP file import/export, and it should work great for creating 3D PCB models.  There could be some problems, such as assembly limitations (such as a low maximum number of parts), or the EULA (so far the 123D End User License Agreement appears to be the standard Autodesk one, with no mentions of restrictions on commercial use).

I haven’t been able to check out 123D’s PCB prowess yet because I haven’t been able to get it to start successfully.  I’ll give it another try in a while.

May 22, 2011   No Comments

Analog Pranks

Pretty funny post over at Paul Rako’s Anablog on pranks, starring analog chip designers.

May 11, 2011   No Comments

My Toolbox — Oscilloscope

Fluke 196 with Pelican Case

Fluke 196 with Pelican Case

Why do I have an oscilloscope?  The real answer is that scopes are cool, and many years ago, I couldn’t resist when Fry’s had Fluke Scopemeters on sale — at 50% off!  So I own a 100MHz dual trace Fluke 196 Scopemeter.  Later I bought the yellow the Pelican case for it; the two are a great combination.

Since software ties everything together, I’m also the “systems” guy, and thus I should be able to troubleshoot the entire machine.  I do use my multi-meter much more than my scope, but the oscilloscope is essential when troubleshooting encoders, hall sensors, and the occasional electrical glitch which won’t show up on a DMM.

I’ve used other scopes, such as the Tek THS720 handheld, the Tek TDS 210 desktop, Tek analog scopes, and a Heathkit analog scope.  Recently, I participated in a hands-on demo of the new Rhode and Schwartz RTO1014 1GHZ oscilloscope.  It’s quite impressive, even intimidating at first, with all the buttons and things it can do.  Fortunately, such high powered scopes aren’t needed for typical factory troubleshooting; a dual channel, 20-100MHz real time digital does fine most of the time.

There is uncommon feature that’s really handy: isolated channels (each channel’s ground is isolated from the others).  With a typical dual channel scope such as the TDS 210, I can only view one differential encoder signal (channel 1 probe on A+ signal, channel 2 on A- signal, display mode set to combine channels).  But with a dual isolated channels, I can view two differential signals (channel 1 probe on A+, channel 1 ground on A-, channel 2 probe on B+, channel 2 ground on B-).

Hand-held scopes, such as the Fluke 196 and Tek THS 720, typically have isolated channels, along with ruggedness, battery power, small size, and a hefty price tag.  However, a 4 channel desktop scope is often cheaper than a 2 channel isolated channel scope.

I once spent a lot of extra time because I was too enamored with isolated channels.  The system had a servo motor with the differential encoder output split, with one set of signals going to a motion controller and the other set going to a custom board.  The motion controller was counting correctly, but the custom board wasn’t.

I set up my Fluke 196 to look at the differential signals.  The B+/B- signal did look smaller (less voltage swing) than the A+/A- signal, but it had to be OK because the motion controller was picking it up.  So I started swapping out components — and kept getting the same problem.

I figured it out when I looked at each signal (A+, A-, B+, B-) individually; the B- signal was dead (because of a broken wire in the cable from the motor).  The motion controller worked because it was less sensitive, managing to count the smaller transitions.  My lesson learned: check everything, and don’t make unsupported assumptions.

May 10, 2011   3 Comments

Japantown Pens

Recently I visited San Francisco’s Japantown, and couldn’t resist picking up even more Japanese pens…so here’s what I bought along with some brief commentary (pens described in order from left to right).

All of these pens were made in Japan, although some of the Sailor 0.38 pens (in colors I didn’t buy) were made in Thailand.

Pens from Kinokuniya (Maido) Stationery

Pens from Kinokuniya (Maido) Stationery

Pens from Kinokuniya Stationery (operated by Maido Stationery)

  • Uni-ball Signo DX 0.38 Light Blue gel pen.  I love my burgandy red Signo DX, so I had to pick up another DX.  This one is also very sweet.
  • Zebra Surari 0.5 Blue emulsion ink pen.  In the past, I haven’t been impressed with Zebra’s pens, but the Surari’s are sweet; I think I like them better than the Uni Jetstream or Pentel Energel.  The 0.5 color range is restricted, but I do like this shade of blue.
  • Zebra Surari 0.7 Purple emulsion ink pen.  Zebra has an interesting range of colors for their 0.7 mm Surari’s, so I went for purple.  I like this pen.
  • Pilot Petit 1 fountain pen.  I’ve been wanting to try a cheap fountain pen, and after extensive testing at Maido, I decided that the Petit 1 is substantially smoother than the Platinum Preppy.  I like the older style better than the new Petit 1.
  • Pilot Petit ink (black and red).
  • Pilot Petit 3 brush pen (solid tip).  I bought this because it’s cheap, cute, refillable, and uses the same refills as the Petit 1.
  • Mitsubishi (Uni-ball) PFK-206 brush pen (solid tip).  It has a fine tip and broad tip.
Pens from Ichiban Kan

Pens from Ichiban Kan

Pens from Ichiban Kan

  • Kuretake brush pen (bristle tip).  I love this playing with this pen, even though I’m not artistic; it’s a steal at $1.75, and I should’ve bought more.
  • Uni-ball PIN 01 pen.  I’m not a big fan of felt tip / marker style pens for writing, but I’m interesting in comparing it to the Sakura Pigma Micron.
  • Uni-ball Noble Metal Gold pen.  I wanted to check out the Sakura Gelly Roll competition.
Pens from Daiso Japan

Pens from Daiso Japan

Pens from Daiso Japan

  • Sailor 0.38 Light Blue gel pen.  It writes well, color is similar to the Signo DX, automatically retracts when put into shirt pocket, but it’s kind of ugly.  Even though I like retractable pens, I think I’d take the Signo DX over this pen.
  • Zebra brush pen (solid tip).

May 10, 2011   2 Comments