Advertisements

Equipping an Electronics Lab on the Cheap

I described how to take advantage of Living in the Golden Age of Electronic Making for HVOpen:

Although you don’t get my patter, perhaps the linkies will make up for the silence:

I filled a table with Show-n-Tell widgets and a good time was had by all: hardly anybody fell asleep.

[Update: The talk addressed folks interested in starting out with electronic projects who have no test equipment at all. The choices would be different for other audiences, but … boat anchors aren’t appropriate here.]

Advertisements
  1. #1 by Keith Ward on 2019-05-03 - 09:25

    +1 – Good stuff Ed, folks should appreciate this.

    • #2 by Ed on 2019-05-05 - 18:10

      Or, hey, they can use me as a Bad Example of somebody being wrong on the Internet. Ought to get some discussion going, anyhow!

  2. #3 by Hexley Ball on 2019-05-03 - 13:44

    Lots of distilled wisdom here. Nicely (Nisley?) done. :-)

    But….there are some things I have to comment on.

    First, the 3rd debugging rule “Quit thinking and look” is, IMHO, inappropriate advice to a newcomer. I prefer this quote “No problem can withstand the assault of sustained thinking.” from that closet electrical engineer, Voltaire. Really, I have seen many times someone who is troubleshooting get mesmerized by the debugging instrument (scope, logic analyzer, code debugger, etc.) and go in circles chasing a symptom rather than stepping back, analyzing the situation, and then going after the root cause. So I think that a better debugging rule for the newcomer would be this quote from that other well-known philosopher, Thomas J Watson: “THINK!”.

    Second, I’m not sure that the JYETech scope is “better than no scope at all”. There is nothing as frustrating as mastering a skill while using a low-quality tool. You, as a grizzled vet, know how to cope with that scope’s limitations. But a newcomer might just get confused and discouraged. So maybe this is time for an exception to the “no boat anchors” rule. An old Tek 2215 or similar scope can be had on eBay or Craigslist for not much more than the JYETech scope, and will be much better to learn on, it seems to me.

    Speaking of quality tools, I hope your verbal accompaniment to slide 39 expanded quite a bit on the bullet “(Un)soldering irons and supplies” — if there were ever a place to splurge in setting up a lab-on-the-cheap, it would have to be the soldering gear. Temperature-controlled soldering station ftw,

    On the topic of color coding, you presented the wiring conventions very clearly, so your students should be able to wire their own gear properly. It might be worth warning them STRONGLY, though, that other builders may not be as well-trained, so they should always verify wiring polarity and not assume that red is always positive and black negative. They could even take a look at your entry https://softsolder.com/?s=tattoo+power+supply to see how the old master himself got fooled once. :-)

    Finally, the QEX article describes some issues that buyers of the ‘6600 signal generator should be aware of. Newcomers probably don’t care about jitter, or about limited output swing at high frequencies, but the issues around grounding the input AC line cord could be important. Of course, the QEX article describes the FeelTech FY-6600, so the JDS version may or may not have the same issues, I suppose.

    Anyway, great job giving these newcomers a leg up. They are lucky to have you as a mentor.

    • #4 by Ed on 2019-05-05 - 18:09

      Dang, would that I had a transcript …

      Part of the problem with debugging electronics, particularly at the start, is you can’t assume anything. Measure the voltages, examine the waveforms, compare with what’s expected: pondering the (possibly incorrect) schematic for days won’t get you past a wiring blunder made obvious by one voltmeter measurement.

      The DSO150 breaks the barrier of not being able to see simple waveforms, because beginners simply can’t / won’t drop $300 on a scope. Starting with a crappy scope for pocket change is definitely a step up from having no scope at all. It has the advantage of working pretty much like a real scope, with an actual knob, so it’s much better than the pushbutton alternatives.

      The entire “Building Things” page got a handwaving run-through, with pointers to Squidwrench for soldering intros and suchlike. I should probably do another talk on tools & suchlike for SqWr; one of these days.

      As far as color coding goes, after I explained about electrical wiring colors, we spent quite a while pondering the outlet box. Black evidently connects the neutral pins to the safety ground pins, with a bonus green wire going off to who-knows-where, and white evidently goes to the hot pins. Moral: trust, but verify!

      Even I don’t care nearly enough about (possible) oscillator phase noise in the function generator for my simple needs, so newbies certainly won’t and it’s all good. FWIW, the one I have runs from a 5 V 2 A wall wart, so they’ve finessed the entire power supply issue by floating the innards; one may (un)safely assume negligible HV isolation, of course.

      It was a fun talk, even if I left out more than I said! [grin]

      • #5 by John on 2019-05-06 - 14:15

        For me the primary hardware debugging problem has always been that I didn’t do what I thought I did, and I simply don’t realize that. That’s one place that measuring saves a lot of time, because it says unarguably that no matter how convinced I am that the output of my 3.3 volt regulator is 3.3 volts, when it’s actually 2.1V and nothing works, that’s where I have to start my looking.

        • #6 by Ed on 2019-05-07 - 07:30

          Those are the hardest errors to find, because you (well, I) know what should be happening and simply don’t see evidence to the contrary. A flat line on a scope, where a sine wave should be, can be rather persuasive, though. [grin]

  3. #7 by Mikey on 2019-05-06 - 02:37

    You had better verify verify verify your outlet box! In US black and red are hot and white is neutral (return, common). White connects to green safety ground only in the main (first) breaker/fuse box and that junction connects to your external ground where your RF grounds should bond too, also.

    Always loved your articles in CC. I’ll wave if I see you in Dayton… if I get to go…

    • #8 by Ed on 2019-05-06 - 08:20

      Fortunately for all of us, electrons don’t care about the insulation colors! [grin]

      Many years ago, I was in Dayton on biz, made it to the Wright-Patterson museum, and stood outdoors under the last remaining XB-70A watching rain drip through the wings … still gives me chills. Haven’t been back since, though.

Spam comments always vanish. Comment moderation may cause a delay.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s