Archive for January, 2016

Research: Value Multimeters for Micro Electronics

Sunday, January 31st, 2016

I did a bunch of homework on Multimeters. Here’s a good beginners guide.

And here’s a more technical guide to buying a good meter.

There’s a ton of great information packed in that video, but unfortunately dude is an experienced no-compromise electrical engineer, so his minimum recommendations cost around $100. And actually, his advice is correct if you have any interest in doing any real electronics work (Cars, AC devices, or really anything more than microcontrollers).

But for me, I’m only really interested in micro electronics. Computers and small devices that draw around 5v or 3.3v (*maybe* as much as 12v), and only a few Amperes. I.e. things like the Raspbery Pi, Arduino’s, old PCs, old video game consoles, etc.

Pro gear is ideal, but I’m not a pro. I do electronics to learn, not to do anything important. Still, I highly recommend that video because it’s packed with experience.

In my research, I chose a Chinese manufacturer that EEVblog doesn’t like, mainly because they compromise (but when I get to talking about Power Supplies, you’ll see other manufacturers compromise WAY more). Again, this dude is a real engineer, and he needs a reliable device that can deal with high voltages (outside the scope of my hobby).

The devices I’ve chosen I believe are ideal for me, and are capable of some higher end work, with the understanding that extra care must be taken when dealing outside the 3.3-5v range, plugging in to the wall directly, etc.

Junk Device: Generic A830L

Cost: $3-$6

junkmeter

To be honest, the product code isn’t even that useful, but there a bunch to be found.

This meter is junk. It’s one of 2 meters that hover around the $3 price range. I’ve included it just to list the cons.

Pros

  • It beeps
  • Resistance tester
  • Diode tester
  • Transistor tester (hFE) *
  • Backlight *
  • Kickstand

Only two (*) redeeming features, but that doesn’t mean they’re good.

Cons

  • Manual range!
  • Poor precision options
  • Combined Voltage and Ampere plug (Unsafe)
  • Manual hold button (not automatic, need a free hand to use it)
  • No Capacitor tester
  • No Oscillator tester
  • No Duty Cycle tester
  • No Temperature tester
  • Low quality connectors
  • Unfused 10A line
  • May have bad leads (order some better leads)
  • 4 digits of precision (????)
  • Kickstand might break
  • Don’t plug in to AC Mains

Frankly, you might spend more money on the 9V battery.

We can do better!!

Value Low End Device: UNI-T UT-136B

Cost: ~$16
Manual: http://www.uni-trend.com/uploads/soft/wanyongbiao/UT136ABCD-Manual-en.pdf

unit-ut136b

After doing my research, to me this appears to be the minimum quality meter you should own. I currently own 2 junk meters I bought from Radio Shack, and I’m pretty sure I spent $60+ on the one because it was “automatic”. What a difference a decade makes.

Pros

  • Separate Voltage and Ampere lines (Safety!)
  • Micro Ampere and Milliampere measurements
  • Automatic decimal place (manual isn’t cool)
  • Good+Fast beeper (lagged sound is really stupid)
  • Resistance tester
  • Diode tester
  • Capacitor tester
  • Oscillator Hz tester
  • Square Wave Duty Cycle tester
  • Some sort of Sine Wave feature (I forget why this is useful, maybe AC power *shrug*)
  • Fused 10A line
  • Kickstand…
  • Support for sleeved banana connectors on leads

Cons

  • Manual hold button (not automatic, need a free hand to use)
  • Some Capacitor testers have a socket for caps, but not this one
  • Not the best quality banana connectors
  • May have bad leads (order some better leads)
  • Fuses are not best quality
  • 4 digits of precision (4000)
  • No transistor tester (not that important, but some devices do this)
  • Kickstand might break
  • No backlight
  • No Temperature tester (UT136C model replaces a feature with temperature)

Here’s a comparison versus a better meter, and while it’s not perfect, it does keep up where it counts.

And more specific breakdown.

I’ve ordered one of these. I think it’s adequate for my needs, but of course I want one of these:

Value High End Device: UNI-T UT-61E

Cost: ~$47
Manual: http://uni-trend.com/manual2/UT61English.pdf

UNIT-UT61E

It includes a few accessories.

accessory

Pros

  • Separate Voltage and Ampere lines (Safety!)
  • Micro Ampere and Milliampere measurements
  • Automatic display with voltage range graph (I forget the name)
  • 5 digits of precision (22000)
  • 6 second automatic hold (not truly automatic, but 6 seconds works)
  • Supports removing the delta of the lead resistance (RMS?)
  • Track and toggle the Peak (Min/Max) Levels
  • Good+Fast beeper (lagged sound is really stupid)
  • Resistance tester
  • Diode tester
  • Capacitor tester with socket accessory
  • Oscillator Hz tester
  • Square Wave Duty Cycle tester
  • PC Connectivity via SERIAL
  • Fused 10A line
  • Kickstand…
  • Support for sleeved banana connectors on leads

Cons

  • It occasionally spikes (rarely)
  • May have bad leads (order some better leads)
  • Fuses are better than the other model, but may not be the best
  • Not the best quality banana connectors
  • No transistor tester (not that important, but some devices do this)
  • Kickstand might break
  • No backlight
  • No Temperature tester (UT-61B and UT-61C models replaces features with temperature)

You can find a very in-depth 4 part video series here that tests and even calibrates the device:

And a comparison of other meters in the same quality range (albeit higher cost).

It’s not his favourite, but admits that it’s ideal for what I describe as my usage scenario (plus it has very high resolution).

EEVblog hates it because of the quality compromises.

Anything better?

A better device would have the following:

  • Backlight
  • Fast Display Refresh Rate
  • Good/Sharp Leads
  • Better Fuses
  • Better Banana Connectors
  • Rubberized Casing (to help when you drop on a hard surface)
  • Better accuracy and precision
  • Clean levels (no false spikes, likely a software bug)
  • Temperature tester
  • Safer lifetime on AC mains

I’m nowhere near experienced enough to take advantage of a better meter though. Better stuff costs more (Over $100), and as a hobbiest, I don’t need it. Because I don’t have pro gear, there will be times I shouldn’t trust my meter (i.e. occasional spikes, get a 2nd opinion), but it will be more than enough for what I do.

From what I’ve seen, in the price range (~$50), there is nothing better.

Wrapup

At the time of this post I’ve ordered both the junk tester (A830L) and the UNI-T UT-136B. Why the junk? As a backup mainly (or worst case, parts). The meters I have today are really bad.

mycrappymeters

The Radio Shack meter, while automatic, is lacking a lot of useful features like a beeper. Even the junk meter has a beeper!

Some weeks ago I ordered one of those temperature guns (a cheap one), so I’m hoping that’s enough for temperature measurement.

Things from China take weeks, even months to arrive. It’s Chinese New Year, so there’s at least 2 extra weeks to wait, so I probably wont see any of this until mid to late March.

At this time I have *NOT* purchased the UNI-T UT-61E, but you might say it’s on my xmas list. 🙂

Using a PICkit2 on Linux

Tuesday, January 26th, 2016

Summary.

The PICkit connector is 6 pins, but the last pin is the Auxiliary pin.

This pin doesn’t seem to be used that often. The setup could be simplified by snipping the 6th pin.

https://www.kickstarter.com/projects/1897710270/digirule-the-interactive-binary-ruler/posts/1444571

http://www.bradsprojects.com/the-digirule/

After looking in to it, it seems the PICkit 2 is discontinued.

http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=DV164121

There isn’t even a download link there for the software.

I found the source code a rather backwards way. The link is here:

http://ww1.microchip.com/downloads/en/DeviceDoc/PICkit2_PK2CMD_WIN32_SourceV1-21_RC1.zip

A newer device file is here (just overwrite):

http://www.microchip.com/forums/download.axd?file=0;749972

I discovered it by grabbing this package, opening the PKGBUILD file. As it turns out, they still have the files on their website, they’re just not linked publicly.

I’m not entirely convinced this is the latest version, but it is what I found.

Build like so.

That should output this:

You can then program a hex file. Before you start, figure out the PIC chip you’re programming, the name of your hex file, and adjust this accordingly.

References:

http://hsblog.mexchip.com/en/2010/07/how-to-use-the-pickit2-programmer-under-linux/
http://curuxa.org/en/Program_PICs_with_a_PICkit2_using_the_command_line_on_Linux
http://www.waveguide.se/?article=programming-pics-using-the-pickit2-and-pk2cmd
http://askubuntu.com/questions/434948/install-archlinux-package-pk2cmd-plus-on-ubuntu-12-04-64bit