JYE Tech DSO138 Oscilloscope

DSO138 oscilloscope, along with the FG085 function generator, could form the basis of an entry-level electronics bench:

JYE Tech - FG085 Fn Gen - DS138 Oscilloscope
JYE Tech – FG085 Fn Gen – DS138 Oscilloscope

Neither of the kits require advanced assembly skills, but neophytes would definitely benefit from somebody who could guide them through the rough spots. In fact, JYE Tech comped me the acrylic scope case in return for the defects on the function generator PCB: thanks!

Just to rub it in, I suppose, one of the 2 mm nuts required to assemble the case missed the threading operation:

Unthreaded 2 mm nut
Unthreaded 2 mm nut

Took me a while to figure out why I couldn’t make the screw work. No big deal if you’ve got stuff, but it’d be a showstopper for a newbie.

Anyhow, the kit went together smoothly and powered right up:

JYE Tech DSO138 oscilloscope - 1 kHz sine
JYE Tech DSO138 oscilloscope – 1 kHz sine

The trace arithmetic functions work well enough:

DSO138 oscilloscope screen - trace data
DSO138 oscilloscope screen – trace data

The triggering seems finicky and setting the level sometimes moves the trace baseline, although that may be due to my fat-fingering the controls.

The front end is noisy, the bandwidth limited, the screen is small, and you can’t capture / export traces to your PC / cloud / whatever.

It’s an OK starter scope and you’ll shortly realize why you need a dual-trace scope…

Makergear M2 Updates: New Filament Drive Gear with Marlin 1.1.0-RC5

Confronted with a puzzling failure, I decided to perform some long-delayed tweaking…

The folks at Makergear send me (and several others) a new filament drive gear for testing. It has smaller splines / teeth and produces a much finer mark on the filament:

Filament Drive Gear Indentations
Filament Drive Gear Indentations

The obvious stripped section on the right comes from finger-fumbling an absurdly large extrusion distance (something like, mmm, 1450 mm) with a high extrusion speed. Not the fault of the drive gear, that’s for sure!

I remeasured the actual filament length extruded to recompute Marlin’s STEPSPERMM configuration constant. After rediscovering the awkward fact that, when you change that value with an M92 command, Marlin doesn’t recompute the current extruder position, so the next manual extrusion will move a random amount of filament in a random direction, the value eventually converged to 476.9 steps/mm.

I intended to put the M92 in Slic3r’s startup G-Code, but the prospect of random extrusions suggested that now was a great time to update the firmware; again demonstrating that no good idea goes unpunished.

The most recent Marlin version, 1.1.0-RC5 (clearly labeled “Not for production use – use with caution!”), had been released a few hours earlier, so I fetched that and tweaked the configuration files as before.

The firmware now includes thermal runaway / thermistor failure protection for both the bed and hot end. Increasing the two THERMAL_PROTECTION hysteresis values to 6 °C seems to work well.

It also includes a CONTROLLERFAN output that can go active when any stepper is enabled, then off after predetermined time. Setting that to Pin 6 and 30 seconds means the whining fan (it’s a ball bearing replacement in an aerodynamically poor location) in the control box goes off when it’s not needed.

Bumping DEFAULT_STEPPER_DEACTIVE_TIME to 600 seconds means the motors don’t time out while waiting for the platform to reach operating temperature.

Increasing the HOMING_FEEDRATE for the Z-axis to 60*60 mm/min causes it to whack the lever a bit harder and overtravel slightly more. The Z Offset ended up at -2.15 mm, based on the calibration cubes below.

Running a PID calibration on the V4 hot end produced slightly different values: P=17.41, I=1.02, D=74.44. Hardcoding those into the config file does not override the values already stored in EEPROM: you must manually set them with M301, then use M500 to program the EEPROM.

A few Calibration Box iterations settled settled the Extrusion Multiplier at a convenient 1.00 with the new drive gear:

Thinwall hollow boxes - drive gear calibration
Thinwall hollow boxes – drive gear calibration

All in all, that whole process went much more smoothly than I expected.

The config files as GitHub gists:

Sony NP-BX1 Batteries: Wasabi vs. SterlingTEK

The combined results of the six most recent NP-BX1 batteries for my Sony HDR-AS30V helmet camera:

Sony NP-BX1 - Wasabi FG - STK ABCD - Ah scale - 2015-11-03
Sony NP-BX1 – Wasabi FG – STK ABCD – Ah scale – 2015-11-03

One might reasonably conclude all six came from the same factory; the STK B battery looks like a dud. The two replacement batteries from STK performed slightly better than the first pair.

The Wasabi and SterlingTEK batteries all carry a 1600 mA·h rating that’s far in excess of their actual 1000-ish mA·h performance. If they were advertised as 1.0 A·h batteries, they’d meet their specifications (for small values of “meet”), but nobody would buy a second-tier battery with less capacity than the Sony OEM battery’s 1.24 A·h.

If you rummage around in previous posts, I did verify that battery capacity does increase with decreasing test current, but definitely not by the 60% needed to reach 1600 mA·h.

Because most devices these days operate at constant power from a boost supply, presenting the results against a watt·hour scale would make sense:

Sony NP-BX1 - Wasabi FG - STK ABCD - Wh scale - 2015-11-03
Sony NP-BX1 – Wasabi FG – STK ABCD – Wh scale – 2015-11-03

That doesn’t change the overall rankings, such as they are, but does include the effect of higher terminal voltage.

The claimed specifications:

  • Sony OEM – 4.5 W·h
  • Wasabi – 5.7 W·h
  • STK – 5.9 W·h

The Sony battery actually performed about as advertised, but the others fall short on this scale, too.

They should survive for hour-long rides with the GPS tracker turned off, which is about as much as I want to ride at once. I’ll eventually autopsy the STK B battery, which won’t last all that long.

Credit where credit is due: after I sent the first test results to STK, they sent a pair of replacement batteries and, based on the second test results, refunded the entire purchase price. I’m reluctant to give a five-star rating for customer service, because shipping mis-advertised products should carry a zero-star rating.

Wasabi NB-5L: Underperformers

Based on the poor performance of the NB-5L batteries I bought from Blue Nook, they sent me three NB-5L batteries from a fresh batch (date code BNI13) and I ran them through the same discharge test:

Canon NB-5L - OEM Wasabi - 2014-10-29
Canon NB-5L – OEM Wasabi – 2014-10-29

The red line off to the far right is the three year old Canon OEM battery, which remains far and away the best battery at 1 A·h.

The previous cells (BNF27) produced the three scattered traces with the lowest initial voltages, ending around 0.8 A·h.

The new cells (BNI13) produced the three tightly clustered traces. They have a higher initial voltage than the OEM cell, but much lower total capacity (about 0.75 A·h).

These batteries obviously don’t come close to their 1400 mA·h rating. The capacity depends on the load current, but I’m using 500 mA because that’s close to the camera’s drain; the results should correlate reasonably well with actual use.

The higher voltage from the new batteries will produce a longer runtime than the previous duds, but their total capacity is lower and they’re still no match for the old Canon OEM battery.

The new ones start out very similar to each other, but the previous batch hasn’t aged well on their shelf. If the date codes mean what I think, all of these batteries will fail quickly.

All that’s quite disappointing, because their NP-BX1 batteries for the Sony camera turned out quite well. The date codes all have the same format and typography, so I think they come from the same factory.

For whatever it’s worth, I think the date coding works like this:

  • B – factory? shift? OEM? Blue Nook?
  • M – last two digits of year: M=13, N=14
  • K – month: F=6, I=9, K=11
  • 20 – day 

For the four batteries / lots I have on hand:

  • BMK20 = 2013 Nov 20 – NP-BX1 bought in early 2014
  • BNI18 = 2014 Sep 18 – NP-BX1 bought in October – new lot
  • BNF27 = 2014 Jun 27 – NB-5L bought in October – old lot
  • BNI13 = 2014 Sep 13 – NB-5L supplied in late October – new lot

So it goes.

Improved M2 Heated Build Platform: First Light

Although the M2’s heated build platform works well enough, somebody who knows what he’s doing (you know who you are: thanks!) sent me an improved version. It’s a PCB heater, laid out to compensate for the usual edge cooling, firmly attached to a tempered glass plate with genuine 3M thermally conductive tape:

Improved M2 HBP - test setup
Improved M2 HBP – test setup

They designed the heater around the 30 VDC power supply used in their other equipment. Although I had high moderate hopes that a boost power supply would convert the 24 V supply I already had for the stepper driver bricks into the 30 V for the heater, it was not to be. So there’s a 36 V 9.7 A 350 W supply arcing around the planet that (I think) should work better: adjust the voltage down as far as it’ll go, soak up another few volts in the solid-state relay, and Things Should Be Close Enough to 30 V. One can buy a genuine 30 V supply, but it costs surprisingly more than either 24 V or 36 V supplies on the surplus / eBay market and won’t really provide the proper voltage without upward tweaking anyway.

I replaced their standard 0.156 inch square terminals with Anderson Powerpoles, soldered a length of shielded cable to the 100 kΩ thermistor pads, and gimmicked up a connection to the 24 V supply; it delivered 23.7 V at the PCB terminals. The thermistor is 100 kΩ at 25 °C and 11.4 kΩ at 77 °C. The PCB heater is 5.9 Ω at 25 °C and 7.3 Ω at 77 °C; it dissipates 77 W at 77 °C (no, that’s not a typo).

The ultimate temperature looks to be about 90 °C with a 24 V supply, which isn’t quite enough for ABS (which I’m not using in the M2 right now, but probably will eventually). The time constant, assuming the 1-e-1 point is 66 °C, works out to about 9 minutes; it’ll be up to final temperature in half an hour. Those numbers aren’t quite as accurate as one might wish, because the heater power drops as the temperature rises and the copper resistance increases.

A 30 V supply would dissipate 120 W at 77 °C and rumor has it that the ultimate temperature is around 125 °C, which would be fine for ABS. Goosing the power a bit would produce more heat, but I’v been running the Thing-O-Matic at 110 °C and that’s good enough. More power, of course, gets it to the temperature setpoint faster, which is probably a Very Good Thing.

Obviously, you need PWM to control the temperature; given a 9 minute time constant, a bang-bang controller will work perfectly well.

The original data, including the thermistor resistance after I got my act together, plus a cute little temperature-vs-time graph:

Improved M2 HBP - 24 V supply
Improved M2 HBP – 24 V supply

The colored flyspecks are part of the paper; I salvaged a stack of fancy menu cards from a trash can and padded them up as geek scratch paper.

The Embedded PC’s ISA Bus: Firmware, Gadgets, and Practical Tricks — Unleashed

ISA Bus Book - Front Cover
ISA Bus Book - Front Cover

A long time ago, in a universe far away, I wrote a book that (barely) catapulted me into the ranks of the thousandaires. Time passes, companies get sold / fail / merge / get bought, and eventually the final owners decided to remainder the book; the last royalty check I recall was for $2.88.

Anyhow, now that it’s discontinued and just as dead as the ISA bus, I own the copyright again and can do this:

They’re both ZIP files, disguised as ODT files so WordPress will handle them. Just rename them to get rid of the ODT extension, unzip, and you’re good to go. Note, however, that I do retain the copyright, so if you (intend to) make money off them, be sure to tell me how that works for you.

The big ZIP has the original pages laid out for printing, crop marks and all, so this is not as wonderful a deal as it might first appear. The little ZIP has the files from the diskette, which was unreadable right from the start.

Words cannot begin to describe how ugly that front cover really is, but Steve’s encomium still makes me smile.

The text and layout is firmly locked inside Adobe Framemaker files, where it may sleep soundly forever. The only way I can imagine to get it back into editable form would be to install Windows 98 in a VM, install Framemaker, load up the original files, and export them into some non-proprietary format. Yeah, like that would work, even if I had the motivation.

If you prefer a dead-tree version, they’re dirt cheap from the usual used-book sources. Search for ISBN 1-57398-017-X (yes, X) and you’ll get pretty close.

Or, seeing as how I just touched the carton of books I’ve been toting all these years, send me $25 (I’m easy to find; if all else fails, look up my amateur callsign in the FCC database) and get an autographed copy direct from the source. Who knows? It might be worth something some day…

The back cover has some useful info:

ISA Bus Book - Back Cover
ISA Bus Book - Back Cover