The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Electronics Workbench

Electrical & Electronic gadgets

60 kHz Quartz Tuning Fork Resonator Data

The first batch of 25 resonators:

60 kHz TF26 resonators – Batch 1 data

The second batch from the same eBay source arrived a few months later and I finally got around to measuring them:

60 kHz TF26 resonators – Batch 2 data

A dot of green Sharpie on the AT26 cans identifies the second batch:

60 kHz TF26 resonators – Batch 2 marking

The alert reader will notice an un-measured 25^th resonator at the bottom of the first batch. I dropped one from the second batch under the Electronics Workbench, found it, then also found its long-missing brother; now I have a genuine it’s-never-been-used resonator, just in case the need arises.

A quick-and-dirty simulation shows the series and parallel resonant peaks come out close, but not dead on, the actual measurements:

Simulation – 60 kHz resonator

The model obviously doesn’t exactly match reality, which isn’t too surprising. However, I don’t understand something about tuning fork resonators, because the parallel resonance shouldn’t shift upward with the series resonant peak when the circuit gains a 24 pF series capacitance:

Resonator 0 Spectrum

Suffice it to say that doesn’t happen with the simulation.

More study is needed, as the saying goes.

2017-09-07
RAMPS 1.4 Heatsinking

The knockoff Arduino Mega board actually has eight thermal vias on the copper pour around the regulator:

RAMPS Mega – regulator – thermal vias

I sawed up a clip-on heatsink originally intended for a 14 pin DIP, bent it a bit, and epoxied it atop the regulator with enough of a blob to contact the copper pour:

RAMPS Mega – regulator heatsink – clamping

That’s metal-filled JB Weld for good thermal conductivity and electrical insulation:

RAMPS Mega – regulator heatsink

The blob affixing the heatsink to the crystal can was an oopsie, but won’t do any harm. It’s not clear the heatsink will do any good in that confined space, but those regulators lead a rough life and need all the help they can get.

The five stepper drivers sport HR4988SQ chips, rather than Allegro A4988 chips:

RAMPS – stepper driver – HR4988 chip

I’d rather see a knockoff than a counterfeit, although by now there’s really no way to tell if it’s a counterfeit knockoff. The Kynix datasheet looks like a direct rip from Allegro.

They now sport cute little heatsinks, which, for all I know, might help a bit:

RAMPS shield – stepper heatsinks

The driver boards are slightly longer than the spacing mandated by the continuous socket strips under the three-in-a-row layout:

RAMPS – stepper driver board fit

Introducing them to Mr Disk Sander (turned by hand) knocked off just enough to make ’em fit.

2017-09-06
Wasabi NP-BX1 Batteries: Consistent FAIL

The replacement NP-BX1 batteries arrived and, as I expected, perform just as badly as the previous pair:

Sony NP-BX1 – Wasabi GHIJK – 2017-09-01 – annotated

The note I sent to Wasabi’s tech support summarizes the details:

The second pair of NP-BX1 batteries are just as bad as the first two. In fact, all four perform worse than the nearly two-year-old Wasabi batteries I’ve been using.

The graph shows the test results from my CBA III analyzer. All batteries were all charged in a Wasabi wall charger.

The top solid red curve shows the as-delivered performance in late 2015 for the battery I labeled “G”, tested at 500 mA. It delivered only 1 Ah, not the claimed 1.6 Ah, even at that relatively low current, but has delivered over one hour of service in the camera.

The top dotted-blue curve shows the as-delivered performance for the NEW battery I labeled “J”, also tested at 500 mA. It delivers only 0.88 Ah, 55% of the claimed 1.6 Ah, at a much lower voltage while discharging.

After two years, OLD battery “G” has more capacity and a higher voltage than the NEW battery “J”!

The lower curves shows the results for the four most recent batteries I labeled H I J K, all tested at 1 A to better match the camera’s actual current; the dotted traces mark the second test of each battery.

The orange traces show battery K has about 0.77 Ah of capacity, less than half of the claimed 1.6 Ah and much worse than the others.

I also re-tested battery old battery G at 1 A, as shown by the dotted red curve labeled “G:2017-09”. It outperforms ALL of the new batteries!

Batteries H and I have date codes BQF22, which I interpret as 2017-06-22: fairly recent stock.

Batteries J and K have date codes BPL28: 2016-12-28. They’ve been sitting around for a while, which may account for the poor performance of battery K.

These Wasabi batteries cost roughly twice (*) as much as they did in late 2015, have /much/ lower capacity, and, to judge from the date codes, they’ve been consistently poor since late last year.

What is going on?

It’s worth noting that Wasabi NP-BX1 batteries are currently $16 for the pair on Amazon and were $9 in late 2015. Allegedly genuine Sony NP-BX1 batteries run $50 MSRP and a suspiciously consistent $37.99 from all the usual big-box sources, including Amazon, where they’re out-of-stock for the next few months. Combining the number of counterfeits in the supply chain with Amazon’s commingled SKU stock bins, I have my doubts about what I’d get by increasing my battery spend by a factor of five.

I think it’s about time to conjure an external 18650 holder / helmet mount for that camera and be done with it.

[(*) Edit: I screwed up the unit of measure: the old invoice had two single batteries. The new order was one pair, so I now pay slightly less for much worse performance. A refund is wending its way through the system.]

2017-09-05
Sharp EL-531W vs. EL-531X Calculators

(Typo in the permalink: should be W vs. X. Fixing it will break all the auto-linkies. Hate it when that happens.)

When our lass first began using calculators, I put a pair of Sharp EL-531W calculators in harm’s way around the shop, where they still reside. The new EL-531X seems to have an identical key layout and internal logic (*), as well as the same under-ten-buck price, but I don’t like it nearly as much:

Sharp EL-531W EL-531X calculators

It’s maybe 10 mm wider and doesn’t fit readily in my hand. I’m sure the rounded-rectangle stylin’ mimics a phone, but the cheapnified keys look ugly (particularly the ones around the arrow keys at the top) and don’t feel nearly as good.

The new one fills a gap next to the lathe, where it should collect plenty of swarf.

(*) Including engineering notation with multiple-of-three exponents, which I regard as vital.

2017-08-30
Multimeter Banana Plugs

The second banana plug on one of my multimeters failed, so I finally got around to replacing them with a dual plug from the Drawer o’ Banana Stuff:

Dual banana plug – assembled

The bulky test leads don’t quite fit through the convenient retaining ring, so the zip tie holds ’em in place.

A setscrew at the base of each banana jack tunnel crunches the test lead wire against the plug base, but, alone among the collection, this plug had one missing screw. Rather than toss it away (or, worse, back in the Drawer), I decided to Solve The Problem once and for ever:

Dual banana plug – improvised clamp screw

That’s an ordinary M3 screw from the Drawer o’ Random M3 Stuff with its head hacksawed off, a slot crudely hacksawed slightly off-center into the end, then lightly filed to hide the worst damage. With a bit of luck, nobody will ever notice it …

2017-08-29
Knockoff RAMPS 1.4 Printer Controller Hardware Kit

For 36 bucks delivered halfway around the planet, you can get a remarkable pile of gadgetry:

RAMPS 1.4 – eBay parts

With a bit of persuasion, it can become a 3D printer controller based on a RepRap RAMPS 1.4 shield or serve as a generic stepper / servo motor driver with three honkin’ MOSFET power switches, two thermistor inputs, a variety of I/O bits from the Arduino Mega PCB, and a monochrome LCD with a knob.

The persuasion includes un-bending various header pins:

RAMPS shield – bent pin

Correcting bowlegged pin strips:

And clipping offending pins:

The interference between the bottom of the RAMPS power connector pin and the top of the Arduino Mega coaxial power jack seems baked right into the original PCB layout, which is puzzling. If you don’t trim the pins, this is as close as the boards will get:

Well, of course, you could just jam all those headers together and bend the RAMPS PCB.

The bent pin near the Reset button connects to the PS_ON output used to enable ATX-style power supplies. You connect the supply’s 5V_SBY always-on output to the VCC pin, which powers the Mega and most of the logic, but not the stepper motor outputs or the heaters.

To make that work, remove D1 from the board where it’s snuggled along the header strip:

RAMPS shield – D1 D2 locations

D2, next to the fuse near the bottom of the picture, provides reverse-polarity protection for the RAMPS board.

The servo motor power comes from the 5V pin. If you don’t need the PS_ON output and 5V_SBY input, then jumper the VCC and 5V pins together. Otherwise, you could solder-blob those pins on the bottom of the board, which means the servos are always powered.

Configuring the latest 1.1.x version of Marlin should be straightforward …

2017-08-28
Scrap Metal Prices

Earlier this year, I finally hauled a pile o’ scrap metal to the recycler. For future reference, here’s what clattered down on the scale:

Scrap Metal Prices – 2017-04

I think the IRONY tag means ferrous bits & pieces in the mix. There’s a powerful motivation to hand them clean copper scrap, although I stop just after cutting off soldered pipe fittings and before stripping insulation.

Memo to Self: Next time, ask about PCBs and gold-plated connectors.

2017-08-23