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: Science

If you measure something often enough, it becomes science

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

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

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.
2015-11-11
StirlingTEK NP-BX1 Batteries

Because the first pair of Wasabi NP-BX1 batteries for the Sony HDR-AS30V camera faded to the point where they weren’t useful for a typical bike ride, I bought a pair of SterlingTEK (a.k.a. STK) NP-BX1 batteries that, like the Wasabi batteries, claimed to have a 1600 mA·h capacity. These are “second tier” batteries, not the cheap eBay crap I’ve already dismissed, and run a bit under $10 apiece.

Here’s the picture from their product description:

SterlingTEK – STK NP-BX1 battery – as advertised

Here’s what arrived:

STK NP-BX1 batteries

Huh.

That’s a red flag, right there. It’s remarkably tempting to ship a good product for a while, then swap in much cheaper junk that can ride on the good reviews. Not saying that’s what happened, but it’s a possibility.

Here’s how they performed:

Sony NP-BX1 – Sony Wasabi STK – as received

The red and blue curves show that the STK batteries produced less than 1000 mA·h in their first two charges, with the blue battery (I labeled it B) showing considerable variation that suggests it’ll suffer early failure. The green curve shows one of those Wasabi batteries and the purple curve is the OEM Sony battery, both in as-received condition.

SterlingTEK will send two more batteries, in the belief that I received two sub-standard samples. We shall see…

2015-11-06
Sony and Wasabi NP-BX1 Li-Ion Battery Life
Using the Sony HDR-AS30V helmet camera more-or-less daily during the bicycling season chews up batteries as well as MicroSD cards:

Sony NP-BX1 – OEM Wasabi – 2015-10-25

The dotted traces show the most recent status and the solid traces are from almost exactly one year ago:
- Red = Genuine Sony
- Blue = Wasabi Power: cell D, August 2014
- Green = Wasabi Power: cell B, January 2014
All the tests are at 500 mA, approximately half the camera’s load. Oddly, the numeric values along the mA·h axis work out pretty close to the actual runtime in hours:
- Sony – 1:30
- Wasabi D – 1:15
- Wasabi B – 0:40
Given that a typical bike ride takes an hour, the two year old Wasabi B battery’s 40 minute runtime isn’t useful. The Wasabi D battery is a bit over a year old and looks very much like the B battery did last year.

The Wasabi batteries march through the camera and charger in order, so each one gets used about once a week. The Sony battery gets used once every half-dozen complete cycles, just so I have a standard “good” battery.

The Sony and Wasabi B cells over the course of two years:

Sony NP-BX1 – OEM Wasabi – 2015-10 2014-10 2014-01

Much to my surprise, the Wasabi batteries started out slightly better than the Sony OEM battery, at least as measured by the available voltage and energy. The camera runs from an internal switching power supply, so the area under the curve (basically equal to energy in W·h) above the cutoff voltage is all that matters.

In round numbers, I can expect 100 cycles out of each battery before the run time drops below the ride time; at $10/battery, that’s a dime a ride. Any claims that the batteries can be recharged “1000 times!” may be true, but they’ll have a useless fraction of their original capacity by then.

Time to buy a few more batteries…
2015-11-03
Monthly Science: Dehumidification by Rice

As part of a discussion on the M2 forums about using rice to dehumidify 3D printer filament, I replaced the 500 g bag of silica gel in the basement safe with a bowl containing 200 g of long-grain brown rice from our rice supply and let it sit for a while:

Basement Safe Humidity – Rice vs. Silica Gel – 2015-10-31

The abrupt drop in humidity from 52% to the logger’s minimum 15% marks the point where I replaced the rice with a fresh bag of silica gel, with a door opening shortly thereafter. The basement air outside the safe varied between 52% and 54% during that time, so the air inside the safe trended upward toward that goal.

The rice still weighed exactly 200 g after its stay in the safe, so we can conclude it hadn’t absorbed or released any water.

Conclusion: nope, rice doesn’t work as a dehumidifier…

2015-11-01
USB-to-SATA Drive Adapter Performance
The discussion about scrubbing hard drives suggested I really should be using larger block sizes to wring better performance from the hardware.

So I ran variations on this theme:
```
time sudo dd if=/dev/urandom of=/dev/sdc bs=4K count=32K
```
For the BS (“block size”) parameter, 1K = 1024 and 1KB = 1000. Similarly for 1M vs. 1MB.

The results, viewed as a picture because WordPress seems unable to import a formatted spreadsheet from LibreOffice like it used to:

USB-SATA Adapter – Barracuda 7200.10 drive

Each operation transfers 128 MB (128 x 2²⁰ = 131 x 10⁶) bytes. The variations probably come from other stuff going on, most notably the USB-to-serial adapter driving the plotter while I’m testing a tweak to the Superformula demo code.

Reads ever so much faster than writes, so the USB adapter definitely isn’t getting in the way; I assume the drive accepts the commands & data as fast as its little heads can carry them away. The data, being relentlessly pseudo-random, won’t get compressed along the way.

So, in round numbers, the block size just absolutely does not make any difference.

Update: Based on an early comment from Edward Berner to a previous post, I was looking in the wrong place:
```
dd if=/dev/urandom of=/dev/zero bs=4K count=32K
32768+0 records in
32768+0 records out
134217728 bytes (134 MB) copied, 9.63064 s, 13.9 MB/s
dd if=/dev/urandom of=test.bin bs=4K count=32K
32768+0 records in
32768+0 records out
134217728 bytes (134 MB) copied, 10.018 s, 13.4 MB/s
dd if=test.bin of=/dev/zero bs=4K count=32K
32768+0 records in
32768+0 records out
134217728 bytes (134 MB) copied, 0.0385358 s, 3.5 GB/s
dd if=test.bin of=test2.bin bs=4K count=32K
32768+0 records in
32768+0 records out
134217728 bytes (134 MB) copied, 0.45044 s, 298 MB/s
```
I installed an SSD on this box a while ago, so the 3.5 GB/s disk-to-discard speed represents the SSD’s read rate. The 298 MB/s disk-to-disk speed would be its write speed, probably with some clever buffering going on.

So the real bandwidth limitation in wiping a disk comes from the pseudo-random generator behind /dev/urandom, not the disk or USB interface. It would probably be faster to fill a 1 GB (or more) file with noise at 14 MB/s, then copy it enough times to fill the drive at whatever speed the drive can handle it.

Thanks, Edward, for figuring that out!
2015-10-29
Monthly Image: A Year in the Life of a Maple Twig, Resurrected
In 1991 we lived in Tolland CT, where I took one picture of a maple twig every week:

This slideshow requires JavaScript.

That was with a film camera, of course, with negatives. I assembled the printed images into a poster and eventually (perhaps in 2001) scanned / digitally photographed them four-at-a-time, saved the result as a 330 MB Photoshop file with one 2×2 group in each of 13 layers (there are 50 images, probably because vacations), and burned that to a CD.

All I can say: it must have made sense at the time.

Anyhow, here in the future, I found that CD in a pile destined for the shredder, which shouldn’t ought to happen without some attention.

Here’s how I extracted the separate images from that file into standalone JPEGs, cropped them to a uniform size, and smushed them to suitably low quality:
```
convert A\ Year\ in\ the\ Life\ of\ Tolland\ CT\ -\ 1991.psd -quality 95 Tolland-1991-%02d.jpg
for f in {01..13} ; do convert Tolland-1991-$f.jpg -crop "1212x1775+0+0" img-$f-0.jpg ; done
for f in {01..13} ; do convert Tolland-1991-$f.jpg -crop "1212x1775+1212+0" img-$f-1.jpg ; done
for f in {01..13} ; do convert Tolland-1991-$f.jpg -crop "1212x1775+0+1775" img-$f-2.jpg ; done
for f in {01..13} ; do convert Tolland-1991-$f.jpg -crop "1212x1775+1212+1775" img-$f-3.jpg ; done
for f in {01..13} ; do for g in {0..3} ; do convert img-$f-$g.jpg -crop "1100x1650+50+50" out-$f-$g.jpg ; done ; done
sn=1 ; for f in {01..13} ; do for g in {0..3} ; do printf -v dn 'Tolland-1991-Maple-%02d.jpg' "$(( sn++ ))" ; convert img-$f-$g.jpg -crop "1100x1650+50+50" +repage -rotate 90 -define jpeg:extent=200KB $dn ; done ; done
```
Then WordPress assembles the 50 images into a slide show.

Of course, it didn’t go quite as smoothly as all that, but it took maybe half an hour of fiddling to get it right by iterating on the commands until I liked the results. One might tweak the exposures and suchlike, but that’s in the nature of fine tuning.

Now I can shred the CD…
2015-10-15
Monthly Science: Supermoon Eclipse

Lunar eclipses happens so rarely it’s worth going outdoors into the dark:

Supermoon eclipse 2015-09-27 2250 – ISO 125 2 s

That’s at the camera’s automatic ISO 125 setting. Forcing the camera to ISO 1000 boosts the grain and brings out the stars to show just how fast the universe rotates around the earth…

One second:

Supermoon eclipse 2015-09-27 2308 – ISO 1000 1 s

Two seconds:

Supermoon eclipse 2015-09-27 2308 – ISO 1000 2 s

Four seconds:

Supermoon eclipse 2015-09-27 2308 – ISO 1000 4 s

Taken with the Sony DSC-H5 and the 1.7 teleadapter atop an ordinary camera tripod, full manual mode, wide open aperture at f/3.5, infinity focus, zoomed to the optical limit, 2 second shutter delay. Worked surprisingly well, all things considered.

Mad props to the folks who worked out orbital mechanics from first principles, based on observations with state-of-the-art hardware consisting of dials and pointers and small glass, in a time when religion claimed the answers and brooked no competition.

NASA takes much better moon pix, plus a bonus ISS transit, during the previous full moon:

ISS Moon Transit – 2015-08-02 – NASA 19599509214_68eb2ae39f_o

The next eclipse tetrad starting in 2032 won’t be visible from North America and, alas, we surely won’t be around for the ones after that. Astronomy introduces you to deep time and deep space.

2015-10-01