Keith's Electronics Blog

Cort and I would like to embed lithium cells in portable projects and want power management that:

1. steps up the lithium cell’s 3.7 V to a well-regulated 5 V
2. safely charges the lithium cell from some source
3. powers the load while charging the cell

I knew it’d be easy finding power management modules that met the first two points, but I wasn’t sure whether the third point (power the load while charging) would be a ubiquitous feature, or even clearly called out in documentation. Fortunately, while browsing power management modules, I quickly found that the HT4928S mobile power management chip supports all three, and found cheap modules both with and without USB connectors on them, and ordered a batch of each style.

Now I have them and need to test that they work as described, preferably without burning down my house or pocket. The obvious test is to hook one to a secondhand 18650 cell I have lying around. While I’m at it, I may as well 3D-print an enclosure for it and have a spare USB powerbank.

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I see I haven’t posted for three years. Well.

I started this blog to share what I was working on with a handful of close friends, rather than email the same thing to each. I don’t recall that commercial blog hosting was prevalent at the time like it is now; I was at a different place in my career and finances were tighter; and I already had my own domain and ran my own server; so I just set up WordPress at home. In the basement. On my DSL connection. Where it still is.

The WordPress software uploaded the fact that I was blogging and I started getting picked up by Google. I did a few projects of interest and got a few more readers than I expected.

For a while, I had a generous arrangement to host my image files elsewhere, offloading that bandwidth from my home broadband; but that came to an end a while back. The combination of increased bandwidth requirements (making ultra-slow load times) and an increasingly busy schedule has meant no posting for quite a while.

I’ve been looking into migrating the blog to commercial hosting and Ed Nisley has generously shared information about his hosting service and their capabilities, which sounds like just what I need. I’m hoping to get that migration underway sometime soon … which might mean inside the next three years.

Meanwhile, maybe I’ll do some posting again. Images will be horribly slow to load; but anyone who wants to read can read and anyone who doesn’t is under no obligation.

Howdy.

It is a bit surprising to follow a link from an eBay saved search and find a picture that I took.

The original is in this post from 2011.

I have no CC notices posted for the whole site (though I’d be happy to); but of course the Berne Convention provides for automatic copyright upon creation and publication of a work, so this is a blatant copyright violation.

Regardless, why is an eBay seller with only 110 feedbacks (vs one who does business on a scale of 110,000) too lazy to take their own picture of what they claim to have for sale?

Anyone know where to find new, large-capacity SCSI-2 fast/wide hard drives? A computer I supported at a hospital a long time ago has a failing hard drive and I’m happy to assist with replacement but I’m not coming up with any sources for the hardware.

I wouldn’t want to do it for a living, but it’s an enjoyable diversion once in a while, particularly as a favor for a friend.

I aligned each chip’s pins by hand, clamped it to the board with a gator clamp (with heatshrinked jaws), soldered the far row of pins, rotated the board, and soldered the now-far row of pins.

Three rows I was able to do by blob-and-drag (heat the pins at the uphill end of the row, make a big solder blob, and drag it down the row at a pace slow enough to heat the pins but fast enough to keep the surface of the blob from oxidizing too badly, trusting surface tension to bring the blob with you and leave only a lovely solder fillet below each pin). Three rows I ended up doing slop-and-wick (get solder all over the place, then use “Size: Good” solder braid to remove solder bridges from between the pins, leaving a lovely solder fillet below each pin and evidence scorched flux everywhere).

I’d take recommendations on a good flux remover — preferably detailed recommendations indicating whether you have to scrub or just spray, how cleanly it washes off, etc. You can see that the rubbing alcohol I used leaves a bit of residue.

People bring me the most wonderful things!

Anyone have a favorite plastic polish?

I suppose I should build a VoIP phone system and get an analog terminal adapter, eh?