Category Archives: Electronics

Posts about electronics. Usually meaning electrical gadgets smaller than a proper computer.

Resistor Storage

As I continue my electronics part organization spree, I was looking for …something… reasonable for through-hole resistor storage. Resistors are a problem because there are a lot of values, once mixed they’re possible-but-irritating to distinguish, and strips of resistors are awkwardly shaped.

There are some special-purpose drawers, most of which aren’t very flexible (configured to hold exactly the E12 series, or with slots too small for the 4″ strips a lot of cheap resistors come in, or…), and many of which are enormous 3D printing projects in their own right that I didn’t feel like dealing with. There are some systems with small or card-catalog style drawers, but I don’t stock large enough quantities of resistors to invest that kind of money/space, and don’t plan to. I also looked at variations on schemes using card holding binder pages, since I really like the cheap SMT binders (link is the ones Adafruit stocks, mine are all the ubiquitous brown ones with gold-debossed Chinese text because I’m cheap), but after I bought a pack of the appropriate business card slot binder sheets I realized I’d underestimated my size requirements.

After quite a lot of looking around and stalling, the only thing that really appealed to me was cloning Zach Poff’s Edge-Labeled Baggie Method, so I did.

I added some E24 values (like 51x and 75x) that I had stocks of from one purchase or another, and a few other odd labels that I happen to have stocks of. The added labels are missing the cute little colored resistor images because I’m not sure how they were generated and it wasn’t urgent enough to spend a ton of time on – I just put the value and the band numbers on those.

I did cheap out on basically every part; I used 2mil 3×4″ baggies instead of the nice 6mil ones, and I used AmazonBasics 1 x 2-5/8 Inch labels that list themselves as compatible with Avery 5160 labels. Both of those may eventually prove to be a mistake, but for now they work and feel fine.

One thing I am looking to improve upon, I currently have them stored in an old Kroger deli meat tub, which is OK but not ideal. I don’t think I can find something that will hold them reliably and still clear the 3″ height of the drawers I’ve been packing a lot of my component assortments into, so I’m probably looking for something that will close, possibly a large-ish 3×5 card organizer.

Posted in DIY, Electronics, General, Objects | Leave a comment

Akro-Mils/Harbor Freight Small Drawer Dividers (in FreeCAD)

Installed polycarbonate drawer divider, next to the CNC setup it was cut on.

I’ve been doing some component stocking lately, and haven’t really set up a solid storage system, so I picked up a Harbor Freight 40+1 drawer cabinet thing to manage various small size + small quantity parts.

There are slots in the drawers to take dividers, but Harbor Freight doesn’t sell them, and Akro-Mils charges a bit much – somewhere in the vicinity of $10/16pcs – for injection molded dividers that experience says don’t fit terribly well. The set of Akro-Mils drawers I use on campus for kitting out instructional labs has first-party dividers that tend to float just enough to get pins trapped under them, which leaves me less than enthusiastic about spending money on those.

I saw some folks 3D Print their own, but always feel silly 3D printing flat parts, and wanted something clear.

..So I took some measurements, ordered some 0.078″/2mm polycarbonate sheet, and CAD’d up the shape.

FreeCAD render of tool-path, with process tree visible.

I did a quick parametric sketch/extrude/profile in FreeCAD 0.18, and unlike the last couple times I tried to build something in FreeCAD, the Sketch constraint system didn’t bug out, the Path workbench didn’t crash, and it posted reasonable gcode. I am very pleased by this development.

Now, it is a trivial part (rectangular, 2mm thick, 34mm tall, 50mm wide for the bottom 17mm, 51mm wide for the top 17mm), but I had earlier versions of FreeCAD fall over on similarly-trivial projects, usually in the path workbench. I’d really like to have (and be vaguely competent at using) a decent all-FOSS design flow for the router, so this is an exciting development. File here if anyone wants it.

There was the usual CNC fuckery (losing Z steps because I plunged too aggressively for the bit, tapping the Z- stop because I had the spindle raised in its clamp for working off a vise and forgot, etc.), some of which were solved by finally switching my Z axis motor to a slightly higher current since I keep having problems with running out of Z force.

Had I looked a little closer I would have noticed there are third party laser-cut acrylic dividers available for like $0.33/ea compatible with the Akro-Mils small drawer size, but if you ignore the …$1000-odd of CNC machine and tooling and the value of my time… these come out to like $0.16, so it’s not completely absurd from that angle, and it was a good tool-chain test. Also, happily, they fit significantly tighter than the Akro-Mils injection molded ones, so no trapped pins.

Posted in DIY, Electronics, General, Objects | Leave a comment

Router Replacement: Asus RT-ACRH13

RT-ACRH13 being flashed.

I’ve been running a TP-Link Archer C7 flashed with OpenWRT at home since early 2016 (and a TP-Link 1043ND with OpenWRT for years before that), but since I moved into my current place over the summer it has been falling over every couple weeks. It hasn’t been logging anything (I have a flash drive mounted that it persistent logs to) but goes down until hard reset, most likely just because of the load of two heavy stream/video-conference/file-sync users (…and probably not because of my kitten chewing on the antennas. Probably.) Rather than updating/diagnosing I decided that was a good excuse for a new faster router.

TL;DR: The Asus RT-ACRH13 is an excellent current-production OpenWRT host for ~$65 with only minor install challenges, and represents a significant upgrade over the Archer C7.

Continue reading
Posted in Computers, Electronics, General, Objects | Leave a comment

EBAZ4205 Surplus ZYNQ Board

EBAZ4205 FPGA board connected to PSU and serial adapter.

A not long ago there was some noise in places I follow about Zynq FPGA boards surplussed from their role as controllers in retired cryptocurrency mining rigs, for way less than the price of even the bare FPGA SoC. I impulse bought one EBAZ4205 from “College Shop Store” on Aliexpress for $19.08 shipped to try them out, since it seems to to be the most common and documented flavor, and it showed up yesterday. Short version: they look awesome for the price.

Continue reading
Posted in Computers, DIY, Electronics, General, Objects | 3 Comments

Interesting (but disappointing) Mini Buck Boards

I needed some cheap little vregs recently and had run out of and/or lost all of my useful-value 780x linear parts, so I decided to look at what people in this century use. 

I found some little buck boards roughly the size of a TO-220 package that looked exciting. These particular ones are QSKJ Mini DC-DC Buck Step Down Module model “QS-1205CME-3A”, Vendor page here, mine were 5pcs/$9 from Amazon.

Upon analysis they have serious issues with regulating under load, so the hunt for something decent continues, but the form-factor and advertised feature set are really compelling.

Pros:

  • High-efficiency high-frequency synchronous buck instead of a linear heater^H^H regulator.
  • Solder-jumpers for 1.8,2.5,3.3,5,9,12V or a default (fiddly, tiny) adjustment pot output so you only have to stock one device – one easy-to-cut trace to disable adjustable mode.
  • Tolerates 4.5-24V input as long as out < in or so.
  • Good stability to input voltage variation.
  • ~0.25V drop-out.
  • Does appear to have a cutoff for over-current.
  • No perceptible ripple under various load conditions.

Cons:

  • Voltage regulation manages maybe 600mA at 5V before droop becomes unacceptable (<4.8v).

…and that makes it basically useless for most applications. Test data below the fold.

Maybe it could be resolved with appropriate external capacitors and/or offsetting the adjustable to regulate right at a known load or something, but not being drop-in really reduces their charm.

Anyone know of a similar offering that doesn’t suck at output regulation?
(Rel: Anyone know if any of the low-end electronic loads are worthwhile? I’m not looking to spend real-lab-instrument money, but it’s come up often enough lately that I want to be able to dissipate a couple 10s of Watts through a at least stepwise-controllable resistive load).

Continue reading
Posted in DIY, Electronics, General, Objects | Leave a comment

ThinkPad 560E

Complete ThinkPad 560E system.

I’ve been idly looking for one of the mid-90s ThinkPads known to have perfect OpenStep/Rhapsody support for years as a fun collector piece, but been unwilling to pay eBay prices. The other week I scored a pristine IBM ThinkPad 560E for $20 in a Shopgoodwill auction, below is notes on getting it up and running, plus some relevant history and plans.

Continue reading
Posted in Computers, Electronics, General | 13 Comments

Apple 12″ Macintosh RGB Monitor Recap

This post is a retro post on a retro topic – a repair I did in 2017 on a monitor made in 1991. I got a question about (probably) the same problem in another venue and realized I never put it online. I managed to dig up my pictures and notes, so there is useful information to be shared.

My 12″ RGB Display is getting sad.

The end of my (2016) post about Recapping my Macintosh LC I discovered that my matching Apple 12″ Macintosh RGB Monitor ( M1296 ) was going pear-shaped, and speculated that I’d need to recap it.

Continue reading
Posted in Computers, DIY, Electronics, General | Leave a comment

Macintosh SE Health Check

I had my dear old Macintosh SE out for a health check as I slowly extract my vintage computer collection from the (unconditioned) place I’ve been keeping it at my parents house to the basement of the place I’m renting. It had a couple interesting findings that seem worth putting online, including another floppy drive rebuild and a slightly elaborate fan replacement.

Continue reading
Posted in Computers, DIY, Electronics, General, Objects | Leave a comment

Why did a Banggood package I ordered on March 26 just appear in Bahrain on July 5, the same day it finally showed “Shipment picked up?” Did it just get packed into a container and loaded on whatever outgoing vessel … Continue reading

Posted on by pappp | Leave a comment

Anycubic Linear Kossel: Unofficial Owner’s Guide

Anycubic Kossel on its stand

I’ve been working with a number of Anycubic Linear Kossel / Kossel Plus (whatever branding they’re using when you look) 3D printers for the last couple months, including one I bought personally. While I’m overall extremely pleased with them, there are a whole bunch of notes, fixes, and improvements I feel like should be collected somewhere.

Continue reading
Posted in DIY, Electronics, General, Objects | Leave a comment