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Quorten Blog 1

First blog for all Quorten's blog-like writings

I’ve previously searched for DC motors and found no shortage of “1-inch” motors. However, those are rather large for my intended use as a tiny Raspberry Pi Zero machine, and besides, I’ve seen smaller motors than that in a 90’s era Minolta compact automatic film camera, 1 cm diameter to be exact. So, now I go searching for smaller DC motors. And indeed, “10 mm” is the key search term to include.

20191119/DuckDuckGo 10 mm dc micro motor
20191119/https://nfpshop.com/product/10mm-vibration-motor-15mm-type-model-nfp-110-003

There’s plenty of choices on Digi-Key around the 10 mm size range. Most of them are 5-6 V DC motors.

Read on →

Use a soldering iron to weld separate 3D printed plastic parts or as a cheap replacement for a hot air gun for shrinking heat shrink tubing? Nah! A soldering iron is generally too hot for those uses: Unless you have a wide range of temperature control, a 370 degree Celsius soldering iron runs the risk of burning plastic and heat-shrink tubing. Instead, you can use a low-temperature hot glue gun, this will run at 120 degrees Celsius and therefore will be within the temperature range of heat-shrink tubing. A standard temperature hot glue gun is within the range of 200 degrees C, and therefore can be used to weld plastic together.

20191118/DuckDuckGo low temperature hot glue
20191118/https://www.gluegun.com/blogs/tips-tutorials/8349592-low-temperature-glue-guns-glue-sticks-guide
20191118/https://answersdrive.com/what-temperature-does-hot-melt-glue-melt-at-676969

On the other hand, if you want to be more daring, you could use a small fan and a soldering iron to form a small makeshift heat gun that would probably be within the temperature range of heat-shrink tubing. Or, as Wikipedia recommends, you could simply hold the soldering iron very close to the heat-shrink tubing without touching it.

20191119/https://en.wikipedia.org/wiki/Heat-shrink_tubing

Very interesting, back in 1983, Apple produced an Apple II gift catalog that sold a variety of Apple II themed items. One of them was an Apple II jigsaw puzzle. Steve Wozniak did not recall the puzzle himself when being asked about it. It is likely that it was mainly Steve Jobs who was behind the idea of the Apple II gift catalog, who was also at NeXT Computer when they produced the NeXT Gift Catalog.

20191117/https://lowendmac.com/2006/rare-apple-ii-jigsaw-puzzle-found-on-ebay/

Output impedance, what is that exactly? In the simplest case, it is a reasonable way to explain the maximum amount of current a particular power supply can provide. Power supplies, including batteries, can be modeled as having an “internal resistance.” The value of this internal resistance is the same as the “output impedance.” Then, the circuit as a whole can be studied using the resistance and voltage laws of voltage drop based off of resistance. A higher output impedance (resistance) value means that the output voltage will more readily sag when there is a high current draw (low resistance) load attached. Conversely, if a low current draw (high resistance) load is attached, the voltage drop will be negligible even if there is a high output impedance.

Therefore, the output impedance is primarily a measure of how much current can be supplied by a power supply. Low current, i.e. high resistance, outputs can alwyas be connected without issues, but high current, i.e. low resistance, outputs need to be connected with care. Motors are characteristic for causing high current draws and voltage sags in power supply sources. You may need to consider switching to a power supply with a higher current rating, i.e. lower output impedance, if your load’s current draw is too high, i.e. resistance too low.

20191116/https://en.wikipedia.org/wiki/Output_impedance

Read on →

I have notes in various scattered places about the voltages that are used in various I/O connectors, but no convenient summary all in once place. So, here I go. When there is an “absolute maximum” voltage that is rated higher than the maximum signal voltage, I note it in the following list.

Vpp = volts peak to peak

  • “Consumer line-out/in” audio, RCA jack and 3.5mm jack: 0.8 Vpp, absolute max 2 Vpp. Please note that line-out outputs can only drive high-impedance loads, such as a computer or amplifier, and therefore cannot drive speakers or headphones directly.
  • Microphone audio input: 0.002828 Vpp or greater
  • Composite video: 0.7 Vpp without blanking/sync signals, 1 Vpp with blanking/sync signals
  • VGA video: 0.7 Vpp (i.e. differential signaling)
  • Parallel port: 5 V
  • PC Gameport: 5 V
  • MIDI: 5 V
  • PS/2 connector: 5 V
  • USB: 5 V
  • Ethernet: +/- 1 V (100BASE-TX), +/- 2 V (1000BASE-T)
  • RS-232: At least +/- 5 V, +/- 10 V, +/- 12 V, +/- 15 V, absolute max +/- 25 V
  • RJ11 Telephone: 48 V voice, 90 V ring

Read on →

Aww, yes, now that I learned so much more about how capacitors are used inside of electronics, and their tendency to leak and fail when they get old, I am certain that some intermittent failure issues with some of my mid-2000s-era computers are due to capacitor issues. But, why is it that I don’t really have capacitor issues with my late 1980s and late 1990s computers? Surely, is it that I am still experiencing the issues of defective “Chinese capacitors” to this day? Well, looks plausible. The full time range of affected equipment is from 1999 to 2007.

20191115/https://en.wikipedia.org/wiki/Capacitor_plague

Interesting that the “Chinese drywall” issue happened around the same time frame.

20191115/https://en.wikipedia.org/wiki/Chinese_drywall

Minimal components to build a cheapo sound toy, based off of vague observations looking inside a real sound toy.

  • 1 x Super-cheap chip-on-board (COB) microcontroller (MCU)
  • 1 x Ceramic capacitor for MCU power delocalized coupling
  • 1 x Zener diode for MCU power
  • 2 x Resistors for MCU power and low-pass filter
  • 1 x Electrolytic capacitor for low-pass filter
  • 1 x BJT transistor for speaker amplifier
  • Possibly a few more resistors depending on specifics

And that’s all there is to it!

No need for low-pass filter circuits… since this is a toy, it can be designed so that all stored sounds are low-pass filtered before manufacturing, thereby eliminating the need for such circuitry. Not to mention, when the toy is designed only to drive a built-in speaker and not an external speaker, the only speaker at risk of being damaged by low-frequency sounds is the cheap internal toy’s speaker itself.

MIDI 2.0 is finally out!

2019-11-15

Categories: misc  
Tags: misc  

MIDI 2.0 is finally out! It’s been quibbled about being in development for so long, over 14 years! And also, the long overdue updates to the MIDI Manufacturers’ Association website have also finally come too. Also, perhaps most importantly, no longer do you have to buy a copy of the specification and get a printed book, but now you can download the specification free from the website, albeit free registration is required. Also, the site is now titled the MIDI Association rather than the MIDI Manufacturers’ Association. Simply put, the entire ordeal is much more modernized and up-to-date.

20191115/https://en.wikipedia.org/wiki/MIDI
20191115/https://www.midi.org/

So, I took apart a cheap electronic push-button sound effects toy with wires hither-scither in it, then put it back together, but it didn’t work. Ut oh, did I break it? Maybe, but I was able to mitigate the damage to effectively repair it, given the constraints of its cheapness.

The problem was that when I closed back up the case, I wasn’t careful about how I was rerouting the wires, so when I tightened down the screws, I squashed two wires: the power wire and the speaker wire. Just enough to totally destroy the original function of the toy. But, never fear, given the constraints of this being low-power and low frequency electronics, it was an easy fix. I looked at the squashed wires, and carefully bent them back to their original shapes. I could still feel there to be stiffness in the bent wire sections, so I had hope that there was enough wire held tight enough together to give me electrical continuity. Then, of course, I carefully routed the wires and carefully paid attention to their positioning when closing up the case, and this time I confirmed that I could screw down the wires without feeling like there was any additional resistance in the way. Batteries put back in, and what do you know, it worked.

What made the idea of replacing theese wires particularly challenging was that they were really thin wires and had tiny solder joints. Luckily, I was able to make the repair without needing to consider that complication.

Again, it is worth noting that higher poewr and higher frequency circuits are less forgiving, in these cases you are beter off just replacing the wires whole.

Lithium batteries are less likely to leak than alkaline batteries. But what kind, specifically? There’s more than one type of Lithium battery.

Specifically in the case of non-rechargeable batteries, there are two main chemistry designations that are advantageous to use either for their leak resistance, or when they do leak, their tendency to be relatively non-corrosive. The first and most common kind is the “CR” chemistry designation, which is short for lithium manganese dioxide. This is the most common type of chemistry used in 3 V button cell batteries. Reading the types of chemicals involved at glance, you can see that there aren’t any particularly corrosive liquid elements involved. All solid metals or gases.

The second kind of non-rechargeable chemistry is “lithium-iron,” specifically lithium iron disulfide. This is used primarily in 1.5 V AA and AAA batteries. Although sulfur can be used in nasty chemicals, it is a generally non-reactive element that commonly appears in the sulfide and sulfate form in nature.

20191114/https://en.wikipedia.org/wiki/Lithium_battery
20191114/https://en.wikipedia.org/wiki/Button_cell
20191114/https://en.wikipedia.org/wiki/Sulfur


One kind of lithium battery to stay away from is lithium thionyl chloride, because this uses a liquid cathode, and is therefore prone to leaking when the outer casing gets corroded, which is likely to happen due to the inclusion of chloride. And, these batteries can explode when shorted. Alas, the 1/2 AA clock batteries in classic Macintoshes use these as standard, so that is the first thing you want to treat if the battery is no longer providing a useful voltage. “Hazardous waste, Class 9 Hazmat shipment.”