Bodging my way through life

I got an email hint today reading "The LM741 is useful for many beginner circuits but if you are having a lot of trouble getting it to behave try upgrading to a more modern TL072." This makes sense, as far as it goes, but the 741 dates from 49 years ago, and the TL072 is only slightly more modern, introduced 42 years ago.

These parts are known as "op-amps", short for "operational amplifiers". The concept has been around for even longer than these parts, and is an integral* part of a wide variety of circuits, even today.

It is true that the (slightly) newer TL072 is better in pretty much every aspect than the 741, which was one of the early single-chip implementations, and had fairly poor performance in most categories. However, for many years, it was good enough, and well-known enough that many manufacturers offered it, it was made in enormous quantities, and was dirt cheap.

For a while, people would use the cheap ubiquitous 741 wherever it would do, and the nicer and more expensive TL072 where the better specs were required. Later, the TL072 was the go-to chip, and the more expensive 5532 (1977) would be used where a better chip was required.

Time continued to march on, and now the 5532 is cheaper than the older TL072, and a good choice for whenever you need an op-amp. It's overkill for a lot of uses, but these days it's cheap and ubiquitous. The audiophile crowd pooh-poohs it, and likes to swap in fancier chips to get the sonic character they want.

However, in moderate bandwidth analogue electronics, things are simply not obsoleted as rapidly as they are in the digital arena. All of the chips I mentioned are still made, and easily obtainable. There are, of course, more modern chips out there. Overlooking the bewildering variety of special-purpose chips, there are some newer general purpose op-amps to be had. The OPA627 came out in 1989 (a mere 28 years back), and has some truly impressive specifications. However, it costs nearly fifty times as much money as a 5532. The AD823 appeared in 1995 and is a fine chip, and more affordable than the OPA627. However, perhaps you want to use a chip introduced in this century for some reason. And sure enough, a successor to the OPA627, the OPA827 was introduced in 2006, only 11 years ago.

* pun intended: one common use for an op-amp is a lash-up known as an "integrator"

I decided to buy SparkFun's $10 Heaterizer XL 3000 Heat Gun to try for heat stink and desoldering duties. I'm getting more and more opportunities to remove surface mount parts from boards, and this looks like a more cost-effective approach than a surface mount rework station with a bunch of nozzles for different size and shape parts. Hey, it's only $10 and the instruction manual is a hoot! Seriously, give it a read.

( I gave it a try today )

I am quite satisfied with this little beast. It does a lovely job at melting whatever I point it at.

Now that I have the EiBot board running the steppers, I'd like to have it turn the laser on and off too. Normally, the Egg-Bot this board was designed for has a servo to raise and lower the pen. This is controlled with a pulse width modulation (PWM) output. But I needed an on/off signal to feed to the laser. Looking at the documentation, I noticed references to a solenoid output, which sounded like just what I needed. Looking at the earlier versions, I could see the circuitry to drive the solenoid, but that circuitry isn't present on the board I have. Looking at the schematics, the I/O pin that drives it is now used for another purpose. I downloaded the firmware source code and tried to dope out what the current code did, but I wasn't able to figure it out. So I sent a note to the designer and asked him about it. He sent back a prompt and helpful reply, stating that the RB4 output should have the solenoid signal. I soldered a header on the appropriate pins and hooked up an LED (and current limiting resistor). At first, I had the LED hooked from +5V to RB4, but that voltage isn't supplied by the board when it's running from just USB, so no joy. So I hooked the LED between RB4 and ground, and sure enough, it followed the pen up/pen down state.

( Sweet! )

I didn't get a reply to my email for a couple of days, I assume because they were celebrating the New Year. Then I got a note reading:

1. NOw we comfirm your machine is 110V

2. Please check the laser tube has the broken or not inside.  and then tell us, because we think it is mostly the laser tube broken

Much apprecaite

I explained that the laser tube was intact, and I was convinced that the laser power supply was broken. They replied:

Can you please return the problem laser power supply and we will send you a new one

OK?

So I removed laser power supply from the unit, and figured it was worth a look before sending it halfway around the world for replacement. Since the supply appeared totally dead, not even the fan running, I suspected the problem was something pretty basic, and perhaps something I could fix.

So I took the cover off the power supply, and found this:

The power supply had an internal connector that was unplugged! It is a locking connector too, so it had never been fully engaged at the factory. I plugged it in firmly, buttoned up the supply, re-installed it in the cutter, powered it on, and the fan spun! Thus encouraged, I fired up the cooling pump and hit the test button. Nothing. Maybe the tube doesn't strike at minimum power. I turned up the power a little and tried again.

( It worked! )

I did a few other tests, and determined that the laser was emitting plenty of power (even unfocussed, the beam burns through a sheet of paper immediately).

I wrote the manufacturer and explained that I had repaired the power supply and wouldn't need a replacement.

Next step is to replace the control electronics with something more useful. The existing controller only works with nasty ancient software on an MS-DOS PC with a parallel port.

With all the snow on the ground, I decided not to go in to work. I tried working from home, but there was a limited amount of stuff I could really do. After that, I figured I may as well get something useful done with the free time.

When I bought my cell phone, it was the latest and greatest. But it didn't support tethering (using the phone as an internet connection). There was a software update for all the other phones to support tethering, but none had appeared for mine. There was some payware stuff, and I'd tried the trail versions on the train in Massachusetts, but they didn't work very well.

So yesterday, I decided to try one of the open-source ones. There wasn't a working binary for my phone, but I had the Android SDK up and running and figured I'd compile it myself for my phone. This took a fair amount of research and tweaking, but I finally got a clean compile. I rounded up the appropriate cables and my phone and uploaded it. While I was uploading, the power failed (this tends to happen when there's interesting weather afoot). I didn't know if the process had completed or not.

I rounded up the laptop and tried pairing the phone with it and connecting to the internet. I didn't know all the right parameters for this lashup, and things had changed somewhat since the last time I'd done this (I have no idea what Bluetooth DUM and PAN are, for instance). But I tried various things until I got a connection. It took a while to negotiate, but hadn't failed, so I let it be. I went to make a sandwich, and then curled up with a book by the window to eat.

When I got back to the laptop, it had made a connection. So I tried firing up AIM (a utility that doesn't use too much bandwidth) to test it out. It connected, slowly, but I didn't see anybody I knew on. I figured my ISP might be having connectivity issues too, and didn't worry about it. Then I got a message. I didn't recognize the sender, and figured it was just a scammer, but had nothing better to do, so I accepted it. Yeah, looks like junk. In Korean. But a few seconds later, I got another message. Usually the garbage messages send one URL then disconnect. This wasn't a URL, and didn't disconnect immediately. Probably someone trying to talk to someone with a similar AIM ID.

I tried using the Systran widget in my Dashboard (much less bandwidth than firing up a web browser and using Google Translate or somesuch) to make a short message in Korean, explaining that I was probably not the person they wanted. I cut and pasted the result into the chat window and sent it. I immediately got back several lines of text I couldn't read. So I cut and pasted that into Systran, and asked it to translate Korean into English. No joy, the symbols stayed unchanged. Maybe it wasn't Korean? I can recognize many of the scripts used around the world, and it did have that blocky, phonetic look like Korean, but closer examination revealed it was something else.

Oho! A mystery! The sort of mystery my language-loving friends like ayasdollz and dcseain would enjoy. Too bad I couldn't reach them. I tried launching the Facebook app on my phone, but it crashed as usual (I really wish Froyo could come out for this phone, I suspect a lot of things would work better).

I sent some English text, and received a few more lines back that I couldn't read. Maybe it was someone's secret code?

I cut and pasted some into some cryptography software I'd written and did the basic analysis on it. Yup, looked like language, character distributions were consistent with a phonetic language, and several short words occurred more than once. Didn't look like English, however.

With nothing better to do, I chose a few of the short words, pasted them in the chat window and sent them.

There was a bit of a delay, then a brief response. Also short words. Probably useful, but I was out of my element. So I sent a few short words in English.

Another pause, then a very brief response that looked to me like punctuation. Were they asking for more of my text to analyze?

I cut and pasted a couple of simple children's stories and some stuff I'd written, chunk by chunk.

Eventually, I got two foreign words back. I guessed it was "hold on" or "that's enough" or somesuch and waited.

I got back "what is". Okay, sure looks like they're trying to use my language, but don't have a lot to go on. Are they asking what language I'm using, or what? I sent back "I am speaking English."

After a little while, I got back "send more". So I started grabbing whatever text files looked likely and sending them, piece by piece.

Then I got back "Where speak English". English is pretty well known around the world, but maybe they just want to know where I'm sending from. "I am in the United States."

Another long pause, then "Not hear of", followed by "Sun up".

Were they telling me the sun is up where they are, or asking if the sun is up where I am? Sort of like the old Star Trek ep where the Horta writes "NO KILL I", with similar ambiguity.

I replied "The sun is up here. It is snowing. Where are you?" There was no reply to this, and I realized that while they can apparently puzzle out what the words mean, they don't have a workable phonetic mapping, and can't tell me something like "We are in uhzbekeestan" or whatever.

So I sent "What time is it where you are? It is 2:30PM here."

No reply. And the phone battery is running low. Apparently, the local cell site is down and I'm burning transmitter power talking to a more distant site.

I had no idea how distant.

So it seems werewulf wanted an appropriate-looking custom sound player for her Cassandra setup.

( She found a cheap toy at a thrift store that looked likely (pictures) )

Given my history of dinking with electronics, I've burned every kind of component there is, many times over, both intentionally and accidentally. Because of this, I've acquired the ability¹ to identify the burning component by scent. They all smell like burning something, but each has its own specific character. Freshly sharpened pencil scent points to an overloaded potentiometer. A more earthy version is burning Ohmite (resistors). A scorched plastic scent is burning semiconductors. A hot metal/varnish/paper odor is an overloaded transformer. The same, overlaid with oil, is a motor. And a sour, alkaline smell is an electrolytic capacitor giving up the ghost (and its electrolyte).

While playing with the computer tonight, I noticed a worrisome odor in the air. Shortly, I was able to identify it as the scent of a dying electrolytic capacitor. Sniffing around failed to localize it, but I figured it was the computer (which was warm and spinning its fans), its power supply (also warm), the monitor, its power supply, or the external disk drive. I wouldn't be pleased by any of these things popping a capacitor. I also checked the shelf of electronics nearby, but they didn't seem to be the source either. I fired off a backup and shut down all the other stuff, just in case.

Then I stepped out in the hall, and the odor was much stronger. Hmm, the CFL in the hall fixture had flamed out a few months ago, maybe it's the replacement. I unscrewed it and gave it a sniff. Smelt like warm plastic, but not much else. Probably not that, unless the heat was volatilizing spew from the earlier failure, but it seemed a bit strong and sudden for that. Checking fizzygeek's room, the craft room, the bathroom, and the office yielded nothing useful. But the stairway to the kitchen seemed to point the way.

I told fizzygeek what was up and she said she didn't smell anything. But when she came out into the hall, she sure did! She checked around too, and agreed that the other rooms probably weren't the source. But what was?

I had replaced the kitchen lightbulb earlier in the evening, but it wasn't a CFL, as they didn't live long in that enclosed fixture. The previous bulb had been a 100W halogen, but when I ordered replacements (they're oddballs that can fit), they sent me 230W frosted ones by mistake. So I had put one of those in. Sure enough, the globe was uncomfortably hot. Our theory is that the spew from the failed CFL had been vaporized by the heat from the monster halogen, tricking me into ignoring anything that didn't contain electrolytic capacitors!

¹+1000 experience points!