Voltage Regulators 101

Years ago I built a power supply with two adjustable outputs. It works for most of my needs, but it's still a work in progress. I built in an old digital multimeter with *incandescent display* (no, not LCD, not LED, not even vacuum fluorescent). Actually, that's the main reason I built the supply; I had to do *something* with that unusual display.

Functionally:

The two separate channels are completely independent. I could use it as a +/- supply by connecting CH1's positive output and CH2's negative output to GND. Or I could have two separate positive voltage supplies by connecting CH1 and CH2's negative terminals to GND.

The multimeter is connected internally to readout voltage or current from either channel and also has a third voltage measurement input (the middle terminals), the measurement can be selected via the pushbuttons between the voltage-setting dials.

Electrically:

It has two 24V 4A switching power supplies, on top. I think they were from a laptop. I used a simple adjustable-voltage-regulator circuit for the output; each output can vary roughly 2V-22V, and the regulators are rated to 5A.

The current-readout is a little bit flawed... I designed it to measure the voltage across a tiny-valued resistor in series with the output. I wanted the output voltage to be the least-affected over a wide range of loads. Unfortunately, that means the multimeter displays a fraction of the actual current (I think it's 1/100th) which is easy to deal with if you're using it all the time, but kinda confusing if you only turn it on once or twice a year.

So, one of the things I've been planning to do is add a simple op-amp circuit to amplify the voltage across the resistor to something more logical (1mA = 1mV would make sense!). This is more difficult than it sounds. For one thing, I'm not particularly good at op-amp circuits... It might well be because all the old op-amps I inherited from the 70's are burnt out, because I didn't have nearly as much trouble with those same circuits in school.

For another thing, I have to figure out which power source to run it off of! I might have to build two identical amplifier circuits, one for each channel, running off that channel's power supply. I'm not sure how well this will work if the voltages input into the op-amp are right near the rail. Or another option would be to run it off the multimeter's power supply. Either way, there're limitations. None of the internal supplies are bipolar. Also, I have no idea what would happen to the multimeter if it shared a voltage source with the measurement. It's circuitry is way beyond me (what's this piece of glass with wires coming out of it?! And this welded-shut-aluminum box?).

Tonight I had the brilliant idea that the circuit might work off a single-supply... how those single-supply op-amps work is magic to me... but they have example circuits in the datasheets. Anyways, I came to the conclusion it might be worthwhile to explore...

Part of that exploration came to checking whether there'd ever be a case where the output current would be negative. So I thought sure, what if I had one supply set to 12V and the other to 5V, sharing grounds, and I wanted to make use of the 7V in between...

Yeah, enter Voltage Regulator 101:

I hooked up a resistor inbetween 24V on one supply (long story, one of my regulators blew a long time ago and I don't have a replacement) and 20V on the other and was surprised to measure... no current. Zero (measured to .0001V). I measured the 20V output and saw it at 24V (higher than the regulator can output!). I tried a lower voltage setting, measuring it *with* the load resistor (connected at the other side to 24V)... set it to 20V and it looked like it was working. But when I removed the load, it dropped down to 8V!

Turns out, these adjustable voltage regulators *require* a minimum load. That's handled by the adjustment-circuitry, usually. But, by driving current *into* the regulator, that minimum load wasn't met. Sure enough, the datasheet says: "all quiescent operating current is returned to the output establishing a minimum load current requirement. If there is insufficient load on the output, the output will rise."


Anyways, this entire self-indulgent post to point out this little tidbit, because people use adjustable regulators for power-supplies all the time. They work great as long as your load *is positive*!


Realistically, there probably aren't many cases where this is a problem... Most circuitry returns the current back to ground, anyhow, as well it probably should. But part of the point of having an adjustable powersupply is for experimentation... And this is one thing that could be quite confusing. And, I have thought of a case where it might be handy to use the supplies as I just attempted... The minimum output is ~2V; if I needed 1V (and the regulators worked as I imagined before), I would have set one to 2V and the other to 3V and used the difference. But they don't work that way, so I need to put a note on my powersupply... maybe have a warning indicator if the regulators are dropping out.


In the meantime, I guess this makes my amplifier circuitry easier... I don't have to worry about negative-current cases. (Then again, it *did* work when I set the voltage *much* lower... I wonder if that's hard on the regulator circuitry).

catch-22: water filters which remove fluoride use oxidized aluminum... which is thought to cause alzheimers.

(yeh, I was a health-nut at one point).

Jury Duty and prosecutors

I did jury duty once.

Everyone it's come up with seems to have basically the exact same mentality: "only idiots get stuck with jury duty," IOW: if you're smart, you'll get out of it.

I did jury duty once. This is how it went:

Dude1 and Dude2 have known each other for quite some time and got into a fight and Dude1 ended up needing an ambulance. When asked why by 911, his girlfriend said that there was a fight. Because of this, the police were required to come. Because they were required to come, they were required to take Dude2 and they were required to file a report. Because they were required to file a report, it went to the prosecutor who was required to try to get some money for the county for making use of the police (who were required to be called). Because the prosecutor was involved, Dude1 thought he could make a buck suing Dude2.

That's it. Petty bullshit. Neither Dude1 nor Dude2 would have been in court if the prosecutor hadn't been required to at least ask Dude1 to be a witness for her case which wasn't really even about Dude1, it was about getting back some bucks for Dude2's police-involvement (which no one involved even asked for).

And I didn't even mention the pettiness the prosecutor showed in assuming we, the jury, wouldn't uphold *THE LAW* ("innocent until proven guilty, beyond a reasonable doubt") because "he seemed like a shady character who would do something like that" (actually, undoubtedly-so. Then again the prosecutor seemed to be just downright evil and good at hiding it behind legalese and professionalism).

It's a good thing all the smart folks avoid jury duty so all the dumb-folks can put each other away for petty personal-issues on a hunch... until there's not enough dumbfolks to be put away and they start putting away smartfolks for being unpatriotic.

And now my mom wants to work for the prosecutor "to give back to the community," because she's having a petty bickering-match with her boss.

I'm sure there are cases that are positive... hopefully most. Hopefully some against our country's own law-breaking. I just need to keep telling myself that, because mom's trying to work fo the po-po now.

I-Movie

BIG MISTAKE when trying to make a movie from footage that was originally on VHS:

thinking you can capture the *whole video* into a file on the computer then make clips and edit from there. 

After twenty minutes the audio sync is about twenty seconds off. Granted, I'm working with *old/expensive* and *new/cheap* equipment that really wasn't meant to work together... But I don't care enough about this project, at this point, to invest in both a new computer and a DV camera with firewire out and composite-in just so I can make a 3 minute collage from 4 hours of footage taken nearly a decade ago on an old-at-the-time camera that barely worked, and transferred to a worn-out old VHS tape. Presently, there's nothing really going on in my life to justify a DV camera, it's not really a path I'm interested in going down except for this project, and when/if that time comes the camera I get now will be outdated.

I could probably borrow one from a friend of a friend, or maybe the library...  Maybe I'll go that route some day...

"My education at insert tech-college here has given me a career where, above everything, I feel useful and that I'm making a difference."

Combine that with the guy who says "my education at insert tech-college here has given me a career where I can come home at the end of the day and spend more time with my family" and you've got one useful dude; he's on 24/7!

Besides doing something all day where he's making a difference, he's also looking out for the next generation by spending time with his children. On top of that, he gets the joy of being with them and his wife.

I've met him, he was a real go-getter, quite intelligent, a nice guy, and I'm sure a great father...

It was odd, though; at the time it seemed to me his need to feel useful didn't extend beyond *his* need to *feel* useful, as it seemed (at the time, to me) that he hadn't thought-through what *useful* meant in the grand scheme of things, nor the impact of the difference he was making. Otherwise, I was certain (at the time and for a while thereafter), he wouldn't have felt useful and that he was making a positive difference doing what he did.

Now? I have no idea what to think... Things aren't nearly as cut-and-dried as they had once been to me, which is odd considering how much thought and discussion went into coming to those original conclusions.

I wish I was capable of being in his shoes.

On Google+

Yeah, I've been posting a LOT in the past few days... I have a LOT of rants built-up. I'm sure this will slow soon... Especially considering I haven't even touched anything electronic in months prior to this latest burst.

When I thought about starting this blog, I contemplated looking into Google+. I have no idea what it does, I figured it's just Facebook-Google-style. Which wouldn't be so bad for a rant-column like this. But whatever.

On Google: Back in the day there was AltaVista, Yahoo, and AOL... if you used something else, you were outside the realm of normalcy. I had a friend who told me about Google... This dude was into OpenSource... ran Linux and all that. Listened to indie music before indie music had a nickname... believed in online privacy... Yahknow, a real outsider. So, he told me about Google, and I looked at it, and I thought "wow, here's a great search engine that doesn't give you all the garbage, and is a friend of the OpenSource community..." HAH! I won't even go into what it's become. Oh, and then I read an article about their Beowulf clusters (yahknow, thousands of linux machines... COOL!) And then they stood up when the DOJ tried to subpoena search records from them... I actually respected them for that move! Then I found out that they actually have a *censored* version of Google in China... And it makes you wonder... Their algorithms are pretty good at censoring information already, by burying things that
the mainstream isn't looking for under thousands of pages of pop-culture... But who knows what censoring they're *intentionally* doing here already. I remember when searching google meant actually *knowing what you're looking for* and *knowing how to locate it.* Now, if I do a search for "EDID" I get top results for "Edit" and no info on how to correct the search. I miss my raw-text search engines... yahknow 'EDID monitors OR monitor OR vga -edit AND OSX OR "OS X"' if anyone knows of a better one, or a way to convince Google to work the way I remember... please let me know.

Anyways, Google+ is kinda creepy right off the bat. I tried to create an account using a nickname for trial-purposes and here's what I got:

It's not enough that I submitted to their rigorous Gmail sign-up procedure?!
I don't even want to go into the details of *everything that's wrong* with this... It reminds me of a quote, I'm sure I heard it was a literal quote from someone high-up at Google... basically said something like "when your kids turn 18, they should seriously consider changing their names because of the online profiles they had as kids." Google's scary, sorry. Yeah, blogger's via Google... I know. And it's still my only search engine... And, maybe one day if someone actually bothers to read this blog, I could make some money through their targetted advertising... can always hope :)

Here're some fine examples from the Google+ "Name Policy:"

There's more!

Violations!

Nah... we're not talking "recommendations" here, we're talking flat-out "violations." I won't bother to paste all the BS they claim they can and will do if you violate their policies... let's just say it's ugly.

Appeals! This is the best part, seriously... They have this down to a friggin' science... It's more complicated to appeal your name on Google+ than it is to get a replacement Social Security Card (I've had to do it). And you have to give them more *personal* information!

And name-changes... again with the more complicated and rigorously-enforced than Social Security:

I like this part at the bottom of the sign-up page:

HAHAHAHA "and almost nothing with your boss." Why? Because all the people who'd be willing to submit to these terms-of-service either are too young to have a boss, or never aspire to working for a place like Google? 'Cause, seriously... I'm starting to think the Google services are nothing more than weed-out processes for (or great means for spying on) potential employees.

Oh good god, I really worry what tinted-window-vans will be parked outside my apartment after posting this.

RED = POSITIVE, BLACK = COMMON

It's simple... Everything electronic as far back as I can remember (and I've been taking apart electronics since I was 6) has had this scheme. RED is connected to the positive terminal, and BLACK is connected to the common (usually "GROUND", "COMMON", or "RETURN") terminal. We're talking 5V systems, we're talking PCs, we're talking remote control cars, TV remotes, VCRs, CD players... When you enter college for EE you're provided two wires with clips for your power supplies... a black one and a red one. The labels on the power supplies are Red and Black. Guess which terminals they are... For your signal generators you've got a red connector which is the signal and a black wire which is the ground... It may not be rocket-science, it may not even make 100% sense, but it's pretty simple and it's damn-near universal.

So why is it that two devices I've worked on in the past few days have EVADED this scheme?!

Example 1: PowerBook G4: has a connector with three wires; Red, Black, White running to the hall-effect switch used for putting the system in standby. As I recall (I've since closed it, and have no intention of opening it again) RED was the signal back from the hall-effect. WHITE was GROUND, and BLACK was +3.3V.

Example 2: USB mouse. My stupid mouse, the cheapest you can buy, has a break in the cord near the connector... had to cut it apart to resolder... Wait, something's wrong... what's this red wire doing on GND and this yellow wire doing on 5V?! I musta twisted something when I cut the cables... I checked my logic numerous times... opened up the mouse itself... sure enough, the PCB's labelled with the USB connections, and sure enough they're wired in that weird scheme. (Gray and Black are apparently the USB data signals).

I'm just saying...

Example 1A is a little less exemplary: multiple iBooks: have a four-wire connector leading to the LCD backlight inverter. It's handy to have a 1+kV voltage source around... if not to light up LCD backlights, then just to give yourself a good zap every once in a while. (Seriously, it's a health-thing... kinda like accupuncture). Not *certain* they didn't use the regular scheme, but after Example 1, I'm no longer convinced the reason it wouldn't light-up when connected to 5V or 12V was due to one of the other wires being an "enable." (I still have 'em sitting around for later electropuncture experiments, maybe I'll look at the circuitry next time).

Anyways, it's just stupid. Plain and simple. I have a hard time believing it's not intentional... some Chinese kid is laughing his ass off right now because a repair job on a mouse that wasn't even worth the five minutes it woulda taken to repair turned into twenty minutes... Forty, if you count the ranting here. Meh, I guess it's kinda fun to be frustrated sometimes over stupid stuff with no real victims. (Sorry chinese kids).

(And, if you want some other ranting, this German freak I worked for for way too long insisted that Europeans use Blue for positive and Green for ground, and insisted I follow the same scheme, like I never worked with electronics before I worked for him... goddamned German freak... I love him like an uncle, but I'm still not on speaking terms with him... certainly it's because of the Blue/Green thing. And another thing, Blue and Green?! Seriously!? What about people who're colorblind?! What about low-lighting conditions? I'm pretty sure he just made that shit up so he could use two wires next to each other on rainbow ribbon-cables.)