Electrical Engineering - 2013-09-08

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4:36 AM

@jippie Means no mod has taken action on it yet.

5:01 AM

@MattYoung Welcome to the club for "People who the troll hates". Unfortunately it is not an exclusive club, as basically the entire world, sans one, is a member.

5:17 AM

Sure would be nice if he would just go chug some bleach...

@MattYoung Yeah. And @ChrisStratton is feeding the troll all the energy he needs to continue. Chris doesn't realize that he's dealing with a mentally challenged individual.

I really don't get why he continues. If anybody must know what it feels like to be hated by the world, it's him.

@MattYoung It takes diligence not to. Once in a while, he runs out of meds. Today is the worst outbreak I've seen so far.

5:33 AM

electronics.stackexchange.com/questions/81582/… He's at it again.

Grrr. I have learned to despise Chris Stratton. He actually likes that troll. I hope he tries to help TS, that will certainly change his mind!

@MattYoung I have voted to close that question as opinion based.

If I could downvote a users account, I would.

5:49 AM

@NickAlexeev I can't believe that question isn't closed yet.

@DavidKessner Chris likes to be a contrarian. I doubt anything will change that.

@MattYoung You're being too nice.

@MattYoung He sounds young and idealistic. Unworn by the realities of life.

@DavidKessner He's probably older than me, but I tend to agree with Olin on most things.

@MattYoung What do you mean?

@DavidKessner I have a low tolerance for sloppiness, lack of attention to detail, and general stupidity. That anti-establishment whole anti-establishment attitude drives me up the wall. Leave it in the campus coffee house.

@MattYoung Understood. I generally agree with Olin, but sometimes he can come across as grumpy. That being said, I think he's one of the good guys.

6:09 AM

flagging is the new alternative to morning gymnastics

good morning @all

Trouble is that the tolerastic* agenda sounds sooo sweet and attractive for the masses.
* [sic, explanation on request]

@NickAlexeev what is the discussion about this morning?

@jippie Morning.

I was impressed @DavidKessner how easy it was to get my BBB running on Ubuntu server linux

@jippie trolls, troll sympathizers

6:13 AM

@jippie Good to know. I probably won't try it for a couple of months. I have too many other projects to do already.

the most time was taken by downloading the ubuntu image :-p

Looks like our troll called it a night, think I'm going to do the same. Later guys...

Yeah, I can understand and somewhat excuse trolls with mental illnesses-- But I have a hard time excusing people who should know better.

@MattYoung G'nite! I'll be outta here in 5 minutes too.

@jippie Well, when my time comes I'll be sure to bug you about it!

I thought about writing a blog about it, but it is too simple :-s

anyway you're welcome by then

@jippie Showoff!

6:16 AM

software repository is huge in contrast to the Agstrom Linux

but enough about that

@jippie Yeah, I haven't heard good things about Angstrom Linux.

I'm outta here. Later Guys!

night

6:39 AM

Hi @jippie, quick question you might know. If you format an SD card with ext2 which has journalling and power is cut while writing a file, I'm not too worried if that file is corrupt but is it likely to fail to mount again like FAT32 does? This system is running Busybox without fsck for ext2 support and it looks like a pain to upgrade it for various reasons.

1 sec.

ext2+ journalling = ext3

@jippie, ahh yes I see it doesn't have journalling now. Although I wonder if it's less prone to that sort of thing that FAT32?

It is possible that you need an fsck after a power failure to fix the filesystem. The advantage is that (if all went as designed) that there is a journal/log of transactions that can be checked.

ext2 and power outage is synonymous for fingers crossed

I don't know which will be better. FAT32 probably requires a license fee when you want to write to it ..

i believe vfat doesn't

don't know. an un-journalled filesystem and power outage is a bad combination.

@jippie, yeah it's a bit of a pain this BusyBox issue. The system has a bunch of startup scripts that don't seem to work with the latest version (that has fsck) and it'll probably take ages to track down the problems. Not enough room on the FLASH for both and putting it on the SD card would be a bit self-defeating lol.

create a 2nd partition that you don't write to. (also called read only filesystem)

6:47 AM

@jippie Thanks good idea!

@PeterJ if you have an existing ext2 filesystem, you can enable the journaling. But your kernel filesystem driver must support it to actually use it.

@jippie Thanks will look into that as well, I rebuilt the kernel so it's reasonably up to date. Just upvoted an answer and got a message "you have not voted on a question in a while". First time I've seen that message must have been because I'd just been busily downvoting 15 answers.

yeah I've seen that message too the other day

bad boys

1 hour later…

7:59 AM

2

Electrical (Power) Engineering

Proposed Q&A site for professional engineers working in electrical generation, transmission, distribution, and industry - where electricity is measured in kilovolts, megawatts, and MVA. (As distinct from electronics engineering, which is about millivolts and milliamps.)

Currently in definition.

8:11 AM

@ManishEarth, be interesting to see how much traction that gets. Those subjects are all mostly on-topic here although there aren't a lot of questions about it especially from professionals - most I've seen have been more general interest questions on various aspects of power transmission.

@PeterJ you may want to mention that in a discussion over there "Is this a subset of EE.SE"?

I thought EE was mainly about electronics design and not about electric power engineering. Some questions do get an answer though

8:35 AM

@ManishEarth, have done it'll be interesting to see what they have in mind. There are probably some questions about accepted industry practices and certifications etc that would be pretty borderline here, but some of those might be a bit localized and opinion based for a SE site anyway.

:)

8:48 AM

Did you guys (cc @PeterJ, @ManishEarth) check the related questions that pop up there?

Related
Are Hypervisors on topic?
This is on topic on Stackoverflow

?

@ManishEarth just funny

ah

1

Q: Are PLC's on topic?

Proposal: Electrical (Power) Engineering The high power systems are commonly controlled by PLC's. Will questions about these control systems be on topic?

@jippie, haha, just about all of them are weird like "Superuser on-topicness". I guess you have to expect the unexpected in Area 51.

8:52 AM

@PeterJ deep

I really have to install my reed switches on the cat flaps today ...

I have the electronics and programming done

How's the site doing today?

@AnindoGhosh too many serious questions and answers makes flagging difficult. Actually have to read some of the posts

I have an Arduino powered from 4 NiMH batteries. Is there a smart way to prevent deep discharge of the batteries?

9:22 AM

grmbl

@jippie, I gave you an upvote for beating me to it while I was still typing :)

:-p

@PeterJ you have an image in your answer, so your answer will probably turn up highest ;o)

shoot @peter, we totally forgot LDR's

@jippie, haha, yes just saw that and gave it an upvote

@jippie, if the question had been asked 3 or 4 hours ago we'd probably have an answer from the person who no doubt invented them

3

probably. I think the nurse gave him his shot

9:45 AM

I didn't know if LDRs were still in production, but noticed Digikey has a few dozen types in stock and a local retail type electronics shop still sells a couple of different types. I remember as a kid (say in the early 80s) having a few huge ones in a metal enclosure that must have been about 30mm in diameter.

@PeterJ they're still pretty common in my opinion

I think tey're better at detecting day light than a diode,

@PeterJ especially sensitive at yellow/green rather than infra red

iirc

@jippie, that might be a good point. You can get plenty of photodiodes down in that region although maybe some LDRs more closely approximate the human eye. I've seen photodiodes in the past that list that as a feature, although sometimes they are more expensive than the usual wavelengths.

1 hour later…

11:07 AM

@PeterJ Cadmium Sulphide (CdS) LDRs are very much in production, and are used in a large number of designs. Multiple reasons: Works on AC, doesn't need significant amplification, is innately a low-pass filter, and so on.

@AnindoGhosh, all other good reasons I hadn't thought of, just hadn't seen any myself for a while. I thought possibly a photodiode and amp / filter had become cheaper overall for high-volume with SMT etc. But sounds like it's not the case.

11:44 AM

Hello people out there

Here I am to ask if it's OK to... ask beginners questions.

I mean, not here in the chat, but in the main site.

@Anal yes, it's OK, but what's the question?

Well, it's about how when you put voltage in series with opposite directions - I am talking DC - those do subtract each other and they add when they are the same direction. Perhaps others could benefit of this if I made this a question.

More in detail.

when I FINALLY thought to have my mind clear enough to understand what is going on within a chemical cell

BANG

I am getting lost. Why do they sum?

(or, subtract)?.

That's pretty much it. I'd like to deeply understand the details about how electron flows in the circuit.

and how more than one source do affect each other

@PeterJ Also keep in mind that often the light sensor will be remote to the PCB, so the SMD advantage is lost.

So I can go on and post?

Wouldn't I get a -10000 rep and the badge "lamer" ?

LOL

@Anal You might want to change your name on the site, that's more likely to get people looking askance at your posts, than any beginner question you post.

11:58 AM

user image

not entirely how I envisioned it yesterday, but it is a good first attempt at my breadboard screw wing

it allows to use stranded wires with a breadboard :o)

@Anal, most downvoted post at the moment is -11 so if you get to -10000 you deserve a badge lol. But you might want a diagram as well to make it clearer. But if you're after a description at that level maybe Physics.SE would be better but perhaps @ManishEarth could comment there.

That's quite true, it's a nick with an old college story. I am looking about how to change it, if it's possible!

Done.

@Anal where did you change it?

You only changed it on one site. Should I sync your profiles across the network?

Oh, yes please!

Thank you

done. syncing chat..

huh, chat sync not working

done

12:11 PM

Let's test it...

ouch.

@Dakatine works for me

reload chat

Nope, it was my browser. Refreshed! Now I am named like my favorite PEANUTE BUTTER brand.

WFM

Ha!

That's insensitive to people with peanut allergies...

@PeterJ ?

12:13 PM

Yes, but my previous one was insensitive with allergies to enemas.

(just kidding, sorry if it's bad taste :P )

guys

I have put two batteries in series. I can read voltage across several points there, including the "edges" of the series (the circuit is of course open)

@Dakatine, haha no peanut butter tastes fine to me and is better than an enema any day.

but, I can check continuity only between parts of the series... not the two "extremes".

@PeterJ lol

try an enema with peanut but... oh, nevermind.

So another dumb question is: do my multimeter SUCK BIG BALLS?

my answer would be: yeah it does

@Dakatine because of internal resistance I would guess

That would make a massive load of sense

@Dakatine, if you're talking about the batteries don't try to use a resistance / continuity check it won't have a meaniful result. For two batteries connected 'reversed' I'd expect no voltage reading. But if you put a description of a few things you've tried like that it might be a reasonable question.

12:22 PM

@PeterJ ah, that too

Would it make sense to have a microcontroller that has a 1ms ISR, to put a sleep command in the main loop? The idea is that the main loop is only executed once, until the next interrupt.

@jippie, yes if power is critical and it can wake back up faster than that (most can). It's been ages since I've checked but I think most PICs and AVRs can do it more in the order of 20uS.

(depending on the sleep mode and if the clock is changed as well)

@PeterJ, there is voltage reading. It's a 9V battery and a 1,5V battery. If they are turned the same way, voltage is 10,5V. If I invert the small one, I get 7,5V. I want to understand why.

@PeterJ not too advanced, currently experimenting with Arduino. But is 1ms a long time, good fit for intermediate sleep?

powering this little project from a battery

@Dakatine, see what you mean now, actually that would be an interesting question to post so I'd say go for it.

@jippie, I'm about to head off but I'd guess it could be worthwhile. But it depends on how long your code runs while awake. You could always read the datasheet to see how fast it wakes up and the difference in current between sleep and operational mode :p

1:32 PM

@jippie What is the language you are coding the ISR in?

C

void resetCounter0() {
digitalWrite( flapLed , HIGH );
secondCounter0 = 0;
}

that's the longest one

oh the other one is longer

in text

ISR( TIMER2_COMPA_vect ) {
millisecondCounter += 1;
if ( millisecondCounter == 1000 ) {
secondCounter0 += 1;
secondCounter1 += 1;
millisecondCounter = 0;
}
};

@jippie OK, that's not C, that's library calls from Wiring language. Replace DigitalWrite with DigitalWriteFast, add the DigitalWriteFast library from the Arduino site. Using DigitalWrite in an ISR adds about 650 clock cycles to the ISR. DigitalWriteFast is 16 cycles.

The digitalWrite is only done once ever 3 hours or so.

I could write to the IO port registers directly ..

@jippie Yup, DigitalWriteFast does just that, it's actually a macro.

oh wait, an important thing is ... will my outputs be enabled during sleep :-s

1:41 PM

@PeterJ, done: electronics.stackexchange.com/questions/81638/…

I think that adding the tag "beginner" would be nice. I would, but I don't have the rep to.

Thanks for encouraging me to post.

@Dakatine we have a nitwit

Never heard about that word

@jippie ATmega328 has various sleep modes, and no, in most of them (I think excluding one mode) outputs are not enabled. Inputs too are only enabled for interrupt pins if int is enabled.

Sigh, first comment came from somebody that didn't even read it :(

Whatever. Time to get some real life outside home. Thanks everybody!

9

A: How can a let my atmega328 run for a year on batteries?

The Atmega328 provides six power saving modes, ordered from minimal to excellent (estimated current consumptions from this forum post): SLEEP_MODE_IDLE: 15 mA SLEEP_MODE_ADC: 6.5 mA SLEEP_MODE_PWR_SAVE: 1.62 mA SLEEP_MODE_EXT_STANDBY: 1.62 mA SLEEP_MODE_STANDBY : 0.84 mA SLEEP_MODE_PWR_DOWN : 0...

1:56 PM

@AnindoGhosh I only have two inputs (interrupts), a timer and three LEDs to drive

@jippie The LEDs will consume a lot of current unless you're running them at around 1 to 2 mA, and instead of indicating with LED on, indicate by flashing the LED for 10 mS x 5 times (this is what I do for all indication functions)

@jippie Also the Arduino's built in regulator does not have a low power mode, it is always regulating. My solution is to supply power from a buck regulator set to 4.5 Volts, directly to the 5 Volt pin (I think that's the pin, not Vin, but I could be wrong).

@AnindoGhosh 2mA and they're only incidentally on. Flashing is a smart idea, I'm already doing PWM though. I could combine...

@AnindoGhosh lp2985

and I use the 5V input not the regulator

@jippie Yes, I've used PWM with a PWM frequency of around 5 Hz, AnalogWrite (duty cycle) of some small number.

@jippie Yeah, that's a big power saver.

I was actually using the PWM brightness as indicator :-/

@jippie The human eye is more sensitive to flashing than to variations in brightness.

2:05 PM

what I meant to say is that the PWM brightness is an indicator for elapsed time

the brighter the shorter the time

2:18 PM

@jippie You could achieve the same using a varying flash rate, once per second down to once per 0.05 seconds.

@jippie Two advantages: Higher PWM rate = more switching losses. And change in flash rate is more noticeable than change in intensity, especially because ambient intensity affects perception of LED intensity.

m

hey! what do you think about my breadboard screw wing (don't pronounce it too fast though, that's reserved for @DavidKessner)? probably the simplest project I made so far, but I think it is near brilliant ;o) @AnindoGhosh

@jippie I saw that. I use robbon cables soldered to pin headers. I have 4-wire, 10-wire, 20-wire connectors etc, so I just use whatever is required. At one end is the full pin header stri, 4/10/whatever pins, each heat-shrinked to its conductor on the ribbon cable. At the other end are single pin-headers, or sometimes doubles (for V+/GND pairs and signal pairs).

@jippie The pin headers go straight into the breadboard, and I simply hook up the other ends as needed. For situations where I control the remote side, I usually have female pin header strips on the other side, that way I can have a ribbon cable with pin header strips on each side.

2:35 PM

I have an old telephone cable wired from my cat flap (with the reed switch). I hope to be able to keep using that cable, but it is stranded wire and thus a problem with a breadboard. BTW the wing is same size as an Arduino Mini ;o)

@jippie I see. So why not solder that cable to pin header pins?

By the way, the protection diode that is usually applied as a shunt across inductive loads / motors, is there a common term for it? "Shunt Diode" sounds lame.

@jippie By the way, the screw terminals you used, what pitch are they?

5.04

5.08

i wanted 2.54

but I discovered I had these lying around already :)

so I put them back to back

@jippie Yup, I've made some of those but not for breadboard, and never called them "Wings" ;-) See one of my early answers on this site:

3

A: Converting a 2.54mm pitch header to screw terminal blocks

For a similar requirement, converting a 20-pin header strip to screw terminals, we fabricated a tiny adapter PCB with screw terminals like this one: The screw terminals are on 0.197" centers, and they interlock nicely on a 0.2" pattern. The PCB used was thus: The screw terminals are arrang...

@jippie "Another such adapter board of ours uses the screw terminals all on one side of the header strip, with a bit of a gap between the 2 rows of screw terminals. That version's a bit fidgety to use though." :-) Sounds like your "wing" ;-)

just a sec.

@jippie And here's a ridiculously expensive version of your "wing": ebay.com/itm/…

@jippie And here, I found what I bought a few months ago for breadboard use: pololu.com/catalog/product/2428

That's 0.1" pitch, top entry, spring locking, so it replaces your wing and improves upon it :-)

user image

2:53 PM

I'm probably going to regret the latest addition to the cat flap detector ... I added a 3 second bleeper

@AnindoGhosh that covers a lot of useful breadboard contacts!

@jippie 3 rows, yes. But it's nice and stable. If you want to save contacts, clip off one row of those pins.

I like my wings better, you can hardly push those contacts of the thingy on the image

@jippie You know, once you have the hardware and the code all streamlined, you should post as a tutorial on instructibles or somewhere. Anything to do with cats, you'll become instantly an internet rock star ;-)

I call it a wing because @DavidKessner thinks it is a stupid name to call it :o)

@jippie No, actually those spring things in orange press in quite smoothly. I prefer it over screws, but that's a personal preference.

2:57 PM

at 2.54mm?

for my 10yr old nephew maybe

@jippie Yes, you can even press them in with the lead of a resistor (my standard poky thin all-in-one tool)

@jippie Also once you've done it a few times, it becomes habit to just strip and grab a row of wires, press all the buttons at once, and shove all the wires in.

ah the cat flap opened :)

and again

@jippie By itself?

no

by cat

duhh

I think the cat didn't like the BLEEEEEEEEEEEEEEEEEEEEEEEEEEEEP and jumped back

SLEEP_MODE_IDLE: 15 mA => that's about what I see now.

@AnindoGhosh definitely have to play around with the sleep modes after reading your post.

3:26 PM

@jippie Yup, I upvoted your "wings" ;-)

@AnindoGhosh You voted while I was editing in credit to your answer ;o)

Well time for a week's tryout. Next version planned in 7 days ;o)

Also because I need a longer wire to connect the second flap.

@jippie Cool, thanks. Hey, care to take a careful look at the circuit I posted? It works perfectly in reality on a breadboard, but I'm keen to know if there's something I'm missing. The second schematic in this answer:

1

A: Drawn out question in regards to DC power to battery backup

The LEGO LiPo battery is rated for 7.4 Volts, I believe. Thus, a single diode would be enough to switch between the 9 Volt rail supply and the LiPO when the rail voltage fails or falls below 7.4 Volts. Note: If the speed control is DC instead of DCC, then in any case when you set the throttle t...

have to go out for grocery shopping

@AnindoGhosh after shopping

@jippie Sure, no problem. Do remember to look please

@jippie Wings: image.made-in-china.com/2f0j00OCyQPcIqlblZ/…

3:52 PM

@DavidKessner "screw wings" David, "screw wings"

@AnindoGhosh seems pretty complex to me for powering a motor

@AnindoGhosh I probably have to read the text aswell, don't I?

@jippie The OP wants the motor powered by source A until source A drops to a very low voltage or zero, then wants it to be powered by source B, which might be a bit higher than the above threshold value... and switch back to source A when source A voltage rises. I'm open to simplification ideas.

@jippie I saved you the reading.

seems ok to me. Why is the cap so large?

4:07 PM

grEEtings all

morning @rawbrawb

@jippie have you electrocuted your cats yet?

@rawbrawb No. But I made one of the two jump by connecting a piëzo bleeper to the his cat flap

17xx series?

@jippie one simple step away from a remotely operated tesla coil!

What is 17xx series logic?

@rawbrawb tread mill operated

4:15 PM

@jippie seems to ring a bell, but I can't remember or perhaps I am mis-remembering.

@jippie Umm I tried several different caps till I had a good delay on switching.

@rawbrawb Hiya

@rawbrawb electrocat

@rawbrawb he s referring to an NXP ARM Cortex chip :-s

@jippie Oooh, I guess I'm mis-remembering then.

@jippie nxp.com/products/microcontrollers/cortex_m3/series/LPC1700.html

@AnindoGhosh Hello

4:18 PM

@AnindoGhosh I think LPC should have been mentioned

at least

@AnindoGhosh wow a 32 bit processor is now considered "logic" ?

@jippie I agree. It's just the Phillips users just use the series term and assume everyone else either understands, or is not worthy.

maybe in another 20 years we just pull out an ARM controller instead of a 74HCxx

@rawbrawb Uhm, it's like the Arduino folks think the only definition of "shield" is the one they are familiar with.

@AnindoGhosh and they are unlikely to understand or even need to use the "shield" that perhaps is more universal.

4:20 PM

@AnindoGhosh what would it mean if not?

@jippie Actually, in 20 years I'd be surprised if we didn't routinely use arm, leg, shoulder, neck, back, and various other controllers as a matter of routine. Nano-exoskeletons perhaps.

@rawbrawb True

hmm I wonder how an Arduino "specialist" would visualize a shielded cable ...

@jippie EMI protection mechanism, for one thing. On connectors, or those rectangular tin-can things on RF circuitry.

@jippie A cable that connects to a shield? :-)

or maybe a ribbon'like cable that runs from shield to shield to shield to ...

I forget who it is, but they are selling Arm M0, M1+ ucontrollers in 8 pin packages for ~$.40. Cool.

A 32 bit controller for ~ a penny a bit.

4:24 PM

I'd love to see a 3 pin ARM controller

@jippie you could just trim the leads off of a normal one ...

@AnindoGhosh still dealing with the Asshat accountant ? or is that gone?

or a microcontroller in a DO-204

@rawbrawb Oh, I don't want to agonize over it. So I just wrote back to my contact that sure, perhaps we can do business some other time, and sure, I'd still be happy to give him occasional unofficial advice.

@jippie I can sell you microcontrollers in DO-204. They'll take Vcc and GND, and nothing else in or out.

@AnindoGhosh You tease @jippie but I have a friend who has developed a technology that will allow devices to work and bi-directionally communicate in that situation.

@rawbrawb You're spoiling the fun.

4:36 PM

as a matter of fact I saw 2 three lead device, that works from phantom power if you connect its vcc an gnd pins together

I can look for the partnumber in a moment

@AnindoGhosh Well we did "slip" it past @jippie that a shield is another name for a a condom earlier ... so we do have that!

@rawbrawb He wouldn't get that anyway.

@AnindoGhosh In what sense of "get" do you mean?

@rawbrawb Not touching that one.

DS18B20 figure 4, page 6

4:40 PM

Well on that note ... I should go and finish off some documents so they are available for first thing on Monday morning. Ciao!

1 hour later…

6:01 PM

@AnindoGhosh R U there?

@jippie Yes I am, but not definite about your premise... At least not until someone provokes a temper tantrum in the candidate.

Now, I'm not here for the next hour or so

np

@AnindoGhosh enjoy!

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