Electrical Engineering

Anindo Ghosh

19:01

@angelatlarge I will say this: GSM boards have empowered people to do nasty stuff from afar with a low technological threshold of entry. Should they be forbidden? No. Should there at least be some apparent monitoring of people who buy them? As a passive-aggressive deterrent, perhaps.

rawbrawb

@AnindoGhosh Karnataka isn't known for it's resitive nature though ... is it?

@AnindoGhosh I think you mis-spelled that! it should be Stewart?

angelatlarge

@AnindoGhosh I don't know. This whole topic reminds me of nuclear proliferation. Pretty soon everyone will have nukes and the countries that have them now will have to deal with it.

Anindo Ghosh

@rawbrawb resitive? Restive or Resistive? BTW today's blast was the 3 year anniversary of a set of blasts that happened in Bangalore, killing a bunch of people at a stadium.

@rawbrawb That was the insinuation. Insinuations lose their charm if made explicit.

rawbrawb

@AnindoGhosh Again, didn't know/hear that.

@AnindoGhosh as does that one ...

Anindo Ghosh

@rawbrawb Odd how a blast or even one ex-cop psycho gunman in the USA makes headlines for weeks world-wide, yet the US news coverage of the London subway blasts was sketchy at best.

angelatlarge

19:05

@AnindoGhosh Not much for 1.2M or 66kHz on ebay, actually. Are you sure about those numbers?

@AnindoGhosh You are probably right. Hard to tell from here though.

Anindo Ghosh

@angelatlarge Those are two Xtals I picked up last week for cheap, when I was looking for various stuff.

@angelatlarge Not eBay, Lamington Road Market in Mumbai.

rawbrawb

@AnindoGhosh what is worse is when you have THAT stuff, below a headline about Lindsay Lohan ....

@angelatlarge true that!

Anindo Ghosh

@angelatlarge The price of the 1 MHz at the same market was about 4.5 times as much.

rawbrawb

@AnindoGhosh Wow my market cornering is global!

angelatlarge

@AnindoGhosh I see.

Ah, the age old ebay question: 50 for $5 or 5 for $2. I really will never use 50, but they arrive sooner, and are a better value.

Anindo Ghosh

19:09

@rawbrawb Yeah, now that causes me to despair about the future of civilization. I mean, Lohan? Really?

@angelatlarge 50 and resell the unused ones locally. That's what I'm considering doing for some exotic parts.

angelatlarge

@AnindoGhosh More of a pain than it is really worth... I don't have a captive resell audience like you or @rawbrawb

Anindo Ghosh

@angelatlarge I mean, for an additional $3, you get 45 of them, right?

angelatlarge

@AnindoGhosh Yup. Additional 45 that I will never ever ever use.

Anindo Ghosh

@angelatlarge I don't have one yet but I could probably find options if I set my mind to it.

@angelatlarge Oh mail the fricking spares to me, I'll paypal you $3. :-)

angelatlarge

@AnindoGhosh Every time your wife wants to watch a movie with you she has to buy an oscillator :)

@AnindoGhosh Unfortunately, we do not have state-sponsored shipping to India. Or anywhere else for that matter.

Anindo Ghosh

19:12

@angelatlarge I just paid triple eBay price for an ultrasonic sensor module from the local market today, because I needed it now.

angelatlarge

@AnindoGhosh Ok, ok. 50 it is

Anindo Ghosh

@angelatlarge Good idea.

angelatlarge

@AnindoGhosh No! You don't say! Not you too @AnindoGhosh!

Anindo Ghosh

@angelatlarge Bwaaaahahahaha

rawbrawb

well, have to vamoose ... catcha later!

angelatlarge

19:15

@rawbrawb bye!

Anindo Ghosh

@rawbrawb Good, you changed your default sign-off.

@angelatlarge If you want to edit in a schematic, please do. I'd be happy to accept the edit. Thanks.

Also, can anyone help identify a through-hole equivalent for the IRLML2502 please? Ref. this comment:

@AnindoGhosh - thanks again. So can you recommend a non-SMD MOSFET that'll do the job? I'm working on perfboard and am still pretty nervous about SMD soldering. — Brad 1 hour ago

angelatlarge

@AnindoGhosh Will do schematics for points, food, or crystals/oscillators.

@AnindoGhosh Will do digikey searches for points, food, or crystalls/oscillators

Anindo Ghosh

@angelatlarge I offered you the Xtal free anyway. Ergo, you just offered to do schematics for free. :-)

angelatlarge

@AnindoGhosh I'll do it. It will be good practice for me: I never use FETs anyway, always BJTs so I'll learn something in the process.

@AnindoGhosh You better be the one to review my suggested edit though

David Kessner

@angelatlarge I like FET's much better than BJT's.

Anindo Ghosh

19:20

@angelatlarge Will do. Thanks, appreciate it.

@DavidKessner Ditto in all-caps.

angelatlarge

@DavidKessner Well, you know how they say "When all you've got is 1 quart sour cream, three bolts of different sizes, and a pen, everything looks like a riding horse"?

@DavidKessner Being a bit more familiar with BJTs, everything looks like a BJT design.

Anindo Ghosh

@angelatlarge In civilized nations, when you say that, the guys in the white lab coats come for you.

angelatlarge

@AnindoGhosh There is a reference for that that @DavidKessner should know.

@AnindoGhosh For your edification: meta.electronics.stackexchange.com/questions/2777/…

Anindo Ghosh

@angelatlarge MOSFET wiring from MCU pins = calculate gate series resistor for max momentary permissible MCU GPIO current, assuming gate to ground to be a short. Add a gate to source pulldown of 10 to 100k. That's it.

@angelatlarge Hmm, where's his nearest happiness provision facility?

angelatlarge

@AnindoGhosh I thought gates on FETs had a very high (input) impedance, no?

@AnindoGhosh Are you having trouble with the sour cream?

Anindo Ghosh

19:26

@angelatlarge Yes, but also a significant capacitance. The assumption of the short is to address the capacitance charging current at switching time. For that instant, the current pulled from the GPIO should not exceed abs-max.

@angelatlarge I'm lactose intolerant.

angelatlarge

@AnindoGhosh I see.

@AnindoGhosh I wouldn't ride a horse using sour cream then.

Anindo Ghosh

@angelatlarge I wouldn't ride one. They left me smelling of equine excreta the one time I tried it.

angelatlarge

Man, compiling gcc takes a looooong time

user61389

@angelatlarge can't you compile on an external computer? That's what I do with large java files

angelatlarge

@CamilStaps It is easier with Java, I think: less processor and system dependencies.

@CamilStaps gcc is very system specific (for obvious reasons)

user61389

19:32

@angelatlarge hmm, yeah didn't think of that

angelatlarge

@CamilStaps I probably wasn't clear: I am compiling the compiler itself.

For the following reason (yes, I cheated on EE.SE):

user61389

@angelatlarge oh! Yeah I guess that takes some time :P

angelatlarge

2

Q: Unexpected global variable read result in C++ using avr-gcc for (local variable access is as expected)

I am getting unexpected global variable read results when compiling the following code in avr-gcc 4.6.2 for ATmega328: #include <avr/io.h> #include <util/delay.h> #define LED_PORT PORTD #define LED_BIT 7 #define LED_DDR DDRD uint8_t latchingFlag; int main() ...

@CamilStaps BTW, you probably don't want to read that whole question: it's longer than War & Peace

user61389

@angelatlarge I didn't, I've never worked with atmel so I won't understand a word from it ;)

Anindo Ghosh

G'night all!

user61389

19:35

@W5VO / @Kortuk, is there any status for / progress on meta.electronics.stackexchange.com/q/2731/17592?

user61389

@AnindoGhosh night!

angelatlarge

@CamilStaps The upshot: looks like the older version of gcc which I am running places my RAM variables at the same location where a register is read/written. Stoopid behavior results. Appears to be a compiler bug

jippie

@angelatlarge try compiling it on an AVR!

angelatlarge

@AnindoGhosh Goodnight

@jippie Yeah, very funny.

@jippie I didn't know you were still eavesdropping

@CamilStaps Is this something that actually needs progress?

David Kessner

@angelatlarge Absolutely. I prefer MOSFET's cuz I prefer to think about voltage more than current.

angelatlarge

19:37

@DavidKessner I think I might make a question out of this discussion. Though it probably has been asked and I just need to search for it.

user61389

Funny idea. I believe Haskell has some Haskell interpreters. Why not make something like that for a uC as well? :)

jippie

@angelatlarge finished datasheet reading. So I started chat reading

David Kessner

@angelatlarge I must have missed it. What's the Q?

user61389

@angelatlarge progress as in sending it to the team, to Jin, or whatever

angelatlarge

@jippie BTW, my edit of your answer was rejected by one reviewer... "This edit is incorrect or an attempt to reply to or comment on the existing post."

jippie

19:38

@DavidKessner Did you solve the 'drive a mosfet from 3V3 logic'-problem?

@angelatlarge when did you try to edit?

David Kessner

@jippie I drive MOSFET's all the time from 3.3V logic.

angelatlarge

@DavidKessner The question would be something like this: if you needed to switch some load from a uC, what are the advantages/disadvantages of using BJT vs (MOS)FET switch? I think I know some, but clearly not all

@jippie After you left :)

jippie

@DavidKessner power mosfets too?

David Kessner

You just have to pick the MOSFET correctly, or use a simple FET/BJT to level shift.

angelatlarge

@jippie But it was approved (3 approve, 1 reject), just funny

@jippie They must have missed my edit comment

jippie

19:40

@DavidKessner hmm ... My impression is that lot of 3V-friendly MOSFETS are SMD

@DavidKessner can I use a BJT as level shifter too?

David Kessner

@jippie What's the problem with SMD? Many of the MOSFET's that I use are as difficult to solder as a BGA!

@jippie Usually, I use a 2n2222 as a level shifter-- because they are cheap and plentiful.

angelatlarge

@DavidKessner The OP didn't want SMD

jippie

@DavidKessner they don't fit my breadboard.

David Kessner

@angelatlarge Well, boo on them! :)

angelatlarge

@DavidKessner OP was not confident in soldering skills

Breadboarding is also a good reason

jippie

19:42

well actually SMD's do fit my breadboard, but all three pins fit in a single hole.

2

David Kessner

@angelatlarge I don't know all the reasons for using a BJT. But I do know all about MOSFETs, and I feel confident with them. You probably have the same things, but for BJT's.

jippie

I have to order break out PCBs in bulk I guess if I want to keep up with the good stuff

angelatlarge

@DavidKessner Maybe I'll write that up now while I am waiting for gcc to compile gcc

David Kessner

@jippie I have some MOSFET's that are bigger than a breadbox. (Ok, not really, but bigger than some PCB's that I've designed)

jippie

@DavidKessner still don't fit then, do they?

David Kessner

19:45

@jippie These things are designed to dissipate 600 watts (not switch 600 watts, but dissipate it). The heat sink is huge. Oh, and the MOSFETs have screw terminals.

jippie

@DavidKessner even with screw terminals they still don't fit the breadboad, do they?

:-p

Kortuk

@CamilStaps that is an SE thing, and honestly, I am not going to make a major issue out of it. It is not impacting the site, just something minor they can do as they want to. (cc @W5VO)

David Kessner

@jippie I could screw down some appropriately sized wire and stick them into a breadboard. So yes, they do fit.

user61389

@Kortuk yeah, it has become less mayor since the profile page isn't malformed anymore. I'll try on MetaSO then, thanks anyway!

Kortuk

@CamilStaps wait wait

@CamilStaps The developers follow every site meta. If you have reported it here they know about and are tracking it. You dont need to reproduce a bug report there.

user61389

19:52

@Kortuk okay, I'll just wait then - and indeed, don't waste your time on it ;)

Kortuk

@CamilStaps Yeah, it might be slow for something minor like that, no offense intended, but they know about it.

user61389

@Kortuk that's good to know :)

jippie

@DavidKessner maybe I have to fit screw terminals on the SMD MOSFETs too then

Kortuk

@CamilStaps they will respond on high priority bugs no matter what site it is on quickly. We only really have to poke them to share for progress on things like feature requests.

user61389

@Kortuk okay, thanks!

Kortuk

19:54

@CamilStaps Do feel free to bump me on things, I can go ping them and harass them as needed.

angelatlarge

0

Q: BJTs versus (MOS)FET to switch a load from a microcontroller

I would like to know what are the reasons for choosing bipolar junction transistor (BJT) versus a field-effect transistor (FET) (MOSFET or a JFET) to switch a load from a microcontroller. In our hypothetical situation, assume that the load requires more current than the microcontroller can provid...

microcontroller switches mosfet bjt

Free beer for everyone!

(on me :)

user61389

@Kortuk absolutely no need on this! Just wanted to know if you had any information, but it has 0 priority

angelatlarge

gcc still compiling gcc

BTW, can we have some more stars on @W5VO tasting power supply comment? It needs to be nailed to that goddamn wall and never be bumped off.

2

David Kessner

@angelatlarge Well at least it is not tagged Arduino! :)

angelatlarge

@DavidKessner Shoot! Does that mean you will not look at it?

David Kessner

19:57

Although you might want to specifically call out 3.3v logic levels, or 5v levels. Whichever is more important to you.

angelatlarge

@DavidKessner Actually, I should tag it arduino, shouldn't I? That was the Ardweeno users will have a chance to run across it.

@DavidKessner Hmmm... I'd like to know for both: if 3V3 biases towards MOSTFET solution, for instance, that would be good to know.

user61389

@angelatlarge no! If you tag it arduino, it might get migrated for no reason to Arduino.se :)

angelatlarge

@DavidKessner In a sense it does cf. @AnindoGhosh answer on the LED driving question.

jippie

too bad IGBT doesn't fit in @angelatlarge

David Kessner

@angelatlarge Is "Ardweeno" something like a wino. As in, a drunk vagrant?

angelatlarge

19:58

@jippie Do you want me to open it to IGBT's too?

David Kessner

@jippie I think she'd be mad if you even tried to put a mosfet/BJT in her!

angelatlarge

@DavidKessner I think from now on, Ardweeno = user of Arduino.

David Kessner

@angelatlarge I still prefer Ardweeno = drunk user of Arduino. :)

angelatlarge

@DavidKessner Depends on the size and the voltage...

@DavidKessner What about a sober one?

jippie

@angelatlarge Arduino is little more than an ATmega with a USB port on a PCB

angelatlarge

19:59

@DavidKessner Many of them act drunk, does that count?

David Kessner

@angelatlarge From my experience, an Ardweeno has a high probability of drinking PBR over any other beer. Which is the first sign that they are not right in the head.

angelatlarge

@jippie Technically, yes. However, if someone asks something about ATmega, you can usually expect a certain amount a) technical knowledge and b) independent research

@DavidKessner Don't knock PBR: it is cheaper than water.

user61389

I'm leaving, see you!

David Kessner

@angelatlarge But not as good as water.

@CamilStaps Bye!

angelatlarge

@DavidKessner Depends on your goodness metric

@CamilStaps bye!

@DavidKessner Gets you closer to "drunk"

W5VO

20:02

@angelatlarge lol

angelatlarge

@W5VO I still smile every time I see it.

Kortuk

@angelatlarge it is one of my favorites so far also.

angelatlarge

@Kortuk Maybe we should add it to the EE FAQ? Or... will I get massive downvotes if I ask "What's the best tasting power supply?"

W5VO

@angelatlarge It's too bad that April 1 has already passed

angelatlarge

@W5VO Yeah, might have been better than tantalum resistors, though that was good too

Kortuk

20:14

@angelatlarge haha

@W5VO That would have been perfect, but we were specifically asked not to april fools, maybe next year?

(and with prior SE approval)

jippie

/me is out

MLM

@jippie bye

angelatlarge

20:30

@jippie bye

Kortuk

@jippie ciao

angelatlarge

Going to get away for some time. Need to get stuff done.

rawbrawb

22:53

@W5VO @angelatlarge starred the power supply!

angelatlarge

23:23

@rawbrawb Good. We need a few more stars on that. Keep it up

Stacey Anne

hi all :)

someone posted a comment on one of my answers that would be better suited a comment for the question. What's the best course of action?

rawbrawb

23:40

@StaceyAnne you mean this?

2

A: LED Breathing Effect

You need to do two things - the first is make it fade out. The brightness of the LED is determined by the value in the TPM1C2VH register. by changing TPM1C2VH you are changing the brightness. In order to decrease the brightness, you need to switch around the direction so that you're counting in t...

yeah he is referring to the original and his comments are misleading.

@StaceyAnne I flagged it for you.

Stacey Anne

@rawbrawb, thanks, I didn't know I could use flags for that

rawbrawb

@StaceyAnne I just used "Other" and explained it.

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