Electrical Engineering

4:27 AM

did our site do anything for april fools?

I just noticed a pretty poorly implemented april fools joke on stack overflow...

made me think i had a virus for a little bit -_-

5:00 AM

@NickHalden, only thing I noticed on EE was the "chat with an expert", was that what you saw on SO? (I noticed they had the same)

MLM

5:43 AM

@PeterJ just got that message as well

night

Good night. I thought it was a new feature to drive a few more people to chat at first until I tried it.

8:17 AM

good morning

What is this "Want to talk to an expert" pop up lately?

8:56 AM

@jippie, you should try it, I got a good answer to my question "Dropped my iPhone in bucket, how to fix?"

@PeterJ but no matter what question I click on it, I apparently (considering the photograph) get the same expert. what guru must that be that has so much time to spare to answer so many different questions.

@PeterJ what did the expert answer?

@jippie, tomorrow they are sending me their lat/lon so they can install Linux on my iPhone to fix it. I asked for an address but that was difficult, so I suggested that the UPS guy would have a GPS. I should have saved the chat log I got at the end of the conversation.

9:30 AM

?

@PeterJ Are you saying TS is the expert?

@jippie, trust me, whoever it is the guy is a real pro. Try it now with your ZCD question / project, you'll get an answer within seconds.

ah is it an april fool's thing?

Yes so now's the perfect time to ask those "Dropped my iPhone in bucket, how to fix?" questions without any downvotes ;-)

P.S. Just a bot, so it is funny to drop in some random things and see what comes back

10:32 AM

You: How do I measure output impedance?

Expert: I don't know.

some expert

11:46 AM

hello *

@Rick_2047, Hi but about I'm to head off it's getting late here. You'll have to take over as the ask an expert ;)

i am not an expert

12:01 PM

That's no attitude, you can be an expert in anything as long as you sound authoritative ;-)

well.. argument by authority is my favorite logical fallacy

I am an expert then

do you knw why I am an expert? because I say so, and I am an expert in knowing if I am an expert or not

12:15 PM

hey @AnindoGhosh

Anindo Ghosh

Hi :-)

what are you upto?

@AnindoGhosh you foolish old man! you got me worried! where have you been?

@AnindoGhosh I have my Stellaris LaunchPad working

a bit

@jippie stellaris is 32bit right?

@Rick_2047 yes

12:24 PM

@jippie using it for that project you were working on?

@Rick_2047 planning to, but programming it is not as trivial as programming AVR

Mainly to do with the fact that the AVR toolchain for Linux is mor mature than the Stellaris toolchain.

@jippie is stellaris toolchain proprietary?

not the one that I use :)

proprietary toolchains usually mean that linux support is going to suck

A lot is open

12:36 PM

nice decision

but large parts of the stellarisware is more like demo quality than a good point to really start from.

so it needs a fair bit of figuring out how to work with it

is it a new chip?

i think it is

for example, you cannot create your own project outside the stellarisware tree, because some paths are hard coded in the makefile

I believe a year old or so.

yeah, then its pretty new

1:01 PM

what is the difference between a .c and a .h file? @Rick_2047

1:12 PM

@jippie .h is header file, it contains prototypes and contants, such things

@jippie .c is source, it has actual code

ok, .c I understand

but where does the contents of .h come from?

they are written in a .h file

the .h file will only have prototypes

the fucntion definition will reside in a .c file of the same name

but why do I need both?

because .h file does not know what exactly to do. the .h file only has information about name of the function and the datatypes it takes in

the .c file has all of these definitions about what exactly to do after you call the function

@jippie, btw, it is not nessasary to have a .h file. You can have a .c file and just include that

1:34 PM

so what is the use for including an .h file?

it helps you keep things better organized

all the macros, header includes, defines and prototypes go into .h, all the real logic goes into .c

also it helps you hide your code if its proprietary

Hi there! Anyone here who knows Arduino or especially NPN transistors?

@jippie like you can go and precompile your library into a .a file and only distribute the .h and .a file

@MikkoP what do you want to ask?

Hi Rick. I have a radio controller stolen from my RC car's controller. To move forward I need to connect 4,5 V wire to ground. I've connected the 4,5 V wire to NPN collector and the emitter to ground. Now when I connect Arduino to the base the current starts flowing even I don't apply any current there

is the circuit isolated right now? What is the code inside the arduino? is the pin low or high?

1:39 PM

The isolation is fine. At the moment I just use digitalWrite to set the pin 8 low on Arduino.

ok

which npn transistor is this?

It's BC547

okey

where are you taking the output from?

where are you measuring?

Arduino is gettin power from different source than the radio controller because the controller wants 9 V. The grounds are connected to each other. I made sure the voltage is zero on the base by using a multimeter to measure it. I connected ground to ground and the voltage wire from the multimeter in the base pin

measure voltage at collector

1:45 PM

.. or base leg

Says -5 V

Wait

are you holding the multimeter right?

Around -2,8 V

Sorry for that, no minus in there, my bad

are you sure you have connected the transistor right?

can you provide a picture?

@Rick_2047 don't really get it when both the .c and .h files are distributed together, but never mind I'll take it as a fact for now.

Sure, just a moment

1:48 PM

@jippie hmm... my failiure to make you understand

@Rick_2047 No, I'm just beginner when it comes to C

look at it like this, .c files are the actual source, .h files are information about the source

@jippie in most good libraries .h files have alot of comments explaining what a function does, while .c files have a lot of comments says how its done

Hope these are clear enough mikko.peltoset.fi/circuit%20(1).jpg mikko.peltoset.fi/circuit%20(2).jpg

what are the green blue and black wires?

They come from the controller. Blue is ground, black and green are 4,5 V. Connecting green and blue the car goes forward, black and blue makes it go backward

1:54 PM

then your configurations is wrong I guess

Do you have something in mind?

Do you might know what these mean? Two of the transistors say BC547 and on the next line there is 943 and B on top of one of the legs. One of them says BC547 and on the next line 410 and the same B

2:26 PM

BC547 is a quite common transistor

@MikkoP you can easily find the datasheet for them through google or whatever search engine you like. Don't know what 943 and 410 means, they're probably production codes.

B-suffix is again mentioned in the datasheet

I'm not terribly impressed with Stellaris LaunchPad / Stellarisware. Several examples compile but just don't seem to work.

2:43 PM

sup

3:03 PM

hey whenever a mod gets a chance @Kortuk @W5VO can you tell me more about the commitment stage? it's weird the info it asks for...

@NickHalden It is for a launching site, it is wondering what your level of expert will be fore the site so that it has some idea of what level you will be on the site.

@Kortuk ok and as for like full and email?

full name*

i might just wait until arduino is already a site, and then join

@NickHalden it shows your full name and takes your email to email you updates. The email is not shared.

@Kortuk hmmmm ok

@NickHalden area51.stackexchange.com/proposals/49538/…

Scroll down, you can see what mine looks like, and I gave it my real name and email.

Dont worry, SE is very good about private information.

3:07 PM

@Kortuk haha, beginner or learner! nice...

@NickHalden as was discussed at the meetup when I tried to get a simple Arduino program running, I dont know arduino

@Kortuk oh.. interesting

I would hope that once I get through the IDE nuances I can very quickly bridge the gap to the rest and be pretty advanced quickly, but as of right now I am pretty new.

@NickHalden I was having all kinds of issues, which @jippie told me how to turn on more detailed error logging, and the java errors were the ones I immediately recognized when I last used java to use a com port that was already taken, and I just had to release the com port.

@Kortuk ah, fair enough. yeah i've never really had any problems with it until i tried to modify the bootloader and kind of broke it, then tried to reflash the original and screwed up the fuse settings... took me like 3 weeks to get it back to operating condition

@NickHalden I want another arduino so I can make a programmer from it to start doing goofy things.

Like modify the bootloader.

3:13 PM

@NickHalden you'll miss out on the beta badge!

@Kortuk you can always use a normal AVR programmer

the like the mkII

@jippie oh wells

@NickHalden price?

@NickHalden you should have heard him during the hang out ... @Kortuk is really a beginner when it comes to Arduino.

(and Windows)

(and serial COM ports)

(and Google hangout)

(and connecting ethernet shields)

(...)

;o)

@Kortuk like $20

@Kortuk better yet get the avrtinyISP as a kit from adafruit

you are a smart arse @jippie

@jippie I have written my own server apps that dealt with serial ports well

!

3:20 PM

@Kortuk picture or it didn't happen.

@Kortuk my boss just finished writing a serial port bootloader for one of our devices, it's an xmega chip so pretty similar to the arduino bootloader

@Kortuk I use a spare Arduino to program my AVR's. Works like a dream. I use a screw shield for it, combined with a small breadboard.

The only thing I sometimes miss is the ability to use debugWire (in circuit debugging/single stepping)

@jippie you can't use the PDI interface for that? or does the atmega328 not support that...?

@NickHalden what PDI interface?

@jippie avrfreaks.net/…

3:32 PM

haha.

PDI is the name for debugWire on XMEGA?

Q: What's the use of tantalum resistors in audio circuits?

4:26 PM

Could there be a better question for April 1?

1

I've been looking at some "pro audio" sites and saw that tantalum resistors are often mentioned with claim that they somehow improve sound quality, but I've been unable to find any reasonable descriptions for discrete component operation that don't trip my audiophoolery alarm. So is there any re...

@jippie Still wondering about this?

@Kortuk, WTF is the "chat with an expert" box that appeared when viewing a question?

green_leaf

i just clicked it....

4:41 PM

@ThePhoton well yes, but I think I miss some fundamentals because of the fact that I just picked up programming C and am basically learning on the hobby job.

@ThePhoton you are immediately connected to my tablet.

@jippie Header files get included in all the C files that will use those functions, so that the compiler knows the calling convention (input and output types) for all of the functions.

C file contains the actual definitions of the functions, so the compiler only sees those (and generates object code for them) once.

By "included" I mean copied and pasted in place by the C Pre-processor.

Remember this is late-1970's compiler technology.

I wish we were able to send a notification to the professor when someone just copies a homework question here and copies the answer in his homework.

@ThePhoton I know I have to install header files when I want to compile stuff on Linux. Usually called dev files, from a related project.

Yes, if you don't have the .h files, C will assume every function has the convention int f(...)

And I really mean ..., a variable args function.

@ThePhoton that is why I asked if it was us.

but I was trying to compile some stellaris stuff earlier today and it had the .c and the .h file next to eachother in the same directory.

4:46 PM

@ThePhoton Forgot it was 4/1/2013

Did you use '#include <file.h>' or '#include "file.h" '?

@Kortuk no it is 2013-04-01

@jippie maybe 1/4/2013

@ThePhoton eh ... I just typed make

I knew someone would say that

4:47 PM

@Kortuk Didn't see where you discussed it before.

I believe there was an xcde orsomething cartoon on it

@jippie Oh...

@ThePhoton Have to do the kitty litter box before it gets dark outside. Back in a moment, then I'll look for the example

Sounds like a compiler config issue, but I dont' even know what tools you use for Stellaris. Is it gcc?

I use gcc, yes

@ThePhoton hmm ... I have two examples, both compiles, but neither worked when I flashed it

For example the qs-rgb example

qs-rgb.c:#include "qs-rgb.h"

it includes its own header file?

4:57 PM

@jippie Yes. To make sure the header file and the C file match.

If the header file had int f(double y) and the C file had

int f(float y) { ... },

`-rw-r--r-- 1 jhendrix jhendrix 21142 Sep 6 2012 qs-rgb.c`
`-rw-r--r-- 1 jhendrix jhendrix 3829 Sep 6 2012 qs-rgb.h`

all heck would break loose.

@ThePhoton ok, I understand that

Quote marks form is right when both files are in the same directory.

but why a header file is i have the source c file too, which in fact is the main source code file that is being compiled

4:59 PM

Sounds like your bug is an actual error in the files, not just having the files in the wrong place.

@jippie 1970's compiler technology.

Allows compiling each C file to a separate object file.

m

And not having to recompile everything when you just made a change in one place

@ThePhoton I think I switch to java

Sorry I'm no help with the actual bug. Hope I clarified a little bit about H files. I'm off to work now, though.

A: Input and Output Impedance of a BJT

I could do with a peer review:

1

Measuring input/output impedance is little more than calculating the resistors in a voltage divider. Consider the following two situations: simulate this circuit – Schematic created using CircuitLab Important is that the whole circuit is not clipping, so the voltage \$U_i\$ is small...

thnx@ThePhoton yes you clarified a bit.

5:40 PM

Hello *

@Rick_2047 Hello

W5VO

@Kortuk openimpulse.com/blog/products-page/product-category/…

@Kortuk i missed the hangout maan

that sucked

@Rick_2047 We can do another. I may just make a standard one every saturday, early like that so everyone might be able to attend.

and then we can bounce another around to get more coverage.

pcb pcb-fabrication power-supply voltage-regulator

MikeVfromJoisey

1

That user is leaving strange answers.

Don't believe it it TS though.

Hmmm now I am in doubt if I read correctly.

5:48 PM

not TS from the writing, just someone that needs to have a little site explanation it seems.

did you guys hear? there is a labview library for arduinos?

can there be any higher level of abstraction from the circuit?

@Kortuk maybe i just need to re-read couple times :)

@Rick_2047 labview for embedded is really really bad

Labview has lots of bloat and you normally just get overspecced hardware to deal with it

@Rick_2047 I'm unfamiliar with labview. What is it used for / useful for?

I went to a labview for embedded presentation at NI week and the guy teaching effectively said it did not work.

5:50 PM

@jippie its a graphical programming language which just abstract out everything

LabVIEW

LabVIEW (short for Laboratory Virtual Instrumentation Engineering Workbench) is a system design platform and development environment for a visual programming language from National Instruments. The graphical language is named "G" (not to be confused with G-code). Originally released for the Apple Macintosh in 1986, LabVIEW is commonly used for data acquisition, instrument control, and industrial automation on a variety of platforms including Microsoft Windows, various versions of UNIX, Linux, and Mac OS X. The latest version of LabVIEW is LabVIEW 2012, released in August 2012. Dataflo...

@jippie you just drop in pretty looking blocks on a block diagra and we have what we want

the engineers there are rock solid and make some nice hardware though .

@Kortuk when was this?

@Rick_2047 I went to NI week 2 years ago.. no, 3 years ago.

It works, it just has TONS of bloat

for very tiny simple programs it added many kB of overhead

5:51 PM

@Rick_2047 I feel out of control already :-p

@jippie you are, but of course you can drop down to lower levels.

especially when controlling instruments

I effectively wrote the drivers for many devices

@Kortuk oh it has changed a lot since then. I have read that they actively started to focus on removing bloat

rawbrawb

grEEts all

I've used NI libraries ones to control some instruments ... but it was in pascal if I remember correctly, or basic...

@Rick_2047 Yeah, i would still not suggest using it for a micro where any bloat counts, but I can take a look again.

@jippie what instruments wer they?

@Kortuk of course, that is why I was amazed at this move

but its a nice way to get cheap labview

5:54 PM

@Rick_2047 Wavetek Stabilock 4032 and a Philips/Fluke DVM with a couple hands full digits

@Rick_2047 They want everyone to use it. If you have it working and it saves dev time and makes the product you need, who cares about the bloat, it just makes it easy to not let the product work.

is it free to use?

@Kortuk yeah, so this NI guy this time on the Amp Hour and cris explained it like that

@jippie it is the opposite of free, as far away from free that you can be

I'll stick with C then

@jippie this is not a product targeted at you

@jippie @Kortuk but a really nice price point sparkfun.com/products/11225

you get an arduino and labview for 50USD

as cheap an NI product as ever

5:58 PM

@Rick_2047 I mean, that is the world of engineering. Your end goal is a good product at low cost.

actually this product is for non electronics engineers

anyone used stm8 controllers?

@Rick_2047 it is for both.

6:17 PM

but an electronics engineer would always like to go down and dirty on this

i for one would never use LV for my controllers

but I would see how this could lower the barrier for entry

so what would be the typical use case for a labview powered arduino?

some scientist who wants to use several temperature sensors in his/her project. they buy this and several lm35's and stick them at several places, recieve waveform from the arduino and get squiggly lines on a graph

I don't have money for several LM35's. LM35 is so nineties btw

these are physics majors we are talking about

google temperature sensors, LM35 is cheapest result

and available everywhere

i refuse to use 20+ yr old technology.

6:28 PM

you are not physics major who google "temperature sensor"