Electrical Engineering - 2013-05-29

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12:31 AM

if I have a small IC barometer, do I view the GND pin as connected to the input voltage with a negligible voltage drop across the device?

I can't figure out what else it would be

this is what I'm looking at: sparkfun.com/datasheets/Sensors/Pressure/MPL115A1.pdf

I'm not worried about the SPI or anything at all, I'm just working on conceptually getting it hooked up correctly

12:48 AM

Hey guys so I have a question(I'm a total EE noob, so please bear with me). I'm following this tutorial: www.instructables.com/id/Music-Party-Facebook-Connected-Arduino-Powered-/#step1

and I have already soldered some header pins onto the RFID Reader. Now I need to connect the Wifly Shield onto RFID reader. I'm not sure what I'm supposed to do, however I did realize that in their video they connected it via wires. I have some hookup wire but I'm not sure how to go about it(https://github.com/lifegraph/arduino-wifi-setup#soldering-the-wifly-xbee-form-factor)

@ThePhoton The A0-A2 are to address the chip if you have multiple. I think I need to implement the MOSI line to pipe in those commands

user image

1:41 AM

Yo yo yo! I am back! :]

Is it okay to write PWM signals to a motor without any transistor stuff?

2:02 AM

@coding_corgi Hi! Are you working with a servo?

oh wow. Just noticed how late my response was. :P

2:14 AM

@anorton Still here, sorry...

@anorton No motor,

@anorton You didn't seem to notice that I retired from stackexchange.com.... Hmmm...

yesterday, by coding_corgi

I have made my decision to retire from stackexchange.com (unless I have a question that really needs to be answered) Goodbye all!

@anorton Still here?

2:35 AM

Sorry... I saw that my response was really late, and decided that you had probably left. silly me. :)

I don't really have experience with motors... only servos. :\

I'm sorry that you're retiring! :o

(I've been out of the chatroom for a while)

@anorton <jk>Stupid you...</jk> :] I have no life, I am always going to stick around around here, just not as obsessive as before (meaning hanging around here all day), Oh, thanks though...

oh. ok. I thought that by retiring, you meant that you would delete your account, and leave forever! :(

I'm glad to hear that you'll at least be around some times. :D

@anorton Don't worry about me leaving! I learn so much here!

I could say the same thing--I've learned quite a bit on SE (between all the sites)

@anorton Don't worry, I will still have more hours in here than you... ;]

2:42 AM

You wanna bet? :D I have the fanatic badge on Math.SE...

(100 consecutive days)

I missed a single stupid day, otherwise I'd be close to 200 now...

@anorton I know, being around non-techy people makes you feel smart, but when you look around in SE, I feel like a retard

@coding_corgi so true

@anorton Now, now, don't beat your self up for a gEEky-little badge, :]

@anorton Ooooh, that has to suck

Yeah...

@anorton Sadly, I misused this account, made it like two years ago, asked stupid silly questions, and never used it until I get an Arduino, I mean really...

2:44 AM

ah...

Oh--here's a room you might be interested in... chat.stackoverflow.com/rooms/291/rebol-and-red

Ping rebolbot

@anorton I no rebel

;)

Seriously--look at it; it's a full fledged chatbot ;)

@anorton Whatcha doing?

not much, other than pinging RebolBot.

:D

Are you near Fairfax, VA?

2:48 AM

Umm... not really close, but still within a few hours drive. I'm in Roanoke, which is close to Blacksburg (Virginia Tech), and also close to Lynchburg

maps.google.com/…

@anorton Oh, you could've had gone to one of these awesome stores: microcenter.com/site/stores/fairfax.aspx

very cool indeed! :)

@anorton Yes, all money (sadly) goes to that store... :[

;]

haha

@anorton Shhhh!!! It's not funny! :]

2:51 AM

:D I know... I feel your pain.

@anorton Trying to figure out which temperature control (permanent) soldering iron to get, I am going to but another cheap one, just to see if I mastered soldering.... I keep busting my tips!

Cool!

I just got a cheap pencil iron, so I'm going to get started down the soldering road soon... I just have to clear enough time (and enough space on my workbench!)

@anorton Not the busting tips part, which reminds me, I am running out of solder

@coding_corgi True... the temperature control part was cool, though. (Ok... so it's actually pretty warm, but that's a different story...)

@anorton My workbench is always so messy and I have OCD! Bad combination, half the time I am cleaning up!

@anorton Wanna hear something cool about my solder's flux?

2:55 AM

Sure!

ok... I need to go. 'night

@anorton My cheap (test) soldering iron get's hot, like really hot, like not needed hot, so sometimes I apply solder to the tip of my iron and the solder blasts off in every direction like fireworks, leaving trails of smoke, and sometimes hitting my with teenie drops of flux

@anorton Ahh... Bye, Good night!

3:52 AM

good morning everyone

Can anyone see the difference between the first two items in the search here: mouser.com/Search/Refine.aspx?Keyword=UX60SC-MB-5ST

@StaceyAnne $0.18 at qty 1?

More seriously, I'm going to guess either one of them is lead-free or they came on different size reels.

Just double-checked. The one with the (80) suffix is on a reel of 1500, the other one is on a reel of 1000.

you're probably right about the reels. the datasheet doesn't indicate what the 80 means, which confused me

It's bizarre how Mouser passes through the price difference when they buy identical parts on different reel sizes.

3rd line looks like the same part again with (01) suffix, reel of 1000, but priced the same as the (80) part!

I also saw the termination style was solder instead of SMT, but how can SMT not be solder?

@StaceyAnne from the datasheet, the pn should end in -5S8 instead of -5ST for a through hole part, which Hirose also calls a "solder" termination.

4:04 AM

oh, ok. then it's a mistake on mouser's part

so that termination should be SMT since the part no is obviously the SMT part

@StaceyAnne Yeah, but did the put the wrong part number or the wrong termination style? Don't order the full reel !

I'm only ordering 6, don't worry

next question: is there some degree of consistancy between connector footprints from manufacturer to manufacturer for the same connector?

I just realised the RJ45 connector i chose has become a whole lot less available in the few months between the schematic design and now

@StaceyAnne Do you feel lucky?

There's some chance you'll find an alternate with compatible footprint, but it's kind of up to luck what part you picked if you didn't specifically look for that feature when you picked the part.

ok

4:25 AM

Can I use any metal nearby as a makeshift GND for my antistatic wristband?

because...I have an air vent in a very convenient location :<

4:39 AM

@Gnintendo You want to be grounded to the same thing the parts you're working on are grounded to.

4:54 AM

@ThePhoton so the board itself, generally?

ThePhoton hw r u

@Gnintendo If the board has a connection to the building ground, I'd rather connect to the building ground.

@ThePhoton and if it doesn't? or should I make it connect to the building GND while working on it?

@ThePhoton at the lab we have GND wires that go to a stake driven 40 feet into the ground, but I'm looking for the best solution to use in my dorm room

grEEtz

5:10 AM

greetz

@Gnintendo If you have a budget, get an ESD work mat for your desktop and ground that. Usually they also have a place to plug in your wrist strap.

@ThePhoton hmm, my current work mat is just a silicon cooking mat (to solder on, mostly)

@Gnintendo Probably not the best esd protection...

@ThePhoton pfft, only semi-conductive (actually, dunno, not really privy on the molecular structure of 'silicon' mats)

@Gnintendo Probably an excellent insulator.

5:23 AM

@Gnintendo Silicone is not silicon, i.e. it's not a semiconductor. In fact, silicone is an excellent insulator, therefore not excellent for ESD protection.

@AnindoGhosh eeehhhhhhh

@AnindoGhosh but it is excellent for keeping solder from burning holes in my desktop!

:<

@Gnintendo True

well I won't be even touching any ICs or SMT circuits for a while (while in my dorm room, at least), all basic through-hole, so it shouldn't really be an issue until I can scrap up an ESD mat?

good monring

in the meantime, is there anything remotely useful I can do with the antistatic wristband?

2 hours later…

7:10 AM

how do board manufacturers handle cut tape packaging for small production runs? Do I need to buy something like a digireel, or can I give the manufacturer CT and they deal with it? Or should I just ask?

7:44 AM

@StaceyAnne Just ask. The assembly shop I use is happy with cut tape, they just want two extra parts on the tape "just in case", one for each end, which they generally return if unused.

Ok. Thanks @AnindoGhosh

8:34 AM

@AnindoGhosh, not that there's anything wrong with your answer because the question doesn't state it but I guess the person wanting to PWM a motor over +/- 10V mentions the negative voltage as a way to reverse the motor as well.

@PeterJ Yes, I thought about that, and figured that if the question adds such a requirement, I can always edit the answer accordingly.

@AnindoGhosh, fair enough.

5 hours later…

1:51 PM

@rawbrawb hi

@yogece hello

2:28 PM

Yo yo yo!

2:51 PM

WTF?! I am seeing lots of crazy questions like this recently:

-1

Q: LED Shut Off Time

I am looking for information on how much time it takes for a typical LED to shut off long enough that the light can no longer be detected by human eye.

Looks like government workers from Area 51 don't need a college education or any at all!

@PeterJ Yo

3:15 PM

@W5VO Do people ask questions like the one above a lot?

@coding_corgi Meh, the only "weird" thing is that he's not aware that the human eye is the constraining factor

@W5VO Huh, the other day someone was asking a question about sound waves making humans itchy, nausea, etc. !

@MLM Yo

@coding_corgi Hey

@MLM Whatcha doing?

@coding_corgi school

3:24 PM

@MLM Well duh! Is this study hall, or AP class?

@coding_corgi none, everyone has macbook air tho

@MLM Hmmm... My school (that I will go to next year) (the lower school) has 'tablets' which are HPs that you can write on, when I toured I didn't see one sheet of paper, the students do all their work on their tablets, the high school has macbooks though...

@coding_corgi the webfilter blocks stackexchange sites at home :\ except stackoverflow

@MLM Eeesh!How 'bout some hacking? ;]

@coding_corgi sure... I have tried to repeal the block but they havent done anything

archive.lightspeedsystems.com/Archive/…

3:36 PM

@MLM Is it on some server or something?

@coding_corgi ye they set up their own proxy

but i think it just hosts the lightspeed script

@MLM Do you have nmap?

@coding_corgi no?

@MLM Do you have telnet?

@coding_corgi don't know, never use mac

3:41 PM

@MLM Open up the terminal and type telnet or nmap to see if you have them

@MLM You can get nmap here:

nmap.org/dist/nmap-6.25.dmg

@MLM Never had a .dmg file, you might have to extract it...

@coding_corgi I'll pass

@MLM You can do a lot with nmap, scan an entire network, devices (for ports), etc.

2 hours later…

5:20 PM

good morning

@jippie Yo!

@jippie Did you get the dragon (programmer) yet? If so, how do you rate it?

5:33 PM

@jippie Still here?

1 hour later…

6:39 PM

@DavidKessner Yo!

@coding_corgi Oy!

What's up?

7:06 PM

Got myself a nice new Arduino today :)

user image

for free :)

@DavidKessner That LED answer was good, the question wasn't...

@jippie How?

@jippie Leonardo compatible with WiFi?

@jippie Looking good! I have the same wifi module!

@jippie It looks like it's even a Dutch Arduino...

@AnindoGhosh yes

@ThePhoton yes

has a color sensor, wifi

7:09 PM

@jippie what are the key advantages? And what price?

WTH single chip draws 40 A?

0

Q: Differential remote sense circuit for 0.85V DC/DC supply

I have this sort of odd requirement and I'm wondering if someone with experience might have some advice on a circuit to use. I have a chip that draws 40 Amps of current at 0.85V with +/3% tolerance. Now normally I would use a DC/DC supply with a differential remote sense feature to counteract ...

power-supply op-amp

@ThePhoton LED krant is translated to 'ticker' not sure if that is a good translation.

@AnindoGhosh €0,=

@jippie "array" maybe? It's a bunch of LEDs you can light up in different patterns?

@jippie WTF?!

@ThePhoton probably an Intel processor on it's core Voltage

7:11 PM

@AnindoGhosh oh ok, bus fare was 5€

@ThePhoton it shows scrolling characters

@jippie :]

@jippie Marquee?

@jippie ....Forgot what that is called... Isn't there a Dutch company that dominates the market for making those things as electro-mechanical displays?

@AnindoGhosh in HTML that does the same as on the Arduino clone, yes

@jippie So two of them would be twice that cost?

7:12 PM

@AnindoGhosh Bus fare from India would be much higher.

@ThePhoton True.

they're 'sold' out unfortunately :(

it even came with a free cable and batteries

@jippie Oh well

there should be an external EEPROM too

etotaal.nl/upload/schemapakket%20Helios%2C%20e-totaal.pdf

@AnindoGhosh yes so sad. It was a free gadget on an electronics exhibition.

think I have to suspend my FPGA book for a couple of days now.

@jippie You got a good deal...

@jippie Wow, this guy sounds like Woz, i guess he needs a Steve to make money...

7:37 PM

@jippie I was curious as to how the transistor course is going for you.

@rawbrawb The MOSFET course? It didn't really answer my expectations

so I dropped out

@rawbrawb I'm curious how @Kortuk would answer that question.

@jippie Interesting ... how? He is an awesome author ...

It was too much semiconductor physics to my liking, too many e-powers, natural logarithms etc. and too little about how it translates to engineering.

@rawbrawb but I dropped out, maybe I missed the best part.

8:04 PM

time for bed

/me is out

clickkk

8:55 PM

@jippie I'm so sorry. Is it contagious?

@coding_corgi Thanks!

9:16 PM

@DavidKessner The guy seems a little crazy... I wonder what he would do with the info...

@coding_corgi I don't know. But I feel the need to create a sock puppet account solely for the purpose of writing outlandish questions.

@DavidKessner Ha ha!

@anorton Yo!

hi

@anorton Whatcha doing?

crashing after finishing up my tutoring job at the community college. :)

9:19 PM

Fake Question: How can I reliably cause a tantalum cap to go into a thermal runaway condition?

@DavidKessner Do you have any knowledge (I bet you do) on controlling motors?

@coding_corgi Yup.

@DavidKessner Ask that on main... :P See how many up votes it gets!

You ever have one of those problems where the best way to solve it would be to spend a week on the beach in Tahiti? How can I convince my boss of this solution?

@anorton Huh... Sounds like snack time...

9:20 PM

yup

Anyway--walking away from computer for a bit...

@anorton GET TEH OREOS!

Fake Question: I keep shorting out my non-rechargeable lithium batteries and they won't explode or release toxic smoke. Can anyone tell me what I am doing wrong? Tag=Arduino

2

@DavidKessner Hmm.. I seem to have two strange motors that I would like to control, I tried several circuits (they all look the same) sending a PWM signal (I think) from a pontimeter to the transistor, but my motor doesn't run, I connect my motor to VCC and GND and it runs perfectly!

@DavidKessner Ha ha!

@coding_corgi Schematic?

@DavidKessner Ok... Ummm... Let me see....

9:24 PM

@coding_corgi A pot can't spit out PWM on it's own, and most pots can't handle the current of a motor directly. If you don't have a circuit between the pot and the motor then you're not going to get anywhere.

@DavidKessner Really? Because I just hooked up my motor to a pot, and it worked....

@DavidKessner Scroll down: robotroom.com/PWM5.html

Fake Question: I want to design a circuit that can email me when a sensor trips, but I don't want to use any IC's. Just resistors and caps. Where do I begin?

3

@coding_corgi Did you use the circuit that is marked, "Lame! Do not use"?

@DavidKessner Ha ha! Okay, Kessner, we get it...

@DavidKessner Scroll down further

@coding_corgi That circuit does not show a pot. Where's the pot?

@DavidKessner With me, I don't want to use my tiny85 yet, or should I?

9:30 PM

@coding_corgi Well, the PWM signal needs to come from somewhere-- and it won't come from a pot. You could feed the pot into an ADC on the MCU, if it has one. And the MCU can spit out the PWM.

@DavidKessner Ok... (think I just wasted last night)

@coding_corgi Yeah, I hate when that happens.

9:47 PM

@DavidKessner Tell me about it

@anorton You must be filling up a grocery cart up in that kitchen! JK, JK! ;]

10:37 PM

Hello everyone

@Rocketmagnet Yo?

Yo

@coding_corgi Can you help me out, I'm being thick.

@Rocketmagnet ?

OK. I've got 240v AC, and I want to use a transformer to step it down to 6v.

Simple.

Only problem is, I can't seem to find a suitable transformer at Farnell.

@Rocketmagnet 6V AC or DC

10:41 PM

AC

I just need a transformer

All that turns up on Farnell seem to be very expensive ones, or low voltage ones, etc.

@Rocketmagnet Hmm... I really actually have no knowledge in power supplies, I just started EE, would you like to see a helpful video on power supplies?

Am I searching for the wrong term.

Thanks. I'll keep looking.

@Rocketmagnet Wait, that doesn't make sense... 6V AC will change from 0 to 4V then to ground, etc.

Right?

huh?

@Rocketmagnet Huh! :]

10:50 PM

@Rocketmagnet, newark.com/jsp/search/… ?

@ThePhoton Doesn't AC move like that?

(

12 mins ago, by coding_corgi

@Rocketmagnet Wait, that doesn't make sense... 6V AC will change from 0 to 4V then to ground, etc.

)

@coding_corgi Yeah, but if it didn't the transformer wouldn't work.

@ThePhoton Oh... So the transformer would give you a steady 6V AC?

@coding_corgi Steady meaning it keeps changing back and forth between -4.2 V and +4.2 V, yes.

@ThePhoton So it switches back (1V by 1V) and forth or it jumps?

10:58 PM

@coding_corgi It should be changing sinusoidally.

Alternating current

In alternating current (AC, also ac), the flow of electric charge periodically reverses direction. In direct current (DC, also dc), the flow of electric charge is only in one direction. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage. AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical...

11:27 PM

@ThePhoton Thanks...

11:58 PM

@ThePhoton oops ...- 8.5 to + 8.5 ... :-D

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