Electrical Engineering - 2011-03-06

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12:35 AM

@reemrevnivek Because it is yet another question that is just asking for an endless list, there is no way to give a complete list like this and it is very very overly broad. We really should be focusing on answering technical questions, not just making 8000 questions that are very broad and do not serve a technical purpose.

1:02 AM

hehe.. LOL @:

1

Q: Difference between configurations of unity gain buffer using op-amp

Is there any practical difference as to how a unity gain buffer using an op-amp might be configured? For example, the input signal can be connected to the noninverting input and the feedback to the inverting input; but it can also be configured the other way, with the inverting input as the signa...

op-amp practical

1:13 AM

dangit

Went and drank a beer before dinner. Now all motivation to cook is gone.

Just want chimichangas and more beer.

Wait ... this sound like a good thing.

Mmm... chimichangas.

Maybe some bacon -- that counts as cooking.

Man, being single is awesome.

cries

1:28 AM

@tyblu, haha

Chimichangas, delicious, in Texas, OK has one or 2 good restaurants, I refuse to believe you have good Mexican.

@Kortuk wtf.. these are frozen burritos consisting of cheese and what they call beef, but is obviously duck-feet.

... bought in 30-packs for the lazy and depressed... or me (obviously high-spirited and high-energy, like Charlie Sheen)

.. And there's good Mexican everywhere, but I bet it's a lot easier to find in Texas! (or any southern state)

1:49 AM

Hard to find in OK

Wonderful in Austin TX and in New Mexico.

How is your night going?

but, on the note of good mexican, i bet we have different opinions <3

but maybe not, I could be pleasantly surprised.

In New York it was terrible.

2:37 AM

@Kortuk good Mexican is about 4'8"-5'4", cute & slightly chubby cheeks, huge bonanzas and enough around the middle to hold on to. And spicy -- can't forget the spice. Pretty sure we're on the same page.

2:53 AM

@tyblu, you are correct. All good then.

3:19 AM

@tyblu, just flag me in the future.

0

Q: Copying programs from Comcast Scientific Atlanta Explorer 8300HD DVR w/ SATA port to USB unencrypted

I have a Comcast-provided Scientific Atlanta Explorer 8300HD DVR with a SATA port (I can connect a SATA drive to it for more space). I want to copy recorded programs from the DVR to a USB drive. What's the easiest way to do this?: I could get a SATA drive, but that's expensive, and, after I...

So I can just move it. I have to delete your comment to move it.

@Dean Writing quality does not influence me. If you guys would like to edit it it will be a CW at best.

@Dean, @reemrevnivek, It does not fit this site to constantly have people ask, "give me every rule that you would use for doing $*&$."

We could try that, but it just is not possible to condense a list like that and it would take a large amount of work to get them setup and we should take the time if we want them to break down into subsections of EE what we want to do. So, digital design, analog design, power supply, so forth, need serious discussion.

@W5VO, what badge are you getting?

electronics.stackexchange.com/badges/23/fanatic?userid=638

Grats @W5VO!

I just got the "Proof that I have no life" badge

haha

I like to check in atleast once a day, it is hard to keep 100 days without missing

I have visited the site 391 days.

twice as much as me

<3

I have been with the site since it was chiphacker.

Next one will be the voting badge. Half way there, and I refuse to vote on everything

3:26 AM

I will note vote on everything, I wish they did not promote people just giving massive upvotes. I constantly see shite questions get upvotes, and good ones that are long and detailed not.

I think quite a bit of that is that past a certain level of knowledge, people won't up-vote. I know that if a subject is beyond my expertise, I will not vote on good answers because I don't know the answer

ahh

yeah, i think that is it, and have thought of that before.

It is causing massive upvotes for very very basic questions, and good questions that are technically demanding get none.

lol, yet another question dumped to an other site that doesn't want it

I know

Best guess for a site though.

so there's maybe only about a dozen active users with broad expertise that can give useful critique on answers and questions - and even then it's not broad enough for every good question

3:34 AM

Yeah, I can only critique a percentage myself, but I think I am in general able to read and answer and understand enough to give some feedback. when it goes heavy heavy digital design I tap out.

I took a shot

0

A: RFID module always finds the same non-existent tag when seeking

I have spent the start of time looking into this, but I need to spend more. This is what I have found so far. The fact that your tag type is 55 is a big deal. The acceptable tag types are: 0x01 – Mifare Ultralight 0x02 – Mifare Standard 1K 0x03 – Mifare Classic 4K 0xFF – Unk...

Electronics can be a very deep subject - it's taken me 10 years to get to the point where I feel like I'm authoritative on many subjects in electronics.

@W5VO, agreed.

I have only been in electronics seriously for about 4

I'm hoping to leave electronics in another 3-4

but I have my areas, and I do drop the hammer, at least I think, other sometimes disagree.

@NickT, why?

gonna do biomed stuff

EE sucks

3:38 AM

@NickT Yuck

Debating between medical (physician) and biochemistry research

@NickT Dunno - I really don't like squishy stuff. (Hence EE)

actually studied biotech as an EE undergrad. Course called "Engineering of Nanobiological Systems", covering evolutionary theory, PCR recipes, synthetic amino acids, practical lab-on-chip exercises, etc... very cool -- my favourite class, and I enjoyed many of them!

@NickT, I am very interested in biomedical, I would like to work in the field, but fully as a EE. I am doing medical right now to start in that path.

Eh, it seems fairly limited in what you can do though compared with biochem

3:53 AM

have you looked at the tech behind sequencers? Flipping amazing.

Sure, the tools are pretty impressive, especially the development over the past couple decades, but the use of them on the myriad diversity is moreso

@NickT, I just like to do electronics, and most moderns systems are quickly needing electrical controls. I would like to make them dependable and cheap.

I too have dreamed of buying a shotgun sequencer and a yacht, then spending my days scooping ocean water and sequencing whatever I can find ;) .. somehow they get paid loads.

Still, good for you @NickT. As long as you find what you like to do and do it I think it is a good choice.

@Kortuk Have you looked into lab-on-chip development groups? That's an area that desperately needs a boatload of combined IQ in order to start churning out Star Trek-type bio-analysis devices. Doubt I'd ever make the grade, but they're looking. I think you may have told me about one or a few well-known groups at your U, a while ago.

4:01 AM

might have

no idea

Interesting idea though.

Kinda hoping that the chemistry SE site will be moderately high-level

a la math

...but I doubt it

Anyone ever done high-shock (mechanical) electronics design?

how high

like where you can't just pot it all?

no idea - I don't have any hard numbers.

what's the application?

4:08 AM

tap dance shoes

long story

Why is that high shock?

higher than a test PCB sitting on my desk

@W5VO Guess @NickT isn't the only one broadening his horizons!

I don't think that qualifies

alright, I could have come up with a much better joke. Let's just ignore that one.

4:09 AM

probably easier than being in an engine

@tyblu it wasn't bad

I figure you won't have constant vibration, but the shoes will have jolts when they hit the ground / other shoes

What's an upper limit (in terms of acceleration/force) of normal PCB design?

what types of parts

There's a question ;) ... ask for standards or experience.

chip resistors can probably withstand several thousand g without much ill effect

the fiberglass isn't going to do anything

don't forget their solder joints though.

!

4:15 AM

that's what I meant

accelerometer and gyro, micro, RF transceiver, battery (rechargeable)

all you really need to worry about are leaded components, e.g. SMT electrolytics

maybe battery holder.

what about microphonics?

possible detuning of RF circuits?

What are you doing that you would care about microphonics?

RF operates at a somewhat higher frequency than mechanical shocks

4:18 AM

maybe the microphonic effects would modulate the RF?

dunno

I'm trying to come up with failure modes or conditions that I need to consider during the design

I still don't think that your shocks are going to be any worse than engine bay stuff

the main crux of it is where you're locating this thing

The heel of a tap shoe

Should I just build it and see if there are issues?

Could, if you're concerned about the RF, I might ask some FAE

FAE?

Could strap a ZigBee unit (with no through-hole components) to some workboots and kick stuff and see if a constant data stream is interrupted :P

4:29 AM

@tyblu I figured that tap shoes would be "worst case" for shoes, since the heels + taps are rigid

What RF system matches: low latency, low bandwidth, single master + many slaves (2 to 40)?

4:45 AM

** crickets **

@W5VO field application engineer

What's worse might be the rapid change in transmission path length, not really anything mechanical

@W5VO Glad to see you broadening your horizons.

@NickT, EMs idea of transmission path length is not going to be affected by the moving of the shoes.

what?

@NickT that comment is my reference, the shoes moving suddenly will not be suddenly to RF.

I'm don't get it; you're grammar is throwing me off

4:58 AM

hahah

I am sorry @NickT, I never promised I would write well.

Let me try again.

RF is affected by path length changes over time

I edited it.

some are more sensitive than others

2.4GHz will not be affected by the distance that a shoe can move during dancing.

unless he is at the threshold of receiving which is more the problem then the path change.

2.4 GHz is just a carrier; not an RF technology

5:02 AM

They were discussing zigbee.

900MHz would be just as unaffected, and that is occasionally used.

<3

What's the maximum relative speeds of transceivers for it?

forgive me if I am coming off as rude, at work and only able to write quips.

@Kortuk It's more of a response to a challenge than anything physical that I'm doing. Watching me tap dance would be a sad comedy

haha

I can understand, for the first 2 years I did dance I was aweful.

I would be developing them for professionals to try out

5:04 AM

Yeah, I assumed

I feel secure enough to say I have taken classes such as ballroom dancing and enjoyed them.

Ahh, well, back to work.

processor coolers look like motorcycle engines nowadays.

how can anyone resist them.

haha

nice

@Kortuk Don't know why you'd need to feel secure about that - ballroom dancing is usually done as a male+female couple

@Kortuk I may be wrong, but I'm relatively sure that one of the design aspects of RF protocols is the relative speeds between tranceivers

it may only be of note for higher-performance connections, e.g. Wi-Fi, cellular data

@NickT, it is alot less then your feet and not at low speeds like zigbee.

5:07 AM

@NickT I think that's due to the doppler effect

@W5VO, women were beautiful, off to work i go.

@tyblu amazon.com/Cooler-Master-Nickel-Aluminum-Heatpipes/dp/…

@NickT LOL ... should have known better.

@W5VO It's a lot more than that; the same frequency can work or not work depending on aspects of the PHY layer

am I just crazy here? Didn't anyone cover this in a wireless class?

@NickT Sure, lots of issues with multi-path, fading, etc....

But for two objects in free space with different velocities, the only effect on RF should be due to the doppler shift, right?

5:13 AM

Anyways, my point with this would be that if you transmit while one is vigorously kicking their feet it might fail for an instant because you're moving faster than the PHY can handle. For ZigBee, this is probably not an issue though

Yeah, but the implications of how the shift is perceived by the receiver can cause errors or not

Sure. If one object was on a centrifuge, with significant angular velocities, the whole signal would appear to be frequency modulated by a stationary observer

So give the widget some memory, packetize data, and retransmit upon CRC error :P

man i'm a genius.

... I missed it, and no edit history. Blast you, restricted privileges.

I'm trying for it to be low latency :p

To human standards? That's 100ms+...

@tyblu I likened your claims of genius to someone's posterior

5:21 AM

Ah, yes: something like "Your genius is akin to the fame of J Lo's behind." Thank you.

@tyblu It's going to be synchronized with other devices, and I want everything in the system to appear to be happening at the same time. I don't know how much time that gives me. It would be repetitive, so any offset would stick out.

I'm currently in the "I don't know how good is good enough" phase, so I'm shooting for overkill

5:52 AM

serious multitasking going on here: comparing reviews, prices and performance of computer parts for new PC; replying to online dating convo's; drinking 3 different types of beer; doing laundry; cleaning room; and making last-minute bad decisions on what to add to my latest paperback Amazon order.

ending up talking about PC parts to local girls, leaving empty bottles in my room, forgetting about laundry, and spending way too much on sci-fi.

all in all, total failure.

other than the beer part: 100% success.

6:45 AM

so i've been interested in making some sort of PC-connected garage door opener/status monitor and trying to evaluate my options for connectivity

seems like it would cost me something like $100 to get an arduino with network connectivity but for that price i can just buy an ipod touch 2g on craigslist and can probably control it via wifi

Is a computer in the picture, or is it just a stand-alone system?

computer in the picture but on 2nd floor opposite side of house

i know with my jailbroken iphone i can do python scripting I just haven't messed with the dock connector yet and it doesn't seem like anybody else out there has tried to do anything like this yet =)

for this application all i'd need is an audio output to drive a garage door opener button click and maybe feed some sort of sensor as an audio input signal at some point in the future so i can tell whether the door is open or close

why audio, specifically? For drive capability?

yeah it seems simplest... i have no idea what the 'ipod sending/receiving' txd and rxd lines might output or how the API works

but a simple script to play a tone on the lineout pins would probably drive a remote control clicker

well, regardless of drive, you can buffer it with a transistor or op amp if required.

6:55 AM

yeah I'm just going for simplest hardware possible besides the actual ipod touch and a standard garage door opener remote

Also, if you're driving a wireless remote control clicker, why not keep everything on the PC? Grab a $20 USB dev kit and wire the remote directly to it.

won't work from where my pc is located

i mean i could run some wire and probably manage it

is there wifi in your garage?

yeah that's how it would trigger actually... when i come home my iphone automatically connects to my home wifi

which my computer would pick up somehow and send the door open command to the garage if it was closed

get a cheap router and put dd-wrt on it. There's bound to be some old ones that you can pin-out a UART

6:58 AM

hmm, that is a good idea

cheaper than an ipod probably... $50 new?

yeah the old ipod touches are like $50-100

just seems like a lot of untapped potential in a fairly cheap device now

@Kortuk, You get bounty due to OP RMA'ing questioned part and eliminating incentive for more answers... also freeing up myself for another bounty :)

oh and thanks for the answer to my question =)

7:23 AM

@W5VO yes, dopplar shift can cause problems.

@NickT You are correct, this is an issue in some comm systems, zigbee at 2.4GHz is not nearly narrow enough channel or high enough bandwidth for that to become an issue with a moving shoe.

@tyblu What?

@tyblu, ohhh, scratch that, thank you for the bounty.

3

Q: RFID module always finds the same non-existent tag when seeking

I'm wondering whether anyone has any experience with the SM130 Mifare module. I've managed to get my hands on one, sans antenna of course, and seem to be having a few issues with it. I've got the module connected to an FTDI 5V USB to TTL converter via the UART lines. I've added capacitors over t...

@tyblu, i spent a while looking at it yesterday and realized I really needed more and should just let him know what I have found.

@tyblu, thank you. I like your random bounty idea.

@Kortuk Yep -- was a worthy answer for a difficult question with many possible explanations.

There were 8 million, but the 0x55 was a dead giveaway, almost any command could return that for an error.

@tyblu, I wonder if his antenna was too capacitive and was not charging up enough before he tried to read.

I will go leave him a comment.

7:46 AM

2

A: Difference between configurations of unity gain buffer using op-amp

If you use a feedback from the output to the non-inverting input you will find that as the output goes too high it causes the difference to increase and it will rail. You have to use the feedback to the inverting input. What is really happening? An op-amp attempts to take the difference from t...

Glad my answer got your seal of approval @tyblu.

@Kortuk, good. 'Cause I'm never wrong, so you kind of need my seal.

8:12 AM

@tyblu, I giggled.

2 hours later…

10:29 AM

0

A: Thermometer to USB

You can't connect a DS18S20 directly to a USB port, because they both different protocols. You need something in the middle to translate, like a microcontroller. I've done something very similar except I used the RS232 com port on the computer as that allows you to use a much wider range of micr...

@Kortuk: Just saw your comment... I'm not too sure how to do this... I can see how you can send by changing the RTS signal, but how would you read the data back?

2 hours later…

12:24 PM

@BG100 make it so that the RTS/CTS signal(I forget which the computer controls) going high causes the output from the computers UART to connect to drive the chip. When the RTS/CTS goes low it causes the chip to be able to drive the data line. Use the signal as a control for whom drives the line effectively.

will the ICs every be indestructible?

4 hours later…

4:32 PM

This is ridiculous; every 1-2 days I need to take out about 6-10 twists in my headphones cable

whenever I bother to note which way I take them off and put them on, it shouldn't be twisting at all

1 hour later…

5:56 PM

sounds like somebody needs to invent a mechanical headphone untwister

@nvuono i'd have a few concerns with that to do with it breaking the wire or breaking the jack.

System and Method for tracking and mitigating headphone cable rotational stresses in realtime systems

@NickT there is a space-time curl in your vicinity. Suggest analyzing local long-term ion trajectories versus magnetic fluctuations and correlating with changes in mass flow rates through water pipes nearby, as their ion concentrations would skew local fields.

I'll get ltd.-commander Data to help.

Hmm.. he appears to be unavailable -- something about recording a duet with Nemoy.

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