Ask MetaFilter posts tagged with electronics

Modifying electronics.

PowerCat — Sat, 05 Jul 2008 07:53:59 -0800

I bought the POWER TOUR Amp and it's really awesome. However I want to modify it and I don't know much at all about electronics. The unit uses 4 C batteries, adds up to 6 volts. The back of the unit says 2.9W.
I'd like to find a wireless phone battery to plug there instead. Would it be as easy as finding a 6 volt battery and plugging it there? Would the battery fry the amp if the amperage is too high?

Say I have a 6v, 1000mAh battery, would a direct connection to the unit power it on and play properly?

Thanks!!

BUZZ - I know!!

Jakey — Thu, 26 Jun 2008 17:19:00 -0800

Electronics filter. Game show buzzer+. There are tons of simple game show buzzer layouts on the google. What I can't seem to find is an idiots guide to something that would allow you to take an input more complicated that a simple yes/no. i.e. interrupt + [string]. Any pointers?

This shouldn't be happening.

jon1270 — Thu, 26 Jun 2008 13:20:06 -0800

Help me diagnose repeated failure of my lighting dimmers. When I remodeled my kitchen about a year and a half ago, I installed nine line-voltage 4" recessed lights which are controlled by two Leviton Illlumatech preset dimmers, with three cans/150W on one dimmer and six cans/300W on the other (these are 600W dimmers). Everything works fine, except that when a bulb burns out there's a better-than-even chance it will take the dimmer with it. A dimmer has failed three of the four times that a bulb has burned out since the initial installation. Only the slide dimmer fails -- the on/off button continues to work normally.

Leviton has been replacing the dimmers as I mail them in, but their tech support people are, so far, unable to imagine how a bulb's burning out could cause the dimmer to fail. They've speculated that it could be a problem with a fixture or a loose connection, neither of which ideas holds water; the failures have all been simultaneous with burn-outs in different fixtures, and there are no symptoms of loose connections anywhere.

I'm hoping someone here has a brilliant insight to offer. The bulbs, if it matters, are Sylvania 50W PAR20s.

A + B = a trip to Radio Shack?

harkin banks — Tue, 17 Jun 2008 09:54:17 -0800

How can I build my own A/B/A+B speaker selector box? My lab is two adjoining rooms, with a large doorway (but no door) cut into the wall. We have a crappy bookshelf stereo in one room. It is just audible enough in the other room to be irritating, but not enough to really hear what's going on. I scrounged another pair of 6 ohm speakers from another crappy bookshelf stereo, and I was thinking about how to connect them up so that both sides of the lab can hear Talk of the Nation. Commercial speaker selector switches run $50 - 300, and I'm cheap -- plus I think this might be a project within my limited soldering skills, so if I can make it myself I'd like to.

The stereo is an older one, made by Fisher. The speakers say "MAXIMUM POWER 80W (PEAK), 6 Ω IMPEDANCE"; the stereo says "6 Ω MINIMUM". I'd like to switch the speakers in and out with a break-before-make rotary switch like this one. It's easy to figure out how to run one pair at a time (A or B), but how do I wire it up to drive both pairs safely (A + B)? I'd like to wire the speaker sets in parallel, but I know this will drop the impedance of each circuit to 3 ohms, which is below the amp's rating. Is the solution as simple as putting a 3 ohm power resistor in the circuit, to raise the total resistance back up to what it would be for just one speaker? Is there a better way to do this safely, that will sound OK? Lots and lots of people work in this lab and will be using this switch, so I can guarantee you that it will be switched under load more often than not.

Surprisingly Google has failed me on this issue. I can find lots of schematics online for switching two or more amps between one set of speakers, but nothing for the reverse situation. Please help us hear the sweet sweet tones of Science Friday clearly!

How can I learn some basic electronics?

greenie2600 — Sun, 15 Jun 2008 07:56:19 -0800

How can I learn some basic electronics? I've always wanted to learn how to build some simple electronic gadgets, but I've never really known how to begin. had one of those Radio Shack 80-in-1 kits when I was a kid, but I was just following the steps in the manual - I didn't really understand any of the theory behind it. I've done a little bit of soldering, and a little bit of basic repair work. I've picked up a couple of textbooks, but they seem a little too theoretical for an absolute beginner.

FWIW, I'm a fairly accomplished computer programmer, so I understand engineering, troubleshooting, critical/rational thought, and creative problem-solving on some level. I did well at math in school, but I've never learned calculus, and I've forgotten most of what I did learn. I'm willing to learn, though - or, to find a program that will do the math for me :)

What I'm interested in (eventually) building could best be described as electronic art objects: sculptures that incorporate LEDs blinking in sequence, motors turning gobo-like optical wheels, and the like.

Should I just get another Radio Shack kit, and try to actually understand the circuits I'm building? Can anyone recommend a book that's suitable for my situation? I think something more hands-on and demonstrative would be helpful. I learn by doing, so if I'm presented with a basic problem and the tools (e.g., principles) to solve it, I think I could get somewhere.

Lastly: is there any free or cheap software for virtual circuit design? Seems like that'd be a good way to quickly try out different designs, to see what works and what doesn't.

How to repurpose a dead cell phone's electronics

monkishies — Mon, 09 Jun 2008 14:58:03 -0800

Know of any good resources "out there" specific to information covering the salvaging, repurposing, and/or cannibalizing of cell phone electronics? For some strange reason I've had a bit of luck when it comes to locating cellphones that are "dead" or "abandoned". It seems like most of society treats these nifty gadgets like toilet paper. I guess when you can get one free just for signing a 2 year contract it makes it ok to just dump it in the street like everything else?? A horrible excuse if you ask me but lets move on.

Being a pack rat and an amateur solder slinger I've always seen them as a pretty pill box full of possibly useful parts for random projects. So now I have a little collection. Unfortunately finding information on how to salvage these parts and reuse them seems, to me, quite hard to find. So I come to you wonderful folks with the hopes that you'll be able to point me in a direction where I'll be able to satiate my need for making other people's garbage useful. Anything and everything you find will most likely be of some use.

Thanks

Price check, please.

tomcochrane — Mon, 09 Jun 2008 07:33:37 -0800

I'm looking for a site that lists the resale value for used electronics. I'm looking into buying a dslr camera (my first) and am considering getting one used. However, I don't want to get ripped off. So if such a site exists, then I might be able to get a feel for how much I should have to pay for a camera.

ps. I'm looking at getting a Nikon D40 if I can find a decent deal.

Attention Tivo customers: Mars Needs Women

bondcliff — Wed, 04 Jun 2008 07:10:48 -0800

What is the purpose of this random noise my electronics are making? I first noticed this on my Tivo. I’d be sitting around, not even watching TV, when I’d hear a short (< 2 second) burst of “morse code.” Not beeps, but sort of a muted dit-dit-doot-doot-dit-dit. This would happen about once or twice a day. I assumed the hard drive was doing some sort of self check.

Then yesterday I was in a meeting at work when I heard the exact same noise (same pattern of dits and doots, as far as I can tell) coming from one of those starfish-type speaker phones. Nobody was talking on the phone. There goes my hard drive theory. Now I’m thinking perhaps it didn’t come from the Tivo, but perhaps a speaker near the Tivo.

Last night, I heard the same thing from one of my Squeezebox players, or rather from the speakers attached to it. The player was not playing music, though both the player and speakers were powered on, or at least in stand-by.

Now that I think about it, I’m pretty sure I’ve heard this noise on other electronic devices. It's definitely a digital-type signal, as opposed to static.

What the hell is happening? Is something else causing interference? Is there a common component inside these devices that is doing this? Why is the pattern always the same? Are my electronics communicating back to the mother ship, planning the revolution?

I’d prefer a technical explanation (“These devices all use a THX1138 chip, it’s the hammerflanger module recalibrating the DRADIS.”) over a guess, and I’d love to know I’m not the only one hearing this.

HTF Parts needed for a theremin.

KI6ILS — Sat, 31 May 2008 22:51:29 -0800

Where can I find a 50-300µh adjustable coil? I have searched the obvious sites; ie mouser, google, all electronics. This is from a part list for a theremin from the 1967 Popular Electronics. The part list has a few htf parts like those coils. Here is a copy of the schematic. http://www.swtpc.com/mholley/PopularElectronics/Nov1967/PE_Nov_1967_pg30.jpg

Manual for obsolete test equipment wanted.

kc8nod — Thu, 29 May 2008 08:20:28 -0800

I need a manual for a Panasonic VP-8121B AM-FM Stereo Signal Generator. This is an obsolete piece of test equipment that Panasonic doesn't support anymore. Apparently, they're out of the test equipment business altogether.
There are a few used equipment dealers like http://www.testequipmenthq.com/ and http://www.alternativetest.co.uk/ who will sell me a (like) new unit, but won't sell me just the manual.
I have also tried:

http://www.manualsplus.com/

http://www.ebaman.com/

http://bama.sbc.edu/

http://www.consolidatedsurplus.com/

I would hate to have to replace this thing only for the lack of a manual. Help!

Math students, you are getting such a raw deal.

skryche — Wed, 28 May 2008 19:23:41 -0800

Why doesn't Moore's Law apply to graphing calculators? When I was a freshman in college (1994), my parents bought me a TI-85 graphing calculator (6Mhz, 32k RAM) for (I think) around $130. 14 years later, for about the same price, I can get a calculator with about 4 times the speed and 4 times the RAM.

Shouldn't today's calculator be vastly more powerful (or at least much cheaper) -- in line with advances in home computers?

Help me build a simple intervalometer!

lord_yo — Tue, 27 May 2008 02:02:58 -0800

Help me build a simple intervalometer! I'm trying to build a simple intervalometer, i.e. a device which gives my camera regular impulses to shoot a picture at a defined interval. It would enable me to do custom time-lapse series.

Hooking up my camera to such a device is not a problem, as my Canon EOS 400D uses a easily available cable jack for the remote control.

I can solder, and have a basic understanding of electronics components. However, I don't know how to build the device itself. I'm looking for an DIY electronics kit (could be programmable, but doesn't has to be) or cheap hackable gadget (timed blinking lights? kitchen timer?) that I could convert into an impulse-giver.

The device would need to be configurable to set the following parameters:

- Time off - e.g. 500ms
- Time on - e.g. 10ms
- (optional): number of repetitions - e.g. 1000x

Example for a commercially available device: [pClix]

LIGHT SHOW

god particle — Mon, 26 May 2008 16:17:02 -0800

I'm interested in learning how to wire LEDs and program/control them. I want to learn how to wire a lot of LEDs together and then program or otherwise control them, so that I can trigger certain ones to go on or have them play in sync with music, or something of that sort. Preferably I'd like to be able to control the lights by hand through some sort of device/interface. I don't really know much, if anything, about electronics and programming. The most I can do is solder a couple LEDs to a battery and have them turn on. What resources should I turn to to get started?

It's not a feature, it's a bug

TheRaven — Sat, 24 May 2008 16:52:02 -0800

It's not a feature, it's a bug or why do they impair my equipment when not asked to? We have all read about Microsoft's backdoor key. Fortunately, I use a Mac but Steve Jobs, out of the goodness of his heart, has hampered my Mac by only allowing me to play DVDs from one region and not others. As far as I can determine, neither of these "features" was mandated by the authorities.

Can the Hivemind come up with other electronic devices/services where the manufacturer/service provider a) deliberately impaired the functioning, even though not required to do so by law; b) where this offered no benefit to the manufacturer/service provider; c) where the consumer either did not like this or, had s/he known of its existence, would not have liked this?

I am excluding such examples as P2P throttling by ISPs which, nominally, reduce the ISP's traffic and therefore benefit the ISP and where the benefits might be for good reasons, such as safety or environmental reasons, even if not mandated.

I am not interested in moral discussions about the Microsoft/Mac decisions nor the fact that there is some doubt about what Microsoft actually does.

Aurduino or Make Controller

dylanSnow — Sun, 18 May 2008 19:55:53 -0800

I am trying to decide which to (learn) to use, The Arduino or The Make Controller Kit. Which should I choose as a first buy / entry level controller? I am going to have 10 days to sit down and really get down and dirty with a new project. I am very much an autodidact type of person. I have in to build a mind a multi-touch musical instrument.

I am an artist. I am have above average Actionscript 2.0 (working on 3.0) programming skills. I will be using flash to control the multi-touch
device.

At the moment, do to ease of use the Make Controller looks like the best bet, but it is $100. On the other hand The Aurduino seems to have way more how-tos and tutorials and is $35

Any suggestions, guidance or comments would be greatly appreciated.

dylan

Charge me (and my batteries) up

tip120 — Thu, 01 May 2008 13:58:02 -0800

I am charging at least 20, but up to 30 electronic components. Each will draw 300mA at 5-7VDC. What sort of power supply do I need? I have at least 20 (possibly 30) custom electronic devices that are battery operated. Each object has a 1.1A LiPoly battery and a MAX1555 IC charger. These objects are going to be free roaming during the day, and plugged in at night to charge.

I know the circuit works as expected, and have charged one of them off of usb power (100mA 5VDC).

If all the objects are going to be plugged into one power supply at night, am I correct in thinking that I will need a supply which produces a regulated 9A 5VDC? Where can I go looking for something like this (in Europe preferably). Would an old computer supply work?

Where should I go for arts/electronics/performance stuff?

hapticactionnetwork — Wed, 30 Apr 2008 18:04:23 -0800

Help me figure out what to do with some travel money! Specifically interested in arts / electronics / performance festivals, but any suggestions are welcome. As part of a grant I received, I have a not insignificant amount of money that I have to use specifically for travel. The grant is specifically for theater, but the travel doesn't necessary have to be. My interests are pretty wide-ranging, but I'm definitely interested in performance and technology.

Things I've thought of:
- Las Vegas! (Seriously.)
- Disney World! (Also seriously.)
- Ars Electronica! (But, is this a reasonable thing for me to go to, as an english-only speaker?)
- Venice Biennale!

Have you been to any great festivals? Or places that were awesome?

Thanks in advance. You all are awesome.

Static Electricity Fries Garage Door Opener; Faraday Cage Protects?

coffeefilter — Sat, 26 Apr 2008 16:22:12 -0800

(Electronics) Is Static Electricity frying my garage door opener, and can a partial Faraday Cage protect it? In the winter, it is very cold and very dry. Very. Lots of static electricity.

I keep the garage door remote control opener in my jacket chest pocket. It lives there through the winter. To operate the opener, I don't take it out of the jacket pocket; I just press the button through the cloth. The jacket is some kind of synthetic. It crackles with static discharge when I take it off.

(1) Is static electricity harming the remote control? I've gone through a couple. (Alternate culprits might be extreme heat/cold cycles, getting tossed around, low-quality electronics, etc.)

(2) If so, would a partial Faraday cage, e.g., aluminum foil wrapped around most of the opener, protect it? (wrapping it completely blocks the signal that opens the garage door)

Is my mp3 player frying my headphones?

keith0718 — Thu, 24 Apr 2008 11:28:10 -0800

Is my mp3 player frying my headphones? Is this even possible; if so, how? I've been using a Cowon D2 with Shure se530 earbuds for over a month with no problems at all. Tuesday, after enjoying the player/earbuds for the first half of work, I shut the player off for lunch, but left it and the earbuds on my body as they were. (I wear an armband and make sure that nothing touches where the headphones go into the player's jack.) When I started the player up after lunch, there was no sound in the right earbud. This was not precipitated by any kind of warning at all and no amount of wriggling can coax out any kind of short anywhere. The right earbud won't work in other mp3 players either. Wednesday, I went to work with a different/brand new headphones (but same mp3 player) and after just a few hours, the right earbud started to fade in/out. It seemed to be most noticeable after the player has been off for a few minutes, but this could be coincidence. Is is possible for an mp3 player to fry headphones? What do you think is going on?

How can I use my TV speakers as the center channel on my receiver?

odinsdream — Mon, 07 Apr 2008 07:02:13 -0800

How can I use the speakers in my TV as the "center" speaker on my receiver? I have a receiver hooked up to four normal speakers. I'd like to use the speakers in my TV as the center speaker.

My TV has audio inputs for each set of video inputs. These are normal RCA red-white connectors.

Is there some way to connect powered speaker wires to these without breaking the TV? My first thought was to open the TV and disconnect the speakers from the internal wiring and substitute my own. I'd prefer not to do this since the TV is new and still under warranty.

The other problem would be that the TV has two internal speakers, left and right, which I want to treat as one.

Any thoughts?

How do I get rid of static/noise when using American electronics with my TV in India?

smersh — Fri, 04 Apr 2008 04:10:43 -0800

How do I get rid of visual static/noise when using American electronics with my TV in India? Most notably, with my Nintendo Wii? I have an Indian Panasonic Plasma TV connected to a US version of Nintendo Wii, an Apple TV, and an Indian DVD player, all going through an American component switcher (this one)

Without the component switcher, there is some visual interference. It's slight, but annoying. With the switcher, it's intense.

How do I get rid of this static? I use good wires, and my outlet strip is also of good quality. What else can I do to have a clear picture?

How can I keep a receiver cool?

Hogermite — Mon, 31 Mar 2008 16:33:26 -0800

We've got an Onkyo receiver for our new home theater that is running really hot....how can I best place a fan to maximize cooling? My father recently purchased a entertainment center to house all of his electrical components for an awesome new tv/surround sound/etc setup….the tv sits right in the center of the entertainment center and there are two cabinets below for the receiver, dvd player, ps3, etc….the cabinets have glass-paned fronts and he has cut holes in the back to allow for air-flow, however, the Onkyo receiver that he purchased seems to run really, really hot…to try and solve the problem, he purchased a large PC fan and rigged it to sit almost directly on top of the receiver (about a finger or two of space away from the top of the thing), blowing cool air down into the air vents…sorry for all the lead up, but here’s my question….is this the most effective use of the fan? Would the fan be more effective blowing warm air out than cool air in? What if he tilted the fan on its side instead to blow cool air in on top of the vents as opposed to inside of the machine itself it….basically, we’re just trying to figure out optimal fan placement for best cooling in a confined space….thank you!

Oh, and I read up on all of the previous questions regarding this topic and there was actually one that was really similar; however, the responses never really answered the question…so that’s why this is here…

cell phone static and home stereos

minicloud — Sat, 29 Mar 2008 12:17:38 -0800

Why does my cellular phone cause my home stereo speakers to make strange noises? Sometimes it happens when a call is about to come in, but mostly it just happens periodically for seemingly no reason. It sounds like strange beepy static and it happpens much more frequently now that I switched to an iPhone. Is there a way to stop this besides throwing my iPhone across the room?

(Electronics) Cylinder in computer cable - what is it?

coffeefilter — Wed, 26 Mar 2008 12:15:07 -0800

So, on lap top power cables, and USB cables, what is that cylindrical object near the end? Kind of like if the cable was a snake, the snake had gotten hungry and just swallowed a plump, unfortunate hamster. (Or a thirsty, unfortunate snake had swallowed a can of soda.) What is it? What's it called? And what does it do? - Digest electrons?

I'd like to learn about electronics!

DMan — Sun, 23 Mar 2008 16:33:42 -0800

I'm trying to get into building electronics and I need some advice. What would be a good place to start? I recently decided to change my college major to Computer Engineering, which means I'll be taking a lot of Electrical Engineering classes, some of which will involve building electric circuits. While I haven't done much of this, it's something that's very interesting to me, and I'd like to get a head-start on some of the stuff I'll be learning in class, and also go a bit beyond what I'll do in a classroom environment--that is, I want to actually build some stuff.

What I need is recommendations on specific books or whatever to start with. I'd like something that's sort of project-based, so I can build something and in the process learn the concepts behind it--I learn better when I actually do something, and really enjoy making things.

I'm a patient person and I can handle menial tasks if it's helping me build a foundation for further use, but I'd really like to jump into making things. I'll be getting plenty of theoretical instruction in my upcoming classes, so please consider that in your recommendations.

So, in short, are there any books or kits or whatever that you guys can recommend to me to learn more about electronics, and hopefully build a few things in the process?