» MAKE: NOISE — Discuss this article

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• my brother
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  my brother can be a real pain can any1 find out a way to build something that u put on a doorknob and when someone touchs the doornob they get shocked in a budget of $20?
  
  email me at Jpoole908@aol.com
  

  Posted by RockyRaccoon on July 13, 2005 at 13:14:54 Pacific Time

• my brother
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  I would suggest getting an "electric shock pen" (as little as $4 from ebay) and then modify the pen by wiring one contact to the door hardware on the frame and the other to the doorknob. I would also suggest installing a switch, otherwise when you go to open the door you will also receive a shock.
  
  Once the door is closed and the circuit is completed by the closed switch anyone who touches the handle will be shocked, including you.

  Posted by Boba-Fett on July 15, 2005 at 20:32:50 Pacific Time

• My pesky brother
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  my brother can be a real pain can any1 find out a way to build something that u put on a doorknob and when someone touchs the doornob they get shocked in a budget of $20?
  

  Posted by RockyRaccoon on July 13, 2005 at 13:13:50 Pacific Time

• HTPC Control from Universal Remote
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  O'Reilly has a great book that provides the answer to this question any many others you didn't know you had. The name of that book is "Home Hacking Projects for Geeks".
  
  By coincidence the books web-page has a sample excerpt of this specific project ( http://www.oreilly.com/catalog/homehpfg/ ).
  
  However, anyone interested in doing some cool home projects should pick this one up.
  
  Good Luck,
  -Charles

  Posted by Boba-Fett on June 29, 2005 at 19:22:53 Pacific Time

• MP3 Phonograph
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  Hmmm...I didn't think this was possible, but I just did the math. Assuming a SNR of about 40 dB for a phonograph record and a bandwidth of about 15 KHz, the Shannon limit would be around 200 kbps!
  
  Assume the modem you used to convert the analog sound on the record to a digital stream could hit a (not unreasonable) 50% of the Shannon limit, or 100 kbps. Knock off 20 kbps for error detection/correction coding and you're left with 80 kbps, which would be a respectable rate for something like WMA or AAC.
  
  Somebody want to check my arithmetic here? Anybody got a record cutter :-)?
  
  Cheers,
  Bob

  Posted by inuse on May 17, 2005 at 19:53:21 Pacific Time

• Cat 5 Cable Continuity
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  The quickest/cheapest way to test a cable is with a loopback connector like this:
  http://www.cyberguys.com/templates/searchdetail.asp?T1=180+0506
  
  Just connect it to one end, then plug the other into an Ethernet switch or (light equipped) Ethernet card and check the lights.
  
  If it's broken, though, you're back to the wire-by-wire approach with a multimeter.
  
  A cheap discrete tester would be pretty simple to build if you need more than a go/no-go test.
  
  Just connect the anodes of 8 LED's to each wire on an a Ethernet jack and then connect the cathode's together. Connect that common cathode lead to the negative side of a battery supply (9 volts should do) and connect to positive, via an appropriate resistor, to a the common lead of a ten position rotary switch. Connect the first eight switch leads to another Ethernet jack.
  
  Plug your cable into the two jacks. You should see one, and only one, LED light for each of the eight positions. No lights in a given switch position indicates that wire is broken, two or more indicates a short.
  
  Cheers,
  Bob

  Posted by inuse on May 16, 2005 at 19:48:38 Pacific Time

• Cat 5 Cable Continuity
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  You can get a 8-LED cat5 tester for $10
  from mpja.com
  
  http://www.mpja.com/productview.asp?product=15031+TE

  Posted by lardmaster on October 16, 2005 at 21:40:39 Pacific Time

• Wire My House Efficiently
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  Depending on what you're trying to do, Power Over Ethernet (PoE) may be what you're looking for.
  
  The standard delivers +48v at about 13 watts (per outlet) via a Cat5 Ethernet cable. You could locally regulate/switch this down to +12 and/or + 5. All the gear to do this is available commercially and it incorporates numerous safety systems. And you get your 100 MBps Ethernet over the same wire.
  
  Ethernet jacks, faceplates and wall boxes are cheap-as-chips as are the cabling, tools, etc.
  
  If you need to directly distribute 12 volts, you can use your own variant of the PoE standard, but you'll need to build in your own safety interlocks to prevent damage to your supply system or the connected device if it's not wired a
  according to your "standard".
  
  Another problem is the lower voltage will suffer greater resistive line losses, due to increased current draw, for the same power load (which is probably why the PoE standard uses the oddball 48 volts for distribution).
  
  Check out the details at:
  http://www.poweroverethernet.com/articles.php?article_id=52
  
  
  Cheers,
  Bob
  

  Posted by inuse on May 16, 2005 at 19:35:51 Pacific Time

• Wire My House Efficiently
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  Thanks Bob,
  I had come across POE, but didn't understand very well. In particular, its interesting to think about voltage and loss, which presents some fundamental issues with this idea. I've always had a (foolish) fastasy of usb or firewire ports sprinkled around the house, for little data displays and internet usb toaster I'm still waiting for... While it might be nice to follow POE as inspiration, and use the two spair cat-5 wire pairs as 12v and 5v, it's probably better just to wire the house with a 12v DC seperately and realize that even thought its not the cheapest now, data wants to be wireless, and it will be increasingly easy to make it so. It's enough to get rid of wall warts (unless you were using them to heat you house!) and replace them with one nice big effecient 12v power supply, and make the the lights bluetooth or something. So far as an "adult", I have mostly lived on a boat anyway, which comes already with 110vac and 12vdc built-in and a battery backup! In-the-water turns out often to be off-the-grid.
  cheers,
  tim
  

  Posted by manyrobots on June 09, 2005 at 05:57:47 Pacific Time

• Wire My House Efficiently
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  suggest you use 12V only, and on all 4 of the spare wires. Because of the extra wires you'll get half the voltage drop. Also recommend you find a cat-5 cable with higher guage solid wire instead of the stranded kind. If you need 5V, just put
  an LM340 type voltage regulator at the circuit end - input 12V, output 5V, very
  nifty chip. Recommend keeping distances to a minimum to help with voltage drop.
  
  Another solution to voltage drop is to
  feed the POE with a higher voltage to
  compensate, say 16-20V. If you really need a regulated 12V, well just put another LM340 for 12V output.
  
  LM340 is a very standard voltage regulator chip you can get everywhere
  or at DigiKey.

  Posted by lardmaster on October 16, 2005 at 21:46:58 Pacific Time

• Wire My House Efficiently
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  If you go the 12v route, check out Anderson Power Poles. They the standard in the ham radio community and you can find lots of distribution bars, plugs, jacks, crimpers, etc.
  
  Here's an example of a commercial APP outlet bus:
  http://www.westmountainradio.com/RIGrunner.htm
  
  Cheers,
  Bob

  Posted by inuse on June 17, 2005 at 17:50:49 Pacific Time

• Apartment Dishwasher
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  You'll probably want to leave it under the sink, unless you've been working out, but this little guy is only 17x22x20 inches:
  http://about.pricegrabber.com/search_techspecs_full.php/masterid=841436#description
  
  Cheers,
  Bob

  Posted by inuse on May 16, 2005 at 19:22:32 Pacific Time