» MAKE: NOISE — Discuss this article

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• I prefer a DPDT relay
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  I was trying to build one of these as much as possible out of items in my junk box, and found that my DPDT switches all seemed to require too much actuation force. If the motor reversing is done with a small 5v DPDT relay, you can use an SPST switch, and you get a lot more switch choices. Electronics Goldmine has these relays for about $1.25 each.
  My next goal is to build one as tiny as possible, possibly with a push-on/push-off type switch.

  Posted by Robotguy on December 16, 2010 at 22:05:35 Pacific Time

• I prefer a DPDT relay
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  Can you show me the wiring diagram you used for the dpdt relay. I'm having the same problem with the dpdt switches and got a bit confused when trying to wire up the relay.

  Posted by Gina.Calamia on December 03, 2012 at 19:49:39 Pacific Time

• I prefer a DPDT relay
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  http://robotguy.net/blog/2010/12/18/something-useless-for-xmas/

  Posted by Robotguy on December 18, 2010 at 21:36:07 Pacific Time

• I prefer a DPDT relay
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  Great job Robotguy! High five!

  Posted by golim on December 20, 2010 at 10:56:07 Pacific Time

• Great Halloween Project
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  I built 4 boxes so far and I run them at 3 volts. I also mounted the microswitch on motor housing using 2 3/8 round head brass wood screws and I drill a hole in the motor wheel and I use another brass screw to operate the switch. Too bad I can't post a picture as it is a real good hack for the project.
  thanks
  mikelib

  Posted by mikelib on October 12, 2010 at 20:02:43 Pacific Time

• A few pointers.
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  I built this box and the thing is great-I have a few friend who want me to build them one too. I did find a few tips along the way which may be useful to others.
  
  1) One problem I ran into was "bounce-back", where the nub on the lever arm would hit the shutoff lever, cut the power, and bounce off the switch, reactivating the motor. I used a narrow cut section of straw glued to the toggle switch to act as a damper-the nub hit the straw on the lever, compressing the round straw to an oval. The bounce-back was then absorbed by the straw returning to a normal shape. (I wish I could post a picture; it would be clearer).
  
  2) I'm running the system on 3V (with the recommended motor), and it works fine. It helps with the bounceback problem too.
  
  3) I had a hard time cleaning off the hot glue used to temporarily place things-I'd recommend tape instead.
  
  Overall, a great project!

  Posted by Cole's Law on August 29, 2010 at 20:26:00 Pacific Time

• A few pointers.
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  Excellent tips, thanks for posting them!
  
  Using a lower voltage will also slow down the motor's speed, making the machine's action more creepy.
  
  And when using hot-melt glue, very little is needed for a temporary bond. Once you have the parts laid out to your satisfaction, then re-glue 'em using a larger amount for a permanent bond.
  
  Cheers!

  Posted by Brett Coulthard on August 30, 2010 at 09:30:13 Pacific Time

• Frustrating
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  The print issue of the magazine includes horribly incomplete instructions. For starters, it directs a Maker to this site for templates that are missing key features (the 'nubbin' on the arm that will contact the lever switch).
  
  Also, the wiring instructions are incorrect for a DPDT switch designed to reverse polarity.
  
  This has been a terrible first experience building a project found in Make.

  Posted by bfuller181 on August 07, 2010 at 19:53:20 Pacific Time

• Frustrating
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  Sorry that feel that way.
  
  I haven't received my printed copy of the magazine yet, but I have viewed the PDF.
  
  Thanks for pointing out the missing nubbin on the down-loadable template. It will be updated ASAP.
  
  As for the wiring instructions, I'm pretty sure that they are correct. Several folks at Make have built the UM using these directions.
  
  The only difference between a DPDT wired for reverse polarity, and these instructions is one of the cross over wires has the micro-switch in line.
  
  There was a considerable amount of effort expended on ensuring the article was complete and easy to understand.
  
  I hope that you'll take another look at the wiring description and change your mind about the article.

  Posted by Brett Coulthard on August 08, 2010 at 10:11:40 Pacific Time

• The purist in me is bothered
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  I've seen several versions of these machines, and I truly love the concept. But the purist in me still hasn't seen one that quite does what it's supposed to do.
  
  As the article mentions, some actually use some current while waiting to be turned on, and so aren't really off. This version addresses that problem, which is nice, and certainly comes closer to the ideal.
  
  But it still uses a little sleight of hand, because the switch it appears to e using to turn itself off isn't really turning itself off - an internal momentary switch does that and is held in the off position by the arm.
  
  Of course, the challenge if it really did turn itself off at the outside switch is getting the arm to retract. So I have to wonder: Why doesn't anybody design a circuit that includes a capacitor? Before turning itself off, it would charge the capacitor. Then it would move the arm up and turn itself off. Using the charge from the capacitor, the arm could then be moved back down into the box. Any "warm-up" delay needed to fully charge the capacitor before movement begins would actually add to the mystery because people aren't used to a delay when they turn on a motor. In fact, the longer the delay (within reason) the better. A random amount of delay would be icing on the cake.
  
  I would love, love, love to see somebody design one of these that works that way. I wish I had the know-how myself. If I ever see a version like that, then I'll be on my way to the electronic store to pick up the parts.

  Posted by WayneZ on July 23, 2010 at 12:57:33 Pacific Time

• The purist in me is bothered
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  Even simpler than your capacitor idea... eliminate the microswitch and have the servo drive against a constant-force spring. The toggle switch (now a simple on-off switch, not a DPDT switch) simply cuts power and the spring retracts the arm back into the box. Sizing the spring might be a little tricky, because the servo has to be strong enough to drive against it, but the spring has to be strong enough to backdrive the servo when unpowered. There is probably a small variation between the powered and unpowered torques, so you could play with the geometry and moment-arm to tune the retraction torque to your particular spring.

  Posted by SecretSpy711 on November 09, 2010 at 10:39:27 Pacific Time

• The purist in me is bothered
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  The machine does seem to cause most people to ponder their navels, scratch their heads, and think deep thoughts.
  
  I wouldn't call the toggle a 'sleight of hand', I prefer to call it part of a two-stage shutdown process.
  
  I agree with you on having a delay.
  
  A cap might be used, but it would most likely have to be HUGE, and cost more than all the other parts combined.
  
  I racked my brains out trying to come up with a delay that didn't involve lot's of circuitry. But the main thing was to keep the project simple, and a delay wouldn't allow that.
  
  Cheers!
  

  Posted by Brett Coulthard on August 08, 2010 at 10:37:40 Pacific Time

• Voice Across the Sea - Arthur C. Clarke quote
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  Here's what Arthur C. Clarke said about the "Ultimate Machine" in Voice Across the Sea (p. 159, Revised edition, New York: Harper & Row, 1959 and 1974):
  
  But before we go on to the specific project which is the main theme of this book, and which is perhaps the most daring technical feat yet attempted by the organisation, I cannot leave Bell Labs without mentioning one more device with I saw there, and which haunts me as it haunts everyone else who has ever seen it in action.
  
  It is the Ultimate Machine - the End of the Line. Beyond it there is Nothing. It sat on Claude Shannon's desk driving people mad.
  
  Nothing could look simpler. It is merely a small wooden casket the size and shape of a cigar-box, with a single switch on one face.
  
  When you throw the switch, there is an angry, purposeful buzzing. The lid slowly rises, and from beneath it emerges a hand. The hand reaches down, turns the switch off, and retreats into the box. With the finality of a closing coffin, the lid snaps shut, the buzzing ceases, and peace reigns once more.
  
  The psychological effect, if you do not know what to expect, is devastating. There is something unspeakably sinister about a machine that does nothing - absolutely nothing - except switch itself off.
  
  Distinguished scientists and engineers have taken days to get over it. Some have retired to professions which still had a future, such as basket-weaving, bee-keeping, truffle-hunting, or water-divining.
  
  They did not stop to ask For Whom the Bell Labs Toll.
  
  
  

  Posted by pspinrad on July 17, 2010 at 21:49:35 Pacific Time