LoLa platform for sensor testing

To figure out which sensors / switches will reliably trigger sounds from sixteen swinging pendulums on our proposed ‘Lightly Oscillating Linguistic Organ’, I decided to build a test bench. While doing so it occurred to me that like Professor Tanya Monro, I was building a ‘platform for sensing’ (albeit on a slightly smaller scale).

Here is what I did:

  • Hung an old broomstick from a ladder
  • Added a few bearings to make it swing better
  • Added a six inch piece of orange PVC conduit to the top of the broomstick (via some home sprinkler system pieces I had lying around)
  • Wired my sensors to servo leads (from my model planes) and stuck em to wooden pop-sticks (actually tongue depressors)
  • Whacked a cardboard box on the top with arduino, battery and breadboard with holes to shove my sensors into
  • Strapped an android phone running ‘AndroSensor’ to the bottom of the broomstick
  • Carted my laptop out to the shed and collected a bunch of data via arduino serial monitor & pasted into a spreadsheet & from a .csv file that an android phone’s sensors was writing to
  • Bunged the collected data into a few google spreadsheets for analysis by chart

LoLaSensorPlatformTestDataRun1

Here is what I learnt:

  • My $10 freetronics light sensor for android (that gives an analog output proportional to light intensity) mounted at the top is very reliable and copes with really sloppy swings.
  • A $1 glass reed switch under a strong magnet on the bottom of the broomstick works well (once you make it stronger by sticking to a wooden tongue depressor and cover in clear epoxy and when you figure out how to ‘de-bounce’ the signal). 
  • My $10 hall effect sensor for android mounted at the top is easy to use & check but hard to position well for consistent results. You need to have a very smooth swinging pendulum and find the exact centre.
  • The guys building the physical pendulum wave have expressed concern over perceived slowing due to the magnetic force on each pass. This should be measured & tested before giving up on the simple reed switch..
  • The ‘false positive’ readings I was getting from the magnetic reed switch is actually a well known phenomonen called ‘bounce‘ which can be de-bounced in software or via some rather ingenious circuitry! [I’m a little bit chuffed because before I discovered those links, I simply looked at my data on a graph and hacked my code to ignore state changes for a few hundred milliseconds after the first].

Photos:

LoLa sensor platform

Platform for sensing

Sensing platform ctd... LoLa sensors

LoLa sensors

LoLa sensors

LoLa sensors

Creative Commons License

Fang – Mike Seyfang

TriBeardLesBones

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About mseyfang

Interruptus Digitalis
This entry was posted in Hobbies, phd, science and tagged , . Bookmark the permalink.

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