proximity detector

The Sharp has a range of a few millimenters to 1.3 meters -- seems to
fit the bill according to your specs.

In any case there are versions with longer ranges. look at the
GP2Y0A02YK. It has limited close-range sensitivity, but a maximum of
about 2.5 meters.

-- Gordon

  You will find the LM565 ? PLL to be the lowest
 cost and highest performance device .
    Its antenna pattern is distorted by objects
  and the rate is readable .

  Since its a PhaseLockedLoop , it will
 read rate as well as the pull .
 You can gaurd them , so they will be able
 to figure if the object is moving and how
 fast and what direction .
   There is less cost and hassle , using
  LM565 .  But of course you must use
 an ARM 7 , 144 pin , to make it "sing"



   I'm using them and a $20 700by420 pixel
 BW CCD camera to control moving objects
 like robots and cars . It has .01 LUX ( I.R.)
 Im using front surface mirrors that rotate
 in front of the camera , periodically to
 expand the vu of the camera .
   I will scan only every 10th vertical line
 and evaluate it , as a insects compound
 eye does .  Then switch to full scan
  to do slow stuff .
 BTW
  I2C and RS232 and SPI .  Everyone thinks
 they are narrow . But clever people can
 make them work more  .
   You might try using SPI to do RS232
 and vice versa , and  SPI sub for I2C
 etc etc ..

  We read the specs , and get blinded ,
 because spec sheets are poorly written
 leave out stuff and amount to advertizing !
   So we arent brave enuf to experiment .
 I will be booting ARM by many methods .
 I want flexibilty and fault tolerance ,
  so when i want to boot it , i want
 to be able to select many methods of
 booting , at boot time .
   The SPI bus is the lowest cost and
 smartest method , just put a tiny 2K
 EEPROM there .
  If you boot wide , then you'll have to
 configure EXT RAM .  SPI is easier .
 74HC595 and 597 is a generic way to
 do parallel on SPI bus . HC299 also
 works .
    I will use many ARM 7 mcu's to
 do the work .

thank you for the GP2Y0A02YK. suggestion, I didnt know it and I guess
it will be OK.
Concerning the LM565, I confess I did not understand how to use it. If
you (werty) have a link to some schematics I'll be happy to study
it...

thanks!

Alessandro

ignore werty.  in fact, ignore anyone whose name is a linear sequence
of characters on a standard keyboard.  it is unlikely that you would
want to use a phase locked loop for this application.

sharp rangefinders work pretty well.  i have used them on every robot
i've built.

if you want to d.i.y, you could use an infrared led and detector as
available at radio shack.  that, however, would be a luminance based
sensor, so a good reflector at much more than one meter range would
trigger it before a poor reflector at less than one meter.  also, it
would have as wide beam pattern as the led, which is usually pretty
wide.

sharp rangefinders have an infrared led with a focus lens so they have
a pretty narrow beam width.  also, they measure angle, not luminance,
so as long as there is minimum reflection they are unaffected by
target color.

-chris.

  Proximity detectors are electrostatic

  and Piezio ( worthless ) .

  Electrostatic have a long range .

  But cost 1000 times more $$ .

  LM565 has a cap and a coil , the coil

 is the antenna , a big loop of wire .

 Anything that has capacitive coupling

 to the loop of wire , will pull the PLL .

  So look at the DC voltage change

 on VCO  .

  Its easy to experiment .



   BTW I have been studying the ARM
 Instruction set .  Its a closely gaurded
 secret .
  Everyone wants you to see only nuemonics
 and not the binary it refers to .

 Ville Pietikainen of Finland , gave out
 a free xxxx.PDF  on Thumb , but it was
 buggy .  He does not understand the "H"
 bit .
  I've been searching for months , for
 second sources on Thumb ISA .

  Fortunetly ,  Edward Nevill
  enevill@armltd.co.uk  has a more
 accurate chart .

 Its a struggle , cause they want to appear
 a WIZARD , and show you how great their
 assemblers are .  Assemblers are WORSE !
  They lock 2 doors !
  They claim Psuedo ops .  But its supposed
  to be in a "macro" NOT a psuedo op !

   Im doin ARM 7 and 9 .
  I have boxes full of ARM mcu's .

    Every door closed ! ATMEL created
 some helpful tools to boot its AT91xxx .
   Bloat crap , SAMBA is 20MB !
 I will instead program a tiny 35KB Editor
  "Qedit" to do the flashing .

  All the I.D.E.'s and C/C++ compilers
 are a huge waste of effort , in programming
  MCU's for robots .

  You can create s/w in minutes , with a
 modern "loader" in 8 KB of the Flash RAM .

  But exect the same Luddite Loaders
 from all the big companys , ST , ATMEL,
 Philips , all waste the 8KB , it will only
 look in 2 places !  UART and USB ,
  and then , expect deaf and dumb .

  My loader starts in SRAM , so it can be
 fixed , if it dont work , in minutes .
  after weeks of coding , when you have
  not needed to "improve" it , then flash
  it .....
    Always treat your flash as a HDD , and
 use precious SRAM for hi-speed code .

  The performanceof ARM 7 is slowed
 by less SRAM .
  I found 2 ARM7s with  64KB and 96KB
  SRAM .
  Your code running inside , will run very
 fast and at extreme low power !

 Im doin many things ,
   ARM EVBs  , Nintendo DS Lites ,
 GP2X boxes , all ARM mcu's .
  Very powerful !

In order to select the best rangefinder you will want to think about
what type of object you expect.

For instance, sonar should work for solid objects with large surfaces
that face your sensor, but not so well if they are at angles.

IR sensors also have strengths and weaknesses.

You can also use structured light.

And yes, there are electrical proximity sensors...

Best of luck!
    Nelson