proximity detector

hi everybody, I'm looking for the simplest way to add a proximity detector that detects when something moves in front of it, at a range of ~ 1meter - no info on distance is necessary, just on/off. Can you point me to some resource - possibly DIY? I only found until now the Sharp GP2D12, but I'd prefer a slightly larger range. thanks!

Alessandro Magni

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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

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Gordon McComb

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 .

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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...



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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.


Reply to
e c kern


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 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 !

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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

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