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I am novice in electronics, so please bear with me.

I am searching for a small distance sensor (as small as possible) that I can use to measure a distance between 0 and 30 cm precisely (precision less than 1 mm). This sensor must be able to communicate the distance data wirelessly (wifi or bluetooth) with a PC. Could you please tell me if there is any sensor that satisfy these requirements.

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    \$\begingroup\$ More information would be nice. How big can it be? What is the size and material of the part you want to measure the distance? \$\endgroup\$ – kimliv Mar 5 '14 at 10:54
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    \$\begingroup\$ Also is mechanical coupling between the two OK? The 0-1mm type distances will be challenging for many optical and accoustic systems. Also can it be offset back a bit, ie could the range be 10-40cm instead? \$\endgroup\$ – PeterJ Mar 5 '14 at 11:01
  • \$\begingroup\$ @kimliv it must be preferably less than 4 x 4 x 4 cm. The sensor must be fixed on adjustable arm (its length changes between 15 and 45 cm), so it will be used to measure the adjusted length. \$\endgroup\$ – Heavy Rain Mar 5 '14 at 11:05
  • \$\begingroup\$ @PeterJ There should be mechanical coupling because the sensor will be fixed on a sliding part and will be used to measure the distance between the sliding part and a fixed part. In fact, I cannot change the range because the size of mechanical parts is limited. \$\endgroup\$ – Heavy Rain Mar 5 '14 at 11:11
  • \$\begingroup\$ @kimliv concerning the precision, if we have no such solution, it may be tolerated to a 1 or 2 mm. \$\endgroup\$ – Heavy Rain Mar 5 '14 at 11:16
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Have you given any thought to LVDT (linear variable differential transformer) devices? It's been 20 years since I used them and you could get sub 30 mm devices with raw 10-bit resolution.

We measured over a 4 mm range, it was mechanically and electrically noisy and with oversampling 1 um resolution/repeatability was achieved. Processing and analogue was difficult back then, now it would be immensely simple. May just revisit it again just to see.

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To measure the distance in the 0 - 30 cm range IR sensor are good, here are some sensors you can look at:

Infrared Proximity Sensor Long Range - Sharp GP2Y0A02YK0F

IR distance sensor includes cable (10cm-80cm) - GP2Y0A21YK0F

To send data wirelessly to a PC you can use either Bluetooth/WiFi/RF/Xbee modules. Here you want to communicate with PC so Bluetooth/WiFi would be best option. If you are just planning for internetwork, then go for Bluetooth instead of WiFi.

You can use any 8-bit processor for this project I guess.

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  • \$\begingroup\$ The proposed IR sensors from SHARP are quite limited in their capabilities. I initially thought that the analogue output could provide great resolution - I was wrong. The sensors used in this picture are SHARP GP2Y0A41SK0F (4 to 30 cm). Initially I thought that it was my DAC resolution limiting my resolution. After hooking the sensors up to a high-res oscilloscope I got the same readings. The voltage output shifts between clearly visible levels. Increments of approx. 10mV/0.5mm \$\endgroup\$ – Andreas HD Apr 20 '17 at 7:09
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This isn't a complete answer because it doesn't address the wireless issue entirely but based on your comment about it being mounted on an adjustable arm something often used on machining equipment is something called a "scale" that is somewhat like a digital caliper. You can see a question I asked a while back DRO scales 4-pin connector identification to get a general idea of what they look like.

The OpenDRO project has full source code available that reads the values from the scales. From there you could read the scales on a microcontroller and transfer it via Bluetooth / WiFi. Depending on your level of experience that might be quite a bit of an undertaking but it might give you a pointer in the right direction.

I haven't used the RS-232 interface on OpenDRO myself (so you might want to check first with them it's possible) but presumably that could be used to transfer data over a wireless link that supports transparent operation. While somewhat costly that might be another possibility if you're only after a few systems.

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  • \$\begingroup\$ Thank you PeterJ for your proposition. I have already searched and seen all the magnetic linear encoders that can be used. In term of precision, the encoder is the best solution but the problem is that the connection to the PC is via RS232 and if we want to add the electronics for the wireless connection (micro-controller, transmitter, battery, ...), this will increase the size of the sensor to more than 4x4x4 cm. In fact, I am searching for wireless distance sensor where the wireless module (wifi or bluetooth) as well as the battery are already embedded within the sensor. \$\endgroup\$ – Heavy Rain Mar 5 '14 at 12:25
  • \$\begingroup\$ Is there any laser distance sensor that can satisfy these requirements (embedded wireless module and battery) and still small ? Any off-the-shelf sensor? \$\endgroup\$ – Heavy Rain Mar 5 '14 at 12:27
  • \$\begingroup\$ Laser systems are really complex for that resolution - you'd need a phase difference type system so I can't think of anything practical anywhere near that size / power limit. I think what you're after would be possible using various linear encoders but would really have to be a custom design to integrate it all together to achieve that size. Not aware of anything off the shelf myself but there could be. \$\endgroup\$ – PeterJ Mar 5 '14 at 12:37
  • \$\begingroup\$ Please, do you have any idea about the precision of available laser sensors? and the minimum size of such sensors? \$\endgroup\$ – Heavy Rain Mar 5 '14 at 12:45
  • \$\begingroup\$ The only ones I've used on one project quite a while ago were the following, but as you can see they are quite large... sick.com/group/en/home/products/product_portfolio/… \$\endgroup\$ – PeterJ Mar 5 '14 at 12:50
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I have had some experience with ultrasonic distance sensors with the Arduino Uno board. I have noticed that it cannot measure distances as precise as a millimeter(more like cm). You might want to look into infrared distance sensors. Note that the most common Ultrasonic Sensor is 1.5cm height by 4cm length thereabouts and infrared distance sensors range in the same area. For wireless transmission consider getting another board from ebay they sell for 2 bucks.

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You could use an ultrasonic sensor and send the data via wifi or bluetooth, look up Arduino, ultrasonic sensor and wifi/bluetooth.

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    \$\begingroup\$ Welcome to EE.SE. Please provide additional details in your answer rather than simply tell the asker to "look up" something. \$\endgroup\$ – Null Jan 28 '15 at 15:42
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IR sensors pairs are commonly available in market , they are of short range by nature ,,, if you want to measure smaller distance search for ULTRASONIC distance measuring sensors or circuits..

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    \$\begingroup\$ This answer is too hand-wavy: "There are them sensors out there. Go find them." \$\endgroup\$ – Nick Alexeev Apr 7 '15 at 3:33

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