Sensors to Detect an Object's Presence and Uniqueness? - Page 1
Forum section: electronics / projects

author: fuzzoli
author_rank: Regular Contributor
timestamp: April 19, 2015, 09:33:57 pm
content: Hi to all in EEVblogland!I'm researching ways to sense the presence of unique objects on a shelf. Here are some requirements in no particular order:1. Each object has it's place on the shelf.2. Each object is unique.3. The shelf could be dirty, as could be the objects, so mechanical switches might be a bad idea.4. The objects could take a beating during use.5. I might have upwards of 30 objects, so cost per object should be low.To identify when an object is present or not (#1), I was leaning towards an optical solution (#3) with TCRT5000 Reflective IR sensors:http://www.ebay.com/itm/100PCS-TCRT5000L-TCRT5000-Reflective-Optical-Sensor-Infrared-IR-Switch-infrared-/200942957876?ssPageName=ADME:X:EAC:US:3160Depending on the sensitivity, each object might need a piece of tape so as to reflect a greater amount of IR energy. Each emitter would be selected one at a time, and while selected, the corresponding sensor would be polled. This should eliminate any false triggering.To identify each object (#2) , I was leaning towards small NFC tags:http://www.ebay.com/itm/231346847842I'd have a single RFID reader which would scan the tag before placing or removing the object back on the shelf. Software would determine if the object was being placed or removed.My biggest concern is any rough handling could damage the NFC tag. While cheap, I'd hate to have to replace them every few uses. An alternative would be to print bar codes on pTouch tape, and get one of the bar code readers from eBay instead of the RFID reader. I could easily replace the bar code label if need be. I like the RFID solution better though because 1) I think it's "more cool", and 2) swiping a tag across an RFID reader doesn't need to be as precise as moving a bar code in front of a scan tool (think laziness and convenience).So my question to the group relates to alternatives. Is IR / RFID the way to go? Is there anything else out there to detect presence and determine uniqueness (remember #5 -- cost)?Thanks,-FrankHolland, PAUSA

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 19, 2015, 10:49:25 pm
content: RFID is probably the best solution as it won't have a problem with dirt or dust and positioning won;t be critical. Tags come in various shapes & sizes, some pretty robust.If you can give more info one what you're actually doing it would be helpful.e.g. if the objects are metal then RFID may have problems.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 19, 2015, 10:54:33 pm
content: http://computervisionsoftware.com/ObjectRecognition.htmlOne camera, plus clever software.

author: JBaughb
author_rank: Regular Contributor
timestamp: April 19, 2015, 11:02:20 pm
content: Im interested to see what you come up with. I was looking into solution to this problem to create an automatic shopping list by having sensors monitor my refrigerator.

author: JuKu
author_rank: Frequent Contributor
timestamp: April 19, 2015, 11:12:03 pm
content: Can you put an emitter (IR or regular LED) and a receiver, so that the object cuts the beam?

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: April 19, 2015, 11:43:23 pm
content: i think a less complicated (hardware) solution is a camera and a nice algorithm to figure out what object is missing.

author: cdev
author_rank: Super Contributor
timestamp: April 20, 2015, 02:39:38 am
content: Look into opencv, (http://opencv.org) it does object recognition. So, it could definitely tell you when instances of an object are there, for example, different models of parts that can be distinguished by shape. It could not tell the difference between two identical looking parts. It is good enough to do face recognition, and recognize kinds of animals, or fruit. It can run on a Raspberry Pi using a cheap webcam. Its an incredibly flexible tool that can easily solve a great many problems that otherwise would be expensive or impossible to solve. Its extremely fast on a modern computer too.You could probably do it in an afternoon. There is an optimal number of images for training and its not very high. The thing you want to learn about is Haar training.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 20, 2015, 10:54:33 am
content: PTouch and RFID are not mutually exclusivehttp://www.amazon.com/Brother-SZ-2511-P-Touch-Laminating-Compatible/dp/B00CI38RTS

author: Marco
author_rank: Super Contributor
timestamp: April 20, 2015, 05:01:42 pm
content: Quote from: evb149 on April 19, 2015, 10:57:53 pmYou can get antenna coils for less than a buck a piece, if you use 125 kHz just multiplexing them on a single transceiver shouldn't be an issue.PS. bowling shoes?

author: fuzzoli
author_rank: Regular Contributor
timestamp: May 04, 2015, 03:08:02 am
content: Thanks everyone for the long list of solutions. Here's some additional information what I'm working on...(of course, this is all top secret, and set to make me millions of dollars, so please keep it all hush-hush)I have upwards of at least two dozen rechargeable batteries, mostly for battery operated power tools. I've PTouched the packs (i.e. Pack #1, Pack #2, etc.), but that doesn't help me in determining if state of the charge.I'm building a Charged Battery Shelf -- basically a wooden shelf to neatly hold all the various batteries. That's the easy part. I'd like to have each pack uniquely identifiable, hence the RFID or barcode solutions.I'm not sure the optical solutions would work in my case as 1) the location of the shelf is not in the brightest part of the basement, and 2) some packs might be too small to reliably hold a large enough font such as to identify the specific pack with software. However, I do appreciate all of the suggestions surrounding the optical solution.Getting back to RFID, I found this post on TI's site:https://e2e.ti.com/support/wireless_connectivity/f/667/t/269476The referenced YouTube video illustrates almost exactly what I'm looking to do -- even down to the space between the antennas. I'm probably going to pursue this hardware solution -- at least from the RFID perspective.Once each battery pack is identifiable, I can add all sorts of nifty software and a button or two for things like tagging a pack with an approximate level of discharge after each use. Since I wouldn't necessarily recharge the pack after I use it, especially if I just use the tool for a small job, I'll be able to say "this next pack I put back on the shelf is 50% charged", etc. Also, since rechargeable batteries gradually loose their charge, that too can be factored into software, along with addressable RGB LEDs providing visual feedback as to the stage of the charge (looping through a Green->Yellow->Red sequence).Thanks for all the input!-Frank

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 04, 2015, 11:03:35 am
content: Wouldn't it be easier to give each battery it's own place and be disciplined when putting them back?Then you only need to test if there is something in a given place.Lack of light can be solved with a lamp, either you let your system switch the existing lighting or you place a flashlight beside the camera.What is the scope of this project?Is this just for yourself or something that will be used in a big corporation?

author: fuzzoli
author_rank: Regular Contributor
timestamp: May 04, 2015, 11:18:16 am
content: Quote from: jeroen79 on May 04, 2015, 11:03:35 amThat was sort of one of my original ideas. Each slot would have a TCRT5000 Reflective IR sensor, and the "identification" would be a combination of discipline and software.Quote from: jeroen79 on May 04, 2015, 11:03:35 am...just me, and anyone else crazy enough to want to copy it.