CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Object detection / surface scanning

Wed Dec 05, 2018 2:25 pm

Hello everyone,

im new on here and farely new to the whole raspberry game so please excuse me if i misplaced this topic or dont understand basic things.

i had this idea for a serious of shelves with digital led strip ligthing up only where an object has been placed on the self.

forgive my horrible paint skills
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so ive dabbled with some digital led strips that parts is easy but...

does anyone have a good idea for detecting where on the shelf something has been placed?

heres what ive been thinking about:

1. surface sensor - basically would mean id need 1 distance sensor per led along the whole side. thats way to many sensors and i dont know of anything flat proifle that could scan the whole surface in one device.

2. camera - a camera pointed at the shelf could help figure out which led to fire up but that would be a problem if you as much a walk in front of the shelf.

other than that i have no idea i was really planning on using camera images but there no way to mount one and not have it obstructed when you walk in front of the shelf

if anyone got some ideas im curious to hear what the experienced tinkerers can come up with

scotty101
Posts: 3597
Joined: Fri Jun 08, 2012 6:03 pm

Re: Object detection / surface scanning

Wed Dec 05, 2018 3:57 pm

How about ultrasonic or IR reflective distance sensors at either end of the shelf?

You'd probably only be able to predict where a maximum of two objects were on the shelf but it might serve your purpose.

Another suggestion would be a film similar to that used on touch screens.

An even lower tech way would be to make your own touch sensitive film with a conductive foil and an insulating material. You could have it work almost like a keyboard where every 2cm or so is a different "switch" which tells the Pi which LED to turn on. Each switch could be connected via a GPIO expander or an Analogue to Digital converter if the switches are connected via resistors so that each switch can be independently detected.
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Wed Dec 05, 2018 4:20 pm

scotty101 wrote:
Wed Dec 05, 2018 3:57 pm
How about ultrasonic or IR reflective distance sensors at either end of the shelf?

You'd probably only be able to predict where a maximum of two objects were on the shelf but it might serve your purpose.

Another suggestion would be a film similar to that used on touch screens.

An even lower tech way would be to make your own touch sensitive film with a conductive foil and an insulating material. You could have it work almost like a keyboard where every 2cm or so is a different "switch" which tells the Pi which LED to turn on. Each switch could be connected via a GPIO expander or an Analogue to Digital converter if the switches are connected via resistors so that each switch can be independently detected.
thanks for the suggestions

sensors at either end would not tell me how wide an object is if there more than one and if the objects are place a bit more towards the edge or back the sensor wont pick it up

touch screen sound very interesting. like resistive touch. like the oldschool stuff. ill definitly look into it but i figure its not gonna be easy to source something like that or make it on my own

keyboard style contacts does sound interesting and way more doable although i imagine fine tuning that might get complicated.

scotty101
Posts: 3597
Joined: Fri Jun 08, 2012 6:03 pm

Re: Object detection / surface scanning

Wed Dec 05, 2018 4:28 pm

Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Wed Dec 05, 2018 4:37 pm

scotty101 wrote:
Wed Dec 05, 2018 4:28 pm
You might find this interesting.

http://memoir.okno.be/phys_comp_tutoria ... ibbon4.htm
very interesting indeed. love that kind of stuff. but sadly i fail to see how i could implement that to track multiplie object

CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Thu Dec 06, 2018 11:45 am

alright i think i have an idea.

but 1st can someone tell me if i can connect multiple ir sensors to one pi and preferrably differentiate between them?
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heres what i thought might work. what do you guys think? i am still not sure about increasing the resolution / accuracy and how to do it best but in generell i think this is the best option so far because the components needed are small enough that i could hide the pretty well

Idahowalker
Posts: 445
Joined: Wed Jan 03, 2018 5:43 pm

Re: Object detection / surface scanning

Thu Dec 06, 2018 12:58 pm

CluelessGenius wrote:
Thu Dec 06, 2018 11:45 am
alright i think i have an idea.

but 1st can someone tell me if i can connect multiple ir sensors to one pi and preferrably differentiate between them?

Untitled897979798798.png

heres what i thought might work. what do you guys think? i am still not sure about increasing the resolution / accuracy and how to do it best but in generell i think this is the best option so far because the components needed are small enough that i could hide the pretty well
I think such a scheme would work much better with an array of LIDARs or TOF sensors. A scan of the items placed on the shelf before any people are around can be made. When people are around, a-after-person-has-moved-on-scan can be made to determine if the object is still in position. Each LIDAR in the array could be addressed through a MUX, such as a CD74HC4067 16-Channel Analog Digital Multiplexer module. The LIDARs, such as a TFMini, could be placed up to 400cm away from the objects to be monitored, for an object depth of scan of 100cm. The longer the LIDAR distance the higher the price. A TFMini has a beam width of 2 degrees, the more narrow the beam width the higher the price.

Once initial scans are made only periodic scans need be made. Such as adding in a few Micro Wave Motion detectors, you'd only need to scan the motion detected areas, after motion stoppage, to see if your objects have been moved. A motion detector could, also, trigger a video device to begin recording.

I, also, think an optical flow sensor array, could work as well, in the same sense of a LIDAR array.

I use a TFMini to scan an area, with a rotating servo, to produce images like the motion detector used in that Aliens movie.
Last edited by Idahowalker on Thu Dec 06, 2018 5:45 pm, edited 2 times in total.
Without knowing why you are deleting my postings, I will not know how...

CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Thu Dec 06, 2018 1:06 pm

soo... apparently the ir receivers i could find only have 45° angle of detection and i had really hoped to find some addressable ir - rb strip all in one but off course thats not a thing. so i could wire up the leds individually i need be but the angle on the receiver means not only do i have to wire up 2 or 3 per shelf but for this to work i would need to have more like 1 receiver every 20-25 cm when the shelf is 30 cm deep thats 4 -5 receiver per board if a board is lets say 90 cm long times 3 boards i really dont think im gonna be able to handle that with on pi or am i

User avatar
tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Object detection / surface scanning

Thu Dec 06, 2018 2:01 pm

CluelessGenius wrote:
Wed Dec 05, 2018 4:37 pm
scotty101 wrote:
Wed Dec 05, 2018 4:28 pm
You might find this interesting.
http://memoir.okno.be/phys_comp_tutoria ... ibbon4.htm
very interesting indeed. love that kind of stuff. but sadly i fail to see how i could implement that to track multiplie object


Cheap weight sensor cell array to detect multiple objects

Perhaps weight sensing resistor cells instead of ribbons?

BX120-3AA High precision resistance weight sensor US US$6/10 pieces
https://www.aliexpress.com/item/BX120-3 ... 82566.html
https://www.aliexpress.com/item/10pcs-l ... 93327.html
size 2.5mm x 3.3mm (122 BX120-0.5AA)

Update 2018dec07hkt1601

More references

RE: TRACKING MOVEMENT OF GAME PIECES ON A BOARD Postby Tarcas » 2014-Feb-15 Sat 12:28 pm
viewtopic.php?f=37&t=69430

Microchip Technology Interfacing a 4x4 Matrix Keypad with an 8-Bit GPIO Expander
http://ww1.microchip.com/downloads/en/a ... 01081a.pdf

Expanding your senses with I2C Raspberry Pi - Skutter, MagPi16, 2016sep
https://www.raspberrypi.org/magpi-issues/MagPi16.pdf

RE: DETECT CURRENT ON RASPBERRY PI Postby tlfong01 » 2018-Nov-18 Sun 8:46 pm
viewtopic.php?f=37&t=225453&p=1399713#p1399727

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I am an electronics and smart home hobbyist.

CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Thu Dec 06, 2018 2:56 pm

ok unless im just completly stupid now ir wont work cause i wouldnt get good coverage
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CluelessGenius
Posts: 8
Joined: Wed Dec 05, 2018 1:57 pm

Re: Object detection / surface scanning

Thu Dec 06, 2018 3:01 pm

tlfong01 wrote:
Thu Dec 06, 2018 2:01 pm
correct me if im wrong but wouldnt you have to seperate the floor panel for something like that? make tiles so to speak?

User avatar
tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Object detection / surface scanning

Fri Dec 07, 2018 11:46 am

CluelessGenius wrote:
Thu Dec 06, 2018 3:01 pm
tlfong01 wrote:
Thu Dec 06, 2018 2:01 pm
correct me if im wrong but wouldnt you have to seperate the floor panel for something like that? make tiles so to speak?

Pressure sensitive carpet with weight sensors hidden under

Ah, you don't need to cut your shelf into pieces. The weight sensors are already little tiles. You stick the tiles, say 16, on a printed circuit board, and extend the wires to your Rpi and MCP23008. You then place a thin sheet, say plastic, over the whole thing, to make a carpet. The resulting carpet should be thinner than 1cm.

MicroChip application note AN1081 shows you how to detect single key, or multiple keys pressed at the same time. Now you can detect up to 16 objects, left and right, front and back.
There is also a MCP23017 which helps you detect 8x8 = 64 objects! :mrgreen:

And of course if your small shelf can only hold, say at most 6 big objects, then you just need 6 weight sensor tiles and simply read them by 6 Rpi GPIO pins.
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I am an electronics and smart home hobbyist.

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