Lost Item Finder


#1

My daughter goes to Coder Dojo and has been given the task of using the Raspberry Pi. She wants to use it to make a device that helps people “find lost things”. She’s 9. So a lost key finder use case.

I want to help her (I am a noob but a dog with a bone type of noob and a daughter who says impossible is just “I’m Possible” ) with the project so have done some research. I looked at UWB, BLE, Classic Bluetooth, RFID and WiFi technologies and BLE kept coming back as the easiest to achieve if we are talking about indoor positioning systems.

Because using RSSI for location finding requires trilateration and dealing with interference on the easily absorbed 2.4GHz for distance calculation I thought the simplest thing would be to have a BLE tag beep and blink if it is in range of a BLE scanner (RPi in this case). That way we should only have to deal with scanning, sending a command to beep and blink and not get involved with all the maths and extra devices needed to achieve 2D/3D positioning. A good loud beep should be enough of a solution to find the tagged item.

Can the Ruuvi Tag be adapted to have an internal buzzer in a fairly easy manner and will Bluez communicate with a Ruuvi Tag out of the box?

My skill level: Can string together basics in Python, VBA, HTML/CSS, javascript, Scratch, set up a webpage, troubleshoot networks, adapt scripts, use a terminal/command prompt and via Coder Dojo resources (parents and kids) solder and set up basic circuits. And like everyone else I can watch Youtube and use Google-Fu.

I am hoping that the Ruuvi Tag is the answer. The project is to be ready by later in the summer.


#2

Sounds like a cool project! We’re happy to help and I’m sure RuuviTag will fit the need.

About a buzzer: One can be found and used, yes. You’ll need a buzzer that works ~2-3V DC voltage and uses <5mA current. That kind of buzzers can be controlled directly using nRF52832 chip’s IO pin.

Or what about a vibration motor? Recently, I found a neat haptic element which could fit RuuviTag perfectly:

www.murata.com/en-us/products/sensor/guide/sensorguide3/sensorguide/pjfvma

@otso, any tips to the SW side?


#3

Thanks Lauri, so far stockists I could find on the net of that vibration motor is either buy in bulk or not available to buy as Joe Public.

Thank you also for outlining the type of buzzer. This one seems to fit the bill:
http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=291532850541&category=4660&pm=1&ds=0&t=1496714914000&ver=0&cspheader=1

But this one is an active buzzer at minimal 3v so no need to make an oscillator


#4

Please note that the coin cell is going to drop below 3 V relatively quickly, so if you can find a buzzer which works down to 1.8V you’re going to have a lot longer battery life


#5

Maybe this:

or this

https://www.digikey.com/product-detail/en/pui-audio-inc/AI-3035-TWT-3V-R/668-1204-ND/1745457