Is the Key There?

It is often the case that several people use a common key for a device, e.g. car key, locker key, cellar key. It’s annoying when I go for the key but it’s not in the closet. To solve this problem, our idea is to ask remotely with our cell phone if the key is in it's place?

There is a sensor in the key box that monitors if the key is in front of it. The micro: bit to which the sensor is attached, sends a signal to the phone via bluetooth. On the mobile phone, a green key image is displayed if the key is there, red if it is not there.

1. BBC micro:bit - 1 pc
2. TCMT5000 IR tracking sensor - 1 pc
3. Crocodile clip wire - 3 pcs
4. Mobilphone - 1 pc

Buy or make a key box. Drill under the key hanger so that the sensor can detect the presence of the key. The TCMT5000 sensor emits an infrared light beam and its sensor detects rays reflected from the key. Position the sensor so that the blue and the black tracking sensor can light into the hole.

Attach the microbit to the top of the cabinet.

Use crocodile clamp wires to connect the sensor to the microbit. Connect the VCC or V + pin of the supply voltage to 3V, the G pin of the ground to GND, and the S pin of the signal to P0.

The goal of the microbit program is to send the read sensor's value P0 feet via UART channel to the mobile phone via Bluetooth. The sensor gives 0 if it does not see the key, 1 if it feels hooked there.

I also attached the program in * .HEX.

The aim of the application is to receive the signals coming from the UART and change the color of the key on the display accordingly. The characters come in ASCII code, enclosed in parentheses. For example, the signal is transmitted: 0 as (48) and 1 as (49).

And it's done! Have fun building!

György Regele

Hungary