Remindlet is a Arduino based contraption that detects if your Bluetooth device (such as phone or laptop) has left your vicinity. It will notify you immediately if your valuable is too far away from you to prevent loss and theft.
This instructable contains a step by step process of how to make a Remindlet.

This was an OCADU project made by Jade Wu, Clay Burton, John Cho and Do Park

Step 1: Prepare the Materials and Tools

Electronic parts

(as shown in the picture):

1. 2 female to male jumper cables

2. 1 RGB led (any size)

3. 1 Sparkfun FTDI Basic Breakout

4. 1-2k resistors 1-1k resistors

5. Lithium battery (3.7v)

6. Vibration motor

7. Small (or cut) proto-board

8. Arduino Pro Mini 5V

9. HC-04 Bluetooth Module

10. Jst 2 pin connector

11. 4 pin female to male connector

(not shown in the picture):

12. Regular wires

13. 30 pin headers

14. Mini USB cable


Soldering iron, soldering silver


Fabric Material

1/2 yard of soft fabric

1/4 yard of velcro

Step 2: Assembling the Electronics

Step 1) Attach the headers onto the pro mini Arduino with the help of a breadboard and solder the headers

Step 2) Place your soldered Arduino in the middle of your small protoboard and solder the headers onto the protoboard.

Step 3) Connect wires from the Arduino GND to the Ground line and the VCC to the Powerline and solder the wires.

Step 4) Attach 4 male to female pin connector onto the Bluetooth module (VCC, GND, TXD, and RXD) by the female side.

Step 5) Using the male sides of the connector and connect GND wire to Ground line, VCC to Powerline, RXD to Pin 2, TXD to Pin 3 and solder the wires.

Step 6) Create the wire that will connect pin 34 to the protoboard which includes: a wire connected to a 1k resistor and a 2k resistor, which then the 1k resistor connects to power and the 2k resistor goes to ground and proceed to solder the wires. (Refer to the circuit diagram for clarification)

Step 7) Connect the RGB LED using regular wires by having R (from LED) connecting to A0, Power going to the Powerline, G going to A1 and B going to A2 and solder.

Step 8) Connect the vibrating motor’s power to pin 9 and ground pin to the Ground line and solder.

After following through steps 1 to 8 your product should be similar to the one in the photo.

Step 3: Making the Fabric Sleeve

Step 1.) Draw the outline of the template on the fabric of your choice (Refer to template picture)

Step 2.) Cut along the solid lines so you get 3 pieces of fabric

Step 3.) Sew along the seam line so you make 1 Sleeve hoop, 1 battery holder and 1 insert. (Refer to photo)

Step 4.) Stick velcro in the corresponding places

Step 4: Uploading the Code

Upload the following code using the mini USB cable and breakout board to the Arduino.

Don't forget to change the Bluetooth ID to your specific device ID!

SoftwareSerial BTSerial(2,3); // RX | TX unsigned long lastTime; unsigned long interval = 2000; char texto[105]; char *test; char *test2; char *id; int h; int REDPin = A0; int GREENPin = A1; int BLUEPin = A2; int motorPin = 4;

void setup()
{ pinMode(REDPin, OUTPUT); pinMode(GREENPin, OUTPUT); pinMode(BLUEPin, OUTPUT); pinMode(motorPin, OUTPUT); Serial.begin(9600); Serial.println("Any device connected !"); BTSerial.begin(38400); // HC-05 default speed in AT command more

// setting up the bluetooth device with AT command. BTSerial.print("\r"); delay(100); BTSerial.print("AT+INIT\r\n"); delay(100); BTSerial.print("AT+IAC=9e8b33\r\n"); delay(100); BTSerial.print("AT+CLASS=0\r\n"); delay(100); BTSerial.print("AT+ROLE=1\r\n"); delay(100); BTSerial.print("AT+INQM=1,9,48\r\n"); delay(100);


void loop() { //searching bluetooth devices in range delay(100); BTSerial.print("AT+INIT\r\n"); delay(100); BTSerial.print("AT+IAC=9e8b33\r\n"); delay(100); BTSerial.print("AT+CLASS=0\r\n"); delay(100); BTSerial.print("AT+INQM=1,9,48\r\n"); delay(100); BTSerial.print("AT+INQ\r\n"); delay(100); h=BTSerial.available(); if(h>=42){ //if it detects any bluetooth device, id = readSerial(h); // read the signal. Serial.write(id); test=strstr(id,"24DB:ED:F9789F"); // extract the bluetooth ID. if(test) { analogWrite(REDPin, 255); analogWrite(GREENPin, 0); analogWrite(BLUEPin, 0); digitalWrite(motorPin, LOW); Serial.println("DEVICE CONNECTED"); } } else if(h <= 21) //if it doesn't find any bluetooth signal { test2 = strstr(id,"ERROR"); //see if it sends "ERROR" message. if(test2) { analogWrite(REDPin, 0); analogWrite(GREENPin, 255); analogWrite(BLUEPin, 255); digitalWrite(motorPin, HIGH); Serial.write(test2); } } // Serial.println(count); clearAll(); //Clear the remaining info


void clearAll() { for(int i = 0; i < BTSerial.available(); i++) { BTSerial.read(); } }

char* readSerial(int h) { char input; char buffer[100]; if (BTSerial.available() > 0) {

for (int i = 0; i < h; i++) { // the id's start at char 21, se we copy from there input = (char)BTSerial.read(); buffer[i] = input; buffer[i+1] = '\0'; } return buffer; } else { return "No Data"; } }

Step 5: Putting It All Together

Step 1.) Sew the whole electronic part onto the fabric insert

Step 2.) Slip the whole thing into the middle of the sleeve and sew it in place

Step 3.) Connect the female end of the female to male jumper cable to the GND pin on the Arduino (from the opening of the sleeve). Get the other jumper cable and connect the female end to the VCC.

Step 4.) Cut a tiny hole on the top of the bracelet and pull the cable to the outside of the sleeve

Step 5.) Stick the battery holder onto the top of the bracelet using velcro.

Step 6.) Connect the power jumper cable to the positive on the battery and the ground jumper cable to the ground wire on the battery and the Remindlet should start to work.

The LED will be green if it detects your bluetooth device, if not it will buzz and turn red.

<p>That looks neat :)</p>

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