Project help: Arduino Powered Bluetooth Key Finder

  • I want to make a small key finder with ATtiny 45 AVR(microcontroller) ,hc-05 Bluetooth module and buzzer.
    #How can I make a microcontroller stability circuit.

    #Please tell me about the circuit connections.

    #should i want to connect external oscillator circuit
    block diag

  • @Geethesh welcome to makergram. It's is great to know that you are gonna build a ble keyfinder. Let me point out few things to build a ble keyfinder. First of all battery is a main part of a keyfinder. So you should use low power consumption components and modules to build your hardware. HC05 will use pretty much power. So hc05 is not recommended for low power applications. instead you can use an ble module which will works on low energy. A recommended chip is nrf51822 SoC. Wich comes with built in ble. The most using SoC for ble applications in market. Basically you can find it in bluetooth keyboards and mouse. Attiny45 is a good microcontroller for low power applications but I would recommend you to use a ble SoC chip. I didn't get what for the reset button. Can you explain a little bit?

  • @Suhailjr thank you for the help ,is HM-10 is ble .
    i have edited(deleated) the question about the reset .
    plese tell me will hm -10 works for me

  • @Geethesh Hello. First of all greetings from makergram community. I would like to brief you with the architecture aka block diagram that you've mentioned.

    1. The microcontroller which you are trying to use is good for the application. Your choice of component is very appreciable.

    2. Regarding the connection diagram, to answer your question should i want to connect external oscillator circuit my answer is NOO. Because if you look into the datasheet of the Attiny85(same as ATtiny45) you can notice that it has an On-Chip 8MHz oscillator 👇. So, you can breathe now as you don't have to put an external oscillator circuit. Don't worry about the timing issues, they are industry calibrated.


    1. Coming to the architecture part, I suggest you not to use HC-05 because it is a Classic Bluetooth. You cannot use them for BLE applications. So, HM-10 can be used for BLE applications. I guess if you have made an little research about this project on youtube you will come across this video Bluetooth Key Finder Video link Please watch this video where he makes a similar project of finding keys in the room using his BLE remote.

    Please reach us in case of queries. All the best..!!

  • @kowshik1729 thank you for replay

  • Hi @Geethesh, If you are building simple POC (Proof of concept ) or Quick prototype then the HC-05 is enough with the ATtiny.

    • For the ATtiny45 minimum circuit you only need one Pull up resistor for Reset, and one Filter capacitor between VCC and ground and you also need to populate ICSP pins for programming

    • You also need only two external componts HC-05 and Buzzer .

    • In the this project we did't require any external oscillator , the internal 8mhz should be fine .

  • @salmanfaris thank u for the details and circuit

  • @Geethesh , keep in mind ATtiny series doesn't have Hardware Serial, so you should use the SoftwareSerial for that you also need two more for UART communication (Rx, Tx) between Arduino and Bluetooth.

  • @Geethesh In case if you live near kalamassery(where Fablab is situated) I strongly suggest to go to Fablab where you can find all the necessary tools and IC's required.

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