I'm using two circuits for my wireless head mouse project, one of them is a transmitter circuit with Arduino Pro Micro, HC05 Bluetooth module, Elechouse Voice Recognition Module V3.1, GY-521 module based on the MPU6050 sensor. The receiver circuit (Arduino Pro Micro + HC05 Bluetooth) will receive the sensor readings from the transmitter circuit. Both modules were powered by USB from the laptop initially. They worked fine. To make the transmitter circuit completely detached from the laptop, I used a 9V battery, and a voltage regulator of 5V. The receiver circuit was still c. I should mention that I was using voltage dividers for both of the transmitter, and receiver circuit's HC05 Bluetooth modules. onnected to the laptop USB.

. After using the voltage regulator, the module was working fine but suddenly the HC-05 burnt, led stopped working. Transmission failed. HC05 of the receiver module also burnt after 2 minutes. Why did this happen? What's the solution?

Circuit connection: Hc05 connection same for transmitter & receiver circuit HC05 Tx -> Arduino Rx Hc 05 rx -> 2k ohm -> gnd Hc05 rx -> 1k ohm -> hc05 tx Hc05 vcc -> arduino 5v Hc05 gnd -> arduino gnd

Voice Recognition Module tx -> arduino 8 Rx -> Arduino 9 Vcc- 5v Gnd - gnd

Mpu6050 sda - Arduino 2 Scl- Arduino 3 Vcc - 5V Gnd- Gnd

Voltage regulator connection: The connection was 9V battery +ve to input, -ve to ground, output to Arduino 5V

receiver circuit

Transmitter Circuit

  • Can you provide a schematic?
    – Kwasmich
    Oct 6, 2020 at 13:00
  • Please show a schematic. Where exactly did you use voltage dividers?
    – StarCat
    Oct 6, 2020 at 13:10
  • 1
    @StarCat I added the schematic in the question. Have a look. The receiver circuit only has the Arduino and the HC05 nothing special there. So, did not draw that one. Oct 6, 2020 at 13:55
  • have you checked the power supply voltage at HC-05? ... your schematic shows a circuit that provides no power to the components
    – jsotola
    Oct 6, 2020 at 15:27
  • 1
    I've updated the schematic Oct 7, 2020 at 8:28

2 Answers 2


Your voltage divider pins are backwards the HC05 RX pin needs the divider, not the TX pin. Its tx would be 3.3v out and the arduino pin wouldn't care it would still work.

Most likely while you were testing before the HC05 was probably already slowly dying.

the HC05 has a very basic 3.3v regulator on board but only a little over 5V input can fry things. I have always put 75-100ohm in series with the 5V in just in case.

Your circuit is basically good but the the RX/TX pins on the HC05 need reversing. Analog V. regulators are fairly crude and will vary voltage some.

5.000v accuracy is never dead on. I have seen as high as 5.7V out and that would not be good.

Also the HC05 RX pin is receiving a 5V signal back, sourcing thru the HC05 chip.

Even the Arduino help site warns against 5V if it can be avoided.

from Arduino's site https://create.arduino.cc/projecthub/electropeak/getting-started-with-hc-05-bluetooth-module-arduino-e0ca81

Sending Data to Arduino via Bluetooth
HC05 module has an internal 3.3v regulator and that is why you can connect it to 5v voltage. But we strongly recommend 3.3V voltage, since the logic of HC05 serial communication pins is 3.3V. Supplying 5V to the module can cause damage to the module.

You said "I should mention that I was using voltage dividers for both of the transmitter, and receiver circuit's HC05 Bluetooth modules."

Voltage dividers are not a good way to lower voltage for power components. The voltage output will vary based on load, and they also dissipate the excess voltage as heat, so you need high current resistors.

Post a schematic of your system with the specific batteries, regulators etc that you are using.

  • 1
    I added the schematic in the question. Oct 6, 2020 at 13:56

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