Hello I am trying to send temperature data via bluetooth using the HC-06 module. Since TXD and RXD only allow 3.3V I have divided the circuit into two like the below image. Is this method correct? or is there a better way to connect both two?

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Any help is appreciated.

  • I think you have it backwards. You should be dividing the TX from the Arduino (5V) down to 3.3V for the RX into bluetooth.
    – Majenko
    Commented May 30, 2018 at 9:38
  • @Majenko Thank you for your comment. I'm a little confused. Is the below picture correct. So the purple and green wires should be reversed?
    – Satsuki
    Commented May 30, 2018 at 12:12
  • No, the resistors should be on the green wire not the purple.
    – Majenko
    Commented May 30, 2018 at 12:12
  • 1
    Is the lower module a bluetooth master? If I recall it correctly, the HC-06 module have their firmware set to slave only
    – chrisl
    Commented May 30, 2018 at 15:49
  • "Who" is on the other end? Once HC-06 is paired with a master - Nexus 7, f/ex, or PC's with Bluetooth 2 - it will communicate just fine. Just remember the HC-05/06 are Bluetooth 2 devices and can't talk to BLE devices -- current iPhones and many current PCs.
    – JRobert
    Commented Jan 7, 2019 at 13:36

1 Answer 1


As mentioned by chrisl, you cannot use HC-06 as a master device. Its firmware restricts it to behave only as a slave. So even if you are able to process the analog data from LM 35, you won't be able to send it using HC-06. It would be better if you go for HC-05 module and try the command AT+ROLE: x (x = 1 for master/0 for slave) to get the job done.

Coming to the 3v3 voltage constraint, I would suggest you to go for any Zener diode (in reverse biased mode) with 3.3V Reverse breakdown voltage. You can check the circuit for this here and order it from this link. If this is not possible anyhow, then you can also go for LM1117 3V3, but I would personally suggest you to go for zener diode. Comment back if you need any help in future.

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