HC-05 Bluetooth module not showing up for pairing

[Navdagreat]

Hello,
This is my first post on this forum, so forgive me if the format of this post is not standardized

I'm trying to interface the HC-05 Bluetooth module using an Arduino Uno, and I built the circuit as shown below (I have used two 1k Ω resistors in series to create a 2kΩ resistor because I didn't have one):

The HC-05 module starts blinking as soon as I connect the Arduino to a power supply, however, I cannot seem to find the option to pair the HC-05 module with any device, i.e HC-05 simply does not show up while trying to connect with Bluetooth.

I've tried connecting it to my Laptop (running Windows 11) and my iPhone (running on iOS 16.2)

Have I made any mistakes? I have reviewed my connections carefully and also ensured that the voltage divider circuit is made correctly. I have also ensured that the RXD pin is connected to the TX port, and vice-versa. What could possibly cause this?

[groundFungus]

I have seen that the HC05 will not pair with another device if it is in master mode.

I wrote a tutorial for putting the HC05 into AT mode. >> Setting HC05 (ZS-040) to AT mode
With help of Martyn Currie' pages. >> Arduino with HC-05 (ZS-040) Bluetooth module – AT MODE | Martyn Currey

Change to slave mode with AT+ROLE=0

Lots of info about the HC05 from Martyn Currie. >> HC-05 | Martyn Currey

[Nick_Pyner]

@Navdagreat

Have I made any mistakes?

Yes, IOS is incompatible with HC-05, stick with the laptop. If the LED on Bluetooth is flashing about 2Hz, you should be able to see it and pair with the laptop.
All operations are at the laptop end.

[Navdagreat]

Hey, thanks for your reply

I followed your instructions and also used Martyn Currie's pages and your tutorial for reference.
I'm able to get my HC-05 module to get into AT command mode (specified by the slow-blinking LED), however, whenever I enter "AT" (no quotes), I get no response from the module.

I delved further and found that sometimes, connecting EN pin to 3.3V is a possible solution, but there was still no response.

What could be the problem?

[groundFungus]

Please post photos, front and back, of your modules and photos of your wiring.

[Navdagreat]

Nvm, I'd made a stupid mistake, didn't notice that I had wrongly connected RX and TXD

Sorry for the trouble :P. Thank you so much for your help, appreciate it a lot!

[groundFungus]

No problem. Happens to everyone. Hope that you can get your project going like you want.

If your question was answered to your satisfaction, please mark the thread as solved so that other members do not waste their time opening the thread wanting to help only to find that the problem has been solved.

[Navdagreat]

Hey, thanks again for your reply

Now however, the problem that is arising is that the module, disconnects itself automatically roughly 3 seconds after a successfully established bluetooth connection

Why is this happening?

[groundFungus]

No idea, sorry. I have heard of that, but do not know of a resolution.

Is the HC-05 connected to a Mac?

Try a forum search for "HC-05 disconnects"

HC-05 Disconnecting After 2 seconds

Hi there, I have my hc-05 wired up to my arduino using just the four pins, gnd, vcc, rx, and tx. I've tried both my hc-05's now, and they both have the same issue on my windows 10 computer. On my mac, I was able to stay connected. Why might the hc-05's disconnect only after a few seconds?

macOS Monterey can't reconnect to HC-05 Bluetooth without remove/re-add

I'm working on remote operated camera pan/tilt device that uses a HC-05 Bluetooth module to connect a GUI written in Processing and running on a Mac to the Arduino. Everything works great when I first pair the HC-05, but if either the HC-05 or the Mac Bluetooth gets power cycled, they won't reconnect automatically. If I choose the device in the Bluetooth menu or right-click and choose Connect in System Preferences, it spins for a moment and says "connected," but the LED on the HC-05 still blinks…

[Nick_Pyner]

@Navdagreat

that the module, disconnects itself automatically roughly 3 seconds after a successfully established

This might be due to inadequate power.

[Navdagreat]

What if I try to power it with an L298N motor driver (using the 5V output) powered by a battery? Will that be a constant, adequate supply?

[Abeer_goel]

no. the issue is that you are not giving it any inputs. use a btt app on laptop

[runaway_pancake]

@Navdagreat

What if I try to power it with. . .

5V from the Arduino running on USB will suffice.
No text is required to pair - it just has to be On.

[Nick_Pyner]

@Navdagreat

an L298N motor driver (using the 5V output)

It sounds unnecessarily complicated but, if that's all you've got and you can ensure it delivers 5v 500mA into the 5v, or 7.5v into the barrel jack, then yes. Your laptop's USB should suffice.

[Navdagreat]

Hey guys, thank for you your replies. I've found out through thorough research and digging that my HC-05 module is a fake (Version 4.0-20190815 to be exact) and has a dummy chip on top of it. I will be closing this thread now, thank you again for the time that you have put into this.

[brunod6]

Hi, I have a similar problem, when I power the microcontroller which I connected to hc 05 module, I am able to pair the phone with the module but unable to connect them, whereas using bluetooth terminal I am able to connect them(the led starts to blink slowly). I hope you understand and can help me with the issue.

[henrtyuter]

i couldnt solve my problem which was the same?