HC-05 does not work when powered from an electrical outlet

Hi, my HC-05 module works normally when my Arduino is powered via a USB on my laptop but when I power the HC-05 modules from a 9V charger the modules just flash and I can't connect to them. Does anyone please know what to do with it? Thank you in advance

That is because the Arduino 5 volt regulator is used to supply the 5 volts when you use the 9v charger. It over heats and shuts down and restarts, causing flashes.
When you use the USB, the 5 volts goes directly to the Arduino and 5 volt pin, bypassing the regulator.
The solution is to use a 5 volt supply for both and power the Ardiuno 5 volt pin directly with the 5 volt Power.

Are you saying that the Vcc on the module was connected to 9V?

The power supply for the module is typically 4-6V which goes through a voltage regulator to supply 3.3vV to the module. I'm not certain of the specifications on the regulator, but it is probably not designed for 9V and may have been damaged.

I power the Arduino with a 9V charger which supplies power to the Arduino via the input which is in the Arduino Uno board and then from the 5v Arduino pin I have a cable which supplies 2 HC-05 modules, a couple of LEDs and one buzzer.

What is the spec on the 9V charger as to the current it can supply? Maybe it can not provide the same current as the USB connection.

Do you see the Arduino board resetting?

Is the flash pattern on the module the standard not connected pattern or are you talking about something else?

Welcome to the forum.

Modern digital radios require large amounts of current for a very short time. Try adding capacitors to your power supply and close to the radio module.

You may need to power the radio modules separately. Check the specification of the regulator on your Arduino and make sure you have enough reserve. There is also a thermal limit that is often lower than what the datasheet may suggest because Arduino boards do not have the heat sink capability required for full load.

I'm not sure about the buzzer, but a typical 9v 1A wall wart, common amongst Arduino users, should be fine with this. I'm a bit suss about your use of the word "charger'. If you are using a charger for 9v NiCad, you may find it is as miserable as the batteries it is supposed to charge. I have one here that is only good for 250mA, and I have had worse.

Hi, I'm sending a photo of the charger.
Thank you all for the advice.

Check the ACTUAL voltage both unloaded and with a load. Likely to be TWICE the 9 volts with no load.


You have been given several. Try them.

It says 1.0A, so it should be kosher. Your laptop USB port is likely to be only 500mA.

I agree. If the charger is working properly it should be sufficient.

Can you confirm that with no changes to the wiring from the Arduino to the 2 HC-05 modules, the LEDs and the buzzer, that it still works with the usb, but not with the charger.

If so, I would try a different charger to see if it possibly defective.

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