what was my mistake ? And a strange battery phenomena

Hi guys,

I've connected the esp8266through this power supply and 9v battery:

Then connected esp rx - rx to arduino uno and esp tx - tx to arduino uno and did all the needed connections (and shared the GND of the power supply and the arduino)

Everything worked fine, BUT !! esp8266 kept restarting itself. And after some time stopped working.

After hours of trial and error (like putting capacitor between Vcc and GND) I finally put aside the power supply and connected the ESP to 3.3v of the arduino.

Everything works great.

So I realized there is a problem with the power supply, I measured how much voltage it gives (should be 3.3) and it was 1.7v only :expressionless:

then i measured the 9v battery itself and it gave 5.5 volts, and after a second 5.6 and after another one 5.7... and so on until it reached 7v. (after a minute)

I connected the battery to the power supply again, now volt meter showed me 3.3v like expected.

What I did wrong ? the battery can't supply the 200mA needed ?

The esp8266 is a 3.3V device that probably has an LDO regulator that can accomodate a 3.7V Lipo battery input. I think the most it can tolerate is 5V on the input but without the regulator part number I can't say for sure.

What I did wrong ?

Lots of things.

  1. The Arduino is a 5V system it has 5V signals so when you connect a 5V signal to a 3V3 system you damage the input.

  2. “I connected the battery to the power supply” - connecting a battery to a power supply is a bad idea. Is it a rechargeable battery? If not you are asking from trouble, it might explode or catch fire and will not charge very much.

  3. You didn’t do your research before doing your experiment.

You didn't do your research before doing your experiment.

"Gimme 20 pushups !" ;D

Grumpy mike,

I used the wrong terms, when i wrote “power supply” I meant “voltage regulator”.

I figured out using a multimeter that when I’m using the 9v battery it supplies 150mA but when i use the arduino power supply it provides 250mA. meaning the voltage regulator couldn’t pull enough current from the battery.

Finaly to avoid harming the arduino i found an old d-link power supply (and now i really mean power supply) and connected it to the voltage regulator and now everything seems to be working.

As far as to why the battery voltage of your 9v battery increased over time, that is typical of what happens when you discharge a battery (you can even see it with a large capacitor) with a heavy load until it is almost dead. When you remove the load, the battery voltage will rebound as some of the chemistry finishes converting, but, as you observed, it only made it back to 7v (which for a 9v battery indicates you had pretty well flattened it). But, as you observed, a partial rebound with the load removed is typical.

tautau123:
then i measured the 9v battery itself and it gave 5.5 volts, and after a second 5.6 and after another one 5.7... and so on until it reached 7v. (after a minute)

I connected the battery to the power supply again, now volt meter showed me 3.3v like expected.

What I did wrong ? the battery can't supply the 200mA needed ?

No it can't, those PP3-sized 9V batteries struggle from 50mA upwards, they are not for
high current devices.


You call that a battery?

tautau123:
Then connected esp rx - rx to arduino uno and esp tx - tx to arduino uno and did all the needed connections (and shared the GND of the power supply and the arduino)

With the above connection RX-RX and TX-TX are you able to receive Serial data in Arduino?

I connected ESP Rx-Tx of Arduino and ESP Tx-Rx of Arduino. Also used a two resistor level shifter to TX line from Arduino. May not be a clean approach but worked for me.

Esp never powered on from my Arduino 3.3v, I tried it with 5v from Arduino for short time to test the module, not for long run as its a 3.3v device.