ESP-01 not transmitting on batteries (LF33CV regulator)

Hi there,

Im building a small sensor device on the ESP-01.

When running the ESP on my bench power supply on 3.3V (with the uart adapter attached and usb is running) everything is fine and the ESP transmits data.

When I plug the same ESP on the breadboard with batteries and a LF33CV voltage regulator and 4x1.5v Nimh batteries the power LED is on but the ESP does not transmit at all. The voltage should be 6V in total so the LF33CV should get enough voltage. The max. current of the LF33CV is 500mA but the ESP draws 300mA max.
So I dont understand why the ESP does not start/transmit data.
Measuring the voltage gives me 3.3V so everything should be fine.

When I put 3x1.5V Nimhs on the ESP directly it starts and transmits data. But that exceeds the specs of the ESP, right? That would be 4.5V in total and would burn the 3.3v if used for too long?!

See attached my breadboard circuit.

What a Im doing wrong?

Thanks for your help!

Maybe better:

I run the ESP-01 on 4.5V and its transmitting and working the chip does not explode... may this be safe in the long run?

Where are the input and output capacitors for that regulator? They are not optional components.

Thanks MarkT for reply!

My fault… Yes, they shoud be there. I put 0.1uF on the input and tried both 2.2uF and 10uF on the output.

Unfortunatley it still does not transmit anything. Only by attaching 4.5V directly to the power rail.

Any ideas? Is this board maybe 5v? :smiley:

Another strange behaviour:

If I connect CHPD to VCC (what I should) the power LED goes dim and the voltage drops. Still no transmission

I would venture a guess that the regulator isn't quite able to handle the current required by the ESP8266, or doesn't handle the current spikes gracefully. A larger cap on the output might help (22uF? 47uF?), as would a beefier regulator.

3x NiMH is more like 3.6v (NiMH is 1.2v per cell nominal), so you're not actually out of spec... ESP8266 is a 3.3v device, though it is astonishingly tolerant of abuse of that sort (I've heard of people who thought they were 5v devices running them at 5v for at least short periods of time!)

Thanks DrAzzy!

Hm okay. I just bought another regulator LM1086IT-3.3 which should handle up to 1.5A. I hope this one will be beefier.

Sorry... its not NimH. Its just normal AA batteries with 1.5v. But in the final application there should be NimH cells with 1.2V.

So running the ESP-01 with 3xNiMHs without a regulator should be fine anyway?

Thanks in advance!

Can you post a picture of the other side of the ESP01 breakout board please.
I have some and they are 5V input, there is a 3.3V regulator under the breakout board.

Have you tried a 10uF capacitor across the ESP01, between Vcc and Gnd?

Have you measured your battery voltage while these faults occur?

Tom.... :slight_smile:

Hey TomGeorge,

hm… no regulator on the back. See attached image.
I tried to add a cap between vcc and gnd on the esp but still the same.

You can see the voltage drop in post #4. If CH_PD is connected to VCC the voltage drops to 2.3v and the power LED goes dim.

The strange thing: If I connect the ESP to my bench power supply with 3.3v its the same. No transmission. Only if I connect to the batteries with 4.5v.

I really dont understand whats happening here.