ESP8266 Community Forum

- Tue Feb 09, 2016 1:02 pm #40805 Hi all!
First, sorrry for my bad english

I'm having problems with ESP when I connect CH_PD with 3.3v

My circuit is this:

Simulator: https://123d.circuits.io/circuits/15398 ... breadboard


The problem in the simulation is: When I connect Vcc only, the ESP turns on the led. When I connect the CH_PD pin, the voltage oscilates between 3.3V and 960mV.

In the real word, the ESP red led turns blinks only one time. With my voltimeter, I only see 960mV

When I use an Arduino UNO to provide 3.3v to Vcc and CH_PD, I have no problem.

Someone know why I'm having this problem? In google I cannot found anything.


Thanks!!!

- Fri Feb 12, 2016 8:27 pm #41005 When ESP pulls 200mA at 3.3v, its effective resistance is 16.5 Ohm.
So you circuit effective looks like:

Code: Select all                /--- 1440 Ohm ---\
--- 1000 ohm ---+--- 16.5 Ohm ---+---


Which is the equivalent to:

Code: Select all--- 1000 ohm ---+--- 16.31 Ohm ---+---


So the voltage drop on esp8266 becomes 0.096v.

Since it is too low to sustain the device, the simulator reset the device.

In the real world, a reset is not guaranteed, the device could be stuck in malfunction state and could never itself pull out.

- Wed Sep 20, 2017 2:15 am #70134 Here is what worked for me for 4.11V Li-Po rechargeable battery:

VCC, RESET: connected to breadboard - to switch - to 4.11V positive terminal of LiPo battery
CH_PD: connected to 10E (10-ohms) resistor - to switch - to 4.11V positive terminal of LiPo battery

So, ESP8266 VCC seems to tolerate almost upto 4V power supply, but CH_PD won't tolerate that.
The CH_PD terminal draws not more than 1mA of current, more like 0.2mA-0.3mA in steady state.

Since your voltage supply is 4.5V, the current drawn by ESP ranges between 50mA and 350mA, (almost none of that goes through CH_PD), and the ESP can tolerate between 3.3V and 4V (say), if you add a resistor between VCC and your 4.5V we are looking at different resistor values needed for the different operating ranges:
For 50mA current draw: say VCC=4V here, then R = (4.5V-4V) / 0.05A = 10 ohms.
But then,
For 350mA current draw: voltage drop across R=10ohms will be 0.350A x 10ohms = 3.5V! So VCC will drop to 1V!

So, adding a simple resistor won't work. Maybe you can switch to a rechargeable Li-Po battery (3.7V nominal, gets charged to 4.11V) for your power supply.