ESP8266 Community Forum

- Thu Apr 30, 2015 8:31 pm #16144 Hi Guys,

This is my first time posting a question on this forum, so please be kind if I am asking anything stupid.

I am trying to power my ESP using a wall socket mobile charger (as per the circuit diagram below.)



I got 5 V from my AC to DC converter (from an old mobile charger).
Created a voltage divider using a 10K and a 20K resistor to get 3.3V

I am able to measure 3.3V across that resistor.

But here is what happens - As soon as I plug in my ESP8266, the board does not light up and the voltage across that 20K resistor drops to around 1.2V

I don't know what's happening. Is it the internal resistance of the board which is messing with my voltage divider? Is it anything else that I don't see??

Please advise.

- Thu Apr 30, 2015 9:56 pm #16147

I don't know what's happening. Is it the internal resistance of the board which is messing with my voltage divider?

Yes, sort of... The ESP is in parallel with the 20k resistor, but it does not have a constant resistance or current consumption, therefore the voltage drop across the resistors won't be constant. Also the 10k resistor will limit your power draw to (5V-3.3V)/10kohm = 0.17 mA, but the ESP needs up to ~300mA.
Simply put: you can't use voltage dividers to power stuff. You need an LDO or buck converter with an max. output current of at least 300mA (pre-built modules are available from ebay or aliexpress for about 1-2$).

- Thu Apr 30, 2015 10:28 pm #16151 Yes you are "overloading" your voltage divider. The effective resistance of the esp is say 10-25 OHMs. If you can't wait to get hold of a voltage regulator I would recommend just hook it up with a couple of C or D cells == 3v.

Cheers,
John

- Sat May 02, 2015 12:02 pm #16298 The capacitor also way too small. You need 100uf one.

Make something useful. 'Eat your own dog food' DevKit for IoT.
http://www.nodeusb.com