ESP8266 Community Forum

- Tue Mar 01, 2016 12:16 pm #42176 Hi all,

Assuming that I have a clean 5v regulated supply being further LDO regulated down to 3.3v for an ESP12, from what I read here and in other places it seems to be recognized good practice to include decoupling capacitors on the 3.3v supply to stabilize and filter the supply. I do have 0.1uF and 47uF capacitors available to use and a range of smaller than 0.1uF and greater that 47uF caps available to me.

So far as I can tell, the larger capacitor is usually placed near the 3.3v source and the smaller capacitor is ideally placed right next to the ESP Vcc in and ground pins.

Right now I have no other components connected to my ESP12 other than an occasionally connected TTY/USB convertor for programming and my question: is using a 47uF cap going to be safe to use or is this too large? In addition to that I guess a more general question is: are large capacitors bad for the life expectancy of an ESP8266 board / how is correct capacitance calculated for a circuit?

Please be gentle - as you can see I'm obviously a bit clueless with electronics

Thanks for any help
Joe

- Tue Mar 01, 2016 12:31 pm #42177 On general electronic devices, only 0.1uF decoupling is usually used.
But since ESP is a power hungry beast, you need both, the 0.1uF for filtering, and the 47uF for power reserve for when spikes occured.
Both need to be near the ESP simply because of wire resistance.
The value 47uF is not really high, I'm personally using even bigger 220uF.
Physical size can be a limitation, but since the ESP is running at 3.3V, if the capacitor is 5V or 6.3V, size still small enough.

- Tue Mar 01, 2016 3:03 pm #42187 Sounds good thanks, you've put my mind at rest about a 47uF capacitor causing damage. It's a 35v 47uF electrolytic cap here which is fine so far as physical size goes.

From what you've said it seems as though any size (in terms of capacitance / microfarads) capacitor is safe for smoothing the supply so long as the cap rated voltage stays above the supply voltage.

And if I understand correctly about the smaller 0.1uF capacitor this works as a frequency filter on the DC supply.

- Tue Mar 01, 2016 3:24 pm #42191 Yes, the 0.1uF (100nF) are for filtering.
If the size of the 47uF start bothering you, there are some ceramic ones too that are quite small :
http://www.ebay.com/itm/50pcs-1206-CAPA ... 1440283127
You can even put some in parallel to get high value, therefore better power reserve for your ESP.