ESP8266 Community Forum

- Sat Mar 12, 2016 3:40 pm #42961 Hello,
I'm starting the my journey with esp8266. First of all I have to power it and I'm not a electronics engineer so please advice.
I have couple of 5v power supplies and I have to convert it to 3.3v. I know to do that LM1117 is commonly used. Unfortunately I don't have such one now.
I found that I could use voltage divider but I heard it might not perform well (not sure why).
I'm also wondering if I could use 2n2222. I have bunch of them and as far as I understand datasheet, the collector is able handle 500mA current.
So basically I have to questions:
- Why voltage divider is not good idea?
- Is 2n2222 with some capacitors connected to ground will be sufficient?

Regards

- Mon Mar 14, 2016 6:55 am #43083 A voltage divider only works as long as the load has a constant resistance: when designing your circuit, remember that your ESP will act as a resistance of unknown value, wired in parallel to the output resistance of your divider; you cannot design a divider to work reliably under such conditions.

And mostly the same applies to using a transistor.

- Mon Mar 14, 2016 8:07 am #43090 I think this one gives you more option(diode!!).

http://ww1.microchip.com/downloads/en/D ... er%208.pdf

- Tue Mar 15, 2016 6:07 pm #43263 Well, If I was stranded on a desert island and my only way off was to use a handful of 2N2222's that were laying around I'd build one of these:

dividerReg.png

The above circuit uses the transitors as a Darlington Pair Emitter Follower to "stiffen up" the voltage divider R1/R2. It assumes the 5V supply is regulated to 5V. As show with a 10 Ohm load to represent 330mA current drain, T2 would be dissipating around 0.5Watt so this would be about as much as you'd dare draw from it. The Output regulation is pretty dire though, around 0.3V from 1mA to 330mA load but the ESP8266 would work ok.

If you replace R2 with a 4v7 Zener as below you could improve the regulation a bit and cater for a 5V input that wasn't spot on 5V. But I guess a Zener may also be unavailable to you.

ZenerReg.png

If you do try building it, I hope you have a meter handy to check the voltage before you wire it to the poor little ESP8266!

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