ESP8266, by default, operates on 3.3V and because of the same reason, care must be taken when connecting ESP8266 with any micro controller or Arduino boards which operates on TTL Level i.e. 0-5 volts.
If we drive ESP module through a power supply of 3.3 volts then the only remaining point of concern is the RX pin which will receive 5 volts from Arduino or any other micro controller TX pin and will burn RX pin of ESP module eventually. Therefore it needs to be scaled down in the range of 0 – 3.3 volts.
Following circuit did exactly that.
The TX pin of ESP module also works on 0-3.3 volts logic but we don’t need to scale it to 0-5 volts because in TTL logic 3.3 volt signal is already considered as HIGH logic therefore we can directly connect it to our micro controller RX pin.
We made a simple adaptor board to convert TTL logic into 3.3 volts using the above circuit diagram.
Although Arduino has a 3.3 volt power pin on board but we should not drive ESP module from it because ESP module on average draws 130mA current which is quite a bit for Arduino board to provide and may damage the board eventually.
Sources to purchase ESP8266 and PL2303 Modues
Note: PL2303 is not the only USB to TTL converter in the world, check out the following alternates, compare prices to make a decision when buying
If you don’t have OR for some reason don’t want to use a 3.3v supply to power ESP module than you can modify the circuit and add a regulator to drive the ESP module (explained in detail in this article)