–Yes you are right What do you suggest to solve this problem? How can i create digital 3.3v outputs from digital arduino pins ? using regulator is a solution for this ? I mean if i use two more regulator it will cost a lot i think there must be a easier way ?
A voltage regulator on a data line? Bad idea. Just use a voltage divider (20K / 10K, or 18K / 10K if you want E12 values).
–Also for PNP transistor ESP resets itself when there is ground coonection on reset pin of ESP8266. So transistor will stay closed for normal time and it will be open to reset it for a short time. If i am not wrong PNP looks more logical to me and again it would be wrong please tell me if it is
I think that’s wrong: a PNP transistor conducts when its base is at a lower potential than the emitter.
This means that it is closed when there’s 5v on its base and 3.3v on the emitter. (Logical 1 on base). When it’s closed, the reset pin will be at ground potential, so the ESP will reset. In this state, virtually no current is flowing through the transistor.
If the base is at 0v (logical 0), current will flow from the emitter, that is at a higher potential (3.3v) to the base, causing the transistor to conduct. When the transistor conducts, the reset pin is at 3.3V, meaning that the ESP will not reset.
However, current is flowing through the transistor, through the resistor at the collector, and through the ATmega’s I/O pin.
If you use an NPN transistor, the ESP will also reset on a logical 1, and run normally on logical 0, but the difference is that no current flows in normal operation, only while resetting.
It’s not that important in this case, but I just didn’t expect a PNP here, an NPN seems much more logical.
–and last question
“The difference is that the nano is a 5V board, so it runs straight off of the 5V provided by the USB connection. If you want to use the onboard 5V voltage regulator (via the Vin pin) you need at least 7V as well.
This board seems to run @3.3V, so you’ll need a LDO (Low DropOut) voltage regulator like the 1117 3.3v to go from 5V to 3.3V.”
I couldnt understand the difference between arduino nano and my board because i used exactly same layout and schematic for nano. I also run my board with 5v usb connection there should not be any difference. please tell me if i am wrong.
The difference is that the Nano has an extra 5V voltage regulator for input voltages that are higher than 5V.
This voltage regulator has a voltage drop of ~2V, so the minimum voltage input is 7V (5+2).
It doesn’t matter in your design, since you’re always using USB power, so there’s no need for a 5V voltage regulator.