I am experimenting with a circuit to send temperature & humidity readings every 15 mins to a web site. Its working really well, but I have an idea to simplify the circuit and need some advice please.
The circuit currently consists of ESP-01 module (8 pins), an SHT21 i2c temp/humidity sensor, a cp2102 usb to serial adaptor module and an ams1117 3.3V regulator module. Also 2 x pushbuttons, 2 x 4K7 pullups (for i2c lines) and 1 x 10K (for reset line) pullup resistors and 100uF and 0.1uF caps.
The regulator is fed 5V from the USB serial adaptor and provides enough current for the ESP. But I am wondering if I could use the 3V3 output from the USB serial adaptor instead of the ams1117.
According to the CP2102 data sheet, up to 100mA can be drawn from its built-in 3V3 regulator. This is, on the face of it, not enough to power the ESP, which can use ~200mA for short bursts. However, on average the ESP must use much less than that.
In my circuit, the ESP spends around 5s connecting to Wifi and sending its data. Then it spends 15 mins idling, when it uses only a few tens of mA. Even during the 5s of activity, the current only peaks to 150mA+ for very brief periods and averages perhaps half of that. I don't have a scope to measure it, just a DMM, which does not make taking peak and average readings easy!
With the 100uF cap connected to the 3V3 and ground pins, I am hoping that the short bursts of peak current demands will be smoothed out, resulting in an average current of less than 100mA. This would mean that the cp2102's 3V3 output would be sufficient and not stressed too much.
Can anyone suggest how I can calculate whether the 100uF is large enough, and whether the cp2102 would have a long life if I ditched the ams1117 regulator?