Hi all, i want to ask do I use LM317T or LM317LZ voltage regulator circuit to connect the output pin of the sensor to the esp8266 input pin? as LM317T output current is about 1A while LM317LZ output current is about 100mA and i am not sure how much current is too much for the esp8266 input pin. many thanks and i have attached a circuit diagram from the datasheet
The subject of your post doesn't match your question. The LM317 is a voltage regulator, so it's used for power supply. You cannot use to convert the signal of a 5V sensor to the 3.3V of an ESP8266.
Please provide more details about what you're trying to achieve.
I am connecting a 5v PH sensor to the input pin of esp8266 nodeMCU. if that the case do i use voltage divider circuit or there is no need to reduce the voltage? or is there any other recommendations? and I dont know is this related but may i also ask how much current can the Vin pin of the esp8266 nodeMcu handle?
If you mean to connect to the analog input pin, look up the allowed input voltage range for your particular NodeMCU board (they differ). Compare that to the output voltage range of the pH meter.
If the latter voltage is higher, you will need a precision voltage divider.
Oh, beware when doing that.
I assume at least you're using some pH board that produces an analog output, so it's got to connect to the analog input of the NodeMCU.
The typical(!) range of the NodeMCU analog input is 0-3.3V, but the range of the ESP8266's ADC is 0-1V (where the 1V, which is probably some kind of band gap, no doubt has some tolerance but I've never been able to find actual specifications of that tolerance). To do this, the NodeMCU is using a voltage divider of its own: 220kΩ + 100kΩ normally, iirc. So the voltage divider you use for your pH sensor will be affected by this divider.