Thanks for your answer. I Will add a wifi or bluetooth module to send data to web site lately, but at the moment I am developing the timer with Arduino nano to get values and show them. The sensors are:
- Gravity: Analog TDS Sensor/ Meter for Arduino
Signal Transmitter Board
- Input Voltage: 3.3 ~ 5.5V
- Output Voltage: 0 ~ 2.3V
- Working Current: 3 ~ 6mA
- TDS Measurement Range: 0 ~ 1000ppm
- TDS Measurement Accuracy: ± 10% F.S. (25 ℃)
- Module Size: 42 * 32mm
- Module Interface: PH2.0-3P
- Electrode Interface: XH2.54-2P
- DFRobot Gravity: Analog Signal Isolator
Operating Voltage: 5.0V
Response Time: 4 seconds (Typ)
Analog Error (both ends): <± 20mV (Typ)
Interface Type: PH2.0-3P
No load Current: 75mA
Dimension: 42 * 32mm / 1.65 * 1.26 inch
Non-isolated Terminal (Arduino Side)
Supply Voltage: 5.0 ± 0.1V
Analog Output: 0 ~ 5.0V
Isolated Terminal (Sensor Side)
Output Voltage: 5.0 ± 0.2V
Analog Input: 0 ~ 5.0V
This Is connect to Gravity: Analog pH Sensor / Meter Pro Kit V2 with this specification:
Signal Conversion Board (Transmitter) V2
Supply Voltage: 3.3~5.5V
Output Voltage: 0~3.0V
Probe Connector: BNC
Signal Connector: PH2.0-3P
Measurement Accuracy: ±0.1@25℃
Dimension: 42mm32mm/1.661.26in
I power directly all the sensors with 5V externally and I reduce the voltage to 3.3V with a Voltage Regulator to Power Arduino. So each component has its own source. I thought to MOSFET to give Power or not to the sensors from Arduino.