pH ORP DS18B20 Circuit

flux

Yes — a few sensors fit this board architecture well because you already have 3.3V, GND, I2C, 1-Wire, ADS1115 differential analog inputs, and high-impedance probe conditioning.
Good matching additions:

Table

SensorBest InterfaceWhy it matches
EC / TDS / conductivity probeExtra analog front-end + ADS1115 or separate ICCommon companion to pH/ORP for water quality. Needs AC excitation, so it is more complex than pH/ORP.
Dissolved Oxygen (DO) probeAnalog front-end + ADCUseful for water quality. Probe type matters: galvanic/polarographic/optical. Analog DO needs careful conditioning.
Turbidity sensorAnalog or digital moduleEasier add-on; can feed ESP32 ADC or ADS1115 if a channel is free.
Water temperature sensor, second DS18B20Same 1-Wire DQ busVery easy. Multiple DS18B20 sensors can share the same DQ line.
Water level / float switchDigital GPIOSimple safety/status input. Needs an extra J2 pin or separate connector.
Leak detector / wet contact sensorDigital/analog GPIOUseful for enclosure or tank monitoring.
Pressure sensorI2C or analogUseful if measuring pipe/tank pressure. Prefer I2C 3.3V sensors.
Flow sensorDigital pulse GPIOUseful for dosing/flow monitoring. Needs one ESP32 GPIO input.
Best recommendation for your current project:
  1. EC/TDS sensor — most useful companion to pH + ORP, but requires new analog circuitry.
  2. Second DS18B20 — easiest; no schematic change needed except maybe documenting multiple sensors on the same DQ bus.
  3. Turbidity sensor header — practical and beginner-friendly if you use a module.
  4. Flow sensor or float switch header — useful, but J2 would need extra GPIO pins or a second connector.
I would not add all of them to this same board unless you expand the connector/header plan. For your current clean 5-pin ESP32 interface, the easiest “no major redesign” upgrade is multiple DS18B20 sensors on the same DQ line.
Compare sensor options
Add EC/TDS planning
Add turbidity header
Multiple DS18B20 guide
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Files

Schematic

Layout

Preview

U1
C4
Capacitance
1 µF
C1
Capacitance
100 nF
C8
Capacitance
100 nF
C17
Capacitance
10µF
C2
Capacitance
100 nF
C18
Capacitance
100nF
C10
Capacitance
100 nF
C6
Capacitance
100 nF
C11
Capacitance
100 nF
C7
Capacitance
100 pF
C13
Capacitance
100 pF
C16
Capacitance
100 nF
C14
Capacitance
100 nF
C12
Capacitance
100 nF
C9
Capacitance
100 nF
C3
Capacitance
10 µF
C5
Capacitance
10 µF
C15
Capacitance
100 nF
R12
Resistance
1000000 Ω
R3
Resistance
1000000 Ω
R11
Resistance
4700 Ω
R6
Resistance
1000 Ω
R5
Resistance
1000 Ω
R10
Resistance
1000 Ω
R9
Resistance
1000 Ω
R8
Resistance
10000 Ω
J3
J2
R14
Resistance
10000 Ω
R4
Resistance
1000 Ω
R13
Resistance
1000 Ω
R2
Resistance
100000 Ω
R1
Resistance
100000 Ω
R15
Resistance
10Ω
R7
Resistance
10000 Ω
J1
U2
U3
J5
Project Specification
Project
ESP32-C3 ADS1115 pH/ORP Sensor Interface
Current Design Scope
This project is a 3.3V-powered analog front-end for measuring pH, ORP, and temperature with an external ESP32-class controller. The board does not include batteries, TP4056 charging, debug headers, or an onboard ESP32. The ESP32 connection is through one 5-pin header carrying power and digital signals.
External Interface: J2
Use these names for firmware and wiring documentation:

Table

J2 PinNameDirectionPurpose
13.3VInputExternal 3.3V supply from ESP32 board or regulated source
2GNDCommonCommon ground with ESP32 and probes
3ADS1115 SDABidirectionalI2C data to ADS1115 module
4ADS1115 SCLInput to ADS1115I2C clock from ESP32
5DS18B20 DQBidirectional1-Wire data for DS18B20 temperature probe
ADS1115 ADDR is fixed locally to GND through R14 = 10kΩ for default address 0x48. ADS1115 ALERT is intentionally unused/no-connect.
Power Architecture
External 3.3V enters at J2 pin 1 and feeds the filtered analog rail through R15.
Text
J2 pin 1 3.3V -> R15 10Ω -> FILTERED 3.3V
FILTERED 3.3V -> C17 10µF to GND
FILTERED 3.3V -> C18 100nF to GND
The FILTERED 3.3V rail powers U1 ADS1115 module, U2/U3 MCP6002 op-amps, J3 DS18B20 sensor power, pull-ups, and the analog bias/reference networks.
Sensor Architecture
  • J1 is the pH BNC input connector.
  • J5 is the ORP BNC input connector.
  • J3 is the DS18B20 temperature sensor header.
  • U1 ADS1115 module digitizes pH and ORP in differential mode.
  • U2 MCP6002 buffers the pH signal/reference paths.
  • U3 MCP6002 buffers the ORP signal/reference paths.
ADC Channel Map

Table

MeasurementADS1115 ModePositive InputNegative InputFunctional Net
pHDifferentialA0A1ADS1115 PH A0 - ADS1115 PH A1
ORPDifferentialA2A3ADS1115 ORP A2 - ADS1115 ORP A3
Firmware must read pH as A0-A1 and ORP as A2-A3. Do not use single-ended readings for the final measurement because the analog design relies on differential cancellation of the mid-supply reference.
Key Component Values
  • R15 = 10Ω analog supply filter resistor
  • C17 = 10µF analog rail bulk capacitor
  • C18 = 100nF analog rail bypass capacitor
  • R1/R2 = 100kΩ / 100kΩ mid-supply bias divider
  • C4 = 1µF bias filter
  • R3/R12 = 1MΩ pH/ORP probe input protection resistors
  • C7/C13 = 100pF high-impedance input RF filters
  • R5/R6/R9/R10 = 1kΩ ADS1115 input series filters/protection
  • C8/C14 = 100nF differential ADC input filters
  • C9/C10/C11/C12 = 100nF ADC input-to-GND filters
  • R11 = 4.7kΩ DS18B20 DQ pull-up
  • R14 = 10kΩ ADS1115 ADDR pull-down
  • R7/R8 = 10kΩ optional/DNP I2C pull-ups to FILTERED 3.3V. Leave unpopulated by default if the ADS1115 module already has onboard SDA/SCL pull-ups; populate only if no other I2C pull-ups are present.
Simulation Summary
Final simulation of the updated circuit with R15/C17/C18, local decoupling, and PH/ORP guard-ring modeling gives:

Table

ResultValue
Overall functional resultPASS
FILTERED 3.3V rail cutoff~778 Hz
Rail attenuation at 100 Hz-0.0716 dB
Rail attenuation at 1 kHz-4.221 dB
Rail attenuation at 10 kHz-22.18 dB
Rail attenuation at 100 kHz-42.16 dB
pH/ORP differential bandwidth~481.8 Hz
pH ADC range for ±414 mV probe inputA0 ≈ 1.236V to 2.064V, A1 ≈ 1.650V
ORP ADC range for ±1.0V probe inputA2 ≈ 0.650V to 2.650V, A3 ≈ 1.650V
Guard-ring verificationPH guard tied to PH REF; ORP guard tied to ORP REF; neither tied to GND
Simulation plots:

Final 3.3V rail filter response

pH and ORP differential gain vs frequency

pH transient step response

Firmware Requirements
  • Configure ADS1115 at address 0x48.
  • Treat R7/R8 as optional DNP hardware pull-ups: do not solder them if the ADS1115 module or ESP32 side already provides I2C pull-ups.
  • Use differential reads: A0-A1 for pH, A2-A3 for ORP.
  • Use lower ADS1115 data rates and averaging/median filtering for stable readings.
  • Read DS18B20 on J2 pin 5 / J3 pin 2 using 1-Wire.
  • Calibrate pH offset at pH 7 and slope using buffer solutions.
  • Temperature compensate pH slope using DS18B20 reading.
Current Validation Status
ERC reports no open errors or warnings. PCB routing is still expected to require DRC/airwire cleanup after layout routing.

  • Project

  • Current Design Scope

  • External Interface: J2

  • Power Architecture

  • Sensor Architecture

  • ADC Channel Map

  • Key Component Values

  • Simulation Summary

  • Firmware Requirements

  • Current Validation Status