Water Level Sensor Circuit Design
1:58
Considering resistor options.
Evaluating resistor options.
Accessing knowledge base.
Searching for components.
Searching library for: "100kΩ Resistor"
Searching library for: "6.8kΩ Resistor"
Searching library for: "10kΩ Resistor"
Creating search plan for: "100kΩ Resistor"
Creating search plan for: "6.8kΩ Resistor"
Creating search plan for: "10kΩ Resistor"
Searching.
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Found 77 results.
Searching: "100kΩ Resistor"
Searching.
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Found 70 results.
Searching: "6.8kΩ Resistor"
Found 76 results.
Searching: "10kΩ Resistor"
Finished searching for components.
Proposing resistor options.
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Pull-down resistor
- Use a 100 kΩ pull-down on the Pico GPIO to define a solid LOW when no water bridge is present.
- At 5 V this draws only 50 µA, minimizing corrosion and power drain.
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Voltage level shifting (only if you must keep the probe at 5 V)
- Because the Pico’s GPIO is not 5 V-tolerant, add a simple divider:
- R1 = 6.8 kΩ from the probe to the GPIO node
- R2 = 10 kΩ from the GPIO node to ground
- This yields ≈2.98 V at the pin—well above the ~2 V logic-high threshold and within 3.3 V tolerance.
- Because the Pico’s GPIO is not 5 V-tolerant, add a simple divider:
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Better alternative
- Power the probes from the Pico’s 3.3 V rail instead of 5 V and omit the divider. The 100 kΩ pull-down alone is then sufficient.
- Or implement a capacitive water sensor using PCB pads (per soil-moisture-sensor best practices) to avoid galvanic corrosion altogether.
Table
| Function | Part |
|---|---|
| 100 kΩ Pull-down | CRCW0603100KFKEA |
| 6.8 kΩ Divider R1 | CRCW08056K98FKEA |
| 10 kΩ Divider R2 | RC0805FR-1310KL |
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