CALIBRATION.md

Sensor Calibration Guide

Calibrate sensors before final enclosure assembly for best results

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Light Sensor Calibration

1. Setup:

   • Connect multimeter to light sensor output (A0)
   • Use smartphone light meter app as reference

2. Procedure:

   Condition	Expected Voltage	Calibration Value
   Complete dark	0V → 0%	darkValue = analogRead(A0)
   100,000 lux	3.3V → 100%	brightValue = analogRead(A0)

3. Update Code:

   // In sensors.cpp
   float sunlight = map(analogRead(LIGHT_SENSOR_PIN), darkValue, brightValue, 0, 100);

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Capacitive Rain Sensor

Dry/Wet Calibration:

1. Leave sensor completely dry for 24 hours

   Dry baseline:  # Serial monitor command
   > CAL_RAIN DRY
   > Value saved: 582

2. Submerge sensor in distilled water

   Wet baseline:
   > CAL_RAIN WET
   > Value saved: 183

Field Calibration:

Rainfall	Expected Reading	Adjustment
1mm	15-20%	Increase sensitivity if <15%
5mm	60-70%	Decrease if >80%

Code Implementation:

// In takeMeasurements()
int rainRaw = analogRead(RAIN_SENSOR_PIN);
data.rainfall = constrain(map(rainRaw, dryValue, wetValue, 0, 100), 0, 100);

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DHT22 Temperature Compensation

1. Ice Bath Test:

   • Submerge sensor in 0°C ice slurry
   • Record temperature offset:

   tempOffset = measuredTemp - 0.0;

2. Body Test:

   • Hold sensor in hand (should read 32-36°C)
   • Adjust if deviation >0.5°C

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Sleep Cycle Optimization

1. Measure current draw with multimeter
2. Adjust sleep cycles in power_manager.h:

   // Current: 0.45mA (good)
   // Target battery life: 6 months
   uint8_t cycles = minutes * 7.5;  // 8s/cycle

3. Balance between data frequency and battery life