ESP8266 Witty add Thermistor to ADC

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01:31:55

ESP8266 Witty extend Temp Sensor to ADC
NTC-MF52-3950 (1..100 kOhm / -20..85'C)
 
The Witty Cloud board have a LDR ligh sensor.
This circuit append a thermistor to the ADC.
GPIO5 used to enable (HI) or disable (LO).
The GPIO provides only 3.0 V at HIGH.

Parts you need:
- thermistor NTC-MF52-3950 (1..100 kOhm)
- resistor 680 Ohm, 10 kOhm, 470 ohm
- diode 1N1111

The diode disable current flow to GPIO.
Resistor 680 reduce LDR to 535mV.
Resistor 470 maximize THERMO to 1V.
Resistor 10k provide range -20..85'C.

1. GPIO=LOW messure V1 (light)
2. GPIO=HIGH messure V2 (thermo)

V-light = V1
V-thermo = V2 - V1

You need a lookup table to get lux and temp.

published 8 years ago

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