Battery powered temp sensor, minimize drain?

  • I have build a simple battery powered sensor using a simple voltage divider as described here. The resistor (10k) is connected to Vcc just as the battery and I measure voltage between thermistor(10k) and ground. Will this constant connection drain the battery or should I have one pin powering the circuit just when I want to wake up the sensor and measure?

  • Mod

    @Efflon yes that will drain the battery. A 10k resistor will give 3.3V/10000=0.00033A = 0.33mA. AA batteries normally supply about 2,000mAh. With 0.33mA drain, the voltage divider alone will drain the batteries in about 6,000 hours or 250 days. The Arduino and sensors will add to that drain to make battery time even shorter.

    See for the official MySensors recommendations for battery-powered sensors.

  • @mfalkvidd Thanks, I have read the link and followed the instructions regarding the LED. I will re-build my sensor to use a dedicated pin for power instead.
    But wait! Since it's only when measuring I have a voltage division with 10000, the normal case would be 3.3V/(10000+~10000)=0.15mA and thus 500days? Well, a bit of code instead of changing batteries is better.

  • Mod

    @Efflon yes, that's correct.

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