Hi
I used the following circuit to connect to the ADC input pin.
1. R13:10M R12:2.43M
When BATTERY_DET1 input voltage is 2.1V, the ADC reading is only 1.7V.
When BATTERY_DET1 input voltage is 0.9V, the ADC reading is 1.1V.
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Hi
I used the following circuit to connect to the ADC input pin.
1. R13:10M R12:2.43M
When BATTERY_DET1 input voltage is 2.1V, the ADC reading is only 1.7V.
When BATTERY_DET1 input voltage is 0.9V, the ADC reading is 1.1V.
I tried to add a 0.1uF capacitor. It seems that the ADC reading value is very stable.
The reading value is very similar to the value obtained by my calculation of the voltage dividing resistor. The PIR trigger does not affect it.
The calculated value is 2.46V, and the ADC reading is also 2.46V, but when measured with a voltmeter, the actual voltage is 2V, and the ADC reading becomes 2V.
My guess is that the voltmeter internal resistance causes this result. Is my guess correct?
I uploaded the figure again.
V_BAT is connected to the battery, the range is 5V~13V.
BATTERY_DET is connected to the ADC pin of the MCU.
At present, a 0.1uF capacitor is connected in parallel with R12. Is this the recommended value?
What is the effect of the capacitor value being too large or too small?
I will confirm the internal resistance of the voltmeter.