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  • I specified 3.3V to look at... not 8.0V. Grab 3.3V output from NodeMCU board, then you are safe. A single value is not good enough... use multiples. If you have only 10k and 1k resistors, play around with multiple combinations always making sure that A0 input is never above 1.00 V. Since the input impedance of A0 is so high compared to your resistors, the voltage is proportional to the resistance from GND to A0 over total resistance from GND to 3.3V. For example, with 10 K and 2 x 1 K: 3.3V x 2k / 12k = 0.55V; with 1 x 1 K: 3.3V * 1 K / 11 K = 0.3V; with 3 x 1 K: 3.3V x 3K / 13K = 0.76V; and with 2 x 1K parallel:

       3.3V * (1 / ( 1/1K + 1/1K)) / (10K +   (1 / ( 1/1K + 1/1K)))
    = 3.3V * 0.5K / 10.5K
    = 0.16V

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