0 votes
asked by (120 points)
Hi could some one please clarify this issue,

I'm trying to do some simple Voltage readings with my ESP8266 AI_Thinker.

Reading the Infos on the web, the max input on ADC should be 1Volt.

When I supply 1V to A0 I get a ADC reading of 325

When I connect the 3.3V supply of the ESP directly to A0 I get a reading of 1010.

So, to me it seems that max input voltage is rather 3.3V and not 1V.

Please comment


commented by (3.2k points)
The AI Thinker Schematic shows a Ext-voltage-220K-100K-Gnd voltage divider or 3.2 divider chain, so 3.3v input = 1.031 so subject to a small ADC error is what your getting 1010/1023 = 1.3% error
commented by (120 points)
Thank you, that explain it.
I tried to find a schematic of AI Thinker but without success. Where could I find one.

1 Answer

0 votes
answered by (300 points)

Hi Uli,

Max input for the chip is 1 Volt, but many esp8266 boards have a voltage divider that translates A0 inputs in the 0-3.3V range to voltages in the 0-1V range for the chip. Your observation suggests that your board has one too.

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