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

thanks

Uli
commented by (2.7k 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.
greetings
Uli

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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