ESP8285 ADC (max voltage)

skywave
Posts: 16
Joined: Sun May 17, 2015 3:33 am

ESP8285 ADC (max voltage)

Postby skywave » Wed Feb 22, 2017 6:18 am

Hi There,

I would like to connect a temperature sensor to the ADC (TOUT) pin. What's the max voltage ADC can read? Is it 1V? If yes, does applying a 2V voltage to the ADC damages the ESP8285? Between 0ºC and 80ºC the voltage will go from 1V to almost 0V, but below 0ºC the voltage will go up to 1.5V or 2V. This kind of voltage on ADC pin could damage the ESP8285 chip? We don't need to measure below 0ºC so it it's safe we don't mind reading always the max value (1024) from the ADC.

Looking forward to hearing from you soon,

Pedro

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pratik
Posts: 416
Joined: Wed Jun 29, 2016 7:17 pm
Location: India
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Re: ESP8285 ADC (max voltage)

Postby pratik » Wed Mar 01, 2017 2:15 pm

The pin external voltage is specified to 1V (max) when using the SARADC as it is an internal pin. But if you want to be safe (higher voltage can produce unreliable readings), you can limit the input using two forward biased diodes to ground (with series resistor of course). Then ADC input will not exceed say 1.2V. :)
No huge addition to system cost either!
Regards,
Pratik Panda
Website: http://www.PratikPanda.com

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