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Electronics => Electronics => Topic started by: adaschau2 on January 07, 2012, 01:37:58 PM

Title: Atmega8 Maximum Logic 0 Voltage
Post by: adaschau2 on January 07, 2012, 01:37:58 PM

Hello again everybody,
     I just encountered a problem with a sensor that may be resolved by the answer to the following question: what is the maximum voltage that will be considered 0 logic on the Atmega8? I know that I should probably be able to find it on the datasheet, but I cannot for the life of me locate it. Here is the sheet if one of you pros wants to point me in the right direction: http://www.atmel.com/dyn/resources/prod_documents/2486S.pdf (http://www.atmel.com/dyn/resources/prod_documents/2486S.pdf). Thanks for your help!

P.S. For you curious types, my issue is that I have an IR emitter being cut off from a detector, but I'm only able to lower the signal to about 1.5 volts or so.

Title: Re: Atmega8 Maximum Logic 0 Voltage
Post by: billhowl on January 07, 2012, 07:20:41 PM

maximum voltage for logic 0(Low) is 0.2*Vcc, for 5V supply will be 1V.
The info you can find in this datasheet page 242
http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf (http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf)

So for your IR emitter have to lower the signal to about 1 volt.

Title: Re: Atmega8 Maximum Logic 0 Voltage
Post by: adaschau2 on January 08, 2012, 12:56:50 AM

Thanks Bill! I actually did skim through that section, but I guess I missed the "I/O Pin Input Threshold Voltage" graphs among the 80 other graphs in that section on the first pass :P.