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What is the significanse of NOT Gate IC in Cellphone operated robot circuit published on instructables.?

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Picture of What is the significanse of NOT Gate IC in Cellphone operated robot circuit published on instructables.?
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gmoon8 years ago
You should ask the author.

Since the inputs on an AVR (ATMEGA16) can easily be setup to use internal pullup resistors (R4-R7), and any input signal inverted with software, it looks like five components could be eliminated. But there might be other reasons to included them (including programming simplicity), that would compel their use...
heloitsadi (author)  gmoon8 years ago
Still i could not found any strong reason behind includion of these NOT gates and the pull ups, my circuit is working very well even without the NOT gates and the pull ups, I just did the variations in the program to get it right...
Good job. Those gates did seem superfluous.
frollard8 years ago
The IC2 is expecting the opposite signal that the mt8770 is giving out. The IC2 has pullup (or pulldown, dont care to check too much) resistors on the input pins. IC1 is sinking that pullup.
heloitsadi (author)  frollard8 years ago
Is that property of PORT A of IC2(Atmega 16) to invert the input fed to it, or something else. Please be clear.... I am not getting it.
. AKA, inverter. A 74LS04 "hex inverter" in this case.
. Good answer, just thought that term might be helpful to others.