analog

I was wondering if I could measure battery voltage simply by hooking the battery's + to an analog Arduino pin so that my robot can know when it's low on power. From what i've understood, a battery of 1.5 volts is dead when it outputs 1.4 volts (gonna do some research about this). I guess I can apply this approximation to different voltages battery. The only problem is that, if I want to use a battery with voltage superior to 5v (Arduino analog pins set 5v as a maximum), how do I divide the voltage? Again, I guess I'll need op-amps to do that and voltage dividers, but what do I exactly do?

I was wondering if it would be possibly to connect multiple microcontroller IC's by there I/O ports?

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Just had an idea. I'm planning to use a LOT of (tactile) switches on a walking robot. For instance I wanna put several under each foot. But it seems like a waste of pins to use a digital pin for each switch (or use multiplexers). So I thought I might be able to connect the switches in paralel and read several at a time from an analog input using resistors of different sizes connected in serial with each switch. Like this:

Ahoy me hearties!

I'm working on a bot that will have a lot of sensor requirements. It must be able to sense objects both at the top and the bottom of the frame. Since I don't want to have to keep track of 8+ sensors, I was hoping to combine some of the sensor inputs.

For example, the bot will react the same to an object sensed at the bottom as one at the top, can I combine them?

Will this schematic work? And if so, will the adc reading be a sum of both sensors, or merely the highest one?

Hello! i have almost finished my analog inputs on my last project.. i have only one left and i need to attach some potentiometers to do some calibration.. I could really use some nice multiplexing. What i'd like is a chip with some analog inputs and possibly an i2c interface so that you can choose which analog pin to read and get a digital reading. Do you know if anything like this exists ?