We’ve already covered how to use an Analog-to-Digital Converter chip with a Pi. These chips are the best way to read analog voltages from the Pi. However, there’s a way to read many sensors without an ADC! By measuring the sensor as a resistor that is used to ‘fill up’ a capacitor, we can count how long it takes. It’s not nearly as precise as an ADC and its a little flakey (since it depends on the Pi timing itself which can vary based on how ‘busy’ the computer is)
The way we do this is by taking advantage of a basic electronic property of resistors and capacitors. It turns out that if you take a capacitor that is initially storing no voltage, and then connect it to power (like 3.3V) through a resistor, it will charge up to the power voltage slowly. The bigger the resistor, the slower it is.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.