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.
This technique only works with sensors that act like resistors. however, there are quite a few fun sensors that act this way: photocells, thermistors (temperature sensors), flex sensors, force-sensitive resistors, and many more.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? Join the SHOW-AND-TELL every Wednesday night at 7:30pm ET on Google+ Hangouts.
Join us every Wednesday night at 8pm ET for Ask an Engineer!
Maker Business — A field guide to designing your PCBs, learned the hard way
Wearables — A glowing start point
Electronics — Current limiting!
Biohacking — A Gene to Predict Modafinil Response
Python for Microcontrollers — Python snakes its way on the SparkFun SAMD21 Mini, Hackaday.io, 10k thanks, and Tim’s magazine #Python #Adafruit #CircuitPython @circuitpython @micropython @ThePSF @Adafruit
No comments yet.
Sorry, the comment form is closed at this time.