[u]Introduction: Using Op Amps to measure signals with an Arduino[/u]
Who is this tutorial for? Well, not "newbies" or anyone happy to just connect together modules. If you have a LITTLE knowledge of electronics, have perhaps used a transistor or a FET to extend the output capability of an arduino, and want to learn about ways to handle different Analog inputs, than read on!
What will you need? All you will need to carry out a few simple experiments is a breadboard, a couple of (very inexpensive) op amps - I'd recommend the MPC6002; a few resistors, maybe an LED, phototransistor or photodiode, and any other odd bits you have lying around.
What is a signal?
In our Arduino world its a value - usually a voltage or current - that carries information. Your Arduino will have signals going in - Analog or digital values; and signals out, to control motors, lights etc. This tutorial focusses mainly on issues in dealing with Analog input signals.
The ANALOG inputs found on most Arduinos is well suited to measuring signals of a few volts from a low resistance source, but there ARE signals that dont match well to those analog inputs. For example many high quality sensors produce only very small currents or voltages, and have a very high resistance, so they arent suited to direct measurement with a conventional Analog to Digital Converter (ADC). Examples include Photodiodes, Piezoelectric Sensors, Accelerometers, Hydrophones, Humidity Monitors, pH Monitors, Chemical Sensors, and Smoke Detectors. Even common sensors like audio pickups and microphones will have their performance impaired if connected to a low resistance input.
Operational amplifiers ("Op Amps") offer an easy way to prepare these signals for measurement.
This tutorial aims to provide an introduction to the use of Op Amps, and offer help in choosing the right one for your particular application.
Topics: 1: Measuring voltages with an Arduino 2: What is an "Op Amp" 3: Basic circuits using Op Amps 4: Example application 1: Photodiode amplifier, including sketch 5: Choosing the right Op Amp for your application 6: Powering your Op Amp circuit - single or split supplies 7: Important characteristics explained 8: Example 2: Small signal with dc offset - using a difference amplifier
I'd like to acknowledge the massive help given to me in developing this tutorial by: Perry Bebbington, Idahowalker, Robin2, MarkT, Raschemmel and Southpark.
Comments feedback or questions on this tutorial to this thread please: