Computer-controlled systems are a big part of everyday life. Cars, refrigerators, washers/driers and smart toys are among the many consumer goods that rely on computer control. These systems use an on-board computer to process input from sensors to control the output.
Transducers are devices that convert a physical quantity into an electrical quantity. For example, temperature, a physical quantity, is labeled with or number (i.e., 75 degrees Fahrenheit). A transducer or sensor converts this value into an electrical current so it can be sent to a computer or controller.
This current flow comes in two types, digital or analog. A digital signal has two states, on or off. Typically, 0 volts or 5 volts. An analog signal is continuous,for example, any value between 0 and 5 volts. This voltage range is converted to a number using an analog-to-digital converter so a computer can process it.
The computer used here is an Arduino microcomputer board. The Arduino is a computer controller. Controllers are designed to accept sensor input to control output devices.
The Arduino micro-controller has six analog inputs and sixteen digital input/output (I/O) pins. The analog inputs accept a 0-5v range. A built-in analog-to-digital converter changes this input voltage to a number between 0 and 1023. The voltage and number range track with increases/decreases.
The digital I/O pins accept 0v to represent OFF/LOW or 5V to represent ON/HIGH for input. As an output pin, it can be programmed to supply 0 or 5 volts. Coding allows users to program each pin to function as either input or output.
Anything that is powered by electricity can be an output device. A computer can be used to turn things on/off while controlling other electrical devices. Robots use motors for movement. Security systems use a siren to make noise. There are many output devices that serve many functions.
For this project, the output device is a computer monitor. The Arduino board connects to a computer via the USB port. A ‘serial print’ command in an Arduino program sends a reading from an input pin to a connected computer screen.
The input device for this bioreactor is a temperature sensor. Let's bench test this transducer…