ORDERING A CONTROL MODULE

GP I/O Pin is defined as General Purpose Input and Output Pin, which in its simplest term is a pin on a controller unit that monitors an input state, or emits an output signal (voltage). A pin could be connected to a button or switch, which makes it an input pin, or a motor relay, which makes it an output pin.The states of the output pins, whether energized or not, are determined by a program based on the changing states of the input pins and program algorithms.

For our purposes, unless otherwise stated on our product manual: 

1. OUTPUT PINs (logic) are classed as SOURCE, i.e., they supply 5VDC when energized. This voltage can be used to operate "low trigger" relays which are capable of handling higher voltages and current for switching motors and other electrical loads. Output pins provide 40mA output signal, or 20mA continuous current.
2. INPUT PINs (logic) are classed as SINK, i.e., they direct incoming positive voltage/current to ground. These incoming signals are derived from buttons, switches, or sensors, their 5VDC source being the 5V-Out terminal on our controllers.

Switches provide latched signals to Input Pins. A switch that is in the "ON"  position will result in a retained "high-level (energized) state" to an Input Pin, while in the "OFF" position will result in a retained "0" voltage or "low level state."

A button can function either as a MOMENTARY or HOLD button. 

A momentary button is operated with a short press to toggle a state within the program in a controller. It could be used to turn the state of an Output Pin on or off. A momentary button can be programmed to toggle a state exclusively from "0" to "1 or exclusively to "turn on" a load. It can also be programmed to toggle a state to its inverse condition, e.g., to switch a motor at rest "on" or switch a running motor "off."

A hold button is used to control an output, i.e., to power a load while the button remains pressed. This type of control is usually implemented in situations wherein it is not practical to program an output to be continuously energized such as in a micro-step controller for a car lifter.

Sensors provide Input signals to a controller input pins. They can be digital or analog signals. Digital signals have only two states (binary) i.e., "1" or "0;" "1" denotes that the pin is energized and "0" denotes that the pin is not energized. 

Here are some examples of sensors that provide digital signals to input pins:

1. Proximity sensors
2. Reed switches
3. Mechanical contact switches i.e., float level sensors

Some contact switches or relays have two connection points. They are designated as "NO" which stands for Normally Open and "NC" which stands for Normally Closed.  Normally Open "NO" denotes that the circuit is open (current does not flow, the circuit is not complete) when the contacts are not  actuated or the coil, as in the case of a relay, is not energized. Normally Closed "NC" denotes that the circuit is closed (current flows, the circuit is complete) when the contacts are not actuated or the coil, as in the case of a relay, is not energized. Please refer to product data sheets for more information. 

Analog sensors provide varying voltage (or current) to an input pin. They are used to determine dynamic states such as temperature, lighting, tilt angle, pressure, speed, levels, etc.. Our control modules have analog to digital input converters. Some of the sensors we supply with our control units come with self-contained circuitry, which convert their outputs to digital signals that can be processed directly by the controller.

Timing plays a very important role in control automation. Timers can be implemented in different ways. Delay timers can be used to give time for a process step to continue before energizing or de-enegizing an output pin. Timers are also implemented to time process steps. One way they can be used in a program (process) is to determine if a connected equipment is properly working by setting a maximum timer, the time required for the equipment to finish its process. If the process is still running after the set time, a time-elapsed fault flag is raised.

Motors with high current ratings cannot be operated directly with a microcontroller chip. To control them, relays or inverter drives are used in conjunction with the controller. Inverter drives provide acceleration and speed control. 

To monitor process steps in an automated control system, displays and/or LED lights are used. A single LED can provide different information by blinking it slow, fast or keeping it lit. In cases where more detailed monitoring of the control process is required, LCD or Liquid Crystal Displays and screens can be used to display messages for an operator to read.

Controllers and peripherals communicate with each other. Embedded systems use different communication protocols such as SPI, I2C, USART, CAN, USB, ETHERNET, etc., For long distance communication and data transmission Ethernet communication is favoured. However, for speed and security, radio and cellphone frequencies are also used. SMS is a common medium used in control automation.

Analog Input Pins are used to monitor dynamic fluctuating signals. These signals are usually emitted/transferred by peripherals that measure varying levels of states of a sensor, for example a temperature or humidity sensor. The microcontroller converts these signals (in the form of varying voltage or current) into digital form for computer processing.

Pulse Width Modulation (PWM)  is a powerful technique for controlling analog circuits with a microprocessor's digital outputs. PWM generates variable-width pulses for control. The greater the width of the pulse, the higher the amplitude of the signal and vice versa. 

Controlling an LED so that it appears to be changing brightness or dimming is just one of the many uses of PWM. It is also used to provide a signal to an on-board electronic unit, in a servo motor for example, to vary motor speed, tilt angle, actuator position, etc.