Web Controlled Relays Vs Reprogrammable Logic Circuits: A Discussion
Relays are amazing devices in their own right. They are simply electrically operated switches but when used creatively, you can create all sorts of complicated functions and logics using simply relays. Relays have found extensive use in many day to day applications and simple fail safe measures.
However, they are also particularly suitable for student robotics projects. Relays are great for such applications since they are easy to learn and have no learning curve. Many robotics components are a little complicated for a beginner to grasp from the get go and relays are the only major exception (other than obviously resistors, capacitors, etc. but they are certainly not as versatile as relays).
Use in robotics
Your robotics project can implement relays in a variety of different ways. But in order to control them effectively, you might need to use a relay controller. This is usually a dedicated circuit exclusively used to control relays. If your implementation uses a number of relays, it may be better to use a relay controller to exercise control over the device. You can also leverage the power of the internet and use a web controlled relay.
Web controlled relays are unique in that they are basically IoT or Internet of Things devices. You can set predefined circumstances that the system can check over the internet and operate the relays accordingly. If you do not want to implement a full IoT system, you can choose instead to simply send your commands over the internet to the web controlled relay.
The different types of relays
Relays can be of many categories; you can identify them by their specifications, usually listed in their names themselves. A SPST relay means that it is of a Single Pole Single Throw type, meaning that the relay has one input port for a control line and one output port. Similarly you can find DPDT relays which, you guessed it, have Double Pole Double Throw configuration with two input lines and two output lines. These systems can be combined in any number of ways and increasingly complicated systems to create complex logic systems that you can then use to initiate certain actions.
Relays as logic elements
Relays being switches can be compared to transistors. Therefore, if you cannot or do not want to implement control circuits, you can theoretically do the entire thing using just relays. Relays can be used as logic devices very easily but they simple cannot beat the portability and efficiency of an integrated circuit that is consumes less power and can implement more complicated logic systems with greater ease.
Why relays cannot replace IC transistors
Also by using microcontrollers and other logic systems, you retain the ability to reprogram the system if you design it that way. If you build the logic using relays, you are basically hardcoding the logic itself and will not be able to change or reprogram the logic without taking the circuit apart. Therefore, you cannot really make a compelling argument about using relays to build logic over a reprogrammable circuit board.
Good applications for relays
What relays are good for however are high current or voltage applications that cannot be directly controlled using microcontrollers or integrated circuits. Think electric motors or other traction systems. They require high current for operation and a microcontroller pins simply cannot provide that kind of power without burning out the silicon. Using the microcontroller to operate a relay which then switches the motor or even controls the motor speed by modulating the current it flows is a better choice.