Controlling pneumatic circuits is typically achieved using small Programmable Logic Controllers (PLCs) like the Logo or Pico, offering reliability, simplicity, and cost-effectiveness in electrically powered environments. However, what happens when electricity isn’t available, or a non-electrical compressed air circuit is preferable, perhaps due to explosive or fire hazards? While modern applications often rely on PLCs, air logic presents a robust alternative for situations demanding electricity-free operation.
Air logic elements are readily available to facilitate the design of all-pneumatic circuits. Key components include:
* **OR Gate:** Generates an output signal when either of two input air signals is present, maintaining the output as long as an input exists. This is beneficial for sequencing operations contingent on the completion of others.
* **AND Gate:** Produces an output signal only when both input air signals are present, ensuring simultaneous completion of prior operations before proceeding.
* **NOT Gate:** Continuously outputs a signal when the input signal is absent, often used to prevent a sequence from starting prematurely.
* **PULSE:** Delivers a momentary output signal to initiate a sequence, automatically terminating after a set time to simplify control and prevent conflicting signals from poorly designed circuits.
* **TIMER:** Can either delay an output signal for a specified duration upon receiving an input or generate an output signal for a specific duration.
* **INDICATOR:** Provides a visual indication of compressed air presence, using color changes or indicator pins. This offers a convenient way to verify air supply from a distance.
* **POSITION SENSORS:** Generate an output signal based on airflow interruption, detecting object presence or absence.
These components enable the construction of complex air control circuits. However, compressing air generates moisture and contaminants, posing a risk to downstream components. Therefore, maintaining a clean and dry air supply is crucial for the reliable operation of air logic control circuits. Failure to do so will compromise their performance and lifespan.