This PL-Sim unit simulates a different electropneumatic exercise. It incorporates three double-acting air cylinders (A, B and C), each driven by a 5/2 single solenoid valve. The solenoid valves are of theelectrical type, each having a positive (A+, B+ and C+) solenoid; the return is mechanical spring type. All cylinders are provided with negative (a0, b0 e c0) and positive (a1, b1 e c1) limit switches. The limit switches and solenoids are fitted with status LEDs. A LED ON status indicates that a limit switch has been energised or a solenoid has been enabled. Solenoid valves have manual override control buttons.
Assuming that the cylinder is at the negative limit switch, the positive solenoid, if energised, toggles the solenoid valve status and hereby allows the compressed air to flow into the positive chamber of the cylinder and flow out through the negative chamber. The piston, by advancing from the negative limit switch, will perform the positive travel and stop at the positive limit switch.
On the other hand, if the solenoid is de-energised, it enables the spring to toggle the solenoid valve position, returning it to a stable position. In this case, the compressed air can flow into the negative chamber and flow out from the positive chamber. The piston, by retracting from the positive limit switch, will perform negative travel and stop at the negative limit switch.
When the solenoid is energised, the solenoid valve status is toggled; but as it is a single solenoid valve, it remains in the toggled position while the solenoid is active. By de-energising the solenoid, the solenoid valve returns to its original position.
The manual override control buttons, at the side of each solenoid valve, allow switching into manual mode and are therefore useful when tuning a program. By pressing this button the solenoid valve status can be toggled and the cylinder can perform positive travel. By releasing this button, the solenoid valve toggles again and the cylinder can perform negative travel.