Quote:
Originally Posted by euhlmann
If you'll excuse bad diagrams finger-drawn at 1am, here's how a double solenoid does shifting
*snipped 2 images*
Here's a single solenoid connected to the same shifter
*snipped 1 image*
A spring is needed since there can only be pneumatic actuation on one side. We wanted pneumatic actuation on both sides, so we used a double solenoid.
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This is a spring return single acting cylinder.
A single action solenoid can power a cylinder. A single solenoid internally has a valve, a spring, and a solenoid. When the solenoid is not powered, one pneumatic output is connected to pressure, while the other is connected to atmosphere. Think of this as the default state, the spring keeps it there.
When the solenoid is powered, the solenoid pulls the valve to the other position, against the spring. the pneumatic connections are reversed. The bonus is when power is cut (including at the end of a match*), the valve returns to it's original state since there is nothing holding the spring back.
*= Not certain, depends on how WPILIB and the PCM are implemented. It should say in the source somewhere..