Quote:
Originally Posted by cgmv123
It depends on the cylinder, but most cylinders have 2 air inputs, so a Double Solenoid would be appropriate.
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That's not correct.
The number of cylinder ports do not determine if a single/double solenoid is used.
Both single and double solenoids perform the same actions and have the same number of available ports.
They actually use identical bodies, but the double replaces the return spring with another energizing coil.
Why we choose one over the other has to do with how their behavior differs.
A single solenoid has a spring return to a home position.
It is energized to move it to the opposite position and will automatically return to it's home position when the energy is taken away.
- One advantage is that it only takes up one solenoid breakout output, so you can have 8 single solenoids on one Solenoid Breakout and therefore control twice as many cylinders as an equivalent Breakout full of double solenoids.
- An advantage might be that, went the robot is Disabled, the solenoid will return to it's home position, e.g., your robot just made it to the bar and hooked on, but the match ended before you could pull up, if you set the home position right it will still retract upon being Disabled and get you that 10 pts for hanging.
- A possible advantage is that the robot automatically returns to it's starting configuration, so no hooking up after the match before it fits back on the cart.
- A disadvantage might be that same home position when Disabled. Instead of stopping the robot cold when Disabled it may unexpectedly shift positions. E.g., if you're holding an arm up in the air with a cylinder, and someone (me) goes to look at something under the arm and a helpful person quickly Disables the robot for safety, then the home position could bring the arm snapping down onto said person's head (me).
A double solenoid does not have a home position.
It stays in whatever position it was last ordered to.
- An advantage is it does not have to be kept energized once the move has been completed, although the energy savings is miniscule.
- An advantage is that remaining in position is generally safer when the robot becomes Disabled unexpectedly. On the other hand we should Disable the robot before we get close to it anyway.
- A disadvantage is it takes up two Solenoid Breakout outputs for the same functionality as a single, so only 4 fit can be controlled by a Breakout.
- An advantage is that doubles have been donated for free to the KOP for a couple of years, and free is good.