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Originally Posted by Stephen Kowski
single won't hold it's position after you lose power while a double will keep it's position.....im sure there are other differences, but that is the most glaring.....
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Stephen noted the only real difference.
A single solenoid requires power to actuate (for example, extend a cylinder), but returns to its normal state when you lose power. So, if you lifted something, it would fall.
A double solenoid requires power to change state in either direction. So if you actuate the solenoid to extend, you have to actuate the solenoid the other way to retract. So, if you lifted something, then lost power, the solenoid, and whateveer you lifted, will stay like they were.
Something else to remember with a double solenoid is that a cylinder can continue to extend or retract after you lose robot power.
Our 2004 robot used pneumatics to lift itself onto the bar. As long as we had actuated the lifting solenoid before time ran out, it would continue to lift itself until we were fully up on the bar. In one match, when time ended we were still touching the floor, but after the short holding period for robots to settle, we were up and scored 50 points.