Pneumatics Extend Automatically

[Joshua May]

Sorry, I dont have the time to search before this post, so please excuse me. I'm right here in the middle of the Las Vegas Regional and we have match in a few minutes, but there's a problem. Everytime we turn the robot on, arm piston extends automatically. We've checked the programming, and nothing comes up to make it seem like this is the problem, so we think its the tubing arrangement.

we have a single solenoid that is black and grey (dont know the company set up like this:

Exhaust | From tank | Stop
To Piston | To Piston

If anyone knows the answer can we PLEASE get a quick response, not much time!

EDIT: We took out the stop, but now we can't retract the piston, answer please?

[Max Lobovsky]

A single solenoid will always move the cylinder to one or the other position. When the robot is disabled, the solenoid will always be in its off position, and the cylinder will consequently always be in the same position. If you would like the piston to be in the other position when the robot is disabled, you need to switch the hoses going to the two ends of the cylinder.

[Joshua May]

Originally Posted by Max Lobovsky

A single solenoid will always move the cylinder to one or the other position. When the robot is disabled, the solenoid will always be in its off position, and the cylinder will consequently always be in the same position. If you would like the piston to be in the other position when the robot is disabled, you need to switch the hoses going to the two ends of the cylinder.

Yeah, the problem is that we need the solenoid to go to the off position during the match, it already goes there at the end. Thanks.

[Max Lobovsky]

You mean the solenoid is not switching states at all? Well in that case, there are basically 3 places you need to check for failure, and they are all pretty easy to check.

Your input (joystick, whatever) - use dashboard or printf's to check wether the input is actually being inputted

Relay (Spike) - if the light on it is switching from orange to either red or green, you are good. if not, check fuses and the signal cable from the RC

Solenoid - there is an indicator light on at least some of them that should go on and off. If yours doesn't have it, well... well if the other two things are not broken, the problem is probably here... Also, make sure its actually getting pressure to its inputs.


EDIT: I reread your post like I should have done before posting this and realized I am probably not helping you. IIRC, the stop should not be there as it is the 2nd exhaust. Maybe the solenoid is just broken?

[sanddrag]

Originally Posted by Max Lobovsky

A single solenoid will always move the cylinder to one or the other position. When the robot is disabled, the solenoid will always be in its off position, and the cylinder will consequently always be in the same position. If you would like the piston to be in the other position when the robot is disabled, you need to switch the hoses going to the two ends of the cylinder.

Just to speak a little further on this:
The solenoid "defaults" to a position when no current is applied and switches positions when current is applied. When your robot is disabled, no current is applied so if goes to whatever the default is. When you turn the robot on and it uis extending or whatever, then in your program or on the relay, you need to see if current is being applied to the solenoid. If so, don't have it do that. Or if not, do apply current (switch the relay on) Or, swap the hoses. Doing one of those things should reverse the action to get the desired effect.

Or just replace the unit with a double solenoid so you have total control over it.