How to use a solenoid on a robot?

[gabrielau23]

I'm a relatively new member (1 year) on a robotics team and I would like to know how solenoids can be used on a robot. I did a little research and found some industrial applications such as pinching, locking, and latching, but realistically HOW is a solenoid attached to and used on a robot?

[JJackson]

In 2004 we used a linear solenoid as a to hold a spring loaded pin which locked our arm to keep it from falling out. This meant no matter what, after the robot comms were disconnected our arm locked. We used a spike to control the solenoid.

[CalTran]

Generally I've just seen pneumatic solenoids, and used for controlling pneumatics. Whether this means a claw (Logomotion), arm, or even "unconventional" methods such as stingers (Rebound Rumble), anywhere there's a pneumatic piston, there's generally an accompanying solenoid.

[gabrielau23]

@CalTran
Do you know of any FIRST team that's used a solenoid not on pneumatics? I was studying my team's robot from Logomotion, and while the gripper worked nicely, I think it could have been improved. I looked up solenoids and found they LOOk like they could be perfect for the job. However, our team generally tries to stay away from pneumatics unless there is a very good reason to do so. If this is the time, though, I would be open to it.

[EricH]

Originally Posted by MICHAELABICK

Solenoids are illegal to use on an FRC robot for anything other than pneumatics

They were, through the 2011 season, that I can recall.

The 2012 rulebook, however, includes the following:

[R46]
Each power-regulating device (speed controller or relay module) shall control one and only one electrical load (motor, actuator, electric solenoid, or compressor).

[R48] J. electrical solenoid actuators, no greater than 1 in. stroke and rated at no greater than 10 watts continuous duty
at 12V,

Also see [R50].

Now, as to what the 2013 rulebook has, I'm as in the dark as you are, so we'll see if they're legal or not.

[slijin]

Originally Posted by MICHAELABICK

Solenoids are illegal to use on an FRC robot for anything other than pneumatics

The 2012 Rebound Rumble manual begs to differ.

[R48] The only motors and actuators permitted on 2012 FRC Robots include:

...

J. electrical solenoid actuators, no greater than 1 in. stroke and rated at no greater than 10 watts continuous duty
at 12V,

Do note that this rule was new in 2012 and is not guaranteed to reappear in 2013.

That being said, to answer the original question, solenoids are generally used to toggle an actuator between a discrete number of states (in FRC, this is always two).

In FRC, there are a number of situations where a linear solenoid actuator can be used (although whether such a solution would be permissible under the rules is not always clear, given the power restrictions on such solenoids). It can be used to shift gears. It can lock and unlock a mechanism. It can serve as the trigger mechanism for an appendage.

More commonly in FRC however, solenoids are used within pneumatic systems, to switch the direction of airflow.

[aaron2]

you'll need to fabricate some kind of spring to pull the shaft back out after the solenoid pulls it in. in this tutorial i just wrapped some insulated wire around the shaft to create a make-shift spring

[FrankJ]

Outside of valves solenoids provide relatively short linear motion. Think of them as a really small pneumatic cylinder. So to use them on an FRC robot.

1) You need an application where a short linear motion would be useful. Locking pins, shifting transmission gears, setting/releasing brakes come to mind.
2) You need to find a solenoid that fits the application & rules.
3) You need to design brackets & attachments to fit the solenoid into the mechanism.
4) In 2012 rules the solenoid would be wired to the control system through a Spike relay.