Dead Mans Switch

[ferret_guy]

my main concern is that it gets away from someone so I wanted to implement something that required no thinking to engage, I thought that a big red button may not get pressed by the time something bad happens.

[Chris Hibner]

Originally Posted by ferret_guy

my main concern is that it gets away from someone so I wanted to implement something that required no thinking to engage, I thought that a big red button may not get pressed by the time something bad happens.

Is the person riding the robot, or is the person walking along / behind the robot?

This is an important question for the design of your switch.

If the person is riding the robot, then a lawn mower style deadman switch is probably not appropriate. When people get scared, their natural reaction is to grip tighter, not let go. Furthermore, if the robot is truly getting out of control, then you really don't want them to let go since the robot will most likely throw them causing injury.

If the person is walking along or behind the robot, then a lawn mower style dead-man switch is appropriate.

[D.Allred]

Originally Posted by ferret_guy

my main concern is that it gets away from someone so I wanted to implement something that required no thinking to engage, I thought that a big red button may not get pressed by the time something bad happens.

Mark,
That's not an "Emergency Power Off" button, although it looks like one. It's a spring loaded momentary contact switch. It can be wired so that you have to press and hold the button down just like your grip bar example at the top of the thread.

[FrankJ]

Lawn mower dead man switches typically ground the coil. Often, they are a piece of metal, not a switch in a conventional sense.

You can use the leaf limit switches that were on first choice this year. Or a spring return push button switch. You can also get them at Radio Shack. They will not carry motor current though. You can use them with a relay is rated for the current (Best) or drops the signal to the motor controllers.

[Clinton Bolinger]

You might want to look at something like a "Enabling Switch"

http://ab.rockwellautomation.com/Pus...ing-Switches#/

These are commonly used in Industrial Robot Cells. They are a 3 position switch: Open = Disable, Middle Position = Enable, Closed (all the way) = Disable. If you close the switch all the way you have to go back to open before it will enable again.

We have used this as a wired (2009 Driver Station) and wireless e-stop for our robot. The problem with the wireless version that we made is that we have to simulate the "Enter Key" for disable and "F1" for enable. It just isn't that reliable because we have to repeatedly send the "Enter" key and it will freeze up some computers.

This issues we had are from our implementation of the switch. If this is going to be directly on the robot, I would recommend that you electrically control the motors/disable function and NOT rely on software for a safety issue.

Hope this helps,
-Clinton-