finger limit switch's in starter kit

The limit switch’s work in autonomous mode when plugged into 11 &12 ports microcontroler.
I want finger limit switch’s to work in the non-autonomous mode, i.e. when I am controlling robot, is there a way of doing this.
Also is there a way to have the finger switch’s action reversed, in other words if I mount the switch under the robot and the finger rides on the floor, if it runs out of floor space, the switch is tripped and the robot stop’s.
I have the starter kit components.

I am pretty sure that without the programming kit, you wont be able to do either of those things. To make it stay on a table, it would have to have the switches constanly pressed down, and when they are released(when it goes off the table) it would trip it.

im pretty sure there is something in the guide about that switch below the robot to stop it from falling off a cliff or table

or read the limit switch functions, and see which port will stop the drive motors when its released

the starter kit has a section where it talks about cliff sensors… there is a default program loaded into the microcontroller that will operate the switches in the way that you request. There. (or to the best of my knowledge)

on what page is the default program discussed in the starter book? I did not see it.

In the logic section of the starter kit, pg. 7.18, the cliffbot mode is described. But its not clear if it can be operated in “23” mode. Can this be achieved with a jumper? Or is it possible at all?
thanks for any input on this.

VEX Manual, Pages 7-18 and 7-19 talk about this concept, but in practice it might not work with the “Default Code” because the Limit switch would be Closed while on a Flat Surface.

Two State Switches come, well Two ways… Normally Closed (NC) and Normally Open (NO). The Bumper Switches and the Limit Switches seem to be NO.

The Bumper Switch connected to the “Tag/Emergency Stop Sensor” (Analog/Digital Ports 9, 10) have been programmed for a NO Switch, so the Switch needs to be Open when YOU want to control the Robot.

In the VEX Manual, Pages 7-18 and 7-19, the Limit Switch would be Closed, so if it was “directly connected”, YOU would NOT be in control. You would need to connect the Limit Switch to something (like a Relay) that would “invert” the signal. Even using a Jumper on Port 13 and placing left and right Limit Switches (on Analog/Digital Ports 11, 12) would not work since they are also operated in NO mode, until a collision with an object which will close them.

Take apart your limit switch, goto an electronics store (or the interweb) and purchase the switch portion in a NC configuration. Now, replace the insides with the NC and you should be okay.

You might even consider hitting your RS and buying a couple extra limit switches (I think they are only $3) so you can have a few NC and a few NO switches. Be sure to mark em though :wink:

I have not taken apart the Limit Swiitches or Bumper Switches. The Limit Switch’s “micro-switch” might (if your lucky) even have both a NO and NC contact. Then you just Move the wire over… But more likely you will need to follow “fryfrog’s” advice, and get a different “micro-switch”.

I opened up limit switch’s and had a NC post available. I moved the wire from the NO post to the NC post, on both limit switch’s.

I then plugged limit switch’s into 9 &10, with no jumper. Jumper would put me in autonomous mode which I do not want.
Anyway I did these things, I thought it would work. Dissapointed, the limit switchs are both pressed down (open) and when I let them go into NC mode (at rest) the wheels kept turning.
What now? I thought by converting limits to NC, it would work. Any idea what I am doing wrong?
Thanks for help by the way.

It has both!?! Great!!! But sounds like it is not really NC… Did you test it with a Volt-Ohm Meter (VOM)??

You want this Switch to be NC, because Looking at the VEX Manual, Pages 7-18 and 7-19, the Micro Switch is mounted low enough, that the Switch is Depressed, making the NC switch Open. This lets you “drive” the robot, until the “floor”, drop away, then the Switch becomes “un-depressed” and returns to “normal”, and since the switch in now a NC switch, it “triggers” the “Tag/Emergency Stop Sensor” (Analog/Digital Ports 9, 10), which will cause a 2 Second Pause, and will let you back away.

Also I can see some limitations with the VEX Manual, Pages 7-18 and 7-19… If the Limit Switch is further forward than the Front bumper switch, it will be run into walls and items on the floor, bending or breaking, or worse yet, bending and not detecting the “floor” dropping away… Carpet it looks like would Snag the Limit Switch as well. If the switch was turned around, it would be fine until you went in reverse, then it would Snag, plus the Robot would have to travel closer to the edge until the Limit Switch would “change states” and cause the Robot to stop…

IIRC, our Roomba, uses Infra-Red (IR) to detect to “floor” dropping away…

You would almost need to develop a “skid plate” (think of the metal plate on the front/bottom of an Off Road motor cycle or here “”), that would track the ground, and keep the Limit Switch “pressed” in the Open position, but rounded up, on all edges so at to not catch or snag on carpet or joints in a concrete floor or rocks or debris…

Anyone know what I might be doing wrong?

Did you actually verify that the switch is behaving as expected? An electric meter should do the trick, or at the very least a little light and a battery should figure it out. Its possible the switch isn’t doing what you think it is.

One might also use a wheel dangling down to trigger the limit switch in some way. That way, the wheel is perfectly happy rolling on anything until there is nothing under it and… blam, the switch is triggered.

What would be really awsome would be to wire in a tiny switch on the limit (or bumper) switch that you can flip to turn it from NC to NO!