What switch can be pressed from both directions?

[Bob Steele]

Take a look at this switch
Its a roller plunger limit switch... it would work going both ways with some sort of pin on the moving piece.

http://www.mcmaster.com/#7076k26/=vn1q8t

Hope this helps..

[yonisav]

This seems pretty much like what I need. Thank you

One more question, we have a few of these:
http://www.clasohlson.com/medias/sys...3445556254.jpg
Can they be used for the same purpose?

I found these: http://www.amazon.co.uk/Roller-Plung.../dp/B007Q81BTS online, just to make sure, will it work for us?

[EricH]

You could also use a beam-break sensor. It's a small light and a small receiver. In ordinary operation, a beam of light goes from the light source to the receiver. If the beam is interrupted by something (say, a tote), then there is something there.

This sort of thing used to be quite common in FRC for various applications.

[GeeTwo]

Originally Posted by EricH

You could also use a beam-break sensor.

If you are trying to do this with something much smaller than a tote (like a tab of angle aluminum), you can get an integrated system. Sparkfun also sells the breakout board. For about $4 you can have a sensor that's ready for a PWM-style cable that can plug directly into a DIO port. I just ordered ten of these yesterday, so I had the URL handy:
https://www.sparkfun.com/products/9299
We used one of these (or something very similar) and a plastic disk with holes as an encoder on our first robot for Rebound Rumble.

[Ben Wolsieffer]

A roller rocker switch would probably also work (such as this). I think there was one in the kit a couple of years ago, because we have a couple laying around.

[Bob Steele]

Originally Posted by yonisav

This seems pretty much like what I need. Thank you

One more question, we have a few of these:
http://www.clasohlson.com/medias/sys...3445556254.jpg
Can they be used for the same purpose?

I found these: http://www.amazon.co.uk/Roller-Plung.../dp/B007Q81BTS online, just to make sure, will it work for us?

You could try the limit switches that you have... I think they could work but you have to be careful about movement in both directions yielding the same push...

The UK switch would work fine... but don't forget those are from the UK and it might take awhile to get them... plus shipping... 3 weeks left....

There are a number of solutions to this... i agree that photo sensors would work well too... these would be more expensive (the ones we used on our robot were probably $50-$60 a piece ) but you could make them yourself... lots of DIY type photo sensors could work.

Another route you could take is to encode the motor that is driving your elevator and choose positions... more programming .... but an elegant solution.

Another idea is a string potentiometer like this one from AndyMark
http://www.andymark.com/product-p/am-2618.htm

Definitely you want a pin or a tab on the elevator that activates any kind of limit switch. pins work nice.. could be something as simple as a bolt that sticks out of the frame.

good luck

[Ether]

Originally Posted by Bob Steele

Another route you could take is to encode the motor that is driving your elevator and choose positions... more programming .... but an elegant solution.

Another idea is a string potentiometer like this one from AndyMark
http://www.andymark.com/product-p/am-2618.htm

I hear an echo :-)

[GeeTwo]

Of course, with any of the roller or rocker switches, the switch should be beside the load so that as it moves past, it and shoves the roller or rocker aside. Alternately, it could be tucked safely behind the stop so that just the button sticks out. Somehow, you should ensure that your sensor doesn't get smashed when the load hits the stop a little faster than you intended.

[yonisav]

We are probably going to end doing something like this: (sorry for my awful painting skills)
http://oi59.tinypic.com/2rcsi1e.jpg

Aside from the placement, which will have to be precise, what other problems may arise?

[Brandon_L]

Originally Posted by Ether

I hear an echo :-)

A triple echo?

A potentiometer or an encoder, depending on how your powering your system up and down, is what you would want to use here. You can count the rotations of the motor that powers your system with an encoder and do some math to convert that into distance traveled, and just tell the system to go to X height with a PID loop or something. Something similar can be done with a potentiometer.