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Ground contact switch, finally something that shows promise!

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Posted: 2008-12-17 18:39 
Here is an image of my tibia with ground contact switch. It's rugged and seems to work reliably. I'm hoping to build it up and test it over the break. 8)


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Posted: 2008-12-17 18:51 
Interesting. In what directions does it work (in what angle from just right up/down direction)? Did you use a hidden spring to avoid the microswitch to "lock up"?

Anyway, your saying its reliable and that sounds great!

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Posted: 2008-12-17 19:04 
It works at up to ~45°. I'm depending only on the small spring inside the micro switch to return the pushrod to the extended position. The problem with springs are they increase the required force to engage the switch. I'm hoping to avoid them if possible. I should have taken pictures of the exploded view to see what's going on inside there. I will try to do that and maybe a video.

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Posted: 2008-12-18 16:47 
Kaaaboooommm!!!! :shock:

Exploded view... 8)



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Posted: 2008-12-18 16:54 
Great, I see... No secrets anymore!

I can see your camera and your hands too.. :wink: :lol:


Its all.. Crystal clear.

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Posted: 2008-12-18 19:23 
Terrific!

I'm looking for a leg that can sense bump-contact as well, independently. Any idea's?

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Posted: 2008-12-18 19:53 
nice and simple. much more sensitive than the air pressure sensor made by Freescale! i think anyway.

look forward to the vid!
nice work once again.
when will you be adding this to LM website?

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Posted: 2008-12-18 20:56 
A DIY setup from the past to test using the ssc-32 to detect surface contact, stop the servo movement and determine the stopped servo position.









Last edited by zoomkat on 2009-11-02 19:49, edited 1 time in total.

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Posted: 2008-12-19 06:08 
This looks great Jim! Very… KISS :LOL:
Great to see the differences between analog force sensors, vacuum sensors and the switches. Great work!

I think that having a digital signal is more than enough. I’m also thinking of using some electronics to convert the analog force sensors to a digital signal.

Another cool thing is that you can pick up the front legs by the tip and the legs will still feel the contact. The middle legs will adapt and placed on the ground like showed in Matt Denton’s vid (1.23m).
8)

Xan

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Posted: 2008-12-19 13:32 
In other areas I've heard of using momentary switches like below on the tips of legs. May not be a very durable option, but would be fairly simple, quick, and inexpensive for testing ideas.

http://www.radioshack.com/product/index ... PerPage=60



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Posted: 2008-12-19 13:40 
Quote:
May not be a very durable option


nice idea and yes would be good for testing. but they usually fail very quickly especially on applications like this. i would bet 6 months of full testing and it would fail!

very useful and neat switch tho! good find!

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Posted: 2008-12-19 14:22 
The idea with the momentary switch button would be one could be testing foot pressure sensing in an afternoon. The switch could be mounted on an "L" shaped piece of metal with the mounting hole in the bottom of the "L". The side of the "L" metal could be hot glued (which is generally removable when desired) to the lower side of the leg (or one could just skip the "L" bracket and just use hot glue short term). I just like to do proof of concept testing as far into an idea as possible just to make sure the idea will be workable and worth while in the end. One could also start working on the software to make use of the new gizmo.


 

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