From: mike w. <mi...@mw...> - 2005-10-13 16:51:37
|
Hello all, I am on the last tech hurdle to finishing my robotics project, and I figured you are all smart people.... I need to measure the force being pulled on rope... I've looked at load cells and they are just a bit too expensive. Any ideas? I need the data to interface with my microcontroller or with a PC via USB or Serial. Thanks alot everyone! mike |
From: Craig H. <cr...@gu...> - 2005-10-13 17:26:47
|
My first inclination would be to go to Walmart and get a $5 digital bathroom scale, crack that open, and steal parts out of it -- or at least see what they use. C On Oct 13, 2005, at 9:52 AM, mike weisert wrote: > Hello all, > > I am on the last tech hurdle to finishing my robotics project, > and I figured you are all smart people.... > > I need to measure the force being pulled on rope... I've looked at > load cells and they are just a bit too expensive. Any ideas? I > need the data to interface with my microcontroller or with a PC via > USB or Serial. > > Thanks alot everyone! |
From: Keith O. <kso...@gm...> - 2005-10-13 20:48:06
|
mike weisert wrote: > Hello all, > > I am on the last tech hurdle to finishing my robotics project, and > I figured you are all smart people.... > > I need to measure the force being pulled on rope... I've looked at > load cells and they are just a bit too expensive. Any ideas? I need > the data to interface with my microcontroller or with a PC via USB or > Serial. > > Thanks alot everyone! > > mike This may seem little 'Rube Goldberg'ish, but what about attaching a rod & spring to the end of the rope. On the rod, mount an optical comb that can slide through an opto-interrupter module from a ball-style mouse. By setting how far apart the teeth on the comb are, you can adjust the precision. (NOTE: If you set the teeth too close together and the rod moves too quickly, you can get 'data jitter' as the OIM can't read the changes fast enough and misses some. To make your life easier, print out a series of different spacings and tooth widths on a transparency sheet and experiment with those until you find the right balance. If you make your rod with a pin sticking out at each end and small holes at either end of the combs, you can easily try different combs.) While this won't give you the actually force, it /will/ tell you how far and in what direction the end of the rope has travelled. A little calculation will tell you what you want to know. This will not only allow you to record ongoing force changes, but will be simple to interface, as either a USB, PS/2, or serial mouse. +-----+ +-----+ \ \ \ \| | | | \ \ \ \ | | | | \ \ \ \ | | | | \ \ \ \| | \ \ \ \ \ \ \ | | \ \ \ \ | |O\ \ \ \ \ \ \ \O| | \ \ \ \ | | \ \ \ \ \ \ \ | | \ \ \ \| | | | \ \ \ \ | +----------------------+ | | \ \ \ \ | |o +--+ o| | | \ \ \ \| | | |! ! ! ! ! ! ! ! | | | +-----+--| |----------------+ | | +| |------------------+ | |+--+ | | | | | +----------------------------+ -- Keith Olson K-Soft Consulting oth...@pm... hco...@fm... zou...@hp... rdi...@sb... pen...@ls... ela...@ea... gin...@mw... fcu...@np... fwh...@hs... rra...@ga... |
From: Jonathan B. <jbr...@ea...> - 2005-10-14 01:49:38
|
On Thu, 2005-10-13 at 09:52 -0700, mike weisert wrote: > Hello all, > > I am on the last tech hurdle to finishing my robotics project, and I > figured you are all smart people.... > > I need to measure the force being pulled on rope... How much force? How accurately? > I've looked at > load cells and they are just a bit too expensive. Any ideas? I need > the data to interface with my microcontroller or with a PC via USB or > Serial. You could get an electronic strain guage and attach it to a strip of metal to measure the strip's strain. Attach the rope to holes drilled in the metal strip. http://zone.ni.com/devzone/conceptd.nsf/webmain/C83E9B93DE714DB08625686600704DB1?OpenDocument HTH, -Jonathan |