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Electronics Forum / Basics / March 2007hard drive header position
Hi, I have a little project that I am undertaking that requires accurate position feedback and I thought of using a similar approach to the way hard drive headers are used for positioning, afterall they are extremely accurate and fast. The difference is that I need to be able to adapt it into a linear position sensor. The other option I have been considering is using similar technology used in digital vernier calipers but again I am struggling to find any good information. Can anyone point me to some good resources, I am finding it a little hard to find good places. I am also fairly new to electronics. Any help woud be appreciated thanks. mark > Hi, > [quoted text clipped - 3 lines] > extremely accurate and fast. The difference is that I need to be able > to adapt it into a linear position sensor. But you've missed a step. It would be far better to start with what it is you are trying to do. Because this may be a false start with the hard drive scheme, but we won't know that unless we know what you are trying to do. Time after time, people ask for solutions that they "know" will work, and it turns out what they thought was a solution wasn't valid because they missed some intermediate step. Michael > The other option I have been considering is using similar technology > used in digital vernier calipers but again I am struggling to find any [quoted text clipped - 6 lines] > > mark >> Hi, >> [quoted text clipped - 12 lines] > and it turns out what they thought was a solution wasn't valid because > they missed some intermediate step. So what your saying Michael is that you don't have a clue about what he's asking? > Hi, > [quoted text clipped - 3 lines] > extremely accurate and fast. The difference is that I need to be able > to adapt it into a linear position sensor. Right, so now all you need is embedded servo information in whatever you're trying to position over, and make sure that it's constantly moving. > The other option I have been considering is using similar technology > used in digital vernier calipers but again I am struggling to find any > good information. It's just a foil pattern. An accurately etched PCB. > Can anyone point me to some good resources, I am finding it a little > hard to find good places. I am also fairly new to electronics. What exactly are you trying to do? Sounds like what you want is a LVDT. http://en.wikipedia.org/wiki/LVDT > Any help woud be appreciated thanks. > > mark On Mar 28, 1:22 pm, a7yvm109gf...@netzero.com wrote: > > Hi, > [quoted text clipped - 24 lines] > > - Show quoted text - As mentioned regarding LVDTs we may be able to help you www.macrosensors.com Contact Harold Schaevitz On Mar 28, 7:22 pm, a7yvm109gf...@netzero.com wrote: > > Hi, > [quoted text clipped - 25 lines] > > - Show quoted text - Thanks for the information I will certainly take a look at the LVDT suggestion. Just to explain a little more about what I am trying to do: I currently have a moving body controlled by a stepper motor that traverses along a bar (not lead screw), the problem is that I can't rely on the number of steps of the motor to garauntee movement because the system can (and does slip) intentionally along the bar. The current feedback mechanism comprises of a type of potentiometer (printed carbon ink), this carbon ink process is proving difficult to manufacture linearly down to the accuracies I require (need to detect at least 0.1mm movements over 100mm travel), I am calibrating most of the inaccuracies out but still needs to be improved. So, I am researching any other avenues that I could take with this project. I was looking to perhaps make use of the current guide bar in some way (hence the suggestion of digital vernier technology), the guide bar turns with the step of the stepper motor, which forces the body to move along the bar (rolling ring technology). Another option I had thought of (albeit a little far fetched and limited by my konwledge) is to use some type of piezo system with the guide bar. The guide bar is clamped tightly by the moving body so perhaps measuring the time it takes for a sound wave to travel along the bar and back again. I am currently ruling this out as I am thinking the 100mm travel in 0.1mm increments is too small to measure accurately in this way and the electronics probably too comlicated and expensive. Space is also a limiting factor too. regards, mark > On Mar 28, 7:22 pm, a7yvm109gf...@netzero.com wrote: >> [quoted text clipped - 38 lines] > turns with the step of the stepper motor, which forces the body to > move along the bar (rolling ring technology). How about a piece of nichrome wire? > Another option I had thought of (albeit a little far fetched and > limited by my konwledge) is to use some type of piezo system with the [quoted text clipped - 4 lines] > accurately in this way and the electronics probably too comlicated and > expensive. NC (Numerically Controlled, i.e. CAM (Computer Aided Manufacturing)) machines use some kind of optical quadrature position transducer, and they do very long distances, of which you need only 10 cm (isn't that about 4 inches?), with 0.0005 accuracy, which might or might not be close enough to .1 mm - I'm WAY too lazy to do THAT math. ;-) > Space is also a limiting factor too. Isn't it always? <sigh> ;-) Cheers! Rich |
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