On Thursday 10 March 2016 17:53:23 Chris Albertson wrote: > The two hall effect sensors are 2.2mm apart. That means they are > close to 1/3rd of your gear pitch apart. > > ... > > > But my concern is how it works with less than a 6mm tooth to tooth > > spaced gear? Lots of stuff in our toys is smaller than that. > > It is easy to MAKE a gear touch sensor although not as easy as buying > one. Get a 1/4" steel bolt and grind the end to a point. Write a > bunch of magnet with around the bolt and place the printed end where > it is almost in contact with the gear. The on the blunt end of the > bolt place a powerful magnet (maybe salvaged from an old hard disk > drive. Have you ever seen an electric guitar? Same exact thing. > The wire will output a sinusoid wave that matches the gear teeth even > if the ten are very small.
Some minor corrections, Chris. The bolt can be smaller than 1/4", And it should be the softest, cheapest bolt in the bin because you want it easily magnetised. The point needn't be any sharper than about half a tooths peak wide, more output that way. Its output will need to be biased at about half the plus rail, and fed to an op-amp, preferably 3 of them in what is called an absolute amplifier setup because that will null any stray electrostatic hum pickup by 60+ db if good precision resistors are used. At the speeds I have in mind, the gain/bandwidth product of the op-amps should be 20+ megahertz at a gain of 100 in order to maintain the specs up to wherever speeds we might want to watch with it. Today we can do it for a buck, but I can recall when that was a couple kilobucks a channel card each. And it wasn't near fast enough for audio use. TI, FWIW, has some fantasticly good op-amps, even single rail types, with gain/bandwidth products in the 10 GHz range. $1.27, 15 years ago when I had to replace some of Tek/GVG's custom made video amplifiers on a ceramic plate in a 300-3A/B video switcher. Tek/GVG had one left on the shelf, didn't know if it was good yet, but would charge me $1750, with no warranty, to find out. It turned out the TI part, which took about an hour each to install because I was putting a TO-5 can in where an inline package nearly 2" long was coming out. And it was both dead stable and fast enough it messed up the hue lags, and the only way to fix it right was to rip out and change 48 of them for the TI part so all the paths had matching delays again. Sure I know it can be done, but I didn't want to re-invent the whole thing when I can buy it (for bigger stuffs) for less than a 10'ner at onsies prices. Thanks Chris. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785111&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
