---------- Forwarded message --------- From: Gene Heskett <ghesk...@shentel.net> Date: Wed, Sep 26, 2018 at 12:08 AM Subject: Re: [Emc-users] More on bed wear fix To: <emc-users@lists.sourceforge.net>
But finding a camera chip big enough to shine these laser's on so that > the laser stays on the imaging chip cannot be found in an integrated > package that will plug into the 15 pin connector on a pi. The laser > beams are 10x the size of the imaging chips even if they're perfectly > aligned. What? If I buy a normal green laser pointer the green spot is about 1mm in dimmer. If I place a 0.01 pinhole in the path of the laser the spot is pretty close to 0.01. As for a camera that plugs into a Raspberry Pi, any USB web cam will do. But I'd use a notebook PC rather then the Pi. What you probably want is not to shine the beam on the sensor but have a glass or plastic target and use a $20 USB microscope to focus on the target. Glass is good because it will reflect 99% of the laser light away and not blind the camera. As you move the carriage the laser spot should move on the target and the USB microscope will image the back side of the target and you can measure the movement by counting pixels, Software can do better by doing some curve fitting. Even if the bed is very bad I doubt the laser spot move even 0.5mm If the laser spot looks huge, perhaps what you have is a small spot that overloads the sensor. The target may need to do some serious amount of attenuation. And while I said "USB "microscope" I bet a magnifier hot glued to a web cam works. But I did buy a $10 microscope and the image is poor but I can inspect the solder joints on SMT parts, A medium size SMT resister pretty much fills frame, these things are on eBay for $9 to $35 and they all appear to the the same. Pretty much everyone who wants to measure displacement from a line uses a laser. It is hard to find a better reference line If your bed where really bad Just put a steel rule in the tool holder and eye-ball the laser spot in the rule, maybe use a loupe to read it. Something is wrong if the laser spot is large. To get something usable I may have to buy a lensless digital camera for around a 100 dollar bill, which of course has a usb-2 output, and controlling it to get the image data is something I'll have to invent. I've probably spent 20 hours online already looking for something I could use with a pi, or a rock64 since it also has the 15 pin camera connector. I can probably get, from digikey, an imager chip big enough (and low enough resolution, 1 megapixel is a great plenty) but to actually make the supporting circuitry to make a working camera out of it will take more than this old man has left in him. These $15-$25 cameras for the pi all have image chips less than 1/8" square, with as high as 8 megapixels. Some are even microscopic sized pin holes, no lens at all! Nevertheless, I've ordered some 3/8" brass tubing to put on the rear of the "cartridge" to extend a switchable, dimmable power supply out the other end of the spindle some 21" away, a cross polarizing adjustable from ND2 to ND400 filter, and another 12x24 sheet of half inch 6061 to make a new apron plate for the front of the carriage so I can re-arrange things a bit and move the z nut to the right by at least an inch, getting away from the forces from over compressing the left bellows when I'm right at the nose of the spindle. The plate I made was cut from the deck of an old Ampex VR-1200, and has quite a few holes I filled with permatex liquid metal and sanded flat and painted over, and a newly made one will only have holes where I put them. A bit less hacky looking I hope. And I'll clean up that DMT plate and remove the dings that are tipping the tailstock to the back of the bed by several thou when the tailstock is sitting on them. As it sits. I now have around 20 inches of +- a thou. There may be more dings in the edge of that front flat to address. Frankly, this lathe has been beat to hell in its 70 years and I, like a dummy, paid 4x what it was worth. But what's done is done, but I reserve the right to claim I was an idiot to buy it. ;-) The technology, Chris, has run off and left us behind. -- 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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
