Right now what I want to do is beyond my arduino capabilities, but I am working on that.
What I want to do is basicly a CNC type wood lathe. I am good for now with the motor knowledge I have . What I need some info on is the Measurement side of things. I would like to use a laser distance measure. The first thing I need to do is to have a laser scan my entire wood blank to determine high and low spots. If the blank is rotating at the time , I believe I would just have to have the laser travel the length of the piece and it should be able to map the highest and lowest points on the piece, then load those into a program to determine a start and stop distance for my cutter.
Does an arduino compatible laser distancing sensor exist that can do this ? and can the arduino itself handle mapping in this manner ?
Your challenge will be to KNOW how far the laser has moved between measurements. How will you actually move the laser? A lead screw?
Paul
unless I find a better option I will use either a stepper motor driven bicycle chain /with an encoder for distance , it will be also be the same mount that will move my cutter so after alignment one encoder should maintain equal measurements for both the laser and the cutter head for ease of calculations. I know I can use that set up for positioning the cutter head. So I would tell the arduino to enter a measuring mode and the mount would, hopefully position at a preset start point then travel the length of the work piece as the work piece is spinning. Read the whole piece and export the reading to the arduino for reading the lowest and highest points then export those numbers to the variables in my program for the rest of the cuts.
Ah, hope in the design. Post a picture.
Paul
Hope does not work well, most people tend to use a switch to detect the home position.
Unfortunately the only pictures are still in my head. I have drawings from someone elses DIY manual, hand crank, version of this project. And I want to take their basic design and male a CNC type version. I have a pretty good understanding of what the machine needs to do and how to get it there. I am a service Tech for Industrial automated saws, the mechanics I am good with , but not the programing side. And since most of what I do with programs is all PLC based , trying to figure out what I can and can't do with Arduino is a bit tricky.
Start with small and simple projects and build your capability from there.
Paul
It looks like laser tape measures exist that have bluetooth capability, so they can transmit the distance measured. They seem to talk to PC or phone apps though, so you might need to reverse engineer the transmission protocol.
For the mark I version though, you could simply make passes from the max distance and move in. You might try a current sensor on the lathe's power supply to detect when the cutting head starts working.
Well If I set it the same way as my saws it would have a forward and rear limit switch with hard stops , with hydraulics we also use a ramp down switch to slow down the sled
/mount before its stop points but I don't think that will be needed using a stepper to position the sled/mount, and if it is I am pretty sure I could embed that program
I don't need Bluetooth thankfully, hard wired is fine. I figured that the laser would be on a sled and travel the distance of the work bed/ piece. having it at a fixed distance it would actually measure the distance from the sensor TO the material .. the closer the edge of the material to the sensor, the higher the circumference at that point , and reverse for lowest circumference point. What I need to know is which type of laser will read fast enough to take those readings and if the arduino is capable of reading those distances and extracting the highest and lowest numbers generated. and if so what my max speed could be to make those measurements . I can raise or lower the RPM of the work piece and or the speed of the laser mount travel to accommodate the arduino or the laser if needed.
Adafruit carries some time of flight sensors that are laser based using the VL6180. One of them might serve your purpose.
I took a quick look at those earlier, I couldn't determine how fast they could read or if they could measure to a moving piece/variable measurements. Or if the pieces need to be stationary. Ideally think it should be able to read a variable height and stream measurements ,as they read, to the arduino which would then isolate the highest and lowest readings , it would be nice to be able to export those reading to another step or program but as long as you could find and read them. that would work
I found a data sheet - the average read time it mentions is 4.3ms. At that price I'd be inclined to get one and try it out.
Absolutely, went back after I left here, and rewatched some of the video's, at one point some one mentioned 50 ms sample times. I would have been thrilled with 1 sec.That's using the lidar type TOF. Lidar is reflective , and that worried me a little , wood not being a particularly reflective material, but from everything I checked out on LIDAR, it seems to reflect off of , and therefor read , just about anything. That leaves me just needing to learn how to make it work with Arduino to function the way I want. Of course all of this is still in theory and idea stage, and as I keep moving forward I keep finding more functions the Arduino will need to be able to control. I would like to eventually move it to a marketable piece so that means combining in safety features and self calibration features that will eat up a lot space in a program.
It's worth having the end game in mind obviously, but there's a lot to do and learn, so as ever, I suggest that you eat that elephant one bite at a time and find a small piece to work on to get started.
I have just started experimenting with the Adafruit VL53L0X Time of Flight Micro-LIDAR Distance Sensor. (I have NO idea why it's called a Time of Flight sensor).
I am quite impressed with the accuracy of this sensor. The specs say that High Accuracy mode is 200ms, High Speed mode is 20ms.
The range is about 50mm to 2M.
Once, last Century, I worked for a company that developed a system that would scan logs as they entered the debarker to decide what kind of log it was scanning. It determined this by the roughness of the bark. (It could tell if it was fir, oak or pine). Next the log was debarked and another set of IR LEDs and sensors determined the dimensions of the log. The computer then set the saw blades for maximum yield. The whole system cost more than $1 million in 1980. I can guess that it can be done with an Arduino today for a lot less.
Because it is LIDAR? Measures how long the pulse takes to return? Rather than using parallax or interferometry.
Presumably.
That was about when the IBM PC was invented.
It was all done on DEC PDP-8 Mini Computers. The program was on punched tape. We toggled the boot loader with front panel toggle switches. (I think it was 16 instructions).
I remember the PDP-11 having a similar bootstrap program, except the computer I was working with had an actual keypad instead of having to use toggle switches. That short little bit of code actually overwrote itself with the contents of the punched paper tape, which generally would have been the full-featured bootloader needed to load the actual code you wanted to run.
Interesting project. Do you recall where the cost was? I'd have thought that whatever hardware was controlling the mill would be pricey too. PCs were not that expensive then, although even the slowest Arduino now is at least eight times faster. Was a PDP-8 a big ticket item then?