It looks like its semi-standard in that they mostly use DB9 connection, but the pinouts and signaling can vary: https://www.touchdro.com/resources/scales/glass/glass-scale-pinout.html
Single ended or differential.
Usually you'd buy the DRO and scale together as a kit, for a slightly cheaper price. So you wouldn't have to worry about compatibility. https://www.touchdro.com/resources/scales/glass/overview.html
Most of the cheap DRO's have optional RS232, just make sure its actually fitted before buying.
I don't know if that or just grabbing the quadrature signals directly would be easier.
How are you going to push the carriage though? Usually you'd just convert that to ball screw and base the threading off of the rotation of that.
Of course, an advantage to a true linear encoder over a rotary encoder on a lead screw is that the lead screw may have backlash.
Quadrature linear and rotary encoders (except for absolute rotary encoders, possibly in Gray code) usually need an initialization to an index mark on a third channel to be used for absolute position measurements.
or put an encoder on the spindle and a stepper/servo on the leadscrew, a.k.a. "electronic lead screw"
or put an encoder on the spindle and a stepper/servo on the leadscrew, a.k.a. "electronic lead screw"
Yeah that would be good, but I'm guessing OP wants to combine functionality to try to save a bit of money? Or for extreme accuracy?
I don't know, I feel electronic leadscrew as you say and just run the glass scale DRO separately is the way to go. Given a smaller budget.
Thanks for the comments.
@thm_w
I suspected that a lot are SPI or modified SPI (e.g., Mitutoyo, which is not compatible to true SPI). My idea is to save a little money. The DRO (3-axis) on my mill is Mitutoyo and was bought years ago. It was nowhere near the current price. (The quill DRO has not been installed.) Whatever I get will involve writing my own code and probably adding and/or replacing the board in the display. So, a cheap display would give me a nice box and screen (LCD) at a minimum plus something to test my idea before getting too deeply into it. Why just 1-axis? That's all I need, and mounting a scale to by cross slide would be much harder. RS232 is OK, if fast enough, but speed is not an issue with SPI. I think at my age, I can handle changing pinout, if that information is available or figure it out.
Main reason is to save a little money and the fact that the control box will be butchered in any event. It's easier on the budget to butcher a cheap box.
@langwadt
I want DRO, as measuring the actual position effectively eliminates backlash compensation and the need for ballscrews. Ballscrews are or can be a real real disadvantage for a manual machine, because they are too damn smooth and don't hold. I watched a lot of Clough42's videos and actually got the servo encoder he used from Stepperonline. Then I thought, that doesn't really help when making a RH thread and working off the front. My lathe has a threaded spindle, and I am uncomfortable running it in reverse. Moreover, the quick change covers almost any conceivable imperial thread. I have the change gears for metric, but haven't used them. I don't consider setting the gear and using the thread counter a big hassle. What is becoming more difficult is my coordination and timing to disengage the half nuts. My plan is to make that electronic. First, just by stopping the lathe (VFD stops it pretty quickly), then later adding a timing belt and stepper/servo to the threading lever. I thought of starting a separate thread, "OMC machining" (OMC = old man's crutches).
@TimFox
I agree on the DRO linear encoder advantage, which is why I chose that approach. It will also be very easy to mount to the back of my lathe. There are ground ways and a T-slot for a taper attachment, which I don't have. So, T-muts and some setting blocks will take care of mounting. The linear encoders I have so far looked at are absolute; however, that probably won't matter as I will set the zero for stopping.
Refining my question: Has anyone made a hybrid setup of good encoder and cheap display, without regard to whether changing pinouts was needed?
I've done quadrature decoding for a rotary encoder with a PIC. I am not worried about doing that. Do you have a link to the project associated with the picture? It looks very similar to what my first step will be.
I had done a search before posting. Maybe I used the wrong search, but that project didn't pop up on Google.
@thm_w
I suspected that a lot are SPI or modified SPI (e.g., Mitutoyo, which is not compatible to true SPI). My idea is to save a little money. The DRO (3-axis) on my mill is Mitutoyo and was bought years ago. It was nowhere near the current price. (The quill DRO has not been installed.) Whatever I get will involve writing my own code and probably adding and/or replacing the board in the display. So, a cheap display would give me a nice box and screen (LCD) at a minimum plus something to test my idea before getting too deeply into it. Why just 1-axis? That's all I need, and mounting a scale to by cross slide would be much harder. RS232 is OK, if fast enough, but speed is not an issue with SPI. I think at my age, I can handle changing pinout, if that information is available or figure it out.
Main reason is to save a little money and the fact that the control box will be butchered in any event. It's easier on the budget to butcher a cheap box.
Then I thought, that doesn't really help when making a RH thread and working off the front. My lathe has a threaded spindle, and I am uncomfortable running it in reverse. Moreover, the quick change covers almost any conceivable imperial thread. I have the change gears for metric, but haven't used them. I don't consider setting the gear and using the thread counter a big hassle. What is becoming more difficult is my coordination and timing to disengage the half nuts. My plan is to make that electronic. First, just by stopping the lathe (VFD stops it pretty quickly), then later adding a timing belt and stepper/servo to the threading lever. I thought of starting a separate thread, "OMC machining" (OMC = old man's crutches).
DRO indicators and counters [deleted broken old link] send a Ready (RD, pin 4) signal from the gauge to the controller; the ID-C dial indicators do not [deleted broken old link].
Does anyone have experience with the lower end brands and can make a recommendation?
Why just 1-axis? That's all I need, and mounting a scale to by cross slide would be much harder.
The "devil is in the details." That lathe has a threaded spindle, which makes RH threading from the rear with the spindle reversed either impossible or very tricky. I do not want to put a sufficiently tight grub screw on the chuck back to prevent it from unscrewing.
Note that even if you don't plan to cut on reverse you need to swith your lathe forward-and-reverse constantly if you ever need to make metric threads on a imperial machine or vice versa.
Note that even if you don't plan to cut on reverse you need to swith your lathe forward-and-reverse constantly if you ever need to make metric threads on a imperial machine or vice versa.
I have never done metric threads with a thread counter. I thought one would just mark the number used and always go forward at that exact spot before engaging the half-nuts.