RESOLVED -- Interface Question -- Building a lathe turret interface controller

[briuz]

Hello,

I made a new 16 station turret for my CNC lathe that is almost identical to my turret for my portable 5c collet lathe. To make it more versatile I decided to make an interface controller board for it that uses a TeensyLC micro-controller. I am thinking this would work great as it should be possible to program this type of interface such that I can select what sort of interfacing scheme to use. i.e. Send the interface a binary number set via Acorn's relays, use the interface output screw terminals to select the turret via grey logic, etc. All selectable by a jumper on the left of the board.

Today I got the turret working nicely by setting 4 relays on the ACORN relay board to the selected tool in binary. i.e. 0010 is tool 2.

So, here's the problem: I am trying to get feedback from my controller to Acorn.

I thought that if I were to simply tie an Acorn input through an opto-isolator that connects to ground when activated that it would trigger Acorn's input. In the attached schematic, which only shows one opto-isolator, I connected OCIOutput0 to Acorn's Input2. This isn't working. My guess is that the resistance of the opto-isolator is enough to cause a voltage drop such that Acorn's input isn't changed. (I also tested everything for bad connections, non-functional inputs and/or outputs, etc. Tying Acorn's input directly to ground with a jumper works fine.)

So, is there a way to use an opto-isolator directly connected to an Acorn input such that when the opto-isolator is actuated it grounds out the connection or do I need to expand the circuit through a relay, or is there another option....preferably solid state?

Thanks!


On the schematic, Output0 connects to the TeensyLC micro-controller.

[briuz]

Explanation of above board connections starting at top left and going clockwise:

Green Screw Terminal (2 connections): +24vdc and ground
Green Screw Terminal (2 connections): Turret pawl solenoid
Green Screw Terminal (8 connections): Alternate connection to turret pawl solenoid, 6 outputs that are either floating or ground if "active", two grounds.
Green Screw Terminal (3 connections): Hall effect sensor for turret homing
Green Screw Terminal (3 connections): Stepper Motor Controller connections....connected to a Gecko G251X
Green Screw Terminal (8 connections): 6 Inputs and 2 grounds...connect input to ground for an "on" condition
Jumper Block: Used to select interface modes and reverse stepper motor direction.

The potentiometer is used to set the turret's home position.

[briuz]

I've done more testing. Grounds are good, optoisolators are good. Moving from one optoisolator to another doesn't result in any change. Tying an Acorn Input to ground on my interface board works but tying an Acorn input to OCIOutput0 (or any of the other 5 optocouplers) does not result in Acorn detecting an input.

[briuz]

Ok. I discovered that more than one of my opto-isololators has higher (500 ohms or so.) resistance. Checking it's input it's getting 0.3 VDC for some reason. Once I connected to an opto-isolator that has lower resistance across the photo transistor and a higher voltage going into it. (1.3 VDC) it is working fine and has about 200 ohms across the photo transistor. The strange thing is I tested all this prior to hooking the board up to the Centroid Acorn and everything was fine. At this point I am thinking I need to double-check a few connections on the board....that I already previously checked.

At least the theory in regards to the board's operation is fine. So I'll get some boards professionally made.

[martyscncgarage]

May I ask why you wouldn't want to use CNC12 and it's PLC to control the turret? It's the proper way, and CNC12 can do the checking to make sure it's in position otherwise fault.

What is the end game here?
Marty

[briuz]

Hello,

I've noticed there are at least 3 ways to control a turret and the 16 station turret I've built uses a stepper motor and homes via a hall-effect sensor. With the micro-controller it is possible to program the turret to allow for different interfaces.

Right now, I am just calling up a station by setting four relays. The micro-controller notes the change, moves to the proper station, and sends Acorn a signal that the tool is changed. (Since my turret is not single direction, I am also going to program the micro-controller to take the quickest path to the tool in the near future so as to avoid 270 degree tool changes.)

With the micro-controller, grey logic can be programmed as well. I think there is a timing system that could be programmed, too....but I don't know if it makes sense to tackle that system.

So, basically, the short term end game is to build an interface between Acorn and my turret that allows for different control options. With these options I could imagine a situation where I have 4 inputs available and one output or 4 outputs available and one input. Either would work. So there would be options. Longer term end game is to see if there is a market for the turret and this controller.

Another short-term end-game here is to get my CNC lathe running with this turret in a production scenario. However, it's almost identical to the turret in my Portable Production Lathe I've built (viewtopic.php?f=60&t=4379)....so it's tested and works great. (On the Portable Production Lathe, I am controlling the turret as another axis directly from CNC12 by using macros.....which also works great.)

May I ask why you wouldn't want to use CNC12 and it's PLC to control the turret? It's the proper way, and CNC12 can do the checking to make sure it's in position otherwise fault.

What is the end game here?
Marty

[martyscncgarage]

It's always best practice to let the motion controller handle ATCs. Something Centroid CNC12 PLC can do quite well if programmed properly.

If you watch my videos, you'll see several examples of that happening.

Best of luck to you in your venture. Do get your software upgraded. The issue you refer to may have been resolved since then.