Acorn CNC 12 and 0-5VDC Voltage following (e.g. Super-PID)-- (SOLVED)

[EricMack]

I plan to test a Super-PID closed loop router spindle controller with the Centroid Acorn board. (www.SuperPID.com)

From what I see, the SuperPID uses a DC voltage to control speed. This can be 0-5 VDC from a control (e.g. Acorn) or a PWM Square wave which teh Super-PID will convert to DC Voltage.

Seems easiest to me to use the 0-10VDC output of the Acorn to drive the 0-5 VDC on the SuperPID. The question then becomes how to adapt the ranges?

I think I could find a voltage divider circuit to cut the Acorn 0-10VDC in half which would take care of the range for me.

My Super-PID Is set up for a Dewalt DP611 Router and works great on the bench with a 0-5vdc input and tracks well on its internal display.

Before I explore further, I'm curious to know if anyone here has experience setting up a 0-5VDC motor driver or perhaps even experience with the Super-PID.

[EricMack]

From The Super-PID Manual:

Options for PC speed control:
1. Super-PID can directly accept a PWM signal from a parallel port, or PWM from a break outboard.
2. Super-PID can directly accept a speed control voltage of 0v to 5v from a break out board or other controller.
3. Super-PID can accept a speed control voltage of 0v to 10v (or 0v to 12v) from a controller, but this needs to be reduced to 0v to 5v by using 2 resistors, as a simple voltage reducer.


I'm thinking a voltage divider with two 4.7KOhm resistors to halve the voltage coming from the Acorn, this way I don't need to play with numbers to scale anything on the Centroid side.

I used: https://www.allaboutcircuits.com/tools/ ... alculator/



MORE DETAILS FROM READING THE MANUAL
Super-PID v2 requires TWO SIGNAL WIRES from the Breakout Board (BoB);
1. Router ON/OFF - RUN signal wire (logic level): Zero volts=RUN. 5volts=STOP.
2. Router speed control - Speed control analog voltage: 0volts=5000 RPM. 5volts=30000 RPM.
or PWM logic level PWM signal: 0% PWM=5000 RPM. 100% PWM=30000 RPM.

Super-PID and the BOB also need to share a COMMON GROUND WIRE, this should also be a COMMON GROUND with the PC and the power supply GROUND. (see diagram above, please substitute the Gecko BOB for your BreakOut Board)
Sent from my iPhone

[cncsnw]

Somewhere in your PLC program source file you can find lines similar to the following:

Code: Select all

;Convert to integer word for DAC & I/O display
IF True THEN TwelveBitSpeed_W = TwelveBitSpeed_FW

; Bound min to 0, max to 4095
IF TwelveBitSpeed_W < 0 THEN TwelveBitSpeed_W = 0
IF TwelveBitSpeed_W > 4095 THEN TwelveBitSpeed_W = 4095

You can make the Acorn PLC output half its usual voltage simply by changing it to this:

Code: Select all

;Convert to integer word for DAC & I/O display
IF True THEN TwelveBitSpeed_W = TwelveBitSpeed_FW / 2.0

; Bound min to 0, max to 2047 (for 0 - 5V range)
IF TwelveBitSpeed_W < 0 THEN TwelveBitSpeed_W = 0
IF TwelveBitSpeed_W > 2047 THEN TwelveBitSpeed_W = 2047

[EricMack]

Thanks. I figured there might be a trick. I have a question: If I make this change to the PLC Code, does that prevent me from using the Wizard?

Right now, I have not yet ventured into the PCL code or Macros; I am only using the wizard. I know there are many things that can be customized but for now I hope to stay with the wizard until my machine and I are functional and I have more time to learn about PLC and Macro programming.

I am not yet clear if I make changes to the PLC or Macros if they will be overwritten by the Wizard...

[cncsnw]

Probably. Perhaps Marty or Keith, who have worked with Acorn and the Wizard more, can tell what the approved way is of avoiding that when you need to customize the PLC program in a way that the Wizard does not provide.

My guess would be to locate and modify the template file that the Wizard uses to build the PLC source from every time.

Another possibility is to make up your mind, once and for all, what your inputs and outputs are going to be; then give your new PLC program source a different name (to ensure it doesn't get overwritten accidentally) and look around in the Wizard for a checkbox that says you have a custom PLC program that should not be replaced.

[martyscncgarage]

Yes, your PLC program will be overwitten by the wizard. The wizard is essentially compiling the .src file Everytime you write the changes.

The super PID folks are stubborn not to incorporate 0-10vdc input which is pretty standard.
I would text the voltage divider method.

[EricMack]

I used the Voltage Divider Method. I used two 4.7KOhm resistors. seems to do the job nicely.

I'm amazed at hour quiet the SuperPID makes the Dewalt DP611 Router. I can easily have a conversation next to the machine while it runs at 13K- 15K RPM. Beyond that, it gets louder.

[martyscncgarage]

I used the Voltage Divider Method. I used two 4.7KOhm resistors. seems to do the job nicely.

I'm amazed at hour quiet the SuperPID makes the Dewalt DP611 Router. I can easily have a conversation next to the machine while it runs at 13K- 15K RPM. Beyond that, it gets louder.

Thanks for reporting back your success Eric.
Post a video of your router cutting with Centroid Acorn in the Success Stories forum!
Marty

[cnckeith]

Probably. Perhaps Marty or Keith, who have worked with Acorn and the Wizard more, can tell what the approved way is of avoiding that when you need to customize the PLC program in a way that the Wizard does not provide.

My guess would be to locate and modify the template file that the Wizard uses to build the PLC source from every time.

Another possibility is to make up your mind, once and for all, what your inputs and outputs are going to be; then give your new PLC program source a different name (to ensure it doesn't get overwritten accidentally) and look around in the Wizard for a checkbox that says you have a custom PLC program that should not be replaced.

yep two ways to go for custom plc work....you can edit the template and the changes will be incorporated each time you use the wizard to create a new plc program...
or you can edit the .src plc source file, compile it, and then choose "custom plc program in use" in the Wizard and it will NOT overwrite the custom plc program.

[EricMack]

Thanks everyone. I went with the voltage divider (two 4.7k resistors) and that worked great, I am tracking to within just a few rpm across the range of 5000 to 30000.
I hope to do a quick video soon to share.