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Topic: High Power PID Controller (Read 1 time) previous topic - next topic

rymanvw

Hey guys, I was looking around and couldn't really find any PID controllers that were very high current/voltage.

I am building a 3-axis CNC machine and I want to be able to vary/regulate my router RPM. There is a product called Super PID which has a few videos on youtube and a website www.superpid.com. That is basically exactly what I am looking for except I don't wanna $155 on it. I have done PID control before but with 12V CPU fans and a 5V thermistor. So I was wondering what type of things do I have to consider when dealing with a 2-1/4HP 11Amp 220V router? I have a Hitachi m12vc, Currently it has a switch which regulates the rpm from 8000 RPM to 24,000 RPM. I'd like to be able to go down to 5000 RPM such as the SuperPID.

Also I was wondering what would be the best method for measuring the router RPM, I was thinking of using an optical sensor and a some white paint on the spindle head would work?

Okay well let me know if I missed anything, I am using a Arduino UNO with GRBL installed but i could use an external PID controller which I would set manually instead of via gcode.

Thanks
-Ryman

Yankee

#1
Aug 21, 2011, 08:01 pm Last Edit: Aug 21, 2011, 08:13 pm by Yankee Reason: 1
I have the same router and found that it already has some form of electronic feedback for the speed control. If you remove the cover of the router you will find a module that sits over the shaft end. Removing this you will see a circular magnet on the shaft end which fits into a pocket in the module where the magnetic encoder is enclosed. It's been my intention to obtain another router so I can have a spare and then open up the module (it's hermetically sealed in what looks like silicone). Although hacking whatever chip is in there may be difficult, I imagine that the encoder signal could be used with an arduino to create an external PID controller. Take a look and see what you think.

The logic for such a controller is the easy part, I think. The more daunting task to me would be designing a safe and reliable power circuit.

retrolefty


I have the same router and found that it already has some form of electronic feedback for the speed control. If you remove the cover of the router you will find a module that sits over the shaft end. Removing this you will see a circular magnet on the shaft end which fits into a pocket in the module where the magnetic encoder is enclosed. It's been my intention to obtain another router so I can have a spare and then open up the module (it's hermetically sealed in what looks like silicone). Although hacking whatever chip is in there may be difficult, I imagine that the encoder signal could be used with an arduino to create an external PID controller. Take a look and see what you think.

The logic for such a controller is the easy part, I think. The more daunting task to me would be designing a safe and reliable power circuit.


Yes, PID software is a pretty straight forward application function. The trick has always been to be able to get a reliable and accurate input variable (PV, process variable) and a accurate and reliable hardware output circuit able to control the final control element, The output variable, in this case a motor driver circuit.

A decent GUI for user set-point adjustment and the ability to modify the 'PID tuning variables' is also nice but not nearly as difficult as designing and building the input and output interface circuitry.

Lefty

CrossRoads

Don't forget to check the PID library's in the playground

example
http://www.arduino.cc/playground/Code/PIDLibrary
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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