PID -Hardware needed for a software fix

So I use a speed control on both my machines and whenever chatter got nasty I would just move the speed a bit, with either my $20 660 controller or the speed control on the 611.

Seeing AvE bust out this little hack made me realize what the heck was happening.

So know we really need the PID speed controller so we can add in a non stable RPM so we can cut faster. Any EE’s out there have some ideas for the mains power control? The controller (arduino?) side will be easy, I think.



The Code…

The kit …

PCB link …

basic diagram


Its times like these I wish I had taken more meaningful classes in college.

Do you really need PID speed control, which is designed to keep speeds constant in the face of changing conditions? Or instead do you want speed control without PID, which would allow you to make small incremental changes at any time without the lag a PID is going to provide? If the goal is to provide a stable bit rotation speed, whether we’re in air, cutting a straight line or cutting corners or curves, then you want PID. If you want to reduce bit chatter then you want speed control without a PID, which seems like it’d be much easier to implement.


I want PID first and foremost, but with the ability to vary that constant speed at the push of a button or programmed in when needed within a very specific range. I vary the speed on almost every single cut I do, it does really work.

Once we have control over the speed than we can really push the limits. This I think is by far the most lacking part of all small form factor cnc’s. We have no way to control chip load without it, so we play the guess and check game as we cut.

The part I don’t understand is almost all the components I think go into this are super cheap.


Yeah… switch to a brushless motor and use a real speed controller.

That gets pricey real fast, that’s no fun.

Ryan, out of curiosity what are you using for speed control on the 660?

So to run a PID on speed of the DW660 you have to have feedback that provides spindle speed. I see that as being a reflective tag on something spinning, like perhaps the collet nut? You then read that to feed it back to your PID. How would we mount the sensor? I have a little hand held tach, but I don’t have a way to pull that back out to an external PID.

Why not to use one of this sensor that we are using in 3d printers. Proximity sensor plus some Arduino. I don’t know how is with Your 660 or 661 but probably you can find way to connect it to it and read puls. that will be the cheapest solution I guess;P I have few sensors of that type so I will try to make something.

I have this one and the one in the first link, depends on which machine,


Bill, You can either place the optical sensor at the top of the dewalt or on the collet nut with a dab of white paint or some come with a reflective sticker. There are a few places to put the sensor, and actually a few ready made solutions out there but I am not happy with the price or the setup really. One of our members was working on it and even had boards made but then disappeared. I have seen a few solutions that are close and open source. I have actually emailed a few and asked for higher amp ratings but no reply. I will try to modify one but since I am not an EE I won’t sell them as I don’t want to be responsible for wrecking things. There are actually a few that just need to have a slightly higher amp rating in the $30 range that I will try to modify soon.

Krzysztof, The rpms are so high I am fairly certain optical is the only way to detect it. I don’t know if a hall effect sensor can do 30k+. Wish I would have taken more EE classes. No better time to learn than now.


Send the link to one of the $30 ones you’re looking at. If I have the time I might pick one up and help.

I have this one coming, I think it is correct.

It says 5A so that is the 660 I believe, but hopefully a slightly bigger heat sink will work if the current one has issues. But I think at higher speeds it should be fine. The 611 needs to have the speed control bypassed I think. If this does work programming in soft start and different speeds should be easy enough. I have a handful of arduino micros and a few other tiny arduino’s, I have some optical sensors but should probably get the proper ones.

I am hopeful but this is a long shot as far as I am concerned. Just having the ability to control an AC motor to me is the largest hurdle the rest seems fun.


I wonder if there’s a place higher in the dw660 where you could paint a shaft, drill the hole in the side for the led and light sensor. I don’t like messing near the collet.

That light dimmer looks like a good fit.

For sanity, would you build this as a separate Arduino? I think stuffing it into the ramps or Rambo would be a pain. But being able to set the speed in cam would be nice. Maybe the second Arduino would be a slave to the Marlin board. It could read ppm from a servo port.

Or via I2C if a finer resolution is needed

In my head I see it as separate, like the super pid but cheaper and tweak able. Get the desired rpm from the control board. After seeing AvE’s video putting on a button that will vary that rpm by 50-100, or whatever it may need,from the preset rpm. To get fancy a screen and a knob or some buttons for total rpm control.

I think Ryan is trying to get me fired from work. Good thing I dont use the company computer often to look things up. I go to buy the speed controller he mentions above at Amazon and what do I see? “Customers who have bought this have also bought” and there is a picture of a big ol life like womans happy helper. Not exactly safe for work. Hahaha. Nice try Ryan, but not today!

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OMG!@!!! wtf is a “drildo”?

Whatever “power tool” that is there are more of them buying speed controllers than MPCNC users are…and I sell a lot of MPCNC’s. I guess I need a new link, dang.

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If you worked in the sex industry, it would be safe for work… mind blown


Damn, missed it. I did a search for that part on amazon and just got a bunch of other speed controller boards on the “other customers bought” links. Figured for sure I’d get something weird, I have a friend that does app security testing on IOT adult toys so I get linked to them on amazon every now and then. Did you know there’s one with a freaking camera in it!! That’s one POV I never really want to see.

We had to go back to a client site to turn off the porn filter setting on their new firewall we installed. Didn’t know this web design company did porn sites. They were kind of pissed they couldn’t get to their sites!

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