[RomanLini]

Hi, after weeks of development I'm finally allowed to discuss this project. As some of you may know I've been an electronics product developer for a lot of years, and a CNC hobbyist for not so many years.

A couple of months back I created a closed loop router speed controller for my home CNC router, my router is; (here.

The controller uses a reflective opto sensor pointed at the router shaft and a microcontroller to give full PID control. Seeing that the system could be made to work and work quite well, started a discussion with Val from VHiPe.com who does some small quantity electronics manufacturing for me (and I do some contract design for him).

Val is in the process of arranging a forum name and organising to become a site sponsor and the official spokesman for the SuperPID kit product, but he's an oldtimer, not really an internet guy so I will be holding his hand a little regarding product enquiries until he gets more savvy with the forum process. I will be available anyway to answer tech inquiries for the product operation.

After some weeks of testing and refining the Super-PID product is near completion and production underway.

My home PID prototype is seen below, I should discuss how it works and then the differences for the commercial model.

There is a small reflective opto sensor about 5mm diameter that points at the router shaft from about 2mm to 3mm distance. Then a white spot of paint is painted on the shaft. I just used liquid paper for testing (matte white on the black metal shaft) and it has worked without incident for many weeks now so I didn't bother buying proper white matte paint.

The control board detects the router speed and adjusts the power supplied to the router to maintain a constant speed using an industrial PID algorithm. Speed is varied by a single large knob. This means the router can be set from speeds 5000-30000 RPM and will maintain a constant speed even when cutting etc.

The PID algorithm I used is really PID+ as it has much in the way of modification and special additions to improve stability under the very difficult condition of low speed cutting with a router that has very low rotor inertia (low flywheel effect) and only one sensor pulse per rotation, AND only being able to control the mains power pulses at 100 (or 120) times per second. Adding to these issues was the fact that cutting tools like single flute put one huge load pulse on the rotor per rotation which is again a problem very hard to stabilise.

Anyway the weeks of programming and testing are done, the thing works very nicely on my 1/4" router and even a bad case like a little Dremel(!) and should work even better still on all larger diameter routers that have a higher rotor inertia.

My prototype Super-PID has an accurate LCD tacho, and so does the Super-PID. However on mine the "power bargraph" is a row of 10 LEDs, where on the Super-PID it is a much more accurate 48 bar bargraph on the lower half of the LCD. This feature shows the percentage of power applied to the router at all times. So you can see on my prototype at low revs (5000 RPM) there is only one bar lit, the router is being fed around 10% power to maintain speed.

If it starts cutting, the power bargraph will rise to maybe 20-30% depending on the depth of cut and this is shown on the bargraph even though the speed stays at 5000 RPM or very close.

The 2 main benefits of the PID system have been very quiet opration, many of my jobs I can now cut at 10000 RPM or less with the router almost silent, and the other benefit is that the low revs have significant power now so I can take deep cuts in low-melt plastics like polystyrene and leave a clean finish with nice large chips thrown off.

The Super-PID kit will be sold as an assembled and tested PCB with LCD tacho/power display and screw down terminal blocks for the wires. It has 120v and 240v models (to suit all countries) and currently it is planned to sell as "kit" which just means you need to put in in a safe box as it uses mains voltage for part of the circuit (the rest of it's circuit is fully opto-isolated so you can control it with Mach3 etc). The "kit" form with no box was chosen to allow a cheaper price (as this is a low-cost alternative to VFD Spindles).

I'm open for questions and hope this is all ok with the moderators.

There are no proper product photos for a week or so as PCBs are currently being made - product due mid Oct. My prototype that has seen about 6 weeks hard use is shown below;