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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Super-PID new low-cost router speed controller
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  1. #1
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    Super-PID new low-cost router speed controller

    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;
    Attached Thumbnails Attached Thumbnails proto_pid1.jpg   proto_pid2.jpg   proto_pid3.jpg  

  2. #2
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    That is just awesome, I think if the price is in my range I will need to get one for my new machine build in the very near future.
    I have a question regarding the type of spindle that this will control: I am thinking of using a large brushless DC motor for my spindle motor can your SuperPID be made to work with the electronic speed controller that will be needed to drive the brushless motor?
    Tom

  3. #3
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    This sounds like a very useful item. I'll keep an eye on this thread with an interest in buying one also.

    Would it help to make the router run smoother at low rpm if there were two pulses per revolution? Instead of one white dot, use two short white lines on each side of the shaft that are wide enough to be detected reliably.

    CarveOne
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    Looks promising, +1 on the interest in buying.

    What sort of power can it handle?

    J

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    Thanks for the interest guys.

    DeadTom- The product target price was to be under $150 for the fully assembled unit, possibly it could be as low as $120 or $130 but costing is still waiting on one of the parts suppliers (quantity LCDs) and will also depend on some time trials of how long the parts assembly takes. The PCB is a top quality Australian made unit, Australian labour and parts top quailty (metal film resistors, over-rated power componenets etc) so this was designed for the quality end of the market, not bottom-end Asian price etc.

    Sorry no it is not suitable for BLDC motor, and your BLDC controller should include speed regulation anyway? With a router you can run lower speeds (like a BLDC) and fairly quiet.

    CarveOne- There is little point running a finer resolution speed sensor. For one, it causes issues if the 2 dots are not perfectly 180 degrees apart, and that makes it hard to do. Options like multi-slot encoder disks are hard to fit! Also the main low speed issues are that the router inherently has low power at low speeds AND that the mains power comes in low speed pulses (100Hz or 120Hz) - neither would be fixed by encoder resolution.

    All that is irrelevant now as I have refined the PID system to work well within it's design parameters 5000-30000 RPM and the extremely easy to utilise reflective opto sensor system of 1 pulse per revolution.

    I can possibly talk Val into giving a few units away to long term forum members who post good photo build logs (like yourself) so I may be able to get you a free one in exchange for a review/testing. That's pushing the limit of forum advertising etc so I don't want to go into that yet until Val sorts out the forum sponsorship and hopefully gets some feedback from the moderators etc as to the best way to proceed.

    JeremyFisher- It is rated for continuous use at up to 1000W (120v USA model) or 1200W (240v Europe/Australia model). Heatsinking needs are minimal, but if you're like me and like to go extra on reliability and plan to use it at higher power levels for production a small additional heatsink and/or small fan is recommended.

    Thanks again for the interest guys! Later today or tomorrow I plan to pull my routers vac foot off and take a photo of the spindle opto sensor and how I mounted it, that will help to show just how easy it is to attach this to your existing router setup.

  6. #6
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    Ok, I wasn't sure about whether the circuitry could handle 2X the pulse rate, and if there were any advantages if it could handle it.

    Thanks for the offer. I may be interested if you need the help. PM me when you are ready to discuss it. Many of your sales may be from the US and other countries. You'll need to figure out how to handle that.

    CarveOne
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  7. #7
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    I can possibly talk Val into giving a few units away to long term forum members who post good photo build logs (like yourself) so I may be able to get you a free one in exchange for a review/testing. That's pushing the limit of forum advertising etc so I don't want to go into that yet until Val sorts out the forum sponsorship and hopefully gets some feedback from the moderators etc as to the best way to proceed.

    This is a very nice gesture..
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  8. #8
    Community Moderator ger21's Avatar
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    Will this work with variable speed routers, or only fixed speed?
    Gerry

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  9. #9
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    Seems like your next step is to have a modbus interface to Mach so gcode can set the speed of the spindle.

  10. #10
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    CarveOne- We expected to sell to the US as a main part of the market. Australian airmail is reliable and quick enough, it is typically 5 to 10 days to get a small parcel to the US.

    Khalid- Thanks.

    Ger21- It it designed for routers that have no inbuilt speed control.

    In the early testing I removed my router cover and checked, its electronic speed control has a switch pot, so it varies up to full, then the switch goes "click". At that point the switch bypasses the electronic speed control so there is no problem. That is probably a common setup. Also, I actually did some cutting with the router's internal speed control on, and that seemed to make no difference to the operation of the PID unit, they did not interfere.

    All in all I would recommend turning the routers internal speed control off, or bypassing it, but I do plan to do more tests. Thanks for reminding me.

    Brtech- Thanks for the suggestion. Currently it will accept speed control from the pot, or from a 0-5 volt control source. I think some of the break out boards etc can produce a 0-5v speed control signal.

    One thing we have decided since the PCBs went to press is to use a socket on the microcontroller, so it will be possible to add features later and get users to mail the chip back for an "upgraded" chip.


    Photos of my protoype speed sensor.

    Nothing special to look at, just hurriedly applied white paint (liquid paper) I painted on half of the shaft, and a tiny reflective optical sensor beam pointed at it;
    Attached Thumbnails Attached Thumbnails SuperPID_opto1.jpg   SuperPID_opto2.jpg   SuperPID_opto3.jpg  

  11. #11
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    I have been told today the PCBs are finished and with the courier.

    So within a couple of days I can get a unit assembled and take some photos to show what the product actually looks like, and maybe borrow a vid cam and do a youtube of the little beastie in action.

    In the meantime I did get time to add a few nice firmware display features and improved the soft start-up RPM ramp.

  12. #12
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    I was actually going to ask if you could implement a start-up ramp.

    I have another question about the unit though. I have a weak understanding of electric motors so excuse me if this is a silly question but I'm sure others are wondering the same:
    Can running a motor (which is designed to run from mains) at lower voltages (or on PWM current or however your unit works) have a detrimental effect on it?

    The main concern I have is overheating of a motor which is running below its rated RPM and therefore has less airflow running through it while outputting the same power.

    Have you run your router under load for extended periods at 5000 RPM?

  13. #13
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    Re; if running the motor at lower RPM can overheat it, the answer is both yes and no.

    If you were to run the motor at 5000 RPM and full (applied) power, it would probably overheat.

    BUT the Super-PID (being closed-loop) only applies as much power to the motor as is needed to maintain the RPM that you have set.

    I've done some hours of cutting with the PID at low RPMs with no problems. For example, cutting acrylic with a 1/8" end mill at 2mm (0.080") depth and set to 11000 RPM, my router barely shows 15% to 20% applied power on the LCD, and as a 850W router that is under 170 watts being used. A 1/4" endmill in acrylic uses around 20% power.

    Cutting aluminium at 14000 RPM with a 0.5mm (0.020") cut it is still under 25% power applied to the router, and at 14000 RPM the air cooling is quite good anyway, and the router barely gets warm.

    I want to emphasise that you would not be able to use FULL router applied power at 5000 RPM, but that is such a slow speed for a wood router it would only be used for some special needs anyway - I have used for good result cutting low-melt polypropylene flooring sheet and polystyrene electrical boxes, at about 7000 RPM, both soft materials and only needing 10% or so of the router power so barely breaking a sweat.

    An important point is that you can do a lot of cutting at lower speeds now (with the Super-PID) as it makes a lot more torque at lower speeds. So jobs you used to cut at 20000 RPM with reduced tool life, bearing life etc can now be cut at a more optimal 12000 RPM (for example) and prolonging both tool life and bearing life and giving a better cut. For anyone wanting to cut aluminium, plastics; acrylic or cheap PP, PE PS, etc this is a huge improvement.

    There are some initial product specs up on Val's web site;
    www.SuperPID.com
    and I have PCBs on the testbench now and should be able to post a photo tonight.

  14. #14
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    I see this on the website:
    Warning! The closed-loop nature of this motor speed controller means
    that it is capable of delivering significant power to the motor during low RPM
    use. At low RPMs the cooling ability of universal motors is reduced and we recommend
    monitoring of the motor power and heat during low RPM use. We will not be held
    responsible for damage to the router or to the Super-PID device caused by abuse.
    If this is a concern, put a thermister on the router and monitor it with the microprocessor

  15. #15
    Community Moderator ger21's Avatar
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    Would it be possible to use one Super PID with 2 routers? Maybe use a contactor to switch power between the two?
    Gerry

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  16. #16
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    brtech- I don't think it is a big concern, Like I said my router barely gets warm cutting most stuff at low speeds. I think the warning would be better to say something like "This will not turn a 30000 RPM router into a 5000 RPM spindle for milling steel!" or something like that. But it does give you quite a lot of usable power at lower speeds, many times more cutting power than you get from an open-loop router which is pretty much useless under 10000 RPM, and of course the benefit of the speed being fixed so you can tune around cutting resonances etc.

    ger21- Sure it should not be a problem. You would need one relay to changeover the router power (2 wires) and another relay to changeover the sensor (2 wires). Or, you could just have 2 plugs and plug in the router power and the spindle sensor for the desired router. I just have an AC mains line plug on mine, and a 3pin small connector for the sensor.

    It seems an unusual request, I'm guessing you have 2 routers set up and need to use both regularly?

    Photo as promised.

    Here is a shot of the assembled Super-PID product (with no case!) you can see the tacho display and the bar graph that shows how much % of power is being applied to the router. I faked the shot just using a 5 volt supply to get the display working, you can see there is no router attached yet or spindle sensor. I'm a lousy photographer and don;t have th elights etc to get a good shot in the workshop, this was taken in the sewing room (ahem).

    The large metal square is the heatsink bracket, for light use this is enough heatsinking but for serious production use I would use a fan and/or more aluminium attached. The Super-PID was designed for serious use so I went with this system instead of the tiny cheap pre-stamped heatsinks.

    There should be a couple of display colour choices too, currently I only have white on blue (which is good visibility) but Val has ordered samples in some other colours.

    Anyway this photo shows pretty much what you will get as the working and tested product, it just needs a case and a few wires connected.
    Attached Thumbnails Attached Thumbnails SP_02s.jpg  

  17. #17
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    Cool! Looks really good.

    CarveOne
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  18. #18
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    I am really impressed to see the Quality of the Product... I normally doing woodcarving and relief carving with my 25000 fixed RPM Router.. and It runs 8Hrs or more to accomplish a single carving..

    I normally have to replace the bearings and lot of dull tools... This options will be great to reduce the Operating Cost as well as reduce noise..

    I really anxious to see the final product and request to keep me in line for One Super-PID...
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  19. #19
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    Showing my ignorance here (not hard to do) but what's the difference between your speed controller and one that you buy off the shelf?

    Adam,

  20. #20
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    Thanks CarveOne and Khalid! It's had a lot of work in development, seems like it's never ending.

    adam_m- Good question! I'll try to put it in perspective;

    Fixed speed router; Generally 25000 RPM to 30000 RPM, (like Khalid said), very noisy, lots of heat, tool wear and bearing wear and will melt plastic when cutting etc and can burn woods too depending on speeds and feeds.

    Variable speed router OR any typical "speed control"; When you turn them "down" these just send less power to the router. So speeds are about 16000-30000 RPM range, and at lower speeds like 16000 there is very little torque. So if you are trying to use the lower speeds it will droop speed badly and have very little cutting power, or just stall, or speed will vary all over the place depending on cut depth etc. And under 16000 RPM you can pretty much forget about it, so you still get bad issues with melting plastic and aluminium melting onto the tool because you are forced to use too much RPM if you want to get any useful cutting power.

    Super-PID closed loop speed control; This has a infra-red speed sensor pointed at the router shaft, so it measures the exact RPM of the router at all times. Then it uses a high-speed math algorithm called P.I.D. to adjust the power sent to the router, to keep the router spinning at the RPM you wanted. And it has an accurate tacho so you can set a chosen RPM based on speeds/feeds tables as people need for professional production.

    So speed range is now 5000-30000 RPM, and you can get excellent power down to 9000-10000 RPM (used for most plastic and aluminium cutting etc) and even get significant amounts of usable power at the very low RPM range like 5000-9000 (where your router is almost silent!) that can be used to cut fussy materials like low-melt point plastics, fussy woods, and light cuts in materials for the purpose of getting good surface finish etc.

    The idea of the Super-PID was to offer some (most?) of the performance benefits of a VFD spindle setup, but at a lower cost and an simple task of just connecting it to your existing router setup.

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