Variable speed control for 1650 Watt handheld router

Discussion in 'General Electronics Chat' started by PZUFIC, Oct 8, 2016.

  1. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    Hello!

    If I want to use larger router bits in my router I have to reduce the speed but the problem is that there is no speed control at all. So, I want to build some kind of external speed control. The router is powered by universal ac brushed motor. It runs on 230 V mains voltage and has a power of 1650 Watts. So triac chopper should to the trick, but without some kind of speed fecback it will be useless. In my other smaller router there is a magnet and an induction sensor which is connected to speed controller probably based on triac circuit, so the speed is constad, of course if the device is not overloaded. I searched over the web and it's realy hard to find schematics for AC brushed motors. I finally came along this. Will this work if I adjust the components values for my supply voltage and power of a device, what about the speed under load?

    Thank you very much, and feel free to post other suggestions and schematics.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Looks as though it could work. Note in particular the comments about R13, Tr1, U1 and also the lack of mains isolation. It allegedly tries to compensate for load.
     
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  3. crutschow

    Expert

    Mar 14, 2008
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    Just buy a controller such as this and don't worry about trying to do feedback control.
     
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  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There was a device developed by an (ex?) poster here and is being marketed, it may be more than you are willing to pay, it uses a Triac and optic feedback sensor, it was developed for Universal motor routers particularly CNC.
    It is called SuperPID and the member here was THE_RB, but he has been absent from the forums he belongs to for around 2 years.
    http://www.vhipe.com/product-private/SuperPID-Home.htm
    Uses a Picmicro.
    Max.
     
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  5. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    I assume that there would be a substantial drop of speed under load and that would be really annoying and probably influent the results.

    If there are any other designs that uses current feedback please feel free to post it. It's not a problem I can make it myself.

    Thank you very much to both of you.
     
  6. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    Yes, I found this device on web and also many other using some kind of tacho or optic vs. magnetic feedback. The problem is that it's not standalone machine and it's hard to add something on a shaft or inside the case. Something that can senese speed indirectly just on supply cable would be much more easier to realise.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    It certainly would.
    But I know of no reliable way to sense speed from the supply cable since all you can sense are current and voltage and neither of those is a good indication of speed.

    If you want speed control then you will need some physical sensor to directly measure the motor speed.

    A method not requiring direct access to the motor would be measuring the frequency of the motor sound such as by using an FFT in a microprocessor, but you would then have to have some way to calibrate the frequency to the speed.
     
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  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The SuperPID posts on the CNCforum where the SuperPID was launched has many posters solving the sensor mount issue for different makes of routers.
    The is not much difference with a cable on a CNC machine which is still flexing constantly through the cable tray so not much different to a portable application as you still need a sensor cable if you go this route.
    Current is definitely not the way you can monitor RPM especially on a series motor.
    Max.
     
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  9. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    Ok, I will check if there is any possibility to mount the sensor and even entire regulator inside the router. The router is Maktec MT362.
     
  10. BR-549

    Distinguished Member

    Sep 22, 2013
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    Why not try Wally's suggestion and adjust speed by the sound? Or is this an automated process?

    Is there a craftsman involved?
     
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  11. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    I disassembled the router, and there is space in betwen the commutator and dust cup under the upper bearing. Currently is just white plastic, but I can put some white and black paint on. And I think there is enough space for an optic sensor too.

    Any suggestions what to use for a sensor and control unit? Are there any special purpose ic for this task, or maybe solution with AVR microcontroller? I can build it my self but I'm not very experienced at microcontroller programming, more on the computer software. SuperPid is a little bit pricey for my purpose and I really don't need LCD and connection to PC.

    It's just a handheld router used manually by hand or in router planing sled. If there is not overcomplicated way to ensure almost constant rpms I would like to make that. I think it's safer to use to.
     
    Last edited: Oct 9, 2016
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have the retro reflector number somewhere but on the way out shortly so will have to wait for later.;)
    Max.
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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  14. crutschow

    Expert

    Mar 14, 2008
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    Here's an article on controlling AC motors with feedback but I'm not sure it's what you want.

    Controlling an AC motor with feedback to give a stable speed with varying loads is not a trivial task and I don't know if it can be done without some programming experience in feedback control.
     
  15. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    Hello again!

    Recently I get back to thinking about that project and how to proceeded if so. The speed must be constant so open loop is not a solution. I did some research and found the TDA1085C integrated circuit which was meant to be used with washing machine motors. I also found that there are PCBs and kits for sale on eBay, so I think it's not worth it to make PCBs and gather all the parts together.

    I hope there is someone who has already used this ic or has enough knowledge to help me with a few questions. I get through datasheet and also some thesis in which the project with that ic was made, but some things are still confusing to me.

    The following is based on the schematic published by the seller on eBay, refer to link above. Basically it's the same as the one in the datasheet but with minor changes mainly regarding the acceleration ramps.

    • According to datasheet pin 6 is connected to the ground to enable just one ramp for acceleration?
    • What is the purpose of the potentiometer P1?
    • According to datasheet with potentiometer P2 I will be able to adjust the current limit?
    • According to my knowledge the tacho consists of a separate winding of which the output voltage and frequency are proportional to the rotation speed. I will be using an optical sensor (probably something like CNY70) for RPM measurements (1 pulse per revolution). In the datasheet I can see that the digital speed sensing is mentioned, but it's confusing to me again. How should I connect the optic sensor with logic output to this circuit if even possible?

    Thank you very much for help in advance and have a nice day.
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have a TDA1085 circuit that was used in a Treadmill application of a Universal motor, pin 6 is connected to Pin7.
    Pin 3 is the current limit pin.
    The TM circuit used about a 6 pulse/rev magnetic tach system.
    If opto sensor then it would input to P12 the digital speed sense input.
    I used it to control a motor for a band saw.
    Max.
     
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  17. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    If you're using a slotted opto sensor, feed it into pin 12...

    Datasheet TDA1085c..
    https://www.google.co.uk/url?sa=t&s...ggcMAA&usg=AFQjCNGsVHFiXPW8S6PHW2zfgbGQfhZ1PA
     
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  18. tcmtech

    Well-Known Member

    Nov 4, 2013
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    How far do you want to slow it down and how do you plan to keep the motor form overheating when you do?

    What happens to your series wound motor when you slow things down too far but try to keep the power and torque.



    The smoke comes out. That's what. :oops:
     
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  19. PZUFIC

    Thread Starter Active Member

    Jan 7, 2012
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    I was planning to use CNY70 or something similar. I definitely need a reflective type of a sensor. If someone have a better idea for a sensor I will be glad to hear it. What do you mean by connecting to pin 12, directly or using the resistor and capacitor just like with tacho? In case of the CNY70 I will also need to add the pull-up resistor, will that work or the ic will draw to much of a current?

    Is it possible to build a separate power supply unit for driving both the ic and the sensor. In that case I need to connect the output ground of the power supply to one of the mains input or what? I don't like the idea with a transformerless power supply. Also with 15 V on the CNY70 there will be a lot of heat dissipated on the current limiting resistor.

    I don't know the rpm's for sure because I didn't bought the bit jet. I hope that the router cooling fans or windings does not differ from the pricier model that has a build in speed control, but I don't know.
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Here is the version I used,.
    It uses a bridge before the motor to drive it with DC.
    I went down to very low rpm for a band saw.
    Max.
     
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