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  1. #1
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    Default Motor Speed Controller

    G'day
    Not sure if this is the right place to post this but I am replacing a 3ph motor on my buffing/grinding station with a universal wound motor from a washing machine that's in really good nick.
    It's plenty strong enough to run the polisher so the 3 phase motor currently on it is destined for the metal lathe as that 240vac donk is starting to cause me grief.........but that's another story.
    Some chap in Europe has designed a Universal Motor Speed Control Circuit for washing machine motors based on a Triac Controller (TDA1085C) and it's ideal for my purpose - he's posted the files online but unfortunately he's not contactable and I'm having problems trying to work out a few of the capacitor voltages which are omitted in the circuit diag...I have all the other parts ready to go but need these capacitor values so I can order the correct size etc to have the board made...

    I know there are some knowledgeable folk on this forum but would be grateful if someone could have a look at the circuit and let me know the voltage values of those capacitors needed so I can get it sorted...........TIA................Lee.
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  2. #2
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    Hello Lee,

    Because of that great big 6.8 K series resistor and the 63 volt electrolytics, all the other electrolytic capacitors can also be 63 volt ones. The ceramic ones can be any voltage above 63 volts except for C10, which should be a 1Kv ceramic.

    I would add a zener diode or TVR of about 80 to 100 volt rating across the power rail at C2, only as a protection device should the voltage spike and wipe out the IC.

    Would you post the link to the circuit please.
    Thanks.
    Best Regards:
    Baron J.

  3. #3
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    Thankyou very much for your reply BaronJ.....it makes sense now you explain it. I have sent you a comprehensive reply via PM with links and other info on the circuitry for the Controller - hope that helps.

    Over the years I've toyed with other methods to try and control motor speed for universal motors as with cap start and run motors as well but invariably they've always left a lot to be desired or just not suitable...hopefully this controller works out and gets me sorted...If others are interested please let me know and if it's OK with the Mod, then I can attach the Youtube link where the controller circuit is as not sure of the policy these days???

    Thanks again...Lee

  4. #4
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    Hello Lee, PM sent. Thanks.

    PS: A Youtube link is fine here.
    Best Regards:
    Baron J.

  5. #5
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    Default

    Had some enquiries from others who intend similar about the proposed speed controller I'm building so have posted the link to the YouTube video below - where I initially saw it. All the details can be obtained from links under that video if you are interested so your will need to follow those links to get the files but please note there is also an updated version available though the circuitry is the same...I believe the updated version is in Gerber from original Eagle format drawings

    Now I'm no tech nerd just an old fart with a basic understanding of where not to put his finger and what not to touch with my tongue to see if it's live or not but I baulked at the price some companies want to charge to supply a half decent speed controller - that's where this one got my attention being a cheap old fart too... The video is pretty self evident - to me at least...

    Universal type washing machine motors are readily available, will work on AC or DC, and voltage isn't much of an issue, they will even run from a Lithium Battery I had from an old drill - they are reasonably priced or free if you can score one, and with the wiring plugs attached are easy to follow. I have a few that I want to put to use in the shed and this controller should be a cheap way to do that for me.

    I found where this controller differs from others is that it's specifically made for washing machine motors (universal type). From my understanding this circuit is based on the TDA1085C triac controller which was designed to regulate the speed of universal type washing machine motors from the factory. It works on the fact that newer machines incorporate a built-in tacho usually on the opposite pole end to the brushes and that controls the speed back through the IC.

    The TDA1085C is no longer commercially made but can be cheaply sourced from Ebay through various Chinese suppliers - again not sure quality but will soon find out .

    Coupled with the rest of the components it works out much cheaper than using another form of speed controller such as a VFD, PWM, DTC etc...anyway, that's the plan and the circuit diag I posted previously was taken from the schematics which the original designer had made freely available.....

    Hope this link works

    https://www.youtube.com/watch?v=w5kCG-kVcFk

  6. #6
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    Default

    Looks usable for lots of things. I doubt I would use a universal motor for a grinding station though - at least not without a good reduction drive.
    The power output of a universal motor varies a lot with load (since they are generally designed with a more or less fixed load). So the speed variation with a grinding load would annoy me.
    PLEASE, please be careful that you CAN'T exceed the rotational maximum speed for the grinding wheels in use - with the electronic FAILING in any way!
    I know someone who has ruined his health and his life by using a universal motor that ran away on him with a grinding wheel - which then exploded, hitting him in the head! Very sad outcome of a design with just not quite enough knowledge....
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    Before every gets too excited about universal motors maybe have a read of this from https://en.wikipedia.org/wiki/Universal_motor

    A negative aspect [of Universal motors] is the high maintenance and short life problems caused by the commutator, as well as electromagnetic interference (EMI) issues due to any sparking. Because of the relatively high maintenance commutator brushes, universal motors are best-suited for devices such as food mixers and power tools which are used only intermittently, and often have high starting-torque demands.

    Another negative aspect is that these motors may only be used where mostly-clean air is present at all times. Due to the dramatically increased risk of overheating, totally-enclosed fan cooled universal motors would be impractical, though some have been made. Such a motor would need a large fan to circulate enough air, decreasing efficiency since the motor must use more energy to cool itself. The impracticality comes from the resulting size, weight, and thermal management issues which open motors have none of.
    This explains why you still see plenty of many decades old induction motors around on old machinery but it's pretty rare to see working universal motors that are of the same vintage.

  8. #8
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    Default

    Thanks for the warning Joe appreciate where you are coming from but am well aware of grinding wheels..agree with you they are dangerous things even under the best conditions and over the journey I too have seen some pretty nasty accidents caused by either wheel failure or idiocy - hard to distinguish at times but it's prudent to caution people as to their use of them .....my use of this particular motor is on a buffing setup that I can also adapt for grinding belts, not wheels or discs.

    These days i dont get too excited about much especially over motors BobL. ......interestingly the wiki article you quote doesn't say that nearly all of the tens of thousands of washing machines produced each year world wide are made with universal motors that are not contained in nema grade dust or filtered housings but sit in machines that are also not sealed from dust or water ingress in pretty ugly places and they all mostly seem to work alright - they still keep producing them so i don't think companies like Bosch, Samsung, LG, et al would use them if they had the problems wiki suggest as to "high maintenance and short life" to that extent..... must have something going for them....

    Anyway I didnt have last week's winning ticket so this week will have to make do with what's in my shed and that's currently a universal motor....cheers

  9. #9
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    Oh, good, Lee. I'm relieved.
    My previous post didn't show the other side of the story, of course. And that is that ALL angle grinders have universal motors, of course. One of mine is now 40 years old and still in regular use. The cooling fan and right angle drive provide the fixed load which prevents their speed 'runnoing away'. They do generally turn at around 23000+ rpm - at the motor end. The fixed reduction gear ensures that the wheel end doesn't go over the disk size's limitations....
    Good luck with your conversion Lee.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by barkersegg View Post
    T These days i dont get too excited about much especially over motors BobL. ......interestingly the wiki article you quote doesn't say that nearly all of the tens of thousands of washing machines produced each year world wide are made with universal motors that are not contained in nema grade dust or filtered housings but sit in machines that are also not sealed from dust or water ingress in pretty ugly places and they all mostly seem to work alright - they still keep producing them so i don't think companies like Bosch, Samsung, LG, et al would use them if they had the problems wiki suggest as to "high maintenance and short life" to that extent..... must have something going for them....
    I wouldn't hang my hat on the longevity of modern washing machines. They seem to have a design lifetime of ~5 years and with care might last 10 years. The semi open framed motors are housed inside a semi-dust-proof cabinet otherwise they would not be allowed to be used in a domestic appliance. In strict legal terms these motors have too many gaps in them for cooling and would need to be covered if used in an open workshop situation like a mens shed.

    Their bearings are on the ordinary side and their mounting brackets remind me of Mechano toy kits. I have used a few to drive fans and blowers but I put cover over them, and beefed up the fan and mounting brackets ie they all needed some work. The older motors are more robust so will last longer but then again they are older so might not have much lifetime left in them.

    IMG_4222.jpg

    I often have cast off appliances in the back yard usually during council pickups.
    As a result I have half a dozen old washing machine motors and various bits and pieces under the house.
    Last year there was at one stage 4 non working washing machines.
    One was mums ~4 year old Bosch, another was a 2 year old Samsung? - I stripped out the wiring, microswitches and sensors off these but I didn't bother with the motors - the motors are too open and too lightweight to do much with.
    One was a 10 year old Westinghouse which I fixed and was sent to a horse stable to wash horse apparel.
    The other was an 18 year old Asko which I was keen on getting the motor out of, but I fixed that (except for a water pump that leaks intermittently into the garden) and we use it to wash SWMBO horse's apparel.

  11. #11
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    Quote Originally Posted by jhovel View Post
    The power output of a universal motor varies a lot with load (since they are generally designed with a more or less fixed load). So the speed variation with a grinding load would annoy me.
    Joe,
    As this circuit uses the motor’s inbuilt tacho to provide feedback, I assume it’s speed regulation would be good.

    I’m keen to see the finished project.

    Chris
    Chris

  12. #12
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    Hi Guys,

    The IC, TDA1085C, is an obsolete device. It was designed specifically for domestic appliance use, primarily to control washing machine universal motors. Originally manufactured by Motorola, the chip design has changed hands several times, finally belonging to OnSemi in the USA. The only remaining genuine original production is owned by Rochester Electronics. They have about 170,000 in stock. They also have a $250 dollar US minimum order.

    I cannot find any similar device from any manufacturer anywhere. The thing that makes this chip unique is the tachogenerator feedback used to control the motor speed.

    The circuit is straight off the original data sheet for this IC.

    The same IC could be used to control treadmill motors by adding a tacho.
    Best Regards:
    Baron J.

  13. #13
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by BaronJ View Post
    The only remaining genuine original production is owned by Rochester Electronics. They have about 170,000 in stock. They also have a $250 dollar US minimum order.
    There seem to be plenty on ebay from $2. Whether they are originals or not is another matter.

  14. #14
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    Quote Originally Posted by BobL View Post
    There seem to be plenty on ebay from $2. Whether they are originals or not is another matter.
    They probably won't be Bob. My son recently tried to build a brushless motor controller with some H-bridge controller ICs. They were eBay cheapies. Some were DoA and some died when powered up. I ended up buying him name-brand ones from Element-14 at great expense because he had spent so much time on the project and I wanted him to succeed.

    If this project doesn't work, Silicon Chip recently published a universal motor controller. It doesn't have a tacho input, but they claim good speed regulation.
    Attached Images Attached Images
    Chris

  15. #15
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    Hi Chris,

    I would be interested in the rest of that article.

    Current feedback to regulate loaded motor speed works well.
    Best Regards:
    Baron J.

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