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18th Sep 2020, 12:04 AM #16Golden Member
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18th Sep 2020, 08:04 PM #17
Hi Pete,
Can you determine if the 5 volt + pins on the board are all connected to each other ? If they are then its likely that the control panel can be disconnected. Without a scope you won't be able to tell if the up/down signal is a pulse or not, though you could simulate a pulse by applying 5v+ momentarily to the "UP" pin and see if the motor attempts to spin.
I tried running the motor with the SCR controller and bridge rectifier; it ran but made noises that i did not like at all; when adjusting speed upwards with the potentiometer the motor sounds like it is arcing internally and when running at a steady speed there is a humming / groaning sound that is to my ear just NQR. I'm not confident running this good motor with the cheap eBay option unfortunately. If I can somehow give the speed commands to the existing control board it will b happy days.
You can test out the motor using a 12 volt car battery or two. It wont spin very fast but should be smooth and quiet.Best Regards:
Baron J.
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18th Sep 2020, 08:18 PM #18Golden Member
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Thanks again; the two locations marked 'F5V+' are indeed connected to each other on the back of the board. I'll put things back together and try jumping 5v to 'Up' and see what happens.
The motor hasn't been sitting more than a couple of weeks, the machine has actually been in use recently and runs perfectly smoothly when operated by the normal treadmill controls.
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19th Sep 2020, 12:51 AM #19
Hi Pete,
You are the second person to have reported that the treadmill motor runs badly when used with a Triac speed control and rectifier system. I'm going to set up to run a test with one of my treadmill motors and see if I can replicate the problem.
One of the issues that I do know about is that the bridge rectifier doesn't actually produce a clean DC voltage supply. Its actually a very rough spiky DC and would benefit from some smoothing capacitance across the motor to knock the sharp spikes off. The trouble is that the motor takes such a high current that it would need a fairly high capacitance value to provide the current required. I forget the formula for calculating the capacitor value off hand, so I will have to look it up for you.
EDIT:
I cheated and went to Steve's post and copied my text from there.
C = I / 2 x f x Vpp
"C" = capacitance in farads, "I" = current in amps, "f" = frequency in Hz, "V" peak to peak ripple voltage.
I would assume "V" to be 230 VAC x 1.414 = 325 volts / 2 = 162 VppBest Regards:
Baron J.
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19th Sep 2020, 11:27 AM #20Golden Member
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I will try to get my head around that formula and values and see what capacitors I have on hand, would be great if the addition of a capacitor was all it took to run smoothly on the simple controller setup.
Edit: I make that 6 x 50 x 162= 48,600 farads. Seems I must be misunderstanding something.
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19th Sep 2020, 05:07 PM #21Member: Blue and white apron brigade
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19th Sep 2020, 06:33 PM #22
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19th Sep 2020, 07:40 PM #23Golden Member
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Thanks very much guys. Did I mention this stuff is a great darkness to me? I can generally follow instructions with electronics and hook things up without electrocuting myself (well ok there was that one time) but I make absolutely no claim to understand how it works
I may possibly be able to come up with 740uf worth of capacitors, not certain, will have a rummage in my boxes of stuff with wires. Unfortunately I will probably not be able to get back to this until mid next week now though.
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20th Sep 2020, 05:40 AM #24
Hi Pete,
The amount of capacitance is not critical, but the voltage rating should be about 375 volts or more ! Just look at the ratings and values on the ones on the treadmill power unit. The big black ones !
Also be aware that a capacitor of this size can hold enough charge to kill you so make sure that you turn the motor speed down to zero and unplug it before you go touching any wires. Remember "One hand in pocket" !Best Regards:
Baron J.
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20th Sep 2020, 10:16 AM #25Member: Blue and white apron brigade
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11th Oct 2020, 09:57 PM #26Golden Member
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I didn't get a chance to have a play with this thing again until this afternoon. I don't have enough capacitors kicking around to experiment with that aspect properly, however I did hook the motor up to the SCR controller and bridge rectifier with the voltage stabiliser / ballast thingamajig also in line on the input side. It smoothed out the acceleration and seemed to take the arcing sounds out of the motor. However, I'm still not confident that this will be a really good way to power a belt grinder that is going to do some hard work and will also have a lot of work go into the build. I think I'd be better off leaving a perfectly good treadmill alone and acquiring a 3 phase motor and VFD for the grinder. I don't have the desire to educate myself enough on electronics to do a proper job on this conversion, I'd actually rather put that effort into things like my proposed vise build, and leave the electronics to others. So thanks for all the input but it's likely my fitness junkie daughter and son-in-law will get the treadmill.
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12th Oct 2020, 07:27 PM #27
Hi Pete,
I'm glad that you tried the capacitors and saw the effect that it made. Essentially the only difference between the treadmill power supply and using the scr/triac one is that the treadmill psu is a pulse width output into the capacitors at a much higher frequency than the 50 Hz mains, so the capacitors can be much smaller, but the overall effect is the same.Best Regards:
Baron J.
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7th Jan 2022, 04:41 PM #28Senior Member
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Interesting thread. I hope it is ok to continue it from here. I don't like the idea of the Triac/SCR type thing either, read a post elsewhere from an engineer/designer who claims he designed one of the popular treadmill controller boards. He says that the voltage peaks from the cheap Triac module will be too high for the DC motor. I know that a lot of people use this method but he claims that the permanent magnets will be damaged over time (lose their magnetism) and in Australia, with a higher mains voltage, that might happen a bit faster. Again, I know some people do it this way, and claim good results but its not for me.
I do have a crappy 1.5hp treadmill complete with control gear and motor driver board but it really is a bit too light duty to be of use for my lathe. But I came across a 2HP treadmill motor that looks pretty serious and is about twice the physical size of the crappy motor so I'm hoping that by using an overpowered motor and providing enough current, that I can get away without having a complex closed loop speed regulation system... I don't have time to get that deep into things so it will be a bit of a gamble. Not sure if its worth it but I might learn something.
Spent too much time trying to reverse engineer an unknown motor controller board, gave up eventually when the motor drive power rail seemed to be a bit intermittent. Not sure what it was about but might have been some sort of current detecting protection circuit shutting things down. But some of the parts might come in handy for something else depending on which way I go. I didn't even have a pinout of the control panel, if I had the control panel I could have probably figured out what to do to delete it but I don't have that luxury.
So at this point I have a couple of ideas, but are incomplete and will need some time to explore them. I did find a cheap $20 ebay PWM DC motor controller, for motors up to 160V, claims 10A continuous current but 240V on the input side is too much for it.
Too many projects, maybe this is another distraction that I don't need but we will see.
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7th Jan 2022, 09:58 PM #29
Hi Metalmachine,
I know that a lot of people use this method but he claims that the permanent magnets will be damaged over time (lose their magnetism)
As far as SCR/Triac speed controllers are concerned, these have been used for years, but they do have to be configured properly. The basic output is a series of very sharp edged pulses, feeding these into a rectifier will create a unidirectional voltage that needs smoothing somewhat to produce a stable voltage depending upon where about the SCR/Triac is switched on. Its the value of this voltage that will control the motor speed.
Obviously there is more to it than the simple explanation.
The existing motor control board requires a pulse generator in order to take full advantage of it.Best Regards:
Baron J.
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8th Jan 2022, 12:13 AM #30Senior Member
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Hi BaronJ, thanks for the input. You seem in favor of the triac > bridge rectifier method?
I did my time as an electronics tech (17 years of it) and still going, though I am a bit rusty on power supplies and triac switching circuits, and have been going back over some of the theory this evening. I suppose smoothing the waveform with an appropriate capacitor will help a bit but I have however recently built microcontroller based PWM DC motor controllers for small DC motors which worked very well. So with a PWM solution in mind, a quick calc shows that rectified 240VAC would be in theory become 170V DC but of course it could be quite a bit higher (single phase GPO's I've seen go up to 265V, in which case would be 187V rectified). But voltage regulation would be better to have than not, (especially since we want stable speeds) so I will have a look at some old schematics of high power audio amplifiers that I used to service that had 150V rails on the output stages as I haven't had to look at regulation methods of such voltages for at least 10 years. The motor I have is rated at 180VDC. The motor I have is rated up to 180V. I think the PWM method would be a bit smoother, a bit quieter, a bit kinder on the windings, probably less heat and just a bit nicer. I already have a PIC microcontroller or three set up with PWM speed control outputs so have a head start on that part. Am I missing anything? You seem knowledgeable and to have no problems yourself with the triac method, so do you think the advantages of PWM are worth considering? I hope to avoid speed regulation feedback loop for simplicity's sake, just relying on the power available of the setup to maintain a stable speed. There is also an open source arduino micro controlled solution out there, not sure how good it is, have lost the link, will have another look for it.
Thanks again for your thoughts.
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