RPM Speed Controller Suggestions Needed

Uh, no.

The first link is utter gibberish apparently assembled at random for purposes of SEO optimization so as to maximize landing and thus ad revenues. It is totally inappropriate. Did you even read it? A random selection:
Speed Control of Ac Motor Using Igbt - download as Word Doc (.doc), Text file (.txt), PDF File (.pdf) or read online for . Speed Control of Ac Motor Using Igbt Scientech 2714 is a platform which is very useful for Students to understand the concept of Thyristor firing method & working of speed control of motor using SCR by Speed Control Of Ac Motor Using Triac downloads at - Download txt files,ebooks and documents - Dual voltage SCR DC motor speed control for up to 2 H.P. motors Newly listed AC 220V 500W Motor Speed Controllers SCR Voltage Regulator Thermostat Dimming. From China.​

You clicked on it, so it served the intended purpose. Again, keywords merely glommed together without any semantic content. Proof that our AI overlords at Google are still easily fooled by nonsense.

The second set of circuits and explanation are confused and clueless, being taken from elsewhere on the internet without explanation or analysis. Which would identify numerous problems. Not recommended.

What I wrote should give the OP sufficient information to research which type of commercial motor controller is appropriate. I very much doubt that the OP wants to build a circuit for this purpose.
http://www.soloelectronica.net/triac/APPCHP6.PDF I hope, this time, help .
 

The AC motors being controlled in that example were for a vacuum cleaner suction control and food processors, two very different applications than a high-torque motor used for spindle applications. One case appears to be a conduction angle controller. Both are brief uses, unlike a lathe or drill-press motor. The motors in applications like vacuums and food processors are likely specifically designed to take abuse from voltage control. Lathe motors are not.
 
... well, they got the "From China" part right, at least. On the DC front, there are some nicely-integrated 90V motor speed controls out there if the OP wants to re-power. Duplex box-sized with front panel, volts/RPM display, pot and switch already done.

Back in AC, the 'coal standard' (worst possible implementation) I've seen came in on a surplus desktop CNC mill I bought. It had two fan speed controls in series. So apparently the deal was to chop up some AC into little spikes, and then further chop that up into even fewer spikes, then run a DeWalt collet-equipped die grinder with the output. Shockingly, it actually worked fairly well, with enough torque to chew thru some aluminum. Chucked it all in the bin anyway, but points for creativity.

Late add:
Here's a link to a post on Practical Machinist about using a stepper motor as a 0-1200 RPM full-torque motor. Some resonance at some frequencies, but mechanically straightforward. Have not researched whether the 'steps' telegraph to machined surface imperfections...

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He's running a sewing machine motor. Its a universal series wound motor, honestly a vacuum cleaner would be a lot more powerful. I've seen the lathe he's using, its a cute little watchmaker's lathe. Not exactly something you need massive torque to run. Also, sewing machine motors do typically control speed with a simple variable resistor foot pedal, so they're meant to run at reduced voltages. Subbing the resistor pedal with a variac wouldn't really change the situation any.
 
Here's a link to a post on Practical Machinist about using a stepper motor as a 0-1200 RPM full-torque motor. Some resonance at some frequencies, but mechanically straightforward. Have not researched whether the 'steps' telegraph to machined surface imperfections...

Instead of the stepper motor a conventionally variable DC motor is likely a better approach. The resonance issues your correctly identify will not be present and the vibration, leading to inaccuracy in fine detail, will be avoided.
 
He's running a sewing machine motor. Its a universal series wound motor, honestly a vacuum cleaner would be a lot more powerful. I've seen the lathe he's using, its a cute little watchmaker's lathe. Not exactly something you need massive torque to run. Also, sewing machine motors do typically control speed with a simple variable resistor foot pedal, so they're meant to run at reduced voltages. Subbing the resistor pedal with a variac wouldn't really change the situation any.

Ok, but a sewing machine motor is not designed for continuous duty like a lathe motor so it has time to cool off.

A motor controller—notably not a light dimmer—for a small motor like this is not expensive. I've seen them for fifty dollars for low amperage. That is the right way to solve this problem. Not an autotransformer, not a light dimmer, but an actual motor speed controller.
 
One can correctly solve the problem and not worry about motor overheating, buzzing, or burnout, and learn something about how motor control works as well as why asking random people to regurgitate endlessly re-circulating misinformation about power control is a bad idea. Or one can incorrectly solve the problem using a bunch of misinformation which puts the motor at risk of failure and replacement, and creates more dogma and reinforces absolute nonsense.

The fact, and it is a fact, is that slicing and dicing the waveform using phase angle alteration better suited for incandescent dimming—not really well suited for that, either, for the reasons outlined—is always the wrong way to control motor speed.

The proper solution is (a) available and (b) inexpensive. Why not use it instead? The proper solution was explained as well as the mistaken assumptions about voltage control for motors.
 
PWMmotorcontrolcircuit.png
 
Ummmm, of what use is a PWM DC motor control in controlling an AC motor? I must have missed that class.

Beyond the wrong type of motor, that circuit contains a number of severe design issues and outright flaws which would cause it to fail safety certification.
 
Ummmm, of what use is a PWM DC motor control in controlling an AC motor? I must have missed that class.

Beyond the wrong type of motor, that circuit contains a number of severe design issues and outright flaws which would cause it to fail safety certification.


The fact you keep missing is it's a sewing machine motor. It will probably work on ac or dc, at least every one I ever had would.

That was the most simplistic schematic I could find for a pwm speed control. Why don't you find a better one instead of picking everybody else's suggestions apart?

The original speed control was a variable resistor, and has been for over 100 years on sewing machines, so obviously it works.
 
That was the most simplistic schematic I could find for a pwm speed control.

Simplistic is the core of the problem:
http://www.dictionary.com/browse/simplistic
simplistic
adjective
1. characterized by extreme simplism; oversimplified: a simplistic notion of good and bad.
Contrary to what some people believe, simplistic is not a fancy word for simple. Simplistic does not describe things that are easy to understand, deal with, or use. Those sorts of things are simply simple. However, if something is too simple—misleadingly so—then it is correctly called simplistic. An argument that glosses over or omits relevant facts and presents trite, hackneyed, slogan-like statements and sound bites is indeed simplistic.

This is exactly the case: omission of relevant facts and overly simplified explanation.

Why don't you find a better one instead of picking everybody else's suggestions apart?

Uh, no. This is not about everyone running off to search for schematics to be helpful. Wow, that's a misconception of how design analysis works.

A technical question was posed requiring a technical answer. The answers posted revealed a profound misunderstanding of how motor control worked. Designing a motor controller for an AC motor is a non-trivial task. I learned that a long, long time ago. The fact that the many reposters of schematics lack the training, knowledge, or expertise to understand why the simplistic—yes, simplistic—circuits and solutions are inadequate does not mean someone should build it and expect it to either work or be safe.

Simply performing random searches using Google for schematics without understanding what you're looking at is not solving the problem. It is perfectly reasonable to identify the problems, often serious, with the circuits suggested or provided. Most are endlessly recirculated and re-posted internet designs with severe flaws and no analysis. The suggestions made for phase control were similarly incorrect.

I wrote up an explanation about the basic issues involved and included enough material to allow anyone to properly evaluate the suitability for a commercial unit. I suggested the OP find a commercial unit, with UL or CE approval, not a bare-bones Chinese unit which omitted key safety features to save on costs or, worse yet, was deceptively marketed.

The original speed control was a variable resistor, and has been for over 100 years on sewing machines, so obviously it works.

That is a fallacious argument.

People routinely used toxic materials, including arsenic and heavy metals, for hundreds of years. Doesn't mean it "works". Mad as a hatter. Arsenic contamination of the southern agricultural fields to the point that rice is contaminated, and feeding arsenic to fowl leading to a recent ban on the practice. Doesn't mean it "works".

We have considerably evolved our engineering expertise in the past few decades, let alone the past hundred years. The old ways were often highly flawed.

If an AC motor is continuously run at a lower voltage without being designed for additional current it will be damaged. If an AC motor is run with phase control it will not properly function. Those are facts. Yes, some motors will tolerate that abuse being designed for it. This is why such motors become hot with use: excessive current. The circuit itself may become overheated and either self-destruct or cause a fire. This is why UL and other safety testing exists.

Many of the suggestions made were for phase control which is never appropriate for an AC motor, regardless of type.

My explanation was accurate, cogent, and complete. It allowed anyone with this problem to find a suitable motor controller instead of the unsuitable dimmer controller.

If you found an error in my analysis of why phase control is problematic, please post it.

It is better to explain why something doesn't work than rush to endlessly post schematics which are unsuitable without any explanation of how the circuit works, including its limitations and flaws. How is that helpful? How does it solve any problem?
 
I did this on a full size lathe (9” Hercus). Treadmill motor and PWM.

Works great, has plenty enough torque for the type of turning I do, however the biggest issue I have it cooling.

The sorts of scales and torque required for small turning a treadmill motor would be fine, however for a big lathe it does get hot and the fan is simply not enough to cool it properly.

I run my air compressor when I’m really doing jobs and blow cool air through the motor, but looking in to a water jacket setup with a cooling system (a la high end computers), to see if that removes the need to run the compressor.

Can share more info if you like.
 
Simplistic is the core of the problem:
http://www.dictionary.com/browse/simplistic
simplistic
adjective
1. characterized by extreme simplism; oversimplified: a simplistic notion of good and bad.
Contrary to what some people believe, simplistic is not a fancy word for simple. Simplistic does not describe things that are easy to understand, deal with, or use. Those sorts of things are simply simple. However, if something is too simple—misleadingly so—then it is correctly called simplistic. An argument that glosses over or omits relevant facts and presents trite, hackneyed, slogan-like statements and sound bites is indeed simplistic.

This is exactly the case: omission of relevant facts and overly simplified explanation.



Uh, no. This is not about everyone running off to search for schematics to be helpful. Wow, that's a misconception of how design analysis works.

A technical question was posed requiring a technical answer. The answers posted revealed a profound misunderstanding of how motor control worked. Designing a motor controller for an AC motor is a non-trivial task. I learned that a long, long time ago. The fact that the many reposters of schematics lack the training, knowledge, or expertise to understand why the simplistic—yes, simplistic—circuits and solutions are inadequate does not mean someone should build it and expect it to either work or be safe.

Simply performing random searches using Google for schematics without understanding what you're looking at is not solving the problem. It is perfectly reasonable to identify the problems, often serious, with the circuits suggested or provided. Most are endlessly recirculated and re-posted internet designs with severe flaws and no analysis. The suggestions made for phase control were similarly incorrect.

I wrote up an explanation about the basic issues involved and included enough material to allow anyone to properly evaluate the suitability for a commercial unit. I suggested the OP find a commercial unit, with UL or CE approval, not a bare-bones Chinese unit which omitted key safety features to save on costs or, worse yet, was deceptively marketed.



That is a fallacious argument.

People routinely used toxic materials, including arsenic and heavy metals, for hundreds of years. Doesn't mean it "works". Mad as a hatter. Arsenic contamination of the southern agricultural fields to the point that rice is contaminated, and feeding arsenic to fowl leading to a recent ban on the practice. Doesn't mean it "works".

We have considerably evolved our engineering expertise in the past few decades, let alone the past hundred years. The old ways were often highly flawed.

If an AC motor is continuously run at a lower voltage without being designed for additional current it will be damaged. If an AC motor is run with phase control it will not properly function. Those are facts. Yes, some motors will tolerate that abuse being designed for it. This is why such motors become hot with use: excessive current. The circuit itself may become overheated and either self-destruct or cause a fire. This is why UL and other safety testing exists.

Many of the suggestions made were for phase control which is never appropriate for an AC motor, regardless of type.

My explanation was accurate, cogent, and complete. It allowed anyone with this problem to find a suitable motor controller instead of the unsuitable dimmer controller.

If you found an error in my analysis of why phase control is problematic, please post it.

It is better to explain why something doesn't work than rush to endlessly post schematics which are unsuitable without any explanation of how the circuit works, including its limitations and flaws. How is that helpful? How does it solve any problem?

More condescension, and zero help. Any more of that and you will be the first to make my ignore list. How about picking an appropriate motor control like the ones you say can be had for $50?
 
I did this on a full size lathe (9” Hercus). Treadmill motor and PWM.

Works great, has plenty enough torque for the type of turning I do, however the biggest issue I have it cooling.

The sorts of scales and torque required for small turning a treadmill motor would be fine, however for a big lathe it does get hot and the fan is simply not enough to cool it properly.

I run my air compressor when I’m really doing jobs and blow cool air through the motor, but looking in to a water jacket setup with a cooling system (a la high end computers), to see if that removes the need to run the compressor.

Can share more info if you like.

On my small mill drill with the treadmill motor, I still have the step pulley arrangement. I rarely have to change I ratio, but it's there if I need it.

On my giant brown and sharpe horizontal mill, it has a 4 speed car transmission with a 3 phase motor controlled by a vfd.

Maybe you need more than 1 mechanical speed, or a bigger motor.

I've seen people build a duct to force the air from fans through motors before.

If you go the liquid cooling route, you could use a small fountain pump, and a heater core from a car.
 
It is highly appropriate for anyone to recommend products for motor control when (a) such products have not been extensively researched and tested, and (b) where direct experience and design review have been conducted.

Many of these overseas products are poorly designed, poorly assembled, contain fake components, and are labelled with fake safety certification. They are, in short, hazardous and dangerous.

Many of the units sold by catalog companies are sourced from a variety of overseas suppliers, and constantly change. Anything today recommended could change tomorrow when the order is fulfilled. Dissipating power as heat poses a risk of fire hazard.

This problem is rife throughout the industry. I elsewhere posted a teardown of a phone power supply, comparing an Apple power supply unit with the Chinese clone. The difference in engineering quality and safety was profound. Let me see if I can find it. Yeah, here are a few examples:
That should demonstrate the danger of simply suggesting any random product and expecting it to be suitable.

Compare the difference between a company which has a public face and which could be sued vs. the low-cost provider which will be operating under a different name by the end of the week.

Let me be blunt: Chinese suppliers lie, the designs and design practices are poor, the certifications fictitious, and the products are often dangerous and unsafe. Consumers rely upon false safety certifications or non-existent testing by catalog vendors and online stores. All of this adds up to fire hazards and dangers to personal safety.

Asking me to take on legal liability or the risk of harm to someone for suggesting an unknown product which can cause fire or personal injury is inappropriate. I will, however, point out the problems in using such products and the flaws in such circuits.
 
Wow, do you ever have anything helpful to add, or do you just go off on tangents, and talk down to people?

Anybody who has played with electronics knows about Chinese garbage and knockoffs. Even big name brands get suckered with crappy parts. What that has to do with this discussion, I dunno.
 
Wow, do you ever have anything helpful to add, or do you just go off on tangents, and talk down to people?

Why don't you post your analysis of the circuit, then. Explain why my conclusion it is unsafe is incorrect.

Explain why phase control is appropriate and why it won't cause overheating.

Anybody who has played with electronics knows about Chinese garbage and knockoffs. Even big name brands get suckered with crappy parts. What that has to do with this discussion, I dunno.

You wanted me to select a product. See:

How about picking an appropriate motor control like the ones you say can be had for $50?
 
Ok, you just made my ignore list. That's actually quite an accomplishment, because I've never put anybody, on any forum, on my ignore list.

I never said the motor wouldn't get hot, they do that at low speed.

I never said that circuit was safe, but thank you for pointing out it's unsafe. I'm not an electrical engineer, just a hobbyist trying to be helpful.

I didn't say recommend a piece of Chinese junk, I said an appropriate control.

Given the fact you've chosen to provide zero help, can't or won't recommend a solution, and continue to condescend, I will ignore you.
 
I never said that circuit was safe, but thank you for pointing out it's unsafe. I'm not an electrical engineer, just a hobbyist trying to be helpful.

How is it helpful to post circuits for which:
(a) one lacks a basic understanding
(b) one has not reviewed for safety or issued caveats
(c) a basic examination reveals safety issues
(d) are unsuitable for the intended application​

I've explained the basic issues for motor control and the two main types of AC power controllers, and anyone may determine the suitability of phase control vs. cycle control for a particular motor control application.

Your very comment that the motor becomes hot ought to be a concern. How hot does the motor controller become? Does it have overcurrent protection? Does it have UL and CE certification? Likely not.

Pulling random schematics off the internet and suggesting someone use them without analysis can result in a fire. This is not a best practice.
 
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