New guy intro (PM motor concept)

Hello everyone,

My screen name here is williamj but in the physical world everyone just calls me Bill. I am a retired (medical disability really, (bum ticker)) industrial electrician / mechanic. I covered most everything in my job, from fuses and fuse holders to gears and gear cases, to hydraulics, pneumatics, welding and buildings and grounds, I did it all, and boy did my back hurt! As far as the electrician part goes I am most comfortable with motor controls, 3f AC, utilizing relay logic (old tech). I know very little about solid-state and even less about integrated circuitry.

I believe I have the expertise, experience and tools necessary to tackle specific projects. What I lack is space, I have no garage, attic, basement or outbuilding to set up any kind of workshop what so ever. And in this day and age, it’s a sad commentary that, if you leave something alone for very long it will inevitably “grow legs and walk away”. However…

Health and logistics not withstanding, I continuously conjure up “wanna do” projects just to keep my mind from turning to mush. Hence my coming to your fair community for assistance.

Since my joining you community, I have spent the last few days perusing past and present posts related to (what I believe is related) my project. Speaking of which, my current project (conceptual at present) proposes a coil controlled permanent magnet DC motor.

Permanent magnets are adhered to a disk that is keyed to a shaft (shaft and disk are free to rotate). On both sides of the magnet disk are fixed coil plates. The coil plates are made up of “coil sets” (Two coils per set, one coil on one plate and one coil, directly opposite, on the other plate. The coils are actually electromagnets, it’s just easier to type ‘coil’ than it is to type ‘electromagnet’.) The coils are wired so that the magnetic flux, induced by each coil, is opposing (North to South and/or South to North).

As a magnet rotates and passes through the paired coils of the coil set an attract/repulse magnetic flux influence is placed on the permanent magnet. As the magnet approaches the coil set, the coil voltage polarity is such that the magnetic flux is opposite to that of the magnet thus inducing an attractive influence on the permanent magnet. As the magnet passes by the coil set the coil voltage polarity is reversed thus inducing a repulsive influence on the permanent magnet. And the sequence continues as long as there is current flow through the coils. Each coil set is controlled by it's own cintrol circuit.

The difficulty I am having is trying to figure out the control circuit itself. The circuit requires one input and two outputs. The input would be from an optic sensor that is triggered by a light source passing through the magnet disk at predetermined points.

The optic sensor in turn triggers a flip-flop circuit that controls a pair of latching circuits. Each latching circuit in turn controls a single output (one of two). Each output controls a pair of SCRs that control current flow to the coil set. In one pair of SCRs the voltage polarity would be Positive – Negative and in the other pair of SCRs the voltage polarity would be Negative – Positive. The two pairs of SCRs thus control magnetic flux polarity.

The sequence of events would be something like this:

Optic sensor de-activated - coil set pulls magnet towards itself
Optic sensor activated - coil set de-energized, polarity reversed
Optic sensor de-activated - coil set pushes magnet away from itself

This is just a general idea of how the control would sequence. As everything is dependent on the size of the permanent magnets used, no specific component requirements are needed at this point in time.

I am currently trying to upload drawings and diagrams (please forgive if symbols and wiring is incorrect) to a temporary website to try and clarify what it is that I have in mind. Once I get it figured out, (grumble grumble, moan moan, bitch bitch) I will post the URL. I think in pictures, trying to describe what I see in my mind to someone else is a daunting task indeed (hopefully this will help). Although the attempt is there, communication has never been one of my strong points.

As I do not know which components would be required or how they would be connected I am asking for assistance. If someone could sketch up a simple diagram (in general, so I could get to know, understand and follow current flow in the control circuit) I would be extremely grateful.

After reading all the posts (those that I have actually read, not ‘all’) it is readily apparent that the level of expertise here is, to say the least, extremely high. In return for your valuable assistance I would offer what knowledge and expertise that I have, you have but to ask.

thank you in advance,
williamj


factoid:

when it hits the fan it is NEVER evenly distributed.

Hi Bill,
Welcome to AAC!

A couple of comments about your project plans...
SCRs and TRIACS work best with AC. Once they are triggered, they continue to conduct (are turned ON) until the current flow through them drops to nearly zero. With 60Hz AC, this happens 120 times per second, so getting them to turn off is no big deal.

However, if you are working with a DC motor, you will either need to use just 1/2 of a rectified AC power with no filtering (so that the SCR will turn off) or else you will need to use a different type of semiconductor.

Some examples are simple transistors, Darlington transistors (which are pairs wired to multiply gain) and power MOSFETs.

Transistors are basically current controlled devices; you put in a small current into the base, and get a much larger current flow into the collector.

MOSFETs are voltage controlled devices. A voltage level on the gate (normally specified as Vgs, or voltage on the gate terminal relative to the voltage on the source terminal) controls the flow of current from the drain to the source. There is no direct connection between the gate and either the drain nor source.

If you wish to reverse the flow of current through an electromagnetic coil, one option is to use an H-bridge. Searching Google for that term will give you lots of hits. There are ICs that you can purchase which contain all of the circuitry needed for an H-bridge, like the L298.

An easier option would be to use a coil that had a center tap, to which V+ was applied. That way, grounding one end of the coil will give a magnetic field of one polarity, grounding the other end of the coil will reverse the polarity.

Hi Bill. I myself have been Millwrighting for approx. 30 years, am currently a 4th year Electrician, and have played with solid state concepts for about 20 years. I too love motors and thier control.

What you have described can be found almost exactly on a foppy disk drive. Rip one apart, google the driver device and you'll have first hand a working motor.

Cheers.

SgtWookie

Thanks for your welcome and suggestions. The components mentioned in my original post were mearly a from of description, not necessarily what I think would or should work. EVERYTHING is up for grabs. I would just like to keeps thing as simple as possible. I am a firm believer in the 'KISS' method of doing things.

The motor will inded be DC, no AC need apply, so all components will need to be DC compatable (sp?).

I have heard of Darlington transistors and MOSFETS. I beleive Darlington transistors are two transistors connected so that the first transistor feeds directly into the collector of the second transistor. As for MOSFETS... all I can remember is that they have something to do with some sort of "field effect", not sure what or how though.

As for keeping it simple... basic is really all that is desired at this point in time. This is a "Concept" motor, I would just like to see if it would "go" before making anything the best that it could possibly be. Right now, just plug it into DC and see if it goes or explodes.

thanks again

williamj


factoid

Never meddle in the affairs of dragons, for thou art crunchy and most flavorful with ketchup.

Hi GetDeviceInfo (GDI for short if you don't mind. )

Thanks for your response.

What ever happened to the "Good O'l Days"? Where all you had to do was follow a wire till you found where it was messed up or open a cabinet and look for something burnt? I sure miss em! LOL

Rippin' somethin' apart?!?!! NOW!!! yer talkin' mah language!!!

Understanding what I'm looking at is something else entirely. If you could just point me in the direction of some pretty pictures I may be able to begin to get a handle on some of this.

Speaking of which... I just uploaded a few drawings and diagrams to a temporary website. Hopefully seeing these may clear some points that I was able to fog over.

www.williamjbivens.com

thanks again

willianj


factoid

no factoids today, maybe tomorrow, maybe not.

Welcome aboard Bill.

Just curious, ever take a modern computer fan apart? It vaugly resembles what you describe, but simplier.

You'll find we have a Albums section here at AAC, which is very useful for that kind of stuff, including pictures.

Here is a good tutorial on the type motor you are talking about. Brushless DC. In reality, is similar to a synchronous motor except that the field windings are controlled by a fancy controller rather than just the incoming 3 phase line and the rotor has permanent magnets instead of excited coils.
ww1.microchip.com/downloads/en/AppNotes/00885a.pdf

Bill (Marsden)

Thanks for the info. Sorry to take so long in responding but I've been searching and reading and searching and reading and searching and read- well, you get the idea. Sometimes my head gets to spinning so fast grey matter starts to ooze from the centripetal force.

williamj


factoid;

Experience shows that... If oportunity knocks, it's usually for someone else.

BillB (3857)

Thanks for the info. You're right, they really are quite similar in operation to what I'm thinking. I've printed and saved the PDF and will look at it quite closely after the ooze (see earlier post) stops.

williamj


factoid:

As seen on TV... Marriage really is the leading cause of divorce.

Hi Bill, pull apart some old VCR's the capstan motor is usually the type you mention; flat coil stator and perm magnet rotor.

They are another popular type of brushless DC motor (pancake motor) and since you can get old VCRs free anywhere these days it might be worth picking up a couple of motors for experimenting. They make good little low-rpm generators too!

The RB

Thanks for the suggestions, I have such a pile of parts on the floor next to me. The one thing that is irrefutable is that looking at solid state cicuit boards just makes the ooze flow faster. I can replace individual components (if pointed out to me or totally scortched) but tracing current flow is another matter.

I am rapidly loosing ooze by the fluid once, but that's a good thing. Ooze shows that the grey matter cells gave their all for the cause. They didn't just decompose sitting in the dark.

williamj


factoid:

No foactoid today, maybe tomorrow, maybr not.

Okay everybody, they say A little knowledge is a dangeous thing.". Well her's where I get down right suicidal.

After reading and searching and reading and searching this is what I finally came up with. I know that it is probably way off base but I'm just considering this as a starting point.

The cirsuit is just a portion of the final and complete cirduit. This portion is just supposed to take care of reversing magnetic flux polarity by reversing current flow through the coils.

How close did I come?



Thanks for your time and efforts.

williamj


factoid:

If you wake up breathing, that's generally a good sign.

Saw some really stupid omissions when I checked right after posting.

Mucho sorrys and "mia copas"

Did some corrections, hope this circuit is better.

williamj

test Circuit 03

Saw that the coils are wired incorrectly. Wish I knew what I was doing.

williamj

Simple10

Thanks for responding to my post.

I am an aficionado of all things containing bells and whistles (gadget freak, I understand that they have a cure for it now, but I'm not buying. <grin>). And I appreciate the aversion to anything labeled “perpetual motion”. I don’t subscribe to the “something for nothing” theories myself but I do applaud all serious attempts. Man cannot fly, man cannot set foot on the moon, both were the "perpetual motion machines" of their time. More than once, I was actually able to see the shear genius behind an individuals thinking in the presentation of his concept, and to this day it still blows me away when I see it.

This particular DC motor concept had its origins in “perpetual motion” thinking. One day/night (I can’t remember when, this was YEARS back), I came across one individual’s concept of a “perpetual motion” motor. His concept included the notion of an even number of magnets on one rotating disc and an odd number of magnets on a fixed disc. That idea stuck in the nooks and crannies of my mind until recently, when, one guy named Craig (can’t remember his last name) posted his idea of a “hub motor” utilizing photo optics for control.

That’s when it all came together, even number of magnets on rotating disc, odd number of electromagnets on fixed discs sequenced by photo optic control.

And “abracadabra” here I am. <big grin>


Williamj


Factoid:

Walter, speaking out on marriage;

Remember in the wedding ceremony where the bride says ‘Till death do us part’? Well, it’s not until sometime after that you begin to realize that she was actually setting a goal.”

Okay everyone

I think I'm getting a lot closer now.

The drawing below is only to show current flow and switching functionality. The individual componets used here are not neccessarily the ones to be used for a working motor. Component sizing is dependent on coil set load which is, in return, dependent on permanent magnet size and strength. All of which will be determined at a later date.

After beating my brains out through my ears I gave up on the flip-flop and latching circuit afforded by the 555. Instead Im focussing on the H-Bridge as suggested by SgtWookie (thank you).

With the H-Bridge I can use discrete components. I know it's not the best or the easiest way to do this. But by doing it this way, I think, I'm gonna be able to wrap my brain around it and atleast begin to understand the circuitry.

The drawing below can be divided into three distinct circuits, the "power circuit" (on/off), the "switching circuit", and the "H-Bridge circuit".

In the "power circuit" if optical Diode 2 is de-energized then the gate for Transistor 7 pnp (t7) is low and current is allowed to flow to the "H-Bridge circuit". When Optical Diode 2 is energized then the gate for t7 is high and current does not flow to the "H-Bridge circuit".

In the "switching circuit", if optical diode 1 is de-energized then the gates to transistor 5 pnp (t5) and transistor 6 npn (t6) are low and current is allowed to flow through t5 and not t6 setting the H-Bridge gates low. If optical diode 1 is energized then the gates to transistor 5 pnp (t5) and transistor 6 npn (t6) are high and current is allowed to flow through t6 and not t5 setting the H-Bridge gates high.

In the H-Bridge circuit transistors 1 through 4 (t1, t2, t3, t4) are arranged so that when all gates are set low current flows through t4 through coil set A2 to A1 and trough t1 setting magnetic polarity in one direction. And when all gates are set high current flows through t3 through coil set A1 to A2 and trough t2 setting magnetic polarity in the opposite direction.

What I need to work on now is the voltage drop and current limiter circuit. It is anticipated that motor voltages will be in the 12 to 48 volt range.(This particular motor when completed is intended for motorizing a bicycle.)

Not only are comments and corrections welcome, they are very much needed.

thank you all again

williamj

factoid:

I'm way to tired for factoids today, maybe tommorow, maybe not.

Say, Bill -
When you embed images that large in a post, people have to scroll back and fourth to read the text you included. Makes it pretty awkward.

Also, you're using the transistors as common collector on one side of the bridge, and common emitter on the other. While this seems convenient, in actual practice it won't work very well.

SgtWookie

First of all my apologies. When doing these drawings I'm working in a cad program, and in order to save the file as a jpeg I need to copy and paste into an imagining program. What I forget sometimes is, that the scale I'm veiwing the drawing in at the time I copy and paste determines the size of the jpeg image. Can't make any definative promises but I'll definitely try and keep the image size down.

It took me a little while to figure out what you were refering to when you pointed out to me about the common emitters and collectors. Thank you. Sometimes you look at these things so much you just don't see thing that are right in front of you. I believe I found the error and made the appropriate changes.



I think at this point in time I need to get busy and try my hand at coil making. With out the neccessary paramiters the circuit design can't go any further.

step 1
figure out parts and materials needed

step 2
order same

step 3
give it a turn or two or three or four hundred or so

Any suggestions???

williamj

factoid:

I spent most of my money on beer and pizza. The rest I just wasted.

Project has been put on hold for the time being. Wifey has decided to to do a major increase on the honeydoo listing and insistes it be done before Xmas. Major work ahead but will be back.

williamj