Brushless motor control circuit

[reubenT]

Need a circuit to go between the SS460S hall effect IC and MOSFET power transistors (IRF470)


Been searching and haven't found a detailed diagram yet, only incomplete diagrams.

Thanks.





PS; experimenting with different configurations of electro magnets and PM's, got a 13 phase one put together. I know, that takes some extra equipment, but I have it. I put into it a bit of aluminum foundry for a hub, machining of rotor, drilling stators with rotary table, etc.



OK; I found one (hope it's OK to post the link) **broken link removed**
But what I'm looking for is a simple on/off switching instead of polarity reversal.


So is this the book I need to find it? "Hall Effect Sensors, theory and application, by Edward Ramsden"


LOL! I keep editing, but I decided to order the book, looks like lots of good info on something I never dug into before.

 

[Mr RB]

On/off switching of coils won't produce the same power of polarity reversal on the coils, however if you don't need a lot of power and want to keep it simple you can operate the motor by on/off switching, sometimes called "wave drive".

What is the configuration of your "13 phase" motor? Are the coils in pairs (ie 26 coils)? If not then you take another hit to power as you can wire coils as a N S pole pair.

Please post some photos or diagrams of your motor so people can advise you on a simple driver for it.

 

[alec_t]

Have you considered the MAX17630 as an interface between the SS460S and the IRF470?

 

[reubenT]

Sometimes I wish I'd taken electronic engineering, would have been fun and easy for me 30 years ago. But anyway, alec, Is this what yer mentioning? http://www.datasheetcatalog.org/datasheet/maxim/MAX1763.pdf I can't quite see how that would do what I need done. (cause the ss460s to turn on the irf470) unless it would boost the output voltage from the hall IC and do it fast enough and clean enough. around 500 HZ pulse rate.


I have 24 coils, (12 pairs) and 13 PM's in the rotor, so each coil gets a pulse 13 times per rotor revolution, which would give me a pulse starting every 1/8 inch of rotor revolution at the coils, 156 per rev. the configuration I'm using supposedly produced around 1.5 HP per pole for someone, but I can't get all the minute details on it, just general info, so I'm trying to work out the details myself. The basic idea is to make use of the natural pull of magnet to steel (the steel being the core of a solenoid) and then a pulse in the coil causes demagnetization or opposing magnetization of the steel so the magnet will leave it, or be pushed away depending on strength of pulse, and be pulled to the next core. Simple idea, just a slight variation on the conventional brushless motor. Figured I'd try building one and see what it will do, I can adjust pulse width and timing while watching the wave on a scope. Once it's running I'll make a prony brake and test torque, along with current will give me HP, and see what kind of efficiency it will run at.

 

[Mr RB]

Any photos?

 

[alec_t]

But anyway, alec, Is this what yer mentioning?

Oops. Typo. Sorry. I meant the MAX17603
**broken link removed**

 

[shortbus=]

Oops. Typo. Sorry. I meant the MAX17603
**broken link removed**

That driver is meant for a Pmos high side and a Nmos low side switch. He wants to use all Nmos.

 

[shortbus=]

@reubenT, I'd like to see photo's, a schematic or link to this motor also. Having a hard time visualizing how it can work. BLDC motors have 720° electrical rotation for 360° shaft rotation. How are the permanent magnet poles arranged on the rotor? In a BLDC they are oriented alternating, thus needing to have an uneven number of magnets on the rotor.

Please share any other information on this new type of motor.

 

[alec_t]

That driver is meant for a Pmos high side and a Nmos low side switch. He wants to use all Nmos

Agreed. I was thinking just use the Nmos driver bit. It's a dual driver, so 6 ICs would do the job for 12 pairs of coils? Do you know of a better IC?

 

[shortbus=]

Alec, for low side I've had good luck with UCC27423, https://www.electro-tech-online.com/custompdfs/2012/08/ucc27423.pdf. These have two drivers per IC also.

 

[reubenT]

Thanks, that one looks like it would work. I need to see if it's going to run for me, and how well it runs, before it's worth sharing it. this one is a bit different in that it's not pole reversal, all poles the same orientation driven with single polarity pulsed DC. Supposedly the voltage produced by the magnets passing the coil is the same polarity as the pulse applied to make it run, which reduces current draw. I've gotta prove it for myself.

It's fun to play with such things anyway, I started making crude DC brush motors when I was around 13. Going back to making motors again over 30 years later.

 

[shortbus=]

Me too, But I've set my sites on making a "switched reluctance motor". No magnets at all, and no windings on the rotor. The thing I can't find yet is how to size the wire to match the current. No books or web information so far tells that. The regular wire amp charts don't apply to transformer or motor winding.

 

[alec_t]

Supposedly the voltage produced by the magnets passing the coil is the same polarity as the pulse applied to make it run

Isn't the induced polarity as the magnet approaches the coil the opposite of when it moves away from the coil?

I started making crude DC brush motors when I was around 13

Coincidence. So did I (well actually it was only one motor, built from a kit advertised in a boy's comic).

 

[reubenT]

yah, got started from reading library books on motors, my first motors were made of wood and nails, wire from whatever junk I could find, (unwinding old TV deflection coils was common) a piece of copper tubing split and fastened on the shaft made a nice commutator. and a couple heavy copper wires for brushes. Sometimes a PM stator and sometimes a wound stator. Fun learning days back then.

Anyway, the switched reluctance motor is similar to what I'm doing except I have powerful PM's in the rotor. N52 neo. The generated wave looks like a nice clean AC sine wave on the scope, middle of the second half of the wave is where the pulse is applied. With the pulse being the same polarity as the generated voltage at that point. I built one last winter using grade 8 ceramic magnets, it ran fine with a couple stator coils on it, but I didn't have the rotary table yet and I could see my hand hole drilling was off too much to get the timing accuracy good. so I didn't finish it. I set up that one and this one as well, with opto interrupters and a blocking disc, but "light pollution" is causing errant effects, I will try to put a cover on them. But the hall effect control looks like a better option.

 

[alec_t]

The generated wave looks like a nice clean AC sine wave on the scope, middle of the second half of the wave is where the pulse is applied. With the pulse being the same polarity as the generated voltage at that point.

Understood.
What are you using as the core material for your coils?

 

[shortbus=]

Have you seen these? https://www.electro-tech-online.com/custompdfs/2012/08/OPB370T51.pdf They are infrared, this should help with the light polution problem.

 

[reubenT]

Thanks, another option. I will try several. The cores are mild steel, just some 3/8" galvanized brace rod from a chain link fence we disassembled last year. I fastened some little steel washers on the ends to make coil forms.

 

[Mr RB]

Ouch. You have mild steel coil cores, and you plan on NOT providing them with AC but instead just pulsing DC to the coils?

 

[shortbus=]

Are your poles wound/configured as 'salient poles'? How about the magnets? Is this an in runner or out runner style motor? Is it self starting? Is there a name for this type of motor? Sorry for all the questions but this stuff fascinates me. Took me a while researching before I settled on the SRM style.

 

[reubenT]

the hall effect book came, just what I needed, but a lot more than I needed too.

Yah, solid cores and pulsed DC, what's the normal problem with that? eddy currents? Just wondering what I should look for. I do have an oscilloscope to watch what the voltage does, and eddy currents would just heat the cores and limit the speed. (I did a lot of primitive motor stuff when young but then jumped on into radio electronics and never got into more advanced motor technology)

I think it would be called salient poles, except it's not the usual way of doing it. I have taken the basic idea that I came across, and thought up my own configuration of applying it that seemed most practical to build. The coils are just like solenoid coils with steel cores, the PM's are about twice the dia of the coil cores, with maximum magnet size of 3/4" dia. in order to keep the drive pulse short. That was the basic guideline. I used 13, 1/2" dia x 1" long PM's in a 1" thick nonconductive flat rotor disc, matched by two sets of 12 solenoid coils with 3/8" cores inserted in nonconductive stator discs. (anything conductive in the mounting substance would make eddy current drag) One method used by someone else was a drum type rotor and the solenoid coils mounted on a housing for the stator, but that requires the PM's to be cemented in very securely to prevent them from flying out at high speed, something I wanted to avoid. I've been told that using conventional motor design criteria this would appear to be a very inefficient motor, but actual practice proves it's performance to be in the other extreme. (apparently something going on that conventional motor design criteria does not take into account) For me it's still in the "I don't know for sure" realm.

it's very self starting, with that small not so perfect one I made last winter it self started when I got 2 poles installed. With 13 rotor poles reacting against the 12 stator poles with 1/8" per pole separation. it should start itself very strongly, like a normal DC brush motor. lot of magnetic forces going on in there, and applying the timed pulse unbalances it. But when accurately built the rotor will spin freely as if there's nothing there when no power is applied. (my current one is almost that good, just barely noticeable cogging due to slight inaccuracy in coil mounting) If it were made with the same number of poles on both sides the cogging would be so powerful you would not be able to turn the motor shaft with anything short of a long handled wrench. Just holding them I can feel how strongly one of those magnets tries to line up with a steel rod, 26 of those all at the same time would take a whole lot of force to move them. Fully unbalancing the force, I should have a very strong motor. We'll see when i find some more time to play with it.

Right now I'm preparing to go fetch a cousin and his camper he just bought, from Columbus Ohio, his job is ending the end of next week. As of now it looks like we'll be driving our car up there, working for a couple days up there, swapping the work for a '98 ford explorer, and using that to pull the camper back. (a slight bit cheaper than driving my old truck both ways, plus we end up with another vehicle to keep or sell) Along with it we've decided to run up to Michigan and pick up an old milling machine (or 2 perhaps) that are in need of some repair and a salvage company is trying to sell for not a whole lot. But I gotta put a hitch on the car, build a trailer to haul lumber up, (and the machines back) pull some cedar trees outa the woods and saw the lumber, plus make enough extra cash (sell some trees) to buy the machines.