How to use a sensorless brushless motor

[solarbbq2003]

i've got sensorless controllers 24v, 36v and 48v, they work with tongxin motor, not same brand as tongxin use, tongxin ones are not reliable

 

[RB Cats]

I would contact powerbikes.com. They are the distributors of Prima in the U.S. I talked to a very knowledgeable tech there about their Joe Fly bike. I think you may be able to get a controller for this ABB motor from them.

Good Luck

RB Cats

 

[rkosiorek]

Assuming the stator has slots. If so then sure (if not then use a dremel). Go to digikey and order some hall sensors and use some cat-5 network wire for the 5 leads. Heck upgrade the entire harness and you now have a brusless hub motor with hall sensors ready to go! These are the sensors I use btw http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=480-1999-ND

i did not mean the pockets that some motors like the Crystalyte have that the sensors can tuck into. what i meant was the slots in the stator that the windings tuck into. on many motors the hall sensors are just glued beside the stator. they are still close enough to sense the rotor magnets. the slots that the wire windings fill has the highest concentration of magnetic flux. the magnetic field forms in the slot and not in the chunk of metal called the stator. the stator is just used to conduct one end of the magnetic field from a slot that has "S" polarity to another that has a "N" polarity.

the SS40A sensor you selected from Digikey is very common popular to use as a replacement in motor repairs.

rick

 

[rkosiorek]

They don't truely freewheel, the motor spins. With a geared motor the motor is not always spinning. :wink:

a freewheel is a mechanical device that allows something like a sprocket to spin freely in one direction and lock onto the shaft in the other direction. a geared hub motor uses one so that when the motor is running it drives the tire and propels the bike. when the motor is stopped the tire can continue to turn freely in the forward direction. that way the motor will not act as a brake to slow down or stop the bike as the throttle is decreased.

rick

 

[rkosiorek]

Thanks Rick,

That was what I tried to do. Add the sensors somewhere. But I can't open the motor without unlacing the rim.
So it would be my last move.
Can't you do the same thing external to the motor? find the correct orientation and add magnets to replace the stator and hall effect sensors.

I can't find any info on the motor. It is made in Italy by ABB servomotor. Nicely made but difficult to use.

not easily. external to the case you would not be able to sense the magnets accurately, if at all. on large industrial motors what they often do is attach an optical encoder to the output shaft that simulates the position of the magnets. to do this you would still have to open up the motor to find out how may magnets you have around the rotor. then cut some slotted wheels to duplicate the way the magnets pass over the individual winding phases. as long as you have the motor open you may as well mount the hall sensors internally.

takes up less space that way as well.

rick

 

[fechter]

The pedal first controllers like the Crystalyte versions require that the magnets be moving in order to start up. Most of the senorless controllers used on R/C aircraft can self-start from a dead stop.

Something like Castle Creations 110HV might work in this application (with a servo tester interface). http://www.offshoreelectrics.com/proddetail.php?prod=cas-hv110&cat=15

For the price of one of these controllers, you could almost get a new motor with sensors.

 

[rkosiorek]

if you want to add an external adapter to convert from sensorless to sensored you would first need a low voltage supply source 15V or so, that is derived from the battery. you could possibly find a source for this inside the controller. 3 comparitor circuits 4 nearly identical resistor dividers. one to split the battery voltage in half and 3 to split each of the phase voltages in half. a comparison of each phase voltage would be made to half of the battery voltage. when that happens it would be time to either tun on or turn off the output of a simulated hall signal. 3 opto-isolators with open collector outputs to interface the comparator outputs to the controller inputs.

now we would have a system that if the motor was already spinning a couple of rpm if we added some throttle the motor would start up. you would probable have to be moving 2 or 3 MPH (5Kph) before you could engage the motor. but since in your case the electric motor is mechanically isolated from being turned externally, that won't work for you.

you need it to start as soon as you activate the throttle, you would need to add a circuit that would read the throttle position so it could tell when the throttle was activated and then run through some form of start up sequence. most likely some kind of simple micro circuit here. some programming, debugging, swearing when an error is made and because the wrong sequence was used and the output fets of the controller were fried. more swearing,,, etc.

it isn't worth the effort to design or even discuss at this point. the same effort would be involved in designing an entirely new controller

your simplest solution would be to get the controller intended for this motor or a someone else offered a substitute from Tongxin. next in line would be to get a refund and buy a new motor and controller that would work.

if you can't or won't do either of those than you are stuck with taking the thing apart identifying the phases and adding the hall sensors internally.

rick

 

[gmouchawar]

Thanks Rick,

You are very knowledgable at this. I will leave opening the motor as my last chance because I would need to delace the rim.
What about adding rare earth powerful magnets on the case and sensing them with the hall sensors.
It is just a matter of finding where to place them and how many. I am assuming you need 3, 120degree apart!!! but they also have to aligned with something.
In any case, I have a new lead on a sensorless controller. I will post the results on that if it pans out.
Any other ideas are still appreciated. I don't have anything solid yet.

 

[gmouchawar]

Rick,

What your proposed with the comparitors and opto isolators looks very doable. I drafted a schematic based on what you wrote..
If I settle for being moving before applying the throtle, would it work?
What refernce would be tied to the opto output? Wouldn't that still be the same gnd which I assume to be the bat negative?
Or would the controller have an internal reference for that signal?
On the comparitors does the phase signal go the + or -?
I know a co-worker who is good with programming PICs. but I agree if it needs to go beyond what you described in the 1st paragraph it wouldn't be worth it.
Thanks again for your insight. This has been intelectually stimulating regardless of the outcome.

 

[rkosiorek]

Thanks Rick,

You are very knowledgable at this. I will leave opening the motor as my last chance because I would need to delace the rim.
What about adding rare earth powerful magnets on the case and sensing them with the hall sensors.
It is just a matter of finding where to place them and how many. I am assuming you need 3, 120degree apart!!! but they also have to aligned with something.
In any case, I have a new lead on a sensorless controller. I will post the results on that if it pans out.
Any other ideas are still appreciated. I don't have anything solid yet.

you would need as many magnets as there are on the rotor assembly. if it has 36 you need 36. they have to be arranged so that their position duplicates the position of the internal magnets as closely as is possible. then you need 3 hall sensors. their position would have to duplicate the position of the start and stop of the 3 wiring phases of the stator. the relationship of both must remain fixed and must not wander as the magnets rotate past the sensors.

now if you are able to see how many magnets there are inside the case without opening up the case, position a set of external magnets to duplicate those positions as well as locate 3 hall sensors to indicate the start of 3 individual phase windings inside the motor, again without opening it up you either have access to some truly amazing xray imaging hardware or you posses a clairvoyance worthy of a comic book super hero. talents way beyond that of Uri Gellar for sure.

now personally i am hopping you have access to the imaging equipment. i have some potted circuit boards that i would really like to see the guts of....

rick

sorry but since you keep bringing it up i am having a little fun at your expense. but what you are asking to do is not trivial.

 

[rkosiorek]

Rick,

What your proposed with the comparitors and opto isolators looks very doable. I drafted a schematic based on what you wrote..
If I settle for being moving before applying the throtle, would it work?
What refernce would be tied to the opto output? Wouldn't that still be the same gnd which I assume to be the bat negative?
Or would the controller have an internal reference for that signal?
On the comparitors does the phase signal go the + or -?
I know a co-worker who is good with programming PICs. but I agree if it needs to go beyond what you described in the 1st paragraph it wouldn't be worth it.
Thanks again for your insight. This has been intelectually stimulating regardless of the outcome.

first question - is this a geared motor?

rick

 

[gmouchawar]

I don't think it is.

 

[tno]

this motor has 4 wires coming out of it
Is it a 4 phase motor??

can you run a 4 phase motor with a 3phase controller?

 

[rkosiorek]

without measuring the coil winding resistance i could not say for sure. but i would bet that this is a STAR wound 3 phase motor and the 4th wire is connected to the center of the star. some sensorless controllers use this center as a reference to set the zero crossing point of the voltage in the phase wires.

this wire could also be a grounding wire going to the case and could be safely ignored by the controller.

again you either need more information like a technical manual for the motor. OR you need to open the case and see.

rick