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Jun 20, 2005, 12:52 AM
Registered User
Found it... its half-wave and I wasn't looking at those before.

There are a couple places that list it but they are the kind of places that you request a quote, you might beable to get some samples from sanyo, but I can't find a request thing on their site like others have.

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Jun 20, 2005, 04:05 AM
Registered User
I have found a couple of the part numbers of the Ics from Sanyo, LB1667 and LB1674, these are intended for driving minidisc motors etc and start from 1.5v. Obviously some sort of O/P stage would be needed, but they can be simply voltage controlled.
Jun 20, 2005, 06:04 PM
We want... Information!
Bruce Abbott's Avatar
Originally Posted by Joel
I was wondering why you didn't just use 6 N-channel MOSFETs instead of Ns driving Ps?
To use high-side N-Channel FETs efficiently you would have to boost the pre-driver's power supply to at least 6V higher than the supply voltage.

Also what hall sensors do I need? I'm guessing bipolar analog? 4pins?
CDROM motors have the the 4 pin analog (differential output) sensors built-in. To use single-ended Hall sensors, you would have to bias the other input to match the sensor's quiescent output level (perhaps with a trimpot connected across the sensor's power supply pins).

if I'm not using any of the power, will the high voltage jump from the source to the gate? Is that what the Vgs is? How would I get around this?
Vgs is the maximum allowable voltage from Gate to Source. If the FET drivers are off then it should be zero. On-state Gate voltage is determined by the drivers. Usually the low-side is safe, as it will be less than the pre-driver's Vcc (regulated if necessary).

To protect the high-side FETs you could add some resistance in series with the Gate, and back-to-back zener diodes (or a transient suppressor diode) from Gate to Source.
Jul 03, 2005, 10:27 PM
Can't cut a straight line

first week in rc planes nd I''m already playing with cdrom - uggghhh

Originally Posted by Bruce Abbott
It is possible to use a non pre-driver IC with external FETs. Connect a resistor from each motor phase to the supply, and another to ground. Then you can detect three voltage levels using two comparators, one per output FET. This requires 6 comparators and lots of resistors, so is probably more complex than using a pre-driver IC.

I chose the NJM2624 pre-driver for it's simplicity, availability and low cost (just $0.90 each at Mouser Electronics). One thing to watch with this chip is that although it can work down to 4.5V, its outputs can only go up to 1.5V below the supply voltage. Therefore at least a 6V supply may be needed to drive logic-level MOSFETs.

My circuit makes a stock CDROM motor act like a brushed DC motor, which can then be driven by a normal brushed ESC. The breadboard prototype worked very well, so I am now working on a surface mount version. The output switches will be SI4542DY dual N&P MOSFETs, for a total of only 24 parts on the PCB.
I'm trying this out, built the circuit up on a breadboard with huge mosfets

I just finished figuring out the pinout of the cdrom motor I'm going to use, came out of a busted acer cd-rw drive. Wish me luck soldering little wires onto the edge card connector -- haha.

If I can get it to work with stock windings then I'll rewind it with some of that thicker magnet wire I have laying around, and see what 18 turns does to it

This is my first week on egroups and look at what I am doing -- next I'll be building planes out of blucore to put the motor in
Jul 04, 2005, 06:49 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Guys, read this thread, all the information is there, no use to have to separate threads:
Jul 04, 2005, 11:58 PM
Registered User
Well I didn't read all 74 pages of the other thread but I didn't find any sensored IC info, its all microcontroller based sensorless stuff. Maybe we could change the title of this thread to "Sensored Brushless Controllers" or something.

Jul 05, 2005, 08:29 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Tell me when you figured out how to change the title, I have never been able too.

Jul 10, 2005, 04:56 AM
Raj Mulay
I'm new to rc.
I just now become Membar of RC group.
I have purchased this ESC Controller PHOENIX-25 [25Amps Sensor less speed controller]
And the brush less motor [Hi Max-2025-2743 With GB] From Singapore Hobby Supplies Pte Ltd, Singapore.
I Don’t have the Radio receiver.
Can anyone give me an alternative circuit which has Potentiometer to control the speed of Motor,so that I can bench test this motor,where I can connect this wire,orange,red,brown with the connector.
I am sending you one link of mr. Jertjan Kool,there you will find one unit labeled Tester.

Raj Mulay.
Jul 10, 2005, 07:23 AM
We want... Information!
Bruce Abbott's Avatar
Jul 14, 2005, 05:24 PM
Can't cut a straight line
wow, I have had a cd-rom motor working like gang busters with that njm2624 circuit, that was great work Bruce! I just rewound the cd rom motor with 14 turns of #26 magnet wire. it was a tight fit on those last few turns... lets see what happend next to my motor )))
Jul 16, 2005, 08:08 PM
Can't cut a straight line
I want to thank all of you for the hours and hours of fun I have had playing with cdrom motors -- this has been very enjoyable.

14 turns was nice, the prop sounded like it was running on a 400 motor, and drawing only 4 amps, from these old cellphone nimi batteries I salavged (sayno f6m rectangular cells) lol. I just couldnt keep the prop on the motor, the drive shaft kept pulling out of the motor, and flying away -- haha, I guess I need to go throguh the rest of these old cdrom drives, and only keep the motors that have the drive shaft locked down with a clip on the other end

I am way too clumsy to do this up in SMT -- so I could actually fly with it. so I'm going to have to bite the bullet and get a castle creations 10 on ebay.
Sep 05, 2005, 07:01 PM
Gordon Couger

Optical Motor Contolers

Originally Posted by jeffs555
When you use hall sensors to control a motor, you are just replacing the mechanical commutation on a brushed motor with more efficient electronic commutation, so changing the voltage to the motor will change the speed just like on a brushed motor. Here is a page that tells what you should need to design a sensored controller.
Hi Jeff,
I am new to RC but not to motor control and I am working on a project where efficiency at less than full power is the most important criteria. I hope I am not out of like reviving an old thread.

Has anyone tried or considered optically sensing the potion and speed of the motor on motors use on RC air craft and calibrating that instead of Hall effect sensors or unscrambling back EMF wave forms both which in addition to their obvious problems of not having a clear transition have even more when on the same board with the noise of FETs switching hundreds of watts of power on and off very fast.

I realize that optical sensing and making any real use of more accurate information you get requires a CPU that is good deal more expensive than the ones in use on controllers to day. And every installation o a problem of installing the optical sensors in a rather hostile environment. Cost is not much of a consideration on this project. With the current state of embedded computer chips it doesn't have to be that expensive. High motor efficiency at reduced speed is important and no current controller is as good as I think they could be if the rotor position was more accurately known and speed change were spread over several revolutions instead of controller that reacts by changing right now to what I believe to be motor position data that has some error in it.

I will have a better idea of the error in the back EMF controller when I get a recording digital oscilloscope on the motor and hold it at one speed at reduced power and see how stable the position signal is off the best controllers.

Gordon Couger
Stillwater, OK
Sep 06, 2005, 04:42 AM
Registered User
Fourdan's Avatar
Hi Gordon
Between the 3 following principles
a) Back EMF sensing
b) Hall sensors
c) Optical sensors
the optical method offers a lot of advantages:
*Good accuracy
*Independance relatively to excitation of terminals A,B,C
*Absolute position sensing possible (good for starting from stop)

A priori it is a good principle with good associated algorithms
Sep 06, 2005, 03:20 PM
Gordon Couger
Fourdan said
;the optical method offers a lot of advantages:
;*Good accuracy
;*Independance relatively to excitation of terminals A,B,C
;*Absolute position sensing possible (good for starting from stop)

;A priori it is a good principle with good associated algorithms

Thanks Louis,

That is my thinking and I know how to build an optical sensor that works. It looks like back EMF sensors appear to be subject to noise The magnitude of back EMF falls off as the power is decreased and because the pluses are shorter the error in the positron of the back EMF pulse to the actual position of the winding increases.

After looking at some back EMF feed back scope traces it looked to me like the accuracy depend on the pulse that generate the back EMF be properly timed and observation by other on Dynos shows that the efficacy that is amazingly good at top speed falls off by 10 or 20% at low speeds. I suspect that low end performance could be improved at the cost of high end performance but for almost all users that's not a good trade off.

Looking at the back EMF plot I am petty good programmer but not good enough to improve the detection of positional accuracy enough to make any difference. The commercial guys have done lots of work getting it as good as it is. I could probably modify one of their controllers and smooth out the pulse timing changes by inserting a computer in the loop and delaying the change 1 or 2 steps and taking the jitter out of the sensor position readings. It might possibly improve things some at the low RPM at the cost of response to throttle changes. The noise that switching 5 to 20 amps as fast and hard as a motor controller does is something hard to believe unless you have put a scope on it as well. Computers and that kind of noise in the confines of a small plane cockpit are not something I look forward to when I am trying to pick off the first zero crossing of the back EMF 4,000 to 10,000 times and minute.

Hall effect sensing has the problems with clean transitions as well. The noise is also a problem.

If my assessment of this is wrong I would appreciate being corrected. Sensing position using back EMF is and extremely elegant, intensive and efficient process. I am only looking at an optical solution because the I think that there is a bit more efficiency particularly at low speed than can be wrung from a brushless motor using better position and speed measurement and holding the timing steady based on that information with changes spread over a complete revolution not just response to inputs.

I think one optical senor will be easier to build and noise is much less of a problem with them. Doing it on a production level may be too expensive and troublesome for the improvement it gets for most things. The commercial controllers do very well. I just have an endurance project that needs all it can get.

An optically sensing a mark on a rotating disk, the shell of a engine that has a rotating shell or even the prop is not patricianly hard to do if you put sophisticated CPU with timers designed for automotive engine control. The timers for CPUs made for automotive engine control deal with almost the same problem as driving an brushless electric motor. In fact direct fuel injection on 2 stroke gasoline engine and brush less electric motor are nearly the same problem. The gas engine requires shorter duration and the electric motor need chopped current over a longer duration but the timing is very similar as is sensing speed and potion. The interrupts are all there for sensing the potion, speed and stetting the point in time based on position and speed the pulse turns on and off. Most CPUs will run up to 4 outputs this way and most brushless motor only need 1. Some of you that winding you own motors might be interested it driving the windings separately. I don't know if a 2, 3 or 4 phase motor has any advantage over the way they are driven now. From my experience with 3 phase AC motors I think that they might.

This is my first try at doing this and if anyone has been down this stream or knows about some rocks that lie hidden under the surface or speculate that there might be some. I would sure like to hear from you. The view and accomplishments are much better standing on shoulders of others experience than crawling along looking up at those ahead of me back ends trying to catch up. I am willing to share my experience with computer programming.

Gordon Couger
Stillwater, OK
Dec 14, 2005, 11:54 AM
See me! I dey fly!
lanre's Avatar
can a LM324 be usd for the sensor position detectsion as used here: by MR
Takao Shimizu

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