Diy brushless esc

[slowflyer90]

Hi,
I'm relatively new to rc, but i have an interest in electronics and am trying to build a brushless esc. I'm wondering if it would be possible to create a 1 speed sensored controller and then attaching a regular esc to the imput wires so that it would regulate the voltage, therefore regulating the speed. Any ideas?

[Jim Buzzeo]

a brushless controller regulates the speed of the brushless motor by controlling WHEN to turn on a particular set of coils, and when to turn it off.
regulating the voltage does not regulate the speed on a brushless motor.
it IS possible to use the controller board from, say a CDROM or floppy drive motor as a single-speed controller, but it is bigger and heavier than a standard brushless speed controller.

[slowflyer90]

thanks for clearing that up,
im thinking of making a basic 1 speed controller using hal effect sensors and some transistors; so that the hal sensors dictate which transistors turn on, which dictates which set of coils is on. Do you know of any existing circuit diagrams for this purpose?

[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. http://www.allegromicro.com/techpub2/hurst/bldcmot.pdf

[slowflyer90]

Thanks for the link. This should help me with my design. However, I'm on vacation right now, so I can't start building it right away. When I get back, I'll draw up some diagrams and make a trip to radio shack.

[slowflyer90]

Heres my design so far. Please let me know if you have any comments or suggestions.

[slowflyer90]

I know that my diagram's messy, but bear with me, I'm not that great at art

[Norman Adlam]

Slowflyer90,

Sorry, I'm not sure what you are trying to achieve? :confused:

Problems like :-

a) where is the speed control input, in order to vary the motor speed?
b) Transistor aren't generally used - the suffer from too high an 'on' resistance - hence the reason for fets being used.
c) diodes generally take too high a voltage before the turn on, again a wasted voltage drop.
d) (haven't looked at the logic states etc)

Cheers, :D

[slowflyer90]

Norman
First, this circuit is designed to be attached to a brushed speed controller to use it to sontrol the voltage. I'm not very clear on how fets work, so I didn't include them this time. I'll do some research and see if I can include them in the next diagram. As for the diodes, they are necessary for this circuit layout, but can be eliminated if I redo logic gates. I hadn't thought about voltage required to turn them on. I'll try to have a new circuit diagram drawn up soon.

By the way, I have ordered a motor from www.gobrushless.com and will post updates on how that turns out.

Thanks for the comments

[PDK]

Hi slowflyer90,

I had a similar thought a while ago. My plan was to use a servo drive output (the PWM signal that goes to the servo motor) like here (http://members.tripod.com/~TrEbOr69/speedcnt.html) ,for the PWM signal to the fets.

If you have not done so already download the An857 aplication note from microchip (An857) (http://ww1.microchip.com/downloads/en/AppNotes/00857a.pdf) to get a better understanding of what is required. Look especially a the (I think pg 2) 'Sensor versus drive timing'. The coils are energised for 120 degrees then off for 60 then reversed for another120 and off again.

Have a look at my attempt. I have not done more than this as I have been to busy but it may work. Ic3d is the low voltage cutoff, Ic1 A, B, C are the P-fets while the Ic2 A, B, C are the corresponding N-fets. Also the PWM signal is on the Ic2.

The fets / transistors on your design will not work. The high side has to be p channel. N channel can only be used with a voltage boost system of some sort (ie. a driver).

Also I believe that the hall sensors on CD rom motors are linear devices not logic items.

Hope this is of some help,

Best regards
Phil

[slowflyer90]

I have read the application note and see your point. However, would it be possible to use only P-fets and to use only positive voltages for the imputs?
I'm planning on posting another diagram when I have the time.
By the way, my motor from gobrushless came. I have wound phases 1 and 2 and am planning on winding phase 3 tonight.
I'll post pictures when I'm done.

[PDK]

Hi,

I am far from being an expert, but I don't see why not. The only limit is that p-fets are more expensive and usually have a higher on resistance than the n-fets so if they can be avoided do it!

I just thought I should point out that the high side fet (p) input will need to be switched from the the battery input voltage by a transistor or other fet like is shown by Kreature and Quax in the BLCD controller thread. I dont know exactly which page it is on but worth a look through them anyway.

Phil

[slowflyer90]

Hi,
Thanks for the advise on the fets; I was unaware that the Pfets cost more. Saving money is always nice $-). I'll try and find the thread and check it out.

About the motor:
I finished winding it (22 turns) and it is now assembled on my kitchen table. I'll wire it with the wye connection, since it gives more torque and takes less amps. The motor will be mounted to the plane with a long brass tube attached to the back of the stator. I'm planning on cutting out a plywood disk that will fit around the brass tube to glue the Hall sensors onto.

[slowflyer90]

Heres a pic of my motor:

[slowflyer90]

The pics not great, but camera battery died, so its all I've got for the moment.

[slowflyer90]

Here's another circuit layout. Take a look and let me know what you think.

[jeffs555]

There are several problems with using mosfets like you show. The first thing is that driving directly from the logic that way, your motor voltage could be no higher than your logic voltage, or the top mosfets would never turn off. Also, mosfets have very high input capacitance, so at a bare minimum, you would need a series resistor to limit the current from the logic to prevent damage to the logic and you would have slow switching times on the mosfets which would cause them to heat up more. Also, you generally would use nmos for the bottom mosfets. The way you have it shown with pmos on the bottom in the common drain configuration, the bottom mosfets would never fully turn on. To turn them on fully you would need to drive the gates below ground.

[slowflyer90]

To tell the truth, I'm kind of walking in the dark on how you're supposed to wire the fets. Can you help me with this? Any examples would be greatly appreciated.

[slowflyer90]

Here's a correct picture of a p-fet. Thanks for pointing out that the fets in my picture were connected wrong.
A few questions:
Does the gate voltage have to be at least as high as the source voltage? For example, if the source voltage is 9v and the gate is 5v, then will the output be ~9v or ~5v?

[jeffs555]

For a P-channel mosfet, the source has to be positive and the drain negative. To turn on, the gate has to be negative relative to the source. In the specs for the mosfet, there will be a threshold voltage. When the gate is more than the threshold voltage below the source, the mosfet will turn on, if it is closer to the source than the threshold voltage, the mosfet will turn off. For the low voltage mosfets generally used, the threshold voltage will probably be less than 4 volts. Therefore if the source is at 9 volts, and the gate is at 5 volts, the mosfet will be turned on, and the drain will try to pull up to 9 volts, so with 5 volt logic the high side mosfet will never turn off.

With the P-channel on the bottom, the drain will be tied hard to ground and the source will be free to move. This is the common drain configuration which is equivalent to the emitter follower with bipolar transistors. With this configuration, the source will try to stay above the gate by the level of the threshold voltage. If you pull the gate to ground, the source will not go lower than the threshold voltage.

Normally you would use an N-channel on the bottom. On the top, you would use either a P-channel, or because N-channels are usually cheaper and better, another N-channel on the top in the common drain configuration with a charge pump driver so the gate voltage would go above the motor voltage.



Either way, you need a high voltage driver for the top.

[slowflyer90]

Thanks for the explaination jeff, it makes more sense now.

[zagisrule!]

Use logic-level MOSFET's and now you are all set to use logic-level control inputs to your N and P channel MOSFET's.





-Matt

[jeffs555]

One thing you need to watch for with the circuit Matt posted, is the the maximum Vgs spec for your P-channel mosfets. Vgs is the voltage differential between the gate and the source, and the mosfet will be damaged if you exceed the max Vgs. On many logic level mosfets, max Vgs is only 12 volts, and on some it is as low as 8 volts. Since the npn transistor pulls the gate to ground, the full motor voltage is applied across the gate and source of the P-channel mosfet, so supply voltages higher than max Vgs will damage the P-channel mosfets.

It is even worse than that, because the current stored in the windings of the motor will cause a voltage spike when the mosfet is opened as the motor is being commutated. This is recirculated thru the power supply by reverse protection diodes built into the mosfets. That is why you need a very good capacitor with a low ESR(equivalent series resistance) across the power supply right at the mosfets. Section 2.3 of this app note describes why the capacitor is needed, and how to choose it. http://www.st.com/stonline/books/pdf/docs/9214.pdf

Jeff

[slowflyer90]

Zagisrule: thanks for diagram, I appreciate it.
Jeff: I didn't know about the voltage spikes, and I'll include capacitors in my next diagram. I should be able to easily get fets that can handle 10 amps, which should be plenty for the small motor on my plane.

I'll post a revised diagram sometime in the next day or two. Working on a spanish project for school tonight. Adiós!

[slowflyer90]

Well, spanish didn't take as long as I thought it would.
Heres another diagram. If I messed up, let me know. The fets should be wired correctly in this one.

[zagisrule!]

I have no clue as to whether or not this logic-driven circuit would function at all? I am not at all familiar with digital logic devices, my digital experience has been with PIC's and with those I make them do exactly what I want.

I guess it would not be hard to try this out, it is quite simple and it would be neat if it worked! :)



-Matt

[zagisrule!]

While I am thinking about it...

1. Why bother with switching the rail anyway? Just wire the center tap of the motor to Vcc (the wye connection to the + rail) and switch only the ground to each of the motor leads to accomplish commutation. This means you can get rid of all the P-channels and their inverting transistor drivers.

2. Can you explain the thought behind your digital logic switching? I am thinking that it is not going to work. I have started writing sensorless control code (a failure as of yet...can't get rotor lock) for 3-phase motors and frankly I just do not see the logic solution working unless I am missing something on what exactly it is doing. From the looks of it you are just selectively energizing the coils based on the hall inputs.



-Matt

[slowflyer90]

This'll be a long post.
To start off with, I left capacitors off in the diagram because my circuit design program is a demo and it doesn't want to put more than 50 components in one picture.

Matt, your question is a good one, I thought of the same thing when I first started this.
Short answer: Your way energizes 1 coil at a time. The standard way energizes 2 at a time, giving greater power.

Long answer: Brushless Motors are wired so that one coil will attract and one will repel when a phase is energized. If you connect the wye connection to ground, then all coils can only be energized in the same direction (+ to -). If you energized 2 coils in the way you specified, then they would be fighting against each other. This makes it so that only one coil can be energized at a time. If the coils are wired in the standard way, then 2 coils will be energized that will help each other; thus making it more powerful. This may not be too clear, so I hope the diagrams help. The first is with the wye connection connected to ground and one phase energized. The second is an example of a standard motor with one phase energized.

As for your second question, that is exactly what this circuit does. Coils are energized based on the position of the rotor (which is detected by the hall sensors). If the controller were to be connected directly to the battery, it would spin the motor as fast as it could. A normal speed controller needs to be connected to this controller's power wires to regulate the voltage. Therefore, the controller will still spin the motor as fast as it can, but this speed is based on the voltage applied to the coils. If the imput voltage is dropped, then the speed is cut also.

[zagisrule!]

Yes, I am aware of the techniques of commuatating and switching a normal BLDC motor as well as the principles behind how it works.

I simply suggested to tie the center high to simplify your design, as it eliminates half the physical circuitry as well as some of the complexity. I only suggested this because you are obviously only going to be using one-off homemade motors with this. This would cut your number of commutations in half, so you only need 3 commuations per revolution, while a conventional connection scheme requires 6 commuations per electrical revolution.

Also, by energizing two coils you are not actually gaining any power. The two energized coils act as series resistors essentially creating a voltage divider that halves the voltage to each coil. Delta wound motors actually produce more power per wind than wye motors for the simple reason that the driven coil is receiving the full rail voltage rather than half of it. The primary reason people wye wind is for less current draw than a delta wind because driven resistance is higher.

Also, you might consider running your logic and hall sensors straight from the BEC of the ESC, I doubt they would continue function as PWM duty cycle drops and average voltage falls.

Perhaps a good solution would be a commercially available sensored brushless controller IC, there are a ton of options if you choose to go this route that might actually be simpler than your circuit and in my opinion more likely to work. If price is a concern I am sure free samples are available for almost all the options.




-Matt

[slowflyer90]

Your way makes sense, as it would require less circuitry.Running the logic from the battery would be a good idea, because the voltage will certainly drop below 5v around 50% throttle. As for IC's, they would be nice, but I haven't heard of any companies giving out free samples. I'll look around and see if any companies have any that would be suitable.

[zagisrule!]

I know that Allegro has several sensored BL controller IC's and they do provide free samples. http://www.allegromicro.com

Samples are given by just about any company for development purposes.



-Matt

[wsc]

Slowflyer -

One thing you have to be careful of when making a logic circuit like you are is that any glitches on the input will cause a corresponding glitch on the output. IE, the hall effect sensors will have some bouncing and jittering on the transitions from one state to another, and these bounces will cause incorrect commutations on the output. I cant say whether or not this will be a serious issue for your design to overcome, but it could cause you some grief down the road. Anyway, good luck. Very simple idea, could come out very nicely.

[slowflyer90]

WSC-
I'm not sure if the glitches would affect the controller, but theres one way to find out! If it has problems, buying less sensitive Hall sensors could reduce glitching.
Matt-
I checked out their website and I'm impressed that they give free samples on so many of their products. However, the controllers that use Hall sensors all have a minimum supply voltage of 7v or higher. This would be a problem, as I use 7 cell batteries. The voltage will drop well below 7v before the battery is run down. There is a controller with a minimum supply of 5v, but it uses emf sensing. I could use it if I didn't use any Hall sensors.

[jeffs555]

I don't know about Allegro, but my experience lately is that a lot of semi manufacturers seem to be getting a little stingy with the online samples. I have ordered a lot of samples online before that were shipped quickly with no questions asked, but lately it seems that a lot of online sample requests just get routed to a local rep or distributor who calls to verify your needs first. Has anyone else noticed this?

[zagisrule!]

Yeah,

Samples are a little harder to get, I have had to actually call distributors trying to get samples. All said and done though, I have never not gotten a sample of a product I needed.

My favorites are probably Microchip and ON Semi, both of which are blisteringly fast service-wise. ON requires a $11 shipping fee on all sample orders, but they will allow amazing numbers of samples without any question.



-Matt

[slowflyer90]

Well, I've requested Hall sensors from allegremicro yesterday, so I'm expecting them to arrive within a week or two. The questions on the order form weren't too bad and they claim that your order will ship within 1 day of confirmation. When they arrive, I'll post how long it took.
Matt:
I may end up using your simpler design just because its simpler. Another idea is to try both and see which works better. Parts shouldn't be too expensive.

[slowflyer90]

Hall sensors arrived yesterday, so shipping only took 5 days :). However, it turns out that I requested the wrong type of sensors. The Hall sensors I got were intended for surface mounting, so I requested some with longer leads today.

On a side note, I discovered something interesting this morning. I have a slowstick and was testing how many amps my existing motor would draw. With an 8 cell nihm, it drew around 7 amps. The incredible thing was that my controller was only rated for 2 amps and I have been flying with it for over a year! It just seems odd since I'm obviously pushing it past its limit, but it is rairly even warm after flying long flights at full throttle. Makes me wonder if it's ever going to burn out on me one of these days...

[giri arjun]

hello sir,
sent me circuit deagram of 9-pole cd-rom brushless esc.

[Ron van Sommeren]

A cd-rom motor does not need a special controller, as long as it's a brushless controller it's ok. Several do-it-yourself brushless esc designs, notably the Speedy-BL, the Quax and Takao Shimizu's designs:
http://www.rcgroups.com/forums/showthread.php?t=140454

Vriendelijke groeten ;) Ron van Sommeren
• e-motor building tips & tricks (http://www.rcgroups.com/forums/showthread.php?t=240993)
• diy outrunner discussion group (http://www.yahoogroups.com/group/lrk-torquemax)
• int. E fly-in & diy outrunner meet (http://home.hetnet.nl/~ronvans/), August 28th, Nijmegen, the Netherlands

[e-sailpilot86]

I wish there was a far easier design for brushless controllers... I'd have to take an electronics class to learn this stuff. I haven't even taken Java yet...

R/C microflight had a pretty simple one, easy to understand. Used hall sensors.

[Joel]

I hope this thread isn't too old already, but since I've spent a lot of time looking for ICs recently...

I've checked out every datasheet I could find and then some for sensored brushless drivers (trying to make a starter/generator (not hobby related-well a different hobby anyway)). I only payed attention to the full-wave 3-phase pre-drivers. Anyway here's the ICs I like best (mostly because their the simplest without a million pins and features I don't need) some don't have speed control:

NJM2624 - - - 4.5-18V - - - - 16Pins all N-channel Mosfets
NJM2625 - - - 8-18V - - - - - 20Pins
NJM2626 - - - 6-26V - - - - - 16Pins
http://www.njr.com/index4.html

MC33033 - - - 10-30V - - - - 20Pins
http://www.onsemi.com/site/products/summary/0,4450,MC33033,00.html?tax=407

LS7260 - - - 5-28V - - - - - - 20Pins
LS7362 - - - 5-28V - - - - - - 20Pins
http://www.lsicsi.com/products_files/body_products-brushless_dc_motor_controls.htm

I didn't check all of them but the ones I checked are availiable from digikey or mouser for a buck or 2.

For the people that know electronics better than me (I just know what I've learned on the net the last month or so), I was wondering if you can drive mosfets from a non-pre-driver IC. Can you use a P and N totem pole connected to whats supposed to go directly to the motor?

Joel

[robinhood]

Some time back I was looking for ICs for an ESC, I found some fro Sanyo. they have brushless,sensorless controller ICs that are voltage controlled and work on voltages from 1.5v to 3v if I remember correctly. I have lost the the part numbers but I think that they were LB16**. I never found a supplier.
cheers,
Robin

[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 (http://www.mouser.com)). 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.

[Joel]

Bruce:
Thats the IC I like best and since you have already made a circuit with it and I don't know much about electronics I was wondering why you didn't just use 6 N-channel MOSFETs instead of Ns driving Ps?

Also what hall sensors do I need? I'm guessing bipolar analog? 4pins?

I have a question about mosfets in general too, if you don't mind. Since I'm making a starter/generator, the starting voltage is 12v and the generated voltage could be to about 120v unless the stator saturates before then, not sure how the saturation stuff works, but on to the question.... The generated AC would be rectified by the diodes in the mosfets which is cool, but what 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? Could I just use a shunt regulator to keep the voltage down? I need a regulator to charge the battery anyway. I was gonna have a diode with the regulator in parallel with it so the battery doesn't get the high voltage strait from the generator. I know the Vdss has to be high enough too, but I just need to know if a high enough voltage can go from source to gate?

Thanks,
Joel

[Joel]

robinhood:

I haven't looked too much for sensorless drivers since I need the starting torque, but I haven't found a sensorless ic that doesn't need a centertap, or is a pre-driver. I'll probably keep looking though, since I do have several cd-motors.

Sanyo's current sensorless drivers (http://service.semic.sanyo.co.jp/semi/eng/search/search_spec2.asp?CLASS_CODE=34&row_count=0&type=1&preview_count=20&a_d=1&discon=2&Submit=All+products+preview)

All Sanyo 3-phase brushless Drivers (http://service.semic.sanyo.co.jp/semi/eng/search/search_spec2.asp?CLASS_CODE=37&row_count=0&type=1&preview_count=20&a_d=1&discon=2&Submit=All+products+preview)

Joel

[Joel]

Found it... its half-wave and I wasn't looking at those before.

http://service.semic.sanyo.co.jp/semi/eng/search/search_spec2.asp?CLASS_CODE=33&row_count=0&type=1&preview_count=20&a_d=1&discon=2&Submit=All+products+preview

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.

Joel

[robinhood]

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.
Robin.

[Bruce Abbott]

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.

[irwinrc]

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 (http://www.mouser.com)). 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

[Ron van Sommeren]

Guys, read this thread, all the information is there, no use to have to separate threads:
http://www.rcgroups.com/forums/showthread.php?t=200567

[Joel]

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.

Joel

[Ron van Sommeren]

Tell me when you figured out how to change the title, I have never been able too.

Ron

[Raj Mulay]

Hi
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. http://www.solcon.nl/gjkool/brushlessE1.html

Raj Mulay.

[Bruce Abbott]

http://www.uoguelph.ca/~antoon/gadgets/servo4.htm

[irwinrc]

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 :))))

[irwinrc]

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.

[gcouger]

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. http://www.allegromicro.com/techpub2/hurst/bldcmot.pdf

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
www.couger.com/gcouger

[Fourdan]

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
Louis

[gcouger]

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
;Louis

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
www.couger.com/gcouger

[lanre]

can a LM324 be usd for the sensor position detectsion as used here:http://www.rcgroups.com/forums/showthread.php?s=&threadid=127606 by MR
Takao Shimizu :confused: :confused: :confused: :o :o :o

[giriarjun]

Dearsir/madam


I cannot understand about helicopter main rotor brushed motor armature.
so, what type of armature used in helicopter main rotor brushed motor.
Is helicopter main rotor brushed motor armature is same as cassetplayer brushed motor armature?
If it is not same so,what type of armature used in helicopter main rotor brushed motor,how many pole are there?

I requist you sent me the whole information of helicopter main rotor brushed motor armature.

your faithfully
labagiri

[giriarjun]

hello,
sent me the winding method of speed 400 brushed motor armature.

[giriarjun]

hello sir,
Is winding method of speed 400 brushed motor armature is same as casset player brushed motor armature?

[giriarjun]

hello sir
would you sent me the winding method of graupner speed 400 brushed motor armature?

[giriarjun]

hello sir
would you sent me the winding method of graupner speed 400 brushed motor armature?

[beer-man]

here is a thread on speed 300 motors, I posted some links to good info

http://www.rcgroups.com/forums/showthread.php?t=436918

[jayfang]

Don't know if this will help, but check out the February 2006 issue of a British mag called Elektor electonics. It has a lot of theory on brushless motors as well as all the info needed to build a 18 A brushless controller.

Johann