[CNCAddict]

WOW, that video looks great. I've always wanted to program/design my own AC/brushless servo drive but don't have the programming knowledge. Are you planning on releasing the code open source? That way more people could contribute and develop extra features for the drive.

There are no limits to how sophisticated a servo drive can be. All the industrial versions now feature auto-tuning and sophicated control beyond PID. While I don't expect any of that on a simple hobbiest level drive, it does make a great PH.D thesis.

Have you thought about driving the motors without the hall sensors? I'm not sure how your present start algorithm works. But it would be really cool to use "wake and shake" to initilize the encoder to the rotor position. This method is very appealing because it makes an AC drive only 1 wire more complicated than a DC brushed drive. The only downside it the short 2 or 3 seconds to wait for the controller/motor to get synced up. Kollmorgen also has a method that slowly energizes one set of coils. When the rotor starts turning, it moves the commutation point to prevent further movement. This occurs until the rotor and field are aligned. This way the rotor only moves a few encoder counts on start up. Does any of that sound "doable"??

[johan_tr2000]

Hi there,

Any one have consider to use IRMCK201 for the design? I have DL the datasheet from IR. It seems like OK and have the development board.

All the software routine for space vectorPWM, Encoder, Clark Transform, PI already include in the chip. All you have to do is to give the right parameter for the right register inside the chip.
To access this register we can use RS-232C, SPI, or Host Microcontroller.

Few thing I just one to know about this chips:
1. Is there any possibility to use the chip without hall feedback?
2. Is it possible to perform the step & direction to this chip?

Ony one who have experience about this chip, please advise.

TR2000

[HillBilly]

Here is a interesting chip. Newark list them @ $20.00

http://www.irf.com/product-info/imotion/irmck201.html

Darek

I was going to get one of the IC's to putz around with, but it appears the only way to get the comunication software is with the developement board @~$2K.

The chip is setup for +/-10v velocity or torque control.

Darek

[Xerxes]

Have you thought about driving the motors without the hall sensors? I'm not sure how your present start algorithm works. But it would be really cool to use "wake and shake" to initilize the encoder to the rotor position. This method is very appealing because it makes an AC drive only 1 wire more complicated than a DC brushed drive. The only downside it the short 2 or 3 seconds to wait for the controller/motor to get synced up. Kollmorgen also has a method that slowly energizes one set of coils. When the rotor starts turning, it moves the commutation point to prevent further movement. This occurs until the rotor and field are aligned. This way the rotor only moves a few encoder counts on start up. Does any of that sound "doable"??

That's a very cool method! Only concern is inaccuracy when motor is powered under static torque or friction. However I think the error would be small enough in typical applications. Luckily there is a way to get around it by using encoder inxed-pulse to do accurate phasing. Must be worth of try. It would save some MCU pins and few components too.

I haven't made any decisions on the source code yet. I think the easiest way to use custom control methods would be through torque command interface (typically +/- 10V). Making own hacks in the drive source requires 110% understanding of its operation since every bit in the code is critical to operation.

[Xerxes]

Hmm. Discrete MOSFET option seems to be gaining more and more popularity. Maybe it's a better choice after all? For me it's as good as the other three first options.

I have an another poll question: Would You prefer a circuit board that has mostly SMDs or only though hole components? My plan is to sell some PCBs and component sets, not assembled units.

[waughd]

Xerxes
A couple of thing spring to mind.
Are SMDs easy for DIY and are they better or worse for eyesight of those like me that are on the wrong side of 40.
I have only had through hole experience, my son has done some SMD stuff and was complaing about size.
I don't think I am the only one of us that this applies to.
This is probably going to influence anyone's decision to buy.
Des

[H500]

Waughd, SMD is very easy. You do need a temperature controlled fine tip soldering iron, or you risk melting some components. If your vision is not good, a magnifiy glass lamp helps.

[waughd]

Kewl
I have both of those.
Am looking fwd to using the P5s for other than large paper weights, but no rush, I have heaps to keep me busy, and would much prefer you guys have the chance to fine tune it first.
Des

[CNCAddict]

That's a very cool method! Only concern is inaccuracy when motor is powered under static torque or friction.

The max start current is usually adjustable on "industrial" drives so that the start sequence will work for any load. Even setting the current VERY high shouldn't cause problems because it will only be for a short duration. Torque however is very low near the alignment point, no matter what the drive current. However with sinusoidal AC control, even a severe error in commutation point won't affect the motor performance much at all. If you haven't allready, check out the link below where Jacob Tal explains this point very well, under "Brushless motor control". Definately watch all those videos, they're very enlightening.

Oh, and I don't understand why everyone is behind discrete components. Maybe they're worried about shorting out a phase and blowing part of the circuit and only ruining $5 worth of FETs vs, the $20 module. But the integrated solution would allow for a more compact drive which could be assembled a bit faster as well. Less parts = less headaches in my book. Plus, if someone is worried about blowing the module. Just hook up some fuses during testing.

http://www.galilmc.com/training/webconf.html

[CNCAddict]

OH, I forgot to mention. I believe all FET's are rated at 100% PWM duty cycle. Running a 50% PWM at the same output current will heat things up MUCH faster since the FET is now passing twice the current for half the time. I^2*R losses increase very fast the lower the duty cycle. So even a 100A part can blow at a 10A average current in certain situations. Something to watch out for....

[johan_tr2000]

Hi HillBilly,

Do you think IRMCK201 can take the Dir + Step input?

TR2000

[Xerxes]

SMDs definitely are more difficult to solder than through hole types. The MOSFET driver chip as SMD would be that size: http://www.dobbertin-elektronik.de/p...soic8-150m.gif

SMDs would allow to use smaller and cheaper PCBs. I think the cost savings would be around 3-6 dollars (depends on how many boards are produced).

[ger21]

Jmo, but I'd rather pay an extra $6 for an easier to assemble board.

[HillBilly]

TR2000,

I started a thread for the IR IC. http://www.cnczone.com/forums/showth...349#post114349

Darek

[Chris D]

Jmo, but I'd rather pay an extra $6 for an easier to assemble board.

I second that (and I am pretty sure the silent others would too). Dealing with suface mount at the hobbiest level is no where near as easy as the "older", solder in components.

Chris

[walter]

I second that (and I am pretty sure the silent others would too). Dealing with suface mount at the hobbiest level is no where near as easy as the "older", solder in components.

Chris

I`ll pay extra for convenience

[ESjaavik]

SMDs definitely are more difficult to solder than through hole types. The MOSFET driver chip as SMD would be that size: http://www.dobbertin-elektronik.de/p...soic8-150m.gif

SMDs would allow to use smaller and cheaper PCBs. I think the cost savings would be around 3-6 dollars (depends on how many boards are produced).

I disagree! But up until I was shown how to do it, I did agree.
I can place and solder an 18 pin device in 20-40 seconds using SMD. With through hole I'm hardly done bending in the pins and inserting it in that time.
Not to mention a 40+ pin device that is done in almost the same time using SMD. Use the right flux (no-wash, thin as water), lots of it. And the large spoon formed soldering tip filled with solder. Just drag it over the pins. After 4-5 chips training you'll do it so quickly you will not believe it. My eyesight is not very good anymore, but I use a head mounted 2-lens magnifier.

If you solder pins together, you probably used too little flux. Then apply flux again, strike the soldering tip dry and it will work like a de-soldering wick. Fixed in no time flat.

The time saver with SMD is really with parts that have many pins. With SMD resistors and caps, the time required to line them up and hold them makes it take about the same time as with through-hole components after you got a bit of training. The large-pin-count chips also tend not to be available as through-hole components.

Did I mention you should use L O T S of flux. I think I did, but not often enough. Buy a can, it costs less than 3 pen-applicators.

I also resisted the technology before I tried (at 50+ you tend to), but will never look back (at 50+ you shouldn't).

http://www.cnczone.com/gallery/data/.../soldertip.jpg

[Xerxes]

ESjaavik, Very interesting soldering technique! But where do everyone find the right flux and the right solder to make it work? I believe all water like fluxes wouldn't be that good. Solders also have HUGE differences, I have noticed that my self. Cheapest just don't work.

--


Discrete MOSFET design complexity is not something to worry about. Power stage can be built with IR2184 or similar so very few components are needed. I have also been planning a high power stepper driver for months now. Discrete devices are the only solution for such drive. The best thing is that I can reuse this three phase power stage design in my stepper project, only one more fet pair needs to be added.

[tintruder]

My fear with SMDs is that the great majority of them are unmarked and difficult to determine the value of any particular component by looking at it.
Obviously, some items may need to be SMD simply due to availability, but for the common discrete components, there is a limited number of suppliers and no chance of running out to Radio Shack for that one item you forgot.

Also, SMDs are well suited for minuraturization and are typically designed to carry less maximum current than their bigger counterparts. (i.e. smaller traces on smaller boards...at some point the traces act like fuses and burn through...I like the idea of a larger board with wider traces just in case I wire something backwards and "let the smoke out" of some component...hopefully the PCB will survive)

I vote for thru-board components unless there is no alternative.

[chrisw765]

so hows it comming ?? been following thred, ive got 5 1000w one and need thows drives... thx chris