Speed/Torque Boost on Allegro 5804 Based Controller (???)

[FrankG]

I've been scanning for a few hours and haven't seen a clear outline of what I want to do (Already posted)...

I've built a couple of the "Generic" 5804 based controllers and worked out all the typical issues of Parallel port lines (TurboCNC is near perfect...), motor wiring and even did the Voltage boost to 12V w/Current limiting resistors...

My existing mill (3 Axis) has logged hundreds of hours, mostly because it's so damn slow... To improve it's performance, I could replace the 12V supply with a 24V unit, but I want to avoid the additional heat & wasted energy... Are there any basic parameters that a "Chopper" curcuit should follow???

I assume that it is a PWM (Pulse Width Modulator) that varies the current in some relationship to the "Duty Cycle" of PWM... I'm thinking a basic 555 timer and a few MOSFets arrayed...

Or am I being niave and missing some major component... Freq of the above PWM??? would 2Khz be too low???

Also is the performance of Steppers improved with a 5804 based controller with a faster PC... Currently I'm using an old 486DX/2 66Mhz...

These issues are not neccessarily for my existing mill as it's been slow for over a year but does it's near daily work fine otherwise, But I'm almost to the point of having to start into the electronics for a larger machine. The area that it will have to cover will definately need superior speed and likely torque for the heavier moving components...

Any advise, or comments are greatly appreciated.

[FrankG]

This should have been in the Stepper NOT Servo Forum... Sorry...

[MrBean]

I am having similar troubles. I built some cheap & nasty stepper drives, to see if my machine worked before sinking wads of cash into it. The problem is, you can't achieve any kind of speed without losing torque, unless you have a "chopper" type driver. I think the PWM frequency for steppers is somewhere ~ 20Khz. I'm going to have a bash at building the PIC board at www.fromorbit.com It looks to be just what I need. Also I'd rather build than buy ready made ones. At least I'll maybe learn something in the process.

Regards Terry...

[MrBean]

I think you could substitute the current limiting resistors on you existing board/boards, for "tachus42's 3 Axis Chopper Adapter". Shown on this page....

http://webpages.charter.net/pminmo/cncelectronics.htm

near the bottom of the page. It's worth a look....


Hope this helps.

Regards Terry...

[FrankG]

Terry,

I think you may have just saved me a pile of work... likely weeks!!!

I took a quick browse of "Phil's Site", and it looks like everything I need is there...

I just joined CNCZone (literally today...) and can't believe that this much info and quality of content was just a click away...

Thanks again!!!

[pminmo]

Frank,
I don't want to bust your bubble, But Tachus42 chopper adapter was meant to work with the discrete board. You might want to pm him and ask, as I recall somebody else asked if it would work with the 5804 and I believe he said no because of the clamping diodes. Regardless, the real speed up is power supply voltage and yes a chopped current limiting circuit puts on the afterburner. There are other current limiting techniques also other than resistors.

Phil

[FrankG]

Phil,

Thanks for the reply... & the website hosting the circuits, PCB layouts Etc...

It looks like a tremendous amount of work to have compliled, tested and assisted the various users that have given it ago...

I'll finish the 99 page Open Source thread, before I make any solid plans...

I'm in an awkward position with this controller as I already have the 5804's and a circuit that I know works (original CWTech that's been floating around for a few years...), But I also know that this just won't cut it on the machine I'll be using it on...

Again, thanks for all the work you, Tach and possibly others have put into the open source designs...

[HobbyCNC]

Originally Posted by FrankG Phil, Thanks for the reply... & the website hosting the circuits, PCB layouts Etc... It looks like a tremendous amount of work to have compliled, tested and assisted the various users that have given it ago... I'll finish the 99 page Open Source thread, before I make any solid plans... I'm in an awkward position with this controller as I already have the 5804's and a circuit that I know works (original CWTech that's been floating around for a few years...), But I also know that this just won't cut it on the machine I'll be using it on... Again, thanks for all the work you, Tach and possibly others have put into the open source designs...

Have you looked into HobbyCNC drivers at:
www.hobbycnc.com

Dave Rigotti

[FrankG]

Hey Dave,

No I haven't (yet)... I literally just read the last post of the 99 pg epic thread on Phil & Tach's Open source BOB/Driver/chopper design...

I do want to make the board myself, and feel pretty comfortable with the "Chopper" ie; no obvious show stoppers, parts, basic understanding... etc.

I think that I'll try and marry the "FET" output of the "Discrete Component driver" to a 5804 based design, and limit current with the TACHUS42...

I have a couple of weeks to digest everything before I even start assembling the parts pile...