How about the L297\1 and L298HN? surely someone has experience with these?

[mr jones]

If you have any experience with the L297\1 and L298HN motor driver chips and have some advice for new guy with ZERO experience in CNC building i would love to hear from you!

Ive just ordered these chips on the advice of other threads i have read (is this place a wealth of info or what?) and am just curious what pitfalls i can expect to encounter.......ANY input on this topic is greatly appreciated!

Thanks so much in advance

[Manuks]

I also have zero experience in cnc (building, electronics, mechanics and softwre related). I don´t know what is wrong with me but I want to build a cnc mill from scratch.
I´ve chosen L297 for the drivers (for unipolar motors). I just got the chips today so I believe in the next few days I´ll be working on the PCB design. First I intend to make one single driver board in order to start testing the motor directly hooking the driver to the printer port, then if it´s all right I´ll build the other boards including the interface.
Attached to this post there is a scheme of the wirings for the boards I choose. Be aware that it was done by me and I don´t know yet if it is correct.

I hope we could help each other
good luck

[pminmo]

The l297 and L298 combo is a nice pair. A little noisey (audible) by comparion to newer chips, and hot (L298) but they do a really nice job. Take a look at the stuff on my website.

[Robin Hewitt]

I used the L298 off the printer port, thought about the L297 but couldn't figure out whether it would add or subtract the half step if I switched to full step, it's probably simple, but I decided to make my own chopper circuit and drive the other four inputs directly.

I latched 5 printer port data lines used two more to decode which axis I wanted to talk to and the strobe line secures the data. The extra wire switches the 298 between full power and a holding current.

I'm driving it with DOS in 1024x768 because Windows doesn't give you unfettered access to the timer interrupt which makes step rates a doddle.

Sadly the allure of XP graphics is dragging me out of the stone age and I'm reworking it as a USB device but writing Windows code is a steep learninng curve. I've got the .dxf input on screen, I've got some icons and menu's going but I'm having trouble mastering the pop up window

[mr jones]

Manuks.....I am taking it even one step further by designing and manufacturing the "boards" myself......Though my 20 years electrical experience tell me that your little schematic diagram there looks sound enough---i cannot say with any certainty as ive not seen the schematics for those particular boards.

I did find a schematic of a board though included as part of the PDF file for the L296.....

http://www.ortodoxism.ro/datasheets/...onics/1333.pdf

as well as documentation of the L297....

http://www.st.com/stonline/books/pdf/docs/1334.pdf

I intend to follow both pdf articles to the letter and then running the whole thing with KellyCam through my parallel printer port. Ultimately i will build a dedicated CPU with a 20GB HDD "frankenputer" (ive got a ton of old PC's laying around here) to run the thing........but for today im just interested in getting it hooked up and cutting so i can finish my robot.

For those of you who dont know......I am building a 6' 6" tall animatronic robot and this CNC table is being built so the robot can cut out the rest of the parts he needs. You can read about the robot more at ....

http://www.myspace.com/ahg95ww1fph8u

If all goes well i will also be using these same chips to drive many of the robots extremeties (since many of those will also use steppers for accuracy and "fine motor skills") and will post pictures and daily reports here on CNC zone as i make progress........

I just got the chips in the mail today so i will be starting my "unique approach" to circuit building tonight.......Before i show you photos of my "unique" circuit building technique i must warn you all-----I was a master electrician working with heating and air conditioning all of my adult life until 4 years ago during a trip to london i happened upon a job for "The Sultan of Brunei" re-engineering the computerized climate control system in his London Penthouses. I was a heating and air conditioning repairman from Dallas, wasnt I? I should be able to figure out his nightmarishly redundant computer climate control system and re-engineer a new one, shouldnt i? The Sultan thought so and paid me $1000 an hour to figure it out. It took me 9 months to figure out (having ONLY wired houses and air conditioners in the past with NO experience in small electronics whatsoever) and I did manage to get his climate control system working again, but not before he bought me a first class crash course education in electrical engineering!

So my skill level and methods are all self taught......formally i have a 7th grade education.......but even a dummie like me can read and follow a schematic if its labeled clear enough and i go slowly enough....

So bear with me while i struggle through this and advice or criticize at your leisure......i wont turn away a nickels worth of free advice anytime.

PMINMO......I glanced your links quickly though not with the the hours they deserve......tonight when im tired of smelling solder paste and taking a break i will give them more of my attention....thanks for that! Regarding their "running hot"......should i search the scrap bucket for some small heat-sinks?

Robin Hewitt........i have absolutely no idea what half the things you said mean. Forgive my ignorance about DOS and WINDOWS programming....I should know more in this area but i am afraid i just dont. My understanding was that if i programmed the form of the piece i wish to cut out in KellyCam, KellyCam would in turn create the code and programming the G-code wouldnt be a consideration.......is this true or did i buy a lie? in either event i would like to hear more about this project youre working on (regardless of my level of understanding it) so that i might attempt to broaden my horizons a little further.

To all who responded......thanks for your input! i will keep you each in mind tonight when im trudging away......for those of you about to respond.....please do! The more information we get here.....the better.

thanks again-----im off to work!

Mr Jones

[Robin Hewitt]

Originally Posted by mr jones Robin Hewitt........i have absolutely no idea what half the things you said mean.

Hi Mr Jones

My fault. I'm getting old, keep forgetting the new way of doing things.

When I started CNC I didn't realise I was supposed to buy software and black boxes that used G codes, I simply built some electronics then wrote a computer program that wound stepper motors about and cut fancy shapes.

Obviously not the recommended route, probably best to disregard my input

best regards

Robin

PS: My robot design is only 5 foot 4, not a stepper in it

[mr jones]

Robin.....

PLEASE do not mistake my ignorance for indifference.....I love the old way of doing things (i use solder paste in a can with a brush and lead solder and my only GOOD tester is a "Calectro" from before the Eisenhower Administration.....) and employ what i remember about things like "Vacuum tube construction" and "Learning to make my own crystal radio" in my "unique approach to circuit building"....(you will see what i mean after i post pictures)....I am truely interested in what you are saying i simply need it spoon fed to me. do you have any links i could follow to illustrate what you are talking about?

for the record.......i love the "good old days" of electronics and have fond memories of it from childhood.

Truely....tell me more of this wisdom.......

[Robin Hewitt]

Hi Mr Jones

It is hard to beat an old fashioned moving coil meter when you want to read the switched current flowing through stepper coils, those modern digital efforts are too easily confused. There is still a place for your Calectro

Here's a quick education on timer interrupts.

If you want to drive stepper motors the only sensible way is to use a timer interrupt. All microprocessors have timers built in. Set everything up and your program gets interrupted at regular intervals so you can update your motor windings. After the windings have been updated you return to whatever the main program was doing before it was interrupted. This is all hard wired and automatic.

It means you can set up the interrupt to move to a new position in x, y, z then do something else until it arrives. Something like drawing pretty pictures of tools moving on the screen for example. Change the timer reload value and you change the step rate. Smooth accelerations are easy, you are in total control.

I keep two sets of co-ordinates, 'where I am' and 'where I want to be'. My main program only writes the 'where I am' co-ordinates if I am setting an origin. Most of the time I just write the 'where I want to be', then call the interrupt set up routine and do something else until it gets there.

On a PC running DOS the timer is used to generate the system clock at 18.2Hz. When you want to move you save a pointer to the clock, change the pointer so the interrupt goes to your stepper routine and away you go. When the move is complete you max out the timer delay, point the interrupt back to the system clock, done.

On a PC running Windows, Bill Gates is doing all kinds of important things in the background, much more important than what you want to do, and he doesn't guarantee not to keep you waiting when the interrupt fires. Your stepper motors pause momentarily at irregular intervals and your cut finish goes to hell in a hand basket.

To run under Windows you have to add another processor to drive the steppers with it's timer interrupt. Since serial communication ports are becoming a thing of the past on PC's this probably means using a PIC 18F*** with a usb connection. This begs the question, do you make your own pcb or do you buy a ready made board with a PIC on it? Do you want to limit your options for a quick fix?

The L298 limits you to 2 Amps per coil but the volts are good. They run hot so you need a good heatsink but the switching times are fast.

My first CNC was a lathe and I noticed that the X axis next to the L298's had a lot more power than the Y axis which was out on wires. For the mill I made sure the L298's were right next to the motor, see attached. On here I see people using long cables, but I still prefer to stretch the data lines rather than the motor leads. I like to keep the action close to my current sensing resistors

best regards

Robin

[epineh]

Mr Jones, Phil (Pminmo) has schematics ready to go for the 297/298 combo, I was about to go down that path, had the parts ordered and arrive, was getting ready to make the boards, and at the last minute decided to change my router to servo's instead of steppers. The existing drivers were OK, but I felt the 297/298's would be a lot better.

I'm pretty sure Phil also has boards ready for sale pretty cheap, might save you some time... I have no financial link, just what I was looking at doing a little while back, before I got distracted (happens all the time to me ).

Robin, have you looked at EMC ? You get the pretty graphics if you want, but the advantage of a real time kernel, only thing is you have to run Linux, namely Ubuntu 6.06. I have started to play with this and am pretty impressed so far, certainly has improved since I last tried linux.

Russell.

[mohaon]

thanksssssssssssssss

[mr jones]

So after weeks of assembly and waiting on components to arrive in the mail, I am finally ready to show you all my first attempt at building these 2 chips into a circuit.

Please keep in mind that I am not a big endorser of "copper-coated fiberglass boards", and while i understand that these type boards remain an industry standard....I do not have complete faith in such methods and have built these circuits using another, lesser used method.

In my opinion....all components begin as modular components which are then hard-soldered onto the "etched" circuit board by means of heating up the connection and component.....in my experience heat=death to most components and so i try NOT to subject individual "components" to any more heat than is absolutely necessary. My "circuit boards" have plug-in connections for every component so the components remain "modular".....meaning if any individual component fails....another component is simply plugged into its place without the need to subject the board or the component to any additional heat.

Here are photos of my "non-traditional" circuit boards......some still in progress and some completed.

My question is now------How do i hook this silly thing up to my parallel port? am i missing any components, or is the information shown on the L298 pdf datasheet a complete breakdown of everything necessary to complete the stepper motor control circuit? do i hook up the box marked in red directly to the parallel port and if so which pins?

Also.......for the LARGE capacitor (470uf) should i use a cap that closely matches the voltage of the motor being driven or should i use a smaller or larger voltage cap? I have several in voltages ranging from 10 to 60......LOTS of 25 volt caps......however in my 3 axis machine i am using two 24 volt motors and one 5 volt motor; so should I use the 10v caps in the circuit for the 5 volt motor and the 25 volt caps for the 24 volt motor? i think so but some clarification on this would be most helpful!

thanks for looking and thanks a bunch in advance for answering my question

[pminmo]

Clock, cw/ccw goto the lpt port. enable has to be wired either to its true state or controlled by a pin on the lpt port (I recommend).

Cap wvdc should be greater than your power supply voltage plus a minor safety margin.

You could trace my wiring on my l297-8 board and 4axis interface from my website to help with your wiring question.