[gcamlibel]

I constructed a stepper power card using L287 and L298. I used a 12V computer power supply and a big capacitor. It works well.

Today I tried a 27V AC transformator + rectifier + big capacitor. I measured 35V DC at unloaded output.

For a short time I connected this unregulated 35V DC power supply to my stepper control card. I checked this combination at high speeds. My steppers worked very well.

I want to ask will it couse a problem at L298 using unregulated 35V DC power supply?

[davesaudio]

looks like absolute max:
50v for 298
and 10v for 297
http://www.st.com/stonline/books/ascii/docs/1334.htm
http://www.st.com/stonline/bin/hilit...htm&words=L298

[gcamlibel]

Thank you for your support

I downloaded and readed datasheets at design stage. however I think that 50V is for regulated DC power supplies.

I wonder if is it valid for my unregulated but rectified power supply.

[ESjaavik]

Your supply will not exceed 35V even when unregulated assuming your mains voltage does not fluctuate. What it will do is to drop voltage with increased load. This hurts your performance, not your electronics. I also assume you're not feeding braking power back into the supply. But most regulated supplies will not help in this case either. They will just stop supplying power, not shunting down what your drive feeds back. If this is a problem, use a bigger capacitor to store the energy.

[gcamlibel]

I used 13000uF 40VDC capacitors for test.

I connected them alone and two of them connected parallel. Both tests resulted with the same good performance.

I will use one capacitor + one transformator and rectifier for each axis. Becouse high capacity transformators are very big. therefore I will use three of small transformators for each three axis.

[Ferenczyg]

Gunol, could you post some schematics, or better, artwork for the pcb? I think can be a useful board for the CNC OpenSource DIY desing we are involved..

Thanks in advance
Fer

[gcamlibel]

There is a shematic at L298's datasheets 8th page. I used that shematic. You can download it from ST or I can send to you via mail.

I will try to attach it as gif file below

[gcamlibel]

and the same shematic also available at L297's datasheets 1st page.

also it is here below:

[Ferenczyg]

About these schematics (thanks Gunol) I wonder about the /reset and enable signals.. what are they used for? I can imagine the fucntion, but how they apply to 'real world' designs?

Fer

[lt paul]

having designed a system using these chips recently i can say that the only appliction for those signals would be for tying to the ground or the 5v rails. one interesting application note is on parralleing the l298. they can be used for much higher currents in that application. it is also possible to create a discrete bridge to drive larger motors.

[gcamlibel]

I can send datasheets of L297 and 298 who send me an e mail.

Reset: avtive low (0v) resets the chip initial position ABCD=0101
therefore you must give +5v to this pin

Enable: Like an on off switch. therefore you shoul give +5v to this pin.

to IT POULE:
can you describe how to paralleling 298's?

[lt paul]

the instructions are on page 7 of the l298 data sheet but basicaly you tie the #1 and
#3 input together then the #2 and #4 these connect to the phase one and phase two out puts for the first 298 and the phase 3 and phase four for the second 298. the out puts are connected in the same manner. tie the sense inputs togeter and use them normally ie sense 1 for the first 298 and sense 2 for the second.
you may need to reduce the resistance of the sense resistors but i have not gotten that far yet. the enables are handled the same way as the sense inputs.

[gcamlibel]

Thank you,

I will check and test this. and I will post the result here. thank you

[lt paul]

no problem, actually it will be good to get a second opinion. my design is not quite ready i still need a few small parts and iam also considering a dicrete driver

[SJ781]

Here is apic of the 3-axis board I built with the L297 and L298N chips. The jumpers are for enable, full or half step, and control. The the 8pin wiring block is for step and direction inputs, The 4 pin next to it is the power inout 5v,Ground, and up to 50v. The 3 4 pin outputs on the other end are connections for the stepper motors. I may still have artwork for this drive I'll look around and see. I have another single axis contoler that I built first and pushed it until it gave up smoke. I ran it for about 10 minutes at I think 55-60v It's been a while can't remember exactly. I think I still have all of the components needed to build a single board or two I could make you up a kit if your interested. I'll look around and see waht I still have..

[Ferenczyg]

Nice board, I'm interested in the artwork if you finally found it..

Fer

[SJ781]

I looked around earlier today and could'nt find the artwork. I have a few more places I can look. Maybe I did'nt throw them out. I have a bad habit of getting rid of stuff once I'm done with it. I think I threw out the single drive board and all it needed was the two chips replace on it. I did however find enough components to build two single boards. I did find the artwork for my breakout board though. If anybody is interested I'll scan it in and post it. All my stuff was done on presensitized possitive photoresist pc boards. So all my artwork is printed possitive.

[SJ781]

I found the artwork for the 3-axis driver board and the breakout board. It's the actual art that I used to expose the boards which means it's on transparentcies. It will take me a day or so because I will have to scan it and then go back and clean up the traces. I doubt I'll get a scan good enough from the transparencies that I don't have to clean them up. I'll also have to figure out the component layout because I know I don't have my notes. The driver board is double sided and the breakout board is single sided.

[Ferenczyg]

Well, that's one of the major reasons for me to be involved in CNC. Not so interested in wood routing but mainly in pcb milling, just to avoid the hassle of artworks, transparencies, ligths, chemicals and so on. This board will need to be made 'the old way' but i hope that will be the last too

Fer

[tpworks]

Originally posted by lt paul
having designed a system using these chips recently i can say that the only appliction for those signals would be for tying to the ground or the 5v rails. one interesting application note is on parralleing the l298. they can be used for much higher currents in that application. it is also possible to create a discrete bridge to drive larger motors.

about creating a discrete bridge I have some 8 amp steppers I would like to create a drive for how does this work. Do I use the outputs of the L297 as the same way I did the UCN 5804 with a 7414 chip.

Tom