L297 stepper motor controller

I just checked the farnell site for the l298 and it is listed as no longer stocked?????

Any idea why that might be?? I'm worried that these chips are on their way to retirement!!

Is there some other setup which I should be investigating??

any advice would be nice!

jonathan

any advice would be nice!

Jonathon,

It's probably not stocked anymore since Europe is going RoHS compliant, and it's not compliant.

Try this: usually a nice email to the local sales rep will get you three or four samples. Offer to credit them in your next show. Failing that, I believe the chip is still widely available in North America: try this!

PS: it is stocked somewhere in Europe, as the price at this place is in Euro's, five of them...
http://www.bmm-electronics.com/Product.asp?Product_ID=746

Well, its been about 3 weeks since my last post on this thread and by now I should have got a working L297/8 circuit. However, the reality of live, with a job and a family, has meant no electronics fun for 3 weeks and zero progress.

However, I have managed to buy the ICs and now I have a little time i've met my first problem >>> the L298 doesn't fit onto a breadboard. Looking on the data sheet, it is described as a 15 lead Multiwatt package.

Is there an easy way to fit this IC to the b/b?? Or do I need to go some other way??

Thanks as always / Jonathan

Is there an easy way to fit this IC to the b/b??

You are best to skip the breadboard and go straight to a hard-wired version, since there is a lot of power and noise floating around, and the chip has to be heatsinked in any case.

On a perf-board, put pins 1,3,5,7... in one row, and then put pins 2,4,6,8... in the row behind it. A little tricky, but it works. Some pin-bending required.

Once things slow down on my end I will design a stepper driver PCB for it that fits on the Arduino... unless someone else wants to in the meantime? I have the working design with schematics.

Daniel

Hi: this one is a miser solution, but works: I've used an IDE wire (cut it and use each extreme to connect to each file of pins) to put one L298 and one 7805 into a CPU heat sink+fan cooler. It hasn't heatsink grease or mica (I think it's bad).

Thanks for this great post (please, post the schemas ;)!!). Btw. someone could explain how connect the L297 to a darlington for unipolars (or two L297 plus one ULN28003)??

Regards:

Nach.

There is a schematic for using the L297 with a unipolar motor on the L297 application notes pdf (not the datasheet).....

http://www.st.com/stonline/products/literature/an/1734.pdf

its page 15, fig 22.

It involves a darlington array, 4 protection diodes and 4 AND gates.

I'm planning to try it once I get the L297/L298 working together nicely.

Allegro have some new ICs out for controlling unipolar steppers that do the job of the L297 and the darlington array in one chip. I contacted my local sales rep and got some free samples. I haven't tried them yet though. (i'm old fashioned, so I like to learn how to do things the hard way before I use the shortcuts!)

http://www.allegromicro.com/sf/97052/


Regarding heatsinking the L298.... If you plan to step your motor slowly, for instance just a few steps per second, will the IC still need sinking?? How hot does that guy get anyway??

Thanks Jonathan.
Massimo point out that application note in this post too. But after read that little paragraph and look its illustration I can't take anything. It looks like a marvelous egyptian hieroglyphic.
For example: before all the points on this post about bipolars (additions and diferences from the datasheet), is valid the rest of the circuit [L297+L298] with the described ULN2075B? Does It need corrections? But if I want chopping (I want chopping)... what can I do? How can I do it with the ULN28003 (for two axis driver)?

It's very hard and frustrating... After my first toast-session (one unlucky SN74LS158N) I take it carefully.

Yes, just readed your other post I wrote to the ST and they ask me to local dealers. I mailed one local dealer past week but I'm still waiting for a response :'(.

Nach.

owd: I love your 3d diagram of the Arduino board. Did you make it? Can you post a copy of the original files so we can use it to make more diagrams?

Mellis, now you can say "I met Gollum": No! No! It's mineee! My ownnn! My preciousss!
Obviously it's a bad joke: I'll send you (next time, I don't have the files here).

Nach.

hey all:

I was just rummaging through some boxes and found one of my L297/298 stepper motor drivers. It's about ten years old, and still works like a charm. In fact, I regularly throw it across the room when teaching electronics classes, to demonstrate how simple designs can also be reliable and rugged.

Here's a (terrible) pic taken with my laptop camera, showing the driver unit with the cover removed:

The case is Hammond 1590B diecast aluminum. In the pic you can see the L298 screwed to the case at the top for heatsinking, DB9 connectors at the bottom and left for input signals and motor connnections, and the motor protection diodes. There's also a 7805 in the middle to provide internal voltage regulation, and two large power resistors for the L298 current sensing. There are also blobs of epoxy and hot glue on all the hardware, since a loose screw inside something once cost me thousands of dollars and a couple of plane flights to fix it. The whole unit is about one inch by two inches by four inches.

The schematic for this is exactly the same as the one on page 14 of the ST datasheet, with the addition of an LM7805 regulator for the power, a few caps and a reverse-polarity diode.

Jonathan, hope this will help with your UK version!

Daniel

and one more fabulous laptop photo, showing it with the lid on, ready for throwing.

I'm back!! - after 10 days holiday in Prague! and feeling fully recharged by tons of beef and dumplings!

Daniel - thanks for the pictures!! :wink:

So, some more questions....

  1. As discussed earlier, the schematic on the datasheet has loads of capacitors and some more are needed for the 7805. I can see what capacitance I need but I don't know what kind of capacitors to use?? does it matter??

  2. You are using perf board, right?? This is probably a real dumb question, but how do you use perfboard?? Do you just solder wires on the bottom of the board?? Please share any perf board tips or advice!!

The schematic for this is exactly the same as the one on page 14 of the ST datasheet, with the addition of an LM7805 regulator for the power, a few caps and a reverse-polarity diode.

are the extra caps just the ones required for the 7805 and what is the reverse polarity diode doing??

Thanks a million / Jonathan

Hi all
I'm so glad to find here,for there must be some professions to help me.
My teacher asked me to design a stepper motor driver using l297,l298 and 89c51, which can control the speed and direction.I asked him what should i do first and he answered to me,'do it from scratch'....
I collected some materials of l297.l298 and 89c51 such as datasheets but I could not understand clearly that which pin is useful and how to use.What can I do?I wonder if someone could give me the diagram or circuit of what I need.The schematic will be appreciated greatly and profoundly...
A helpless sophomore.

Hi

I made some stepper motor drivers with the L297 and L298 five years ago, and they still work great!

Fabulous!
Could you send it to me?

Dear Dizzy

Unfortunately for you, this place is full of professors like me....

If you just get the project done from somebody here you won't have learned anything...

There is a lengthy discussion about the L297/L298 on this forum.. if you read it while not dizzy you'll get all the info you need.

Sorry if this sounds harsh but this is not a place for people to avoid doing their assignments...

have fun while learning

massimo

Now I have knew the circuit of l297/l298 from the datasheet of them, but how can I connect it with the 89c51 if noly control the speed and direction of the motor.I think the direction of motor may be controlled using the pin17 of l297.Which pin should I use to control the speed, 18 or others?

Hi, I have a few questions about the L298 chip. Ive wired one up to control the direction of electroplating. It has to deliver about 1.4A. Ive noticed theres a 2.4V drop across the L298 and also it gets roasting hot. Is this normal?

My power supply reads 6.5V 1.4A and the voltage across the plates is 3.6V. Im also dropping voltage across the wire going to the plates. The L298 datasheet says that Vsupply must be 2.5V higher than logic Hi (5v in my case). Is this critical?

Also I dont have current sense resistors. I just wired the sense pin to ground as I set the voltage to give me the correct current using my power supply.

Its all working fine Im just a little worried about the heat and whether my lack of current sense resistors matters.

Thanks
Nicky

hi

yes that is normal that it would get roasting :slight_smile: You need a heatsink at that current or the chip will die soon. 2.5V X 1.4A means the chip has to dissipate 3.5 Watts of heat...

The better way to design for your task would be to use a MOSFET H-Bridge, as MOSFETs have a very low on resistance, on the order of milliohms. With them, you would drop perhaps .2V across the bridge. The downside is that they are static sensitive, harder to drive as they need more current, and they don't like to switch in "high-side" applications. But if you can find someone who makes a prepackaged driver IC with logic-level inputs, you will have solved most of that. There is an article here that describes a 30A MOSFEt H-bridge that could be built for under $20. Alternately, you might want to check the local hobby store, as the RC motor drivers that they sell ready-to-go will switch up to 100A. Add some servo code and you are set.

Lack of sense resistors is OK if you have are controlling the current. The Motor supply does have to be minimum 2.5 higher than logic, as it has to overcome the drops on the internal transistor junctions to function properly.

D

Hi Daniel,
Thanks for that. I just had a quick look for a mosfet hbridge IC but they seem to have higher minimum voltages (around 10V). I also am out of time with this project so will have to stick with the L298s for now. So Im sitting here looking at an old AMD cpu cooler, some artic silver heat paste and a drill. Im sure I can get this thing cooled with with this combo. Time to get creative.

Logic Hi plus 2.5 would be 7.5 which gives me a bit too much current. I have a load of diodes and 3.3V regulators. Do you think it would be worth running the L298 at 3.3V instead of 5V? Then I could drop the supply voltage to 3.3+2.5 = 5.8V which would probably be fine current wise.
Thanks and all the best
Nicky