[shahidmk]

Hi All,

I have been reading up all the contributions being made re chopper controllers for unipolar motors to my great benefit. I came across the following 8amp Unipolar chopper driver based on the L297 that I intend to build.

http://www.ifrance.com/mac1/PAP8A/Pap8aul/index.htm

Any comments!

all past, present and futur info is v. much appreciated.

thanks all..

mks

[pminmo]

I can't read french, but I can see how the 297 can be used as a sequencer for a unipolar or bipolar high power chopper.

Phil

[randyf1965]

http://translate.google.com/translat...language_tools

If that doesn't work go to http://www.google.com/language_tools?hl=en and paste the url in the proper line.

[pminmo]

Looks like it's good to go, I'd build it.

Phil

[TigerPilot]

I'm wondering how would you micro step it lower then the half step option. If you want a simple driver look at this one. http://www.p5taylor.btinternet.co.uk/19.pdf. From one chip mentioned only a 1/4 is being used. If you make a 2 or 4 axis driver on one board you don't have to get an other.:-) I was thinking about doing it but gave up on it since I couldn't figure out how to micro step it. :-(

Yoram

[shahidmk]

Thanks for your input phil. I have started converting the schematic into a pcb layout that can be done using tone transfer method. It is hard work I must say. Will keep all posted with my progress.

Yoram: my need isn't for microstepping but for high current. I have progressed from TIP 122 based 4 phase circuits to 5804 circuits driving high current steppers. Where I live the cost of L297 is cheaper than 2 8ohm 20W power resistors hence the employement of current chopping ability of L297. Ideally it would be nice if I could have a current chopping circuit to replace the power resistors in the tip or the 5804 circuits. but my electronics isn't that brilliant that I can muster up such a circuit.

ta
MKS

[shahidmk]

HELP!!!!!!! I managed to build the L297 chopper circuit mentioned in the link. I couldn't get the IRLZ44 here so I replaced it with the IRF510, but there is a problem.

In the test setup, the motor does not rotate and the Mosfets are getting really really really HOT. I have checked the board with the schematics time and time again and cannot find the fault!.. I have traced the signals using a digi V meter and can pick up the pulses generated by the L297 all the way to the end of the 7409.

Any suggestions the direction I should be taking!

Thanks..

MKS

P.S. My motors are 5.2V 1.4A(per phase) 6 wire unipolars!!!!!

[pminmo]

For troubleshooting, pull the motor and put in some resistors that will have a lower current. Your FETS shouldn't be getting real hot, but without a heatsink they will be hot to the touch. Did you build it on a pcb? The 510 isn't as good of a choice as the IRLZ44 for two reasons, the LZ44 has a much lower on resistance show your heat issue won't be as much, but more importantly the gate turn on voltage is lower, more compatable with the 5V logic. Are you getting a low voltage across the current sense resistors r7 and r8?

Phil

[shahidmk]

Phil,

Thanks for your suggestions.

I got the driver hooked upto 5V 8amp PSU. As I am using 0.5ohm 5W sense resistors I set the V ref to .6V. there is humming in the motor but the FETs are still getting v v hot. I am looking for IRLZ44s as soon as I get them I will change over. In the mean time I made a 4 phase driver based on the IRF510 that seems to work. When I connect the 4phase set up to the 7409 it starts getting hot again.

a basic L297 set up without the chopper enabled seems to drive the unipolars ok. but mixing them with the FET gets problamatic....

on the sense resistors I am getting around 0.7 volts......

I do have 4 sla7062s to play with but the difference in total cost of L297 based chopper circuit is coming to USD5.00 for me while the SLA7062 alone is costing 6.50 and is on back order for a month.....!!!!

where to next!!!!!

ta
MKS

P.S. the driver is made on a PCB through toner transfer method...

[pminmo]

how did you connect your 4 phase driver to the 7409's? The commons of the 4 phase would need to go to the appropriate current sense resistor. But you are playing around the point of my concern. By having .7V across that sense resistor, if your 5V is 5V you have a maximum gate to source voltage of 4.3, and that is marginal. Do your fets get hot when u disable the chopping?

Phil

[shahidmk]

Hi phil,
I wasn,t working on the board for a while, I got back to it last night. I am using Turbocnc as the software to test the setup. Last night I changed the pulse width in TCNC to 0!. The motor started spining (what I found was changing the pulse rate in tcnc had no effect on the motor performance). The fet still gets hot. I cannot replase the irf510 with the ilrz as those are not available here at all. The chopping seems to work as well. 5V was the test setup. Today I set up 24V and the board worked. I haven't changed any of the hardware and also have left the V ref at 0.6V. according to TCNC I am running at 35 ipm. If I increase the pulsewidth the motor slows down!! Disabling the chopping stops the FET from getting hot but the motor startes getting warm !. I am baffled...

Ta
MKS

p.s. thanks for patience in coping with my ignorance....

[pminmo]

how fast is your computer? are you running from windows (dos window) or dos with no windows loaded?

Phil

[lietuvys]

Shahidmk,

I have made a controller from this scheme. I found something strange as soon as I have analysed electronic scheme. And it proved me right as I have soldered and tested the board. FETs got hot, so I started to measure voltages. The voltage of IC2 outputs was wrong (nothing like TTL levels).

There are four resistors marked SIL2, 470 Ohms each. They don't let IC2 to work. IC2 outputs can't pull down to low TTL level (below 0.8V). Therefore all FETs are half-open and gets really hot. REMOVE those SIL2 and maybe SIL1 too resistors at all, like I did, and you will have no more problems here.

Good Luck and give a feedback to us

[pminmo]

lietuvys,
Good point. If built as drawn with a 7409 (no other of the 74xxyy series) and VCC at 5V it will be ok. The 470ohms of sil2 will result in 10ma of sink current which an old 7409 will sink just fine, but it would be marginal on a 74LS09. The problem with removing sil2, is there is no active pull up on a 09, so when it is in an off state, the input to the fet is essentially open and just affected by leakage currents, there needs to be a sil2, but at a higher resistor value than 470 ohms. Same for SIL1, it should be there but 470 maybe to low of value for a computer PP to pull low. Try changing sil1 to 2.2k. If you do not have a 7409 in but have subbed a different series of 74xx logic, change sil 2 to a higher value say 2.2K and see if that helps.

[shahidmk]

Hi,
Both emails make sense to me. I had 74LS09N instead of the standard 7409. IRLZ44N is not available the only options I had were IRFZ44 or irf510. So I will be working on using higher value resistors as suggested as well as NO resistors.

Phil, in answer to your earlier question, I am running the software on a p2 233 with 16MB ram on a pure 6.2 MSDOS system.

lietuvys, you mentioned that you had made the controller. What kind of performance did you get out of it!

Just to add some more background to my hobby, I made my first CNC machine about a year back using phase control. I use my machine to do carving in marble, stone and granite. I made a spindle which runs at around 50,000 rpm (estimated!) and I have been using a simple light dimmer switch to control the speed and I use standard diamond and carbide tooling to do my carving or engraving in the stone. It has been very rewarding. The old machine had a working area of 13" by 12" which worked very well for 12x12 tiles (but was kinda V slow!). Now I have started getting requests for carvings and engravings in sizes upto a maximum of 8ft x 4ft. Hence the new machine and the new IMPROVED controller I like making things myself as it is cheaper and I learn a lot in the process.
The machine design is nowhere in sight as I am working on the controller at the moment ! but a 4 axis gantry based would be lovely to build. My background is mechanical engineering and in my home workshop I have a 5ft local lathe, a 2ft 1943 meyford lathe and a small drill which I am in the process of converting to a CNC'd mill drill so plenty going on there....

hope I haven't bored you and really do appreciate all the help that you have been providing me

regards

ShahidMk

[lietuvys]

Hi, ShahidMk,

I have made the controller just for testing purpose. Currently I am building my first CNC router. I just found that steppers run faster with this controller than with simple one. And that it is noisy , so I think I will make smaller capacity and / or smaller resistance in RC oscilator, that frequency would go about 30 kHz.

The last interesting thing I have recently found is cheap microstepping controller Linistepper http://www.piclist.com/techref/io/st...step/index.htm .

It would be nice to increase currents by using more powerfull transistors and resistors and tuning the motors. It just would be nice to try.

[aleslesjak]

ShahidMk
I have similar problem with IRLZ mosfets. I wonder, have you suceeded anything?
Ales

[shahidmk]

Ales,

No I didn't have much luck in getting that particular design to work. I used IRF520's as I couldn't get th IRLz.. But as someone mentioned in one of their posts in another thread I would have problems using IRLz anyways.

Now I am looking at the L297 design for the unipolar on pminmo.com

I have slightly more faith in that design then what I found earlier.

Also do a search for BANSHEE on google, thats another design using L297 and discrete components but the guy sells the plans only. If you come across a chopper circuit for unipolars based on discrete components and allows half stepping an is CHEAP to BUILD let me know as well

hope that helps

Shahidmk

[pminmo]

One thing I might add, you can not be succesfull driving the mosfets with ttl or ls ttl chips, probably not most of the old 4xxx cmos. You need a full 5v swing that 74HC cmos gives, and the source side current that 74HC gives. You might get buy with an open collector ttl output with a pullup resistor to 10V, but you need to size the resistor so it is nearer the source sink current of the part. For example a 74ls07 will max 40ma of sink current on the output. At 10V a 330ohm pull up will give you around 28ma so when it is on, you don't damage the 74ls part, and when it is off it pulls the FET gate drive to 10V at a decent charge rate depending on the fet. Not nearly as good as a mos driver, and the fet may have warm, but should work.

[aleslesjak]

Hello,
in any case, here is a list of possible replacements:

part.no, Vdss, Id, Rds, Vgs(th), on time ns, offtime ns, manufacturer
2SK2095N, 60, 10, 0.1, 2.5, 30, 300, Rohm
BUZ70L, 60, 12, 0.15, 2, 15, 45, Infineon
FQP13N06L, 60, 13, 0.11, 2.5, 8, 20, Fairchild
IRLZ14, 60, 10, 0.02, 2, 9.3, 17, Intl Rect
IRLZ24N, 55, 18, 0.057, 2, 7.1, 20, Intl Rect
IRLZ44, 60, 35, 0.03, 2, 17, 42, Intl Rect
MTP3055VL, 60, 12, 0.18, 2, 9, 14, ON
NTE2984, 60, 10, 0.01, 2, 11, 23, NTE
NTP18N06L, 60, 15, 0.1, 2, 11, 11, ON
RFP12N10L, 100, 12, 0.2, 2, 15, 100, Fairchild
RFP3055LE, 60, 11, 0.107, 3, 8, 22, Fairchild
STP16NF06L, 60, 16, 0.1, 2.5, 10, 20, STM
STP16NF06LFP, 60, 11, 0.1, 2.5, 10, 20, STM
VNP10N07, 70, 10, 0.1, 3, 50, 230, STM

Please note that Vgs (th) is a threshold value and for ttl level signals should be at appx 2V. Or max at 3V in order to have enough headroom to high ttl level. Exact mosfet choose accordingly to your stepper (Vdss, Id, Rds). Choose one with values much higher than your stepper specs. On and off time are not really an issue since max times are for a magnitude faster than any timing your stepper can handle.

Ales