[student1616]

Thanks for the reply kowell
i have some more doubts.
have u tested the circuit? is it really doing micro stepping.
hows the motor running?imean is there any buzzing sound from it etc.

i already build the original linistepper.it worked like charm with a real big heat sink.but this time i want a simple driver which can do micro stepping.

[kowell]

Have I Tested Circuit , Look at photo
Does it work , no I just posted this as a Hoax.
Any buzzing , I hope so.
Micro Stepping , works

Have made three of these ,all work.
Have made three of these ,all work.
Have made three of these ,all work.

Kym

[student1616]

@kowell
sorry if i made you angry.iam just confirming before going to build any.

i liked ur design.simple and with micro stepping.
the reason whey i went for linistepper is bcz of its micro stepping capability and motors won't get hot and they make very low noise.

i hope i get the same from ur design.(it dosen't matter if they hot until they do micro stepping)

thanks once again for help
Regards

[student1616]

and original linistepper was for motors up to 1.5A
using this modified circuit what rated motors i can run.

[Fonfon]

good one.i like this simple to go idea
but the draw back i see in this system is lack of current limiting.
i know using I=V/R one can calculate the resistance required for the motor to limit the current.but still its not the efficient way.

i have Alexander's Current limiter (from pminmo) in my mind.but not sure about its functionality. http://www.pminmo.com/3axisPIC/3axisPIC.htm

has any one worked on the current limiting method.

[James Newton]

Just to be clear: The actual Linistepper (which this thread is NOT) DOES most certainly limit current /actively/ not just with the resistance method. The current sense resistors feed back to the PIC which adjusts the output to compinsate. The maximum voltage is applied at the start of each coil activation, and then is scaled back as the current comes up to the limit. As a result, motor speed does NOT suffer as it typically does in the old style linear drivers which use resistance only.

For more, see:
http://www.piclist.com/techref/io/st...step/index.htm

[pminmo]

James beat me to the punch The original Linstepper uses the linear region of it's bipolar transistors to do current limiting. That is why the transistors need to be heatsinked. Looks like this thread is simply a wave drive driver that needs current limiting. Why the Linistepper is ever mentioned in the context of association with this circuit escapes me. Being wavedrive it only uses on coil at a time which produces less torque. To do half step or microstepping you have to do two phases.

[Fonfon]

sure original linistepper is gem.
i build it on general pcb it worked well.

but the current taking capacity is very low.(1.5A per phase).
most of my motors are rated from 2-3.2A per phase.so i am looking for the other circuits which works as linistepper but can handle more current.

and the previous post from the author made me think

Have I Tested Circuit , Look at photo
Does it work , no I just posted this as a Hoax.
Any buzzing , I hope so.
Micro Stepping , works

is there any other current limiting method(other than Alexander's ) that i can use with this controller?

[James Newton]

The linistepper can manage more amps depending on the mode. In full or half step, it will do up to 5 amps, or more if you replace the transistors with 10 amp units. In microstepping mode, you can do a few amps, with a really good heatsink. I've run them up to 3 amps. Just replace the current sense resistors as explained on the tuning page.

The 1.5 amp setting is how the kit is supplied, and what we advertise in order to keep expectations reasonable.

[student1616]

ok today i made the PCB.3 layouts on one board.(XYZ)
and it took some time to figure out he problems and make it running.
i wonder why i burned out 6 mosfets? no idea.i placed all of them right.still one mosfet keep failing all the time.at last the motor ran nicely.
i used a LED with resistor in series to check the working of each mosfet.(by keeping low pulses in mach3)

motor become quite hot as i powered the broad with 12v with out any current limiting.(how can i calculate the required resistor to limit the current?)

i used 628A with the code from step3.zip file.(only this code is working.i tried rest but they failed)
i powered one motor which is rated 1.5A per phase(so over all 3A per motor). with in 2 mins mosfets become quite hot.so is there any other mosfets which can handle more current than IRF's

[pminmo]

what mosfets did you use, the full part number?

[student1616]

IRFZ44N

thanks for the response pminmo.can u help me towards controlling the current to the motor.my motor is rated 5v@1A and iam planning to run the system at 12V

[pminmo]

IRFZ44N aren't logic level mosfets, they are probably hot because they aren't fully turned on.

[student1616]

what abt using STP55NF06 from ST.
my vendor said they are of same pin config.so shall i go with them.

and do i need logic level mosfets here.if ye,what is the best and suitable ?
thanks

[kreutz]

what abt using STP55NF06 from ST.
my vendor said they are of same pin config.so shall i go with them.

and do i need logic level mosfets here.if ye,what is the best and suitable ?
thanks

I read the whole thread, and am sorry to tell you that there are no micro-steps in this design, as well as that the logic signals coming from the PIC are not able to completely saturate the Mosfets in a short time even if they are "logic Gate Mosfets". There is also no linear stepping, since the mosfets are supposed to work as On-Off switches and not as linear current regulators.

All logic gate Mosfets are not the same, nor they require the same gate driving in order to obtain specific switching times. The maximum current that the micro-controller output is able to deliver and sink in order to reliably turn on and Off the Mosfets (in a short time) is a lot less than required.

The author of the thread assumes that micro-stepping is only a Mosfet switching pattern, it is not, during micro-stepping the switching pattern for the output switches is the same full-step with two phases on sequence. So that is what He is getting. The fact that the firmware outputs a full step after so many input pulses does not mean he is micro-stepping. It is just a pulse divider. Micro-stepping capability was "surgically" removed when he took out the current reference waveform generation from the firmware. Microstepping is only done by coil current regulation following a reference waveform, ideally sinusoidal, with 90 degrees phase shift between the two motor phases (for a "normal" two phases steper motor).

What you have here is a full step drive made from a simplification of the original "Lini-Stepper" firmware, nothing you could not have done better with a L297 and four Mosfets. I said better, because in this circuit there is no current regulation, and the L297 will let you use also a true "half stepping" mode, as well as having chopper current regulation. The designer said he used a current source with some voltage compliance as external regulation (I did not see the schematics for it). Whoever uses this circuit without external current regulation could damage his motor.

Kreutz.

[student1616]

at first i think of same.but micro stepping works.i tried and i can see the change in stepping pattern(imean microstepping) i have no idea how it works :-)
but the only problem i felt is current regulation and mosfet burn out.if i can solve these 2 issues,i can give full results.
and i think ur right kreutz.may be PIC is not switch on and off the mosfet completely.during microstepping that's why they are blowing out.

and what abt current regulation.how to calculate the current limiting resistor value

[pminmo]

The file Sstepper4-7.asm.txt‎ is a wave drive piece of code, thats all.

[kreutz]

at first i think of same.but micro stepping works.i tried and i can see the change in stepping pattern(imean microstepping) i have no idea how it works :-)
but the only problem i felt is current regulation and mosfet burn out.if i can solve these 2 issues,i can give full results.
and i think ur right kreutz.may be PIC is not switch on and off the mosfet completely.during microstepping that's why they are blowing out.

and what abt current regulation.how to calculate the current limiting resistor value

One way you can see micro-stepping in action is by using a fixture similar to my micro-stepper accuracy test fixture, a laser pointer mounted perpendicular to the motor axle and on its center, and projecting the laser light about 10 feet away. Otherwise you would not be able to discern them from a 90 degrees of a full step (0.045 degrees mechanical) or a complete full step (1.8 degrees mechanical on a 200 full steps per rev stepper motor).

A full step sequence is made of 4 movements, hence the 0.045 degrees per movement, if you are able to discern finer than that (micro-stepping) without an instrument, you really have an exceptionally good eyesight. Congratulations!!

The current limit resistors' value is calculated the following way:
R >= (Vps - Vmotor)/Imotor

Resistor power rating calculation:

P >= 2*(Imotor * Imotor * R)

Where P = resistor power rating in watts, use next commercial value equal or higher than the calculated value.
Imotor is the maximum specified current for your motor
Vps is the power supply voltage
Vmotor is the specified motor winding voltage
R is the value of external resistor in ohms, approximate to the nearest commercial value equal or higher than the value calculated.

You could use 2 resistors (in series respectively to the center tap of the phase windings for 6 wires motors) or 4 resistors (one respectively in series with each coil winding for 8 wires motors).

My 2 cents: if you are doing this for learning , please, continue spending money on parts and further experimentation. I also advise to read more about stepper driving at: http://www.cs.uiowa.edu/~jones/step/ in order to understand what you are seeing. If you want real micro-stepping results, please, use the original lini-stepper schematics and give it a try, you already have half of the parts for it.

[student1616]

Thanks kreutz
thanks for the detailed resistance calculation.

and i placed a clip over my motor shaft.(which is 3'' in length) to observe microstepping.
it might not be correct.but i can see the difference between full stepping and other micro stepping modes.and i used both 7.5 and 1.8 degree motors for this trial.

and as i said before original linistepper is sure a GEM.i also build the posix version for my small mill and still its working like charm.thanks guys..
mean wile i am just looking around and trying to build other controllers too(particularly with micro stepping)

[kreutz]

...... i am just looking around and trying to build other controllers too(particularly with micro stepping)

Well you can also check the following links: www.pminmo.com and
http://mardus-kreutz.blogspot.com/ if you want to learn a little more about other DIY micro-stepper drives.