[SteveT44]

I've been looking at the options for a current regulated (chopper design) bipolar driver that can handle more than 4 amps. The available options are in excess of $100 per axis. The other common method seems to be big power resistors inline with the stepper that to me would seem ungainly at higher amperages. Another option that doesn't get much mention on this forum is constant current power supply. It would be an easy matter to wire a LM138/338 5 amp voltage regulator as a current regulator and feed this output into any elcheapo bipolar driver. Has anybody done this?

Steve T.

[CJL5585]

Steve,
Haven't heard of anyone trying it, of course, I might have missed it if they did.

Question:
Since the different phases of a stepping motor are always changing polarity according to whether they are set up as full step, half step, or micro-step, how would you design for this factor in a current regulated stepper controller?

Jerry

[SteveT44]

Jerry,

The current regulated PS would feed a non-chopper single axis bipolar driver which controls your polarity switching. The power sequence would be main PS, current regulated PS, bipolar driver, stepper. There would be a separate current regulated/bipolar pair for each axis.

After further searching I've found OatleyElectronics.com is selling such a system in kit form, though limited to 2.5 amps. I've emailed them to see if their circuit can be boosted to higher amperage.

Steve

[pminmo]

I can't think of any real reason it can't be done. But at 4 amps your going to be pushed on max power dissipation vs power supply voltage. (after looking at the kit I suspect they are doing just that. 3 term adjustable regulators with a resistor to set current, major fan to dissipate heat). I've been toying with a design of a chopper adapter. But the drawing board is all the farther it has gotten.

[eidos]

hi steve
the regulation of the tide that flows in an electric wrapping
it is a very delicate matter.
in particular way when it comes tall amperages.
the solution more adopted and that to feed the motor, not with a tide constant, but with a tide to tall frequency and with very taller voltage generally of the value dc that the motor bears.
this way of piloting the motor is called chopped fashions.
or called more often PWM.
the method of the pwm is used, because feeding the motor to tall frequency, (20 khz-or +) the curve of couple becomes more linear and the motor to certain critical speeds doesn't lose power.
I have realized some drivers from up 10 ampers (RMS) up 150 voltses.
if they serve you I can realize you someone of it
look this link
some my board listed in ( the photos are visible only for registered user .. sorry )
http://www.computerup.it/forum/viewtopic.php?t=1490
look microstep curve
hi

[CJL5585]

About 5 years ago, I designed a stepper interface that used International Rectifier Current limiting MOSFETS.

I don't remember what I did with the design since I did not build or test it, but I am almost certain it would work. You might want to look into this.

The MOSFETS could be purchased with current capabilities from 3 to 50 Amps if I remember correctly. I don't remember the part numbers.

Jerry

[H500]

Steve, using a current regulator has no advantage over using resistors. In either case, a the same amount of power is wasted as heat.

Do you actually need such a large stepper? There are lots of people successfully using 2-3 amp motors.

[SteveT44]

Well I'm building a 50x50" router that I want to be able to mill 3/4" ply reasonably well. I'm looking at some 400 and 600oz bipolar steppers rated at 4 or 6 amps respectively.

Concerning the L297, how is the current sensing implemented with that chip? It appears to accept a 0 to 3volt range that would correspond to the current passing through the bridge it is controlling. Most designs use the complementary L298 dual bridge chip with the L297. There are many other full and half bridge modules available up to 40 amps or more with current sensing features. Has anybody experimented with alternative bridge modules with the L297?

Here's an interesting half bridge chip by Infineon.

http://www.infineon.com/upload/Docum...atasheet_1.pdf

Steve

[ESjaavik]

look this link
some my board listed in ( the photos are visible only for registered user .. sorry )
http://www.computerup.it/forum/viewtopic.php?t=1490
look microstep curve
hi

Hi Eidos,

I did register but still cannot see any pictures.
I must admit my Italian is not much to brag about, so I may have missed an important setting.

Regards
Einar

[creative_mind]

Regarding using the L297 to drive higher current bipolar stepper motors using transistors, here is something I picked up over the internet some time ago - note that the URL does not work.

[eidos]

h steve
look the
Over Voltage Lock Out ! only 30 volts max

Here's an interesting half bridge chip by Infineon.

http://www.infineon.com/upload/Docum...atasheet_1.pdf

Steve

[pminmo]

You can use a L297 to drive discrete components. Bipolar transistors are the simplest way to go, but will dissipate a fair amount of heat at high currents.

[aminear]

I just finished building a PWM bipolar drive using the l297 & l6203 chip combination, if I recall correctly the l6203 output is good for 4 amps.

It works just great, the chips are a little pricy, $7 to 12 each, you need 2 6203's and one 297 per axis.

You can get a sample schematic by doing a search on either chip. I built my on a standard radio shack circuit board. Only problem I had with it was setting up the proper input for my enable.

[eidos]

Only problem I had with it was setting up the proper input for my enable.

hi aminear
what problem did you have, with the signal of enable?
hi

[H500]

The main shortcoming with the 297 is that it don't do microstepping.

[eidos]

hi
him and true it doesn't make the microstepping.
but ago the half step with shape function.
and with motor from 200 steps and broadly enough is as fluidity of rotation that as resolution (400 footsteps to the turn)
hi

The main shortcoming with the 297 is that it don't do microstepping.

[H500]

Resonance can be a big problem in high performance systems that don't have microstepping.

[aminear]

Eidos,

Not much of a problem, I just had the logic backwards had to change it to low enable out of mach3. Embarrassing because I was troubleshooting it for an hour before I checked that I was getting it enabled.