18f4431; driving a stepper IN HARDWARE mode

[DDDvvv]

thanks for the reply Bruce.
im happy that someone is on the same wavelength as me. yes, the waveforms look great. i wish i had checked them with my scope, before dismantling the project from my computer desk. ill set it up again tomorrow.

i was surprised that it worked first time, when i tried it with leds, turning on the individual leds, and varying the brightness using the pot

my stepper could not accept anything under 3ms pauses between steps, but then, i was using 5v and the stepper module on the ql200 board leaves a lot to be desired. im trying to design a stepper output board, just for this particular idea.

newbie in steppers? how about me, a newbie in everything? i stumbled on the picbasic language back in august 2009, after trying (unsuccessfully) to learn assembly. since then, pic programming has been easier for my brain cells.

hoping to hear from you soon and other forum members.

thanks

[Bill Legge]

Thanks for the thread - please keep posting your progress.

There is an excellent application note on the problem of ramping up/down on:

The ATMEL site: AVR446 'Linear Control of Stepper Motor'

It comes up with a good approximation for linear acceleration without over-taxing the MCU. The simple business of making linear changes to the PWM 'sort of works' but is nothing like the smooth motion one get with MACH3.

Regards Bill Legge

[DDDvvv]

thanks for the atmel app note. i've also been thinking about the trapezoid curves, and since all cnc software incorporate them, there's no need to take the trouble for them, unless one wants to control the stepper from serial/parallel, or standalone.
i have a crude power driver on a bread board, and still experimenting on pwm chopping to limit the current. anyone know what's a good pulse frequency for chopping? i've been adjusting it around, ive tried frequencies between 5khz to 56 khz. conclusion; higher frequencies cause more heat dissipation on the power transistors, (which are not heatsinked).

if i can get this pwm to limit/control current, then ill be happy.

thanks for the idea, and back to experimenting.

regards