pic controllers

[DrStein99]

Just want to get a show of hands, please - I'm writing a pic-stepper controller; and want to gauge my speed. My research tells me that geko and other hardware drives steppers 720, 1000 and above rpm.

Can I get some replys please, on other people using pic-controllers what their max rpm's are - on a motor with no load (just spinning with nothing connected).

[CLaNZeR]

Hi

Are you driving the motors from say 4 pins of the Pic Chip bipolar or going for a micro/stepper driver between such as Gecko's, Xylotex etc?
If you are and just going to use your Pic to control the Step and Direction lines then the info below may help.

Never worked out the RPM on my Pic Breakout board , more was the travel speed calculations and this is defined by the pause between pulses, the amount of pulses needed to turn the motors 1 revolution and the pitch on your thread.


1.8 Degree motors require 200 pulses per 1 full turn.
The pitch of the trapezium thread on my machine is 3mm so to move 1mm we would send (200/3)= 66 pulses to the motor if we had it in full step mode.

Most people use Micro stepping mode and 1/8th would need 1600 pulses for 1 whole turn of the motor. So now to move the Axis 1MM it would be (1600/3)= 533 pulses

Now to determine the speed we alter the pause between the pulse sent to the Step line.

Eighth micro Step Timings:
A 2250 Microsecond pause gives 25.4mm or 1 Inch Travel per minute.
A 1125 Microsecond pause gives 50.8mm or 2 Inch Travel per minute.
A 0562.5 Microsecond pause gives 101.6mm or 4 Inch Travel per minute
A 0281.25 Microsecond pause gives 203.2mm or 8 Inch Travel per minute
A 0140.625 Microsecond pause gives 406.4mm or 16 Inch Travel per minute
A 0070.3125 Microsecond pause gives 812.8mm or 32 Inch Travel per minute
A 0035.15625 Microsecond pause gives 1625.6mm or 64 Inch Travel per minute
A 0017.578125 Microsecond pause gives 3251.2mm or 128 Inch Travel per minute

This is based on a 18F4550 running at 48mhz.

Hope this helps.

Regards

Sean.

[DrStein99]

I am using half-stepping; micro-stepping sounds nice - I should research the sequence for that.

I am using six-wire unipolar motors. The two + lines are hooked to resistors, and the four pole lines are triggered by my pic16f628 chip at 20 mhz, thru transistors.

For the sequence, I loop(wait) until voltage is high - then perform step - loop until voltage is low(wait), then repeats to begin again from start. Dont have any delays.