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Messages - john351

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11
FAQs / Re: Step and Dir signals
« on: July 12, 2010, 10:28:28 AM »
sorry. Should have said "thanks" for the compliment

john f

12
FAQs / Re: Step and Dir signals
« on: July 12, 2010, 10:26:34 AM »
yes because thats the way that mach3 allows you to handle them. But on say a board with
a micro processor on it some control signals are often inactive and are often at a high level
during this time. When something has to be done the signal goes low. examples would be chip select,  memory write.

the advantage of the way mach3 allows you to change the active level is that you can use this to toggle individual signals to test the effect (if any!)

john f

13
FAQs / Re: Step and Dir signals
« on: July 12, 2010, 07:46:10 AM »

sorry about the previous posting. it happened because of my inadvertent use of the tab key.

One way of looking at this is to realise that a two bit up/down counter is the basic logic for driving a stepper motor
The signal controlling the direction of the counter is the signal that is equivalent to controlling the direction of the motor.
given two outputs q1 and q2 the table of outputs for one direction is:

   q1    q2
   0     0
   0     1
   1     0
   1     1
   0     0

q1 and q2 are the signals drining the power amplifiers

if dir is reversed then we get

   q1    q2
   0     0
   1     1
   1     0

this shows that the dir signal sets things up so on the next clock another step is taken
clock = step
changing dir by itself does nothing
the waves are not square waves since the time between clock signals can be anything.

It is not really meaningful to talk about these signals as having active levels since they are doing something whatever level they are.
where the sense of the signal can be active low or active high is arbitrary but the ability to swap the sense can be useful for testing

14
FAQs / Re: Step and Dir signals
« on: July 12, 2010, 07:36:44 AM »
One way of looking at this is to realise that a two bit up/down counter is the basic logic for driving a stepper motor
The signal controlling the direction of the counter is the signal that is equivalent to controloling the direction of the motor.
given tw outputs q1 and q2 the table of outputs for one direction is:


15
Chack your breakout borad as follows.
apply 5v to the supply pin. Check this supplies both the computer side of the board and the mill side.
connect each output you want to use, say 2, 3, 4, 5, 6, 7 to a led and each led via a 220 resistor to
a rail connected to +5v
then add a wire to the ground terminal.
use this to touch pins 2 3 4 5 6 7 in turn and see if it turns the led off

For mach 3 go to the config window
go to portsd and pins
set port 1 to enable set port 2 to disable
enable output signals 1 2 3 4 5 6 to enable
set port to 1 for these signals
for output  set pin
1              2
2              3
3              4
4              5
5             6
6             7
for pins 2 to 7 set active low

click apply and end?

you will have to go to congig again then select motor outputs

set      enabkle  step pin  dir pin   step pot   dir port

x         yes        2           3          1             1
y         yes        4           5          1             1
z         yes        6           7          1             1

click apply and end

connect board to computer with leds still attached

leds should be on (or off?)

go back to ports and pins and toggle for each pin the active low
doing this should change the state of the led for that pin


john f



16
General Mach Discussion / Re: stepper signals from breakout board
« on: July 07, 2010, 11:05:43 AM »
details of the breakout board can be found at:

http://www.nbglin.com/CNC25.htm

john

17
General Mach Discussion / Re: stepper signals from breakout board
« on: July 07, 2010, 07:07:34 AM »
In the motor output i have
         motor   enable   step dir  s port  d port
        x          yes        2     3     1        1
       y          yes         4     5     1       1
        z          yes        6      7    1       1

i hope this is ok

john f

18
General Mach Discussion / stepper signals from breakout board
« on: July 07, 2010, 03:39:10 AM »
I have downloaded the demo version of Mach3. I have set up the address etc. I have leds on the outputs of the breakout board.
I can toggle these individually by playing with the active logic level and they work ok.
when I go into the diagnostic mode and use the jog command the dro changes as one would expect but the
signals to the stepper motors never change.
What going wrong?
thanks

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