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Messages - bpgoa

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funny you should say that... they are plane and helicopter parts...  but   :) model plane and helicopter parts.

run the mill on the one axis using it as a power feed (will add the second axis by the end of the week) it's great :)

will change to 8 microsteps as recommended above,,, 

at this resolution, if there is a difference , you're right.... I won't care.

Thanks for your help..  the use of the spindle settings to test were invaluable to me..  I hadn't got that far up the learning curve yet.



I should say at this point.... 

That CNC4PC confirmed the results of my electronics testing above. 

Their  c11v8 cards (current release) will work with the current being delivered from my parallel port card..

a new parallel port card is only £10

Even though this is not their fault, they are rectifying the issue.

Their support throughout (I started this post on a Friday night in the UK as I knew they would not be in the office till Monday and wanted to work on it over the weekend) has been second to none.

to me, the indication of a quality organisation is how they deal with you when things go wrong.

Thanks everyone.


These are my calculations for the sttepping...  do they make sense? are the figures ok?

Resolution required
All the design work is in the metric format therefore it is proposed to allow work to be manipulated to an accuracy of one thousandth of an mm.
Step accuracy required = 0.001mm or 10 microns
The X axis
The x axis (side to side as viewed from the front) is linked via a 2:1 belt drive to a stepper motor.
Each revolution of the machine spindle moves the table 2mm; therefore each motor revolution causes the table to move 1 mm.
The stepper motors move at 1.8 degrees of movement per step therefore has 200 steps per revolution.
This gives a table movement of 0.005mm per step.
Micro step setting
Micro stepping can be set up to allow the following configurations for the X axis
steps   Multiplier   Table movement per step
200 (no micro step)   1   0.005mm
400   2   0.0025mm
800   4   0.00125mm
1600   8   0.000625mm

Configuration of stepper motor driver
It has been decided to configure the micro step settings to 4 giving a movement of 0.00125mm as a starting position.
The motors have a maximum current rating of 2.5A and the drivers can be configured for either 2.4A or 2.7A. As a starting point we will set the driver up to deliver 2.4A
Connection to the breakout card
The X STEP signal is connected to pin 2
The X DIR signal is connected to pin 3
The driver is active low therefore mach 3 has to output a logic 1 (+5v) to count as a pulse.


got the chip datasheets out and traced the circuits.

the circuit is like this

The input pin is conected directly to a lt847 optocoupler..

the output transistor has its input pin at 5v and this is fed to an inverting schmit trigger (74ls14n)

when a voltage is passed (pport pin goes high) the optocoupler produces light and this activates the phototransistor of the output stage which in turn sinks the voltage to ground. the amount of voltage it sinks to ground depends on the input current.

so.... the input to the schmit inverter is high when no current passes on the input to the optocoupler... when enough current passes on the input to the optocoupler it feeds the gate and drops the voltage from 5v to near 0v.  This is then inverted at a clean crossover point by the schmit inverter an produces a 5v (isolated) on its output.  This output is then buffered twice - first to drive the led and second to drive the optocoupled and buffered output to your designated use.

my deduction from the results below is that the optocoupler input (from the Pport) is not providing enough current to get the output transistor to sink enough voltage to feed the schmit inverter with a 0v (logic low signal)

Results below...

got the meter out..

started with the LT847 optocoupler

output set Low to p-port  pin 16

pin7 voltage (taken from pc powered ground) is 0.01v

pin10 voltage (taken from pc powered ground) is 5.15v

output set high to p-port  pin 16

pin7 voltage (taken from pc powered ground) is 1.06v

pin10 voltage (taken from pc powered ground) is 2.63v

onto the 74ls14n

with the output on pin 16 switched on  traced the 2.63 v to pin 13 .

pin 12 it's inverted output (of the pair) is still held low (0.17v)

my conclusion from this is that

The chips are fine

pport pin 16 isn't providing enough current to drive the gate (via light) in the optoisolator  to the point where it sinks the voltage on its output low enough to trigger the schmit inverter.

from that i can only deduce that i need a new pport card .   

can anyone confirm my ramblings?

one more piece of info - all input pins work ok.

ok...   checked on the cable at the point it enters the card and all pins

... 1,16,17

are switching to +5v amd +0.01v

 guess there must be a fault on the card...   

I Hate it when brand new kit doesn'tr work :(


Thanks Jim. that gave me a definite way of checking.(I've never used any cnc progs/machines before - complete noob)

the point was to get the output pins to work and using the charge pump would have allowed me to check pin 17 easily- I thought. 

I've yet to implement limits, homes. spindle speed, suds pum, pdirection or any others(probe!) yet. in fact I've only connected up the one axis. once the second axis is connected then I cannot use the mill manually.

so... following your excellent advice...

in mach 3  I enabled motor spindle as output 1 and 2 then assigned these outputs to each output pin on card one in turn using the commands m3,m4 (m5 to switch off) .  this showed that

pins 2,3,4,5,6,7,8,9,14 worked - could switch them on and off

pins 1,16,17 did not work

in all cases the diagnostic screen in mach 3 showed that it had enabled the relevant output

this was tested using the led  (on the card)and in case the led buffers had blown I also put a meter from these pins to ground to check for a voltage - none.

further info
...this was still after the opto isolators
... tested the parallel cable to ensure all pins wired and yes they are
...checked the port address and there are no conflicts
...there is a second parallel port which is connected to a hand-wheel (which I built) and this works fine
.... can't swap to the other port as I modified the pci card to pass +5v to the hand-wheel using 2 of the common(ex) ground leads
....have not checked directly on the p port to see if there are any signals there yet... job for the morning

any other ideas?

help - i have a cnc4pc c11 breakout card and I cant seem to get the charge pump to work

so far, i have the following working via the card with no issues. (jumper set to ignore charge pump)
... pins 2,3,4,5,6,7 as step/ dir pins on the x,y,z axis (output)
... pin 10 working as an input for e- stop

I can't seem to get the following working
...pin 1 as an output (tried to use this as a step for x axis and failed)
...pin 16,17 working as an output (i tried setting them as enable outputs in Mach 3)
.... charge pump doe not work when set to card 1 pin 17 in pins and ports )

i read somewhere ( i think it was on one the mach 3 forums) that some parallel port cards can't sink enough current on certain pins to drive the opto isolators

can anyone help fill in the blanks for me?  is this correct? what do i do about it?

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