Problem- Abnormal crazy move?? Parallel port bad?

[cjchands]

This problem has occurred to me randomly as sometimes Stepping motors would run by itself when MACH 3 has not yet command any move (No JOG/ No Auto/etc..).

I suspect that the cause came from WIRING connecting is loose?
Any expert advises as why this could cause the problem?


SECONDLY.... I got brand "NEW" PARALLEL port from the shop. Cut the other end of parallel port and connect directly to the drive (no breakout board).
Problem is SOME PINS work...
But other PINS does NOT work.
I checked OHM meter and the cable seem to be perfectly fine.. Doesn't happen only to this cables, but a lot other cables as well.....
Can't figure out what's wrong?
Anyone experience same problem?

Thank you
Jeff

[FXC]

It's highly unlikely for a stepper motor to turn even a handful of steps without specifically timed pulses from a controller software, i.e. Mach3. Some noise during startup or shutdown or randomly in between could make your motors jerk slightly but nothing more than a click or crack.

Therefore, my question is - what exactly do you mean when you say they "run" by themselves?

[Pandinus]

I suspect that the cause came from WIRING connecting is loose?
Any expert advises as why this could cause the problem?

OK First off is input/output impedance and biasing.

An output needs a lower impedance, or it won't be able to affect an input very well....

An extremely high input impedance on a circuit means it will only take micro amps to change the state of the input. If the output is active high, so held LOW, and the input is biased in the high state...

(IC inputs can be in either state when floating as just a tiny amount of semiconductor doping or printing irregularities can change the input bias from a high to a low....think of it as grabbing two random toothpicks... One is more than likely longer than the other by a few microns.)

So the output bias is low and the input bias is high, coupled with a broken contact somewhere... every time the contact opens the input goes high... every time it closes the input goes low...>>>> stepper controller motion.

Second is same as above... but EMF/EMI any length of conductor can act as an antenna... depending on the length of the conductor and the strength of the magnetic fields passing over it, It can generate enough noise to affect a circuit... in the case of an open ended wire, and a high impedance input, the "antenna" can generate enough current to alter states of the input... so connected to the output, input is a stable low, but when the connection breaks, AC noise maces the input High,low,high,low...ETC...>>>>again motion from the controller.


As for the port...make, model, not all are created equal, neither are the drivers, which OS DOS Windows MAC, which pins, input - output... not all pins are input or output... is it an ECP, EPP, standard port what are its voltage levels 5V 3.5V 3.3V??? how about voltage source current capabilities and current sink capabilities??? how are you setting the outputs monitoring the inputs????
So what exactly "isn't working"

Set an output HIGH and measure the voltage without anything connected... if it's less than 4V, there is part of your problem.

[cjchands]

First of all, thanks for detail explanation.

I follow your advice, Here are 2 scenarios:

According to your reference..I do not get above 4V in either LOW active off/on?
What should be my solution?


Here is the tested data:

*****Direct connection PC to Driver**** (this is working!!)
Low Active = OFF (dir and step)
Dir = 0.09V in one direction, 2.0V in another direction
Step = 0.00 V in off state, 0.16V in Jog running state

Low Active = ON (dir and step)
Dir = 0.09V in one direction, 2.0V in another direction.
Step = 2.98 V in off state, 2.83V in JOg running State.

*****Breakout board between PC to Driver****
~ similar to Direct connection except
Low Active = ON (dir and step)
Step = 2.4 V in off state, 2.0V in Jog running state.

[Pandinus]

Without any more info I'd guess that you have a low voltage/low power port... probably 3.3V-3.5Vmax out and very low current source capabilities...
The 2Volt direction signal is just barely within TTL input levels.
If your breakout board is driving opto-isolators directly from the parallel port, there is not enough current to drive the LEDs. That and there would be a voltage dropping resistor to prevent the LED from frying at a 5V level...
Oh the joy of miniaturization ans power saving technologies.

One solution, look for a PCI card that can drive your breakout, second find a breakout that needs less current.

Third option, if you are comfortable with electronics, is to do some circuit design and soldering to improve the output of the port

I had this idea while responding to a similar problem on another forum... I can't say for sure if this would work, or not damage the port outputs, but I "THINK" it would work.

This was basically the post........................................................


It "MIGHT" work with a couple of diodes and a resistor, but no guarantees on this one.... .7v for a regular diode... shotkeys are lower .3ish

supply +5V------>|--------^^^^-----------X---------->|--------+3.5V port
1Kohm

Take your signal at "X" it will boost the output voltage .7V higher and a .7v low... which "should" satisfy CMOS and maybe TTL Levels and only 5mA to sink but the i think the inputs to the drives should be happy with the voltages. (The reason I suggest two diodes is that 1.4V+3.5V=4.9V and 1KOkms on .1v is 100uA so it shouldn't affect the port)

If someone is willing to try this maybe on a PCI card that puts out 3.3 - 3.5 volts I'd love to hear the results, because I just thought of this.

.............................................................................................

[cjchands]

Thank you
I wasn't aware there is such a thing as 3V parallel port. Was assuming everything is 5V and either my wiring is bad so there is a drop in voltage.
I'll change it to different PCI board, and perhaps could use this just for input or limit.
Thanks

[cjchands]

Just an update..
I brought new PCI breakout board....setting the 2nd parallel port and it work fine!!

But what actually happen was:
My breakout to stepper Drive was wiring in a way that I need to connect +5V to PUL+ and DIR+......but I wire Ground Pin to those terminal instead..
So with that said...I rewired and kabooom....I get +4.5V in one direction, 0V in another direction as it should be......
But for STEP pulse...I still get about +0.4V when click JOGGING...
is this sound right?

[ger21]

You can't measure the voltage on the step pin with a meter, as it's turning on and off thousands of times per second.

[cjchands]

Yeah..what was I thinking..thank you for pointing that out.

[cjchands]

I set up NEW COMPUTER today..
Brand new FORMAT, new WINDOW.
Install MACH 3 and check that parallel port address show up as
3F8
378

Like other computer....MACH 3 default should be set up at Ox3F8
But on MACH 3....it show....Oxc00.
Problem is the JOG is extremely slow moving at 100%, but Program and MDI run NORMAL....BUT it is RUNNING!!

So I change to Ox3F8 to match what address should be.

Guess what?? IT is not working...no movement at all.
So I change back to Oxc00........and it work again..and everything is moving fine. With JOGGING at 100%...it is running...

CAN'T figure out why this happen.
DON'T know why this address is working while Ox3F8 that should be working is NOT....

Anyone can figure this out...appreciate it.
Jeff.