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Parallel Port Voltage
« on: September 18, 2010, 08:07:34 PM »
I have been reading a lot of the support forum, but have not been able to find a solution to my problem. The basic problem is low voltage from the parallel port.

Here are some specifics.

I built this PC specifically for Mach3. AMD Athalon 64, 2.0 Ghz, 1 GB ram.

The issue is that the voltage from the parallel port is low. When I measure the voltage during startup it reads 4.44 vdc. So I think it is fair to assume that it is a 5 vdc PP. Once I start Mach3 the voltage drops to 0.07 vdc, which I assume is the low state.

When I run Mach3 and jog the X axis I get 0.10 vdc from pin 2. This is not enough to trigger my C10 BOB.

When I check the 'Sherline Mode 1/2 Pulse Width' checkbox, the system works, but the measured voltage from the PP reads as 0.35 vdc, and the motors respond to jog commands. Why does the system respond in Sherline Mode, but not in normal mode? Does anyone have any ideas as to how to resolve this issue?

Thanks,
James
Re: Parallel Port Voltage
« Reply #1 on: September 18, 2010, 09:11:44 PM »
Hi, just along shot but a circuit with little or no current will display  potential voltage, as soon as current increase the voltage drops , very similar to pinching a garden hose with the tap slightly open. Will spray a single blast but reduces to a dribble. Check the power supply voltage with current flow for a true voltage output. Hope that puts you on the path.
Les

Offline Dan13

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Re: Parallel Port Voltage
« Reply #2 on: September 19, 2010, 02:07:30 AM »
Hi James,

Are you measuring the voltage on the step pin? If so, the reading of the voltmeter doesn't reflect the actual wave voltage. Since it is a square wave and the voltmeter reading would depend on it's frequency. So the 0.1V or 0.35V you're seeing are absolutely meaningless in determining the wave high and low voltages.

If it works for you in Sherline mode, then just leave it this way. Sherline mode outputs wider pulses, so appears like that is what your drive needs.

Dan
Re: Parallel Port Voltage
« Reply #3 on: September 19, 2010, 07:51:51 AM »
Les,

I was measuring the voltage with no load so voltage drop shouldn't be an issue. It looks like Dan is probably right.

Dan,

I though this might be the case. I work with pulsed signals from time to time, but typically see a voltage reading about 1/2 of peak to peak, so the 0.10 vdc seemed very low. Unfortunately I don't have an o-scope so can't really take a proper look at the signal.

What exactly does Sherline Mode do? Does it override the Kernel Speed, or does it modify the only the pulse width and not the timing? Could this problem possibly be cured by increasing the Kernel Speed?

I am running in demo mode so I am limited to the 25,000 hz.

I plan on using this machine in a commercial application so I need it to be as accurate and reliable as possible.


Thanks for the help guys,

Offline Dan13

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Re: Parallel Port Voltage
« Reply #4 on: September 19, 2010, 08:59:53 AM »
Yes, James. As far as I remember, this is what Sherline mode does - increases the pulse width. It shouldn't change the kernel frequency.

Dan

Offline RICH

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Re: Parallel Port Voltage
« Reply #5 on: September 19, 2010, 10:16:29 AM »
PP cards can be single or dual voltage output ( 3.5 or 5 ) and the voltage can vary between the cards. You need a high and a low voltage swing and the internal resistance of the PC can vary. I few cards i purchased went to the trash can as recommended by an  electronics friend. He also made up some boards to guarantee the voltage swing was correct and crisp. I will remark that the boards did nothing for a bad signal generated by the PC. That problem is rather incurable.

FWIW,
RICH
Re: Parallel Port Voltage
« Reply #6 on: September 19, 2010, 11:37:29 AM »
I have been giving James support on this since he is using one of our breakout boards.  The problem is not associated to power on the parallel port because all of our boards can take 3.3 or 5vdc signals with power as low as 0.05mA.  The output is always +5vdc at 24mA (at least). The operating frequency can be from 100khz to 4Mhz (depending on the model).  The C10 can do 4Mhz without significantly altering the original wave form.

The most possible cause for this, may be that the board is not powered right, or that there could be a short of some kind, that could be draining the power, thus leaving some chips underpowered.

Other more rare causes can be: cables and parallel port, bad power supply, corrupted xml file, an hardware or software device affecting the pulse generation.

Arturo Duncan
http://cnc4pc.com
Parallel Port Voltage Update
« Reply #7 on: September 19, 2010, 07:30:53 PM »
I grabbed an off the shelf PCI PP card and had the exact same issue. The motors will only turn in Sherline mode.

Arturo has been very helpful in trouble shooting this problem. He has given me some things to look at tomorrow, so I'll post an update tomorrow night.

I am also going to try to borrow an 0-scope so I can take a look at the waveform being generated by the PP.

I should actually buy an o-scope. I usually need one about once a year, but have always had someone Else's to use. Any thoughts on a good dual trace o-scope that doesn't cost a fortune?

Thanks for the help guys. I'm going to document this troubleshooting as well as I can because I see a lot of posts in the forum where people have had to use the Sherline mode to get their machines to run properly.

James
Re: Parallel Port Voltage
« Reply #8 on: October 01, 2010, 08:51:09 AM »
Jim,

Is this solved?

Arturo Duncan
http://cnc4pc.com
Re: Parallel Port Voltage
« Reply #9 on: October 01, 2010, 07:36:21 PM »
Arturo,

Yes, the problem is solved. You were right, it was not a parallel port problem but a wiring problem.

I used a wiring diagram out of a book. It turned out to be incorrect. Once I used the the proper wiring everything worked great.

Thanks to all for the help.

James

Jim,

Is this solved?

Arturo Duncan
http://cnc4pc.com