Is there any reason to buy this over the newegg product??
Is there a difference in quality between one unit and another??
Just by reading the specs between the two cards the one is a little better and can transfer data faster. Now weather you need to be able to transfer data faster I dont know but the New Egg one will do 1.5mb a sec & the other will do 5mb a second data transfer. Also the better one says it is backwards capatible which may help it work with a older computor if you ever needed it to. The NE one didnt even say if it was backwards capatible. Who knows the cheap one may even be better but the other one does have better specs.
On a nother note here is some onfo on Pcards that is interesting & you should read it. I copy/pasted this from the IH site.
A computer is a horribly complex piece of equipment, lots of pieces, some big, some small, but all important. To make matters worse is the folks who make the computers all get together and make up the rules on how computers should operate. So what does this have to do with CNC?
Nothing and everything. A few years ago every parallel port/card on the planet worked at the 5 volt level. This was “the good old days” as 5 volts is considered a TTL High and the parallel port could be easily connected to any other device and everything worked great. But somewhere between then and now, “they” got together again and started lowering the voltage for the parallel port. Currently I believe the spec is 3.3 volts (don’t quote me on this) and I’ve seen it as low as 2.4 volts. Back to CNC
The problem is CNC devices need some decent voltages. A Gecko for example requires a 5V signal to work properly and most popular breakout boards require at least 3 volts. Without the proper voltage you get erratic operation, no operation, or just flat out flakiness. The Solution
First of all, we had to find a 5 Volt card as for the most part we don’t use a breakout board, so our search for a good card took a little longer than it might have if we used a breakout board. But we went through about a half-dozen before we found the one we like.
The card we like is the SIIG CyberParallel PN JJ-P001122-B and you can find it on the web here and there. It is NOT the cheapest card and I have seen it retail for as much as $45. On the flip side I found it for $18 and bought out all the stock from one web supplier, so the deals are out there, you just have to look.
Just to give this little tip some credibility, I was at a customers place this past weekend and low and behold nothing worked with a bran-new 4 GHZ Gateway. After breaking out my handy dandy silly-scope and saw 2.4 volts on the port I knew the problem. Dropped in a new card and the problem was solved.
Furthermore, when someone purchases a turn-key machine from us, we put a card or two in their PC before we ship it all back. We don’t even test to see if it needs it. It’s simply “part of the deal”. Long and Short
If nothing works, but everything is right.
It’s not acting ‘right’
You’re just really, really smart and want to avoid a headache to start with. Get the card.
I dont know how to find out if the card is 5v beside measering it with a DVOM or calling them up and asking. There may be something in the info of the cards that dictates that it will put out 5v but I am not sure what it is.
The printer port or parallel port on PC is an old I/O interface from the age of 1980's which was originally for IBM PC AT (8086 CPU). Over years, there have been improvement on this interface known as ECP/EPP. However, I think the CNC control software still uses the parallel port in an old standard way.
The standard parallel port usually supports only about 400KHz data rates no matter how fast you really writes to that port, the CPU can simply be blocked by the I/O device. Note that it is a port for printer not for generic high speed I/O.
Theoritically, it is possible to have a transparant USB to parallel port bridge. The driver can trap the access to a parallel port I/O address and forward the request to a USB function device which provides the physical signals as the parallel port. However, with this method, the speed and the latency will be worse than an ordinary parallel port. It looks like the comercial one does not work in this way.
I hate to use a PC for the motor timing. Neither the XP nor the normal Linux was designed for the real-time timing. I'll probably develop an isolated controller with USB and Ethernet interface, if I need to convert a mill to CNC by myself. The first design might be an integrated controller with 4 stepper drivers.