Re: THE GRIZZ
The MX4660 has Opto-Isolated I/O. In general, for outputs they are **pulled** high when it is inactive. So a large value resistor connects it to the positive side of the I/O voltage you provide presenting a digital high. When the output is active a phototransistor is switched on by the MX4660 electronics and grounds the output pin thus presenting a digital low to the outside world. Outputs like this are not suited to driving a load in the inactive (high) state. They can sink a load when active (low) by providing that load's path to ground. So for instance to light an LED when the I/O is active you place the cathode (neg) side of the LED onto the I/O pin so when the path to ground is complete, the LED lights. This arrangement can usually drive a pretty decent load. I did not see a clear indication of the transistor's current limit but I'd say probably 100ma to 200ma would be a safe bet.
Inputs on the MX4660 are similar. The outside world input will be expected to drive an internal LED inside the MX4660 that activates the internal phototransistor to signal your input to the electronics and parallel port. This input arrangement usually has pretty wide input voltage tolerance but some attention to detail is needed if you get higher than 12V. You can use the supplied 12V or your own supply voltage to do this (say 5V if needed). If you go over 12V however you need to add more resistance to stay within the current limits of that internal LED.
Can't speak for the Ethernet Smooth Stepper, but most interface / motion control cards provide Microcontroller / IC type I/O. Usually that I/O is like a SPDP switch inside a chip. The output is in the middle and the IC switches that between it's positive and negative supply to drive the output. Such I/O can directly drive small loads in either high or low output. However they often have very restrictive limits on the current they can provide doing that. Usually 5ma to maybe 50ma per output. They are dangerous to connect up directly to external loads because they can be easily destroyed by either too much current running through them or even a couple volts above the chip's logic voltage. These are usually expected to be paired to opto-isolators as described above to protect the chip from damage.
If the device is described as having a "breakout board" then often (but not always) they provide the opto-isolators or other electronic protection to the I/O pins they expose but you MUST read carefully to understand if they do or don't.
Hope that helps somewhat.
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