On Sun, 2009-04-12 at 19:23 +0200, Lars Andersson wrote: > The text on this site does not say "optically isolated" so probably this > device isn't. It might be more like a digital buffer. The advantage of > opto isolators is that they break the ground connection between PC and > motor driver. > > >This >one looks interesting though: > >http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260360862785
I agree, without knowing what chips are on the board and how they are wired it's harder to recommend using it. Just to fill out some of the issues. For connections between the parallel port and peripheral electronics, a chip like this: http://www.semicon.toshiba.co.jp/docs/datasheet/en/Opto/TLP627_TLP627-4_en_datasheet_071001.pdf Short URL version: http://alturl.com/rt6c On the bottom of page one, pins one and two of the device are connected to an LED. For parallel port output, the output pin is (sometimes) connected to a driver chip: (just one example) http://focus.ti.com/lit/ds/symlink/sn74ls241.pdf or http://alturl.com/mudt then to the LED. Whenever the pin goes high the LED turns on (or off if wired that way). The tiny arrows between the LED and the transistor to the right of the LED, indicate that the connection that controls the transistor is through the light from the LED. There is no electrical connection, so you can fry the transistor and the LED won't transmit any voltage back to the parallel port. The transistor is used to pass the signal to your driver, relay or other boards. For parallel port inputs, the transistor is used to switch a voltage on the parallel port input pin. There is some disagreement on how to interpret the amount of voltage isolation you can get from these devices, but this one indicates 5000V. Another variation of this is the SSR (solid state relay), which has a driver on the transistor side so they can drive larger loads, such as solenoids. http://pewa.panasonic.com/pcsd/product/pmos/pdf_cat/aqv10_.pdf or http://alturl.com/t3jp http://www.crydom.com/en/Products/Catalog/d_o.pdf or http://alturl.com/47zn These isolators can be on a break-out board or on the peripheral's I/O pins, or not used at all. You'll have to check the board's documentation or look on the board for chips that look like optocouplers. One down side is, everything you put between the output and an input will delay or change the original signal a little bit. Usually this is not a problem. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
