On Thursday 08 October 2009, Andy Pugh wrote: >2009/10/8 Kirk Wallace <[email protected]>: >> 74LS244 Data: >> http://media.digikey.com/pdf/Data%20Sheets/Fairchild% >> 20PDFs/DM74LS244.pdf >> (Short URL) http://preview.alturl.com/kjp9 > >Thanks. Perhaps I am being dim, but I don't see how that helps? > >I want 18mA to flow through the opto-isolator in the drive any time >the drive box is powered up, except when the PC takes a P-Port pin >high. >Is the suggestion that I control the "enable" pin of the 74LS244 with >the P=Port, and take the opto currents through a channel each? It >looks to be a logic/voltage device?
Yes, arrange the logic to have enabled=low at the 244 outputs, and feed the + end of the opto device from the 5 volt line, with suitable current limiting of course, per the app notes. That way you will be using the high current capability of the 244 in the logic 0 condition. This should be true for any opto _driving_ device. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> "It is hard to overstate the debt that we owe to men and women of genius." -- Robert G. Ingersoll ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
