Bernhard Kubicek pravi: > > > On Fri, Mar 26, 2010 at 5:21 PM, Slavko Kocjancic <[email protected] > <mailto:[email protected]>> wrote: > > Alexey Starikovskiy pravi: > > As a matter of fact, I already see a big stopper in your board > usefulness. > > You put optical isolation between logic and parallel port, I see 2 > > drawbacks of it: > > 1. parallel ports are quite weak these days (3.3v/~5mA), so > driving LED > > from it directly is not bullet proof. > > > All EPP ports are 5V tolerant and I didn't see the EPP port > diferrent as > open colector with pullups. LED are arranged to be driven low with > external 5V supply. And optocoupler is happy with anithing from 5mA up > to 20mA. So I see no problem. > > If the parallel port is indeed that week, your optocouples might not > recieve the 5mA to switch. Especially, if your pre-opto-resistors are > calculated for 5V. Resistors are calculated for 5V and will get 5V from external source. The EPP port signals can sink at least 20mA (but source only few mA)
> But honestly, I would expect an parallel port to being able to drive > an optocoupler. Can do! I make at least 20 diferent boards in same principle and all worked without problems. > Other option would be some mosfet gate that then switches the > couplers, but then you have might want to avoid touching the connector > pins with bare hands. .... and to get fried at 1'st thunderstorm. > > Otherwise, nice project, personally I would have tried to go for a > much smaller board. The board is big as is drawn to be homemade. And thus traces are thick. If I want to make doublesided board then footprint can be at least half of current. Slavko. ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
