Ahh, of course. The whole topic being on multiplexing should really of been the clue there. silly me...
On Sunday, 6 January 2013 14:58:32 UTC, jrehwin wrote: > > > Why would you need a soft / slow rise time on the anode cut off to > reduce switching noise when the cathodes are toggled repeatedly by the > 74141? Surely that introduces just the same switching noise that would be > produced with just a high side switching FET or BJT? Or does the 74141 > feature a slow transition on its output? I can appreciate the optical > isolation for the high side switching as being a nice part of the > opto-couple solution though! > > It's the sequence of events that makes it work. The cathodes are switched > (hard) by the 74141, but no current flows (and noise is not radiated) as > the anode isn't powered yet. Then the anode is turned on (soft) by the > optocoupler, and the current rises gently, producing minimal radiated > noise. When it's time to switch the digit off, the same thing happens in > reverse, the anode is turned off (soft) by the optocoupler, smoothly > reducing the current, then the cathodes are again switched while the > current is off, thereby not producing switching noise. > > - John > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/nrygAMXXVDYJ. For more options, visit https://groups.google.com/groups/opt_out.
