On 2/22/2012 1:42 PM, Gerrit Heitsch wrote: > On 02/22/2012 07:57 PM, Jim Brain wrote: >> On 2/16/2012 10:49 AM, Gerrit Heitsch wrote: >>> >>> D1 = 1N4148 >> Why is D1 needed? In the reverse mode, the optocouple won't conduct, so >> they're no concerns. > > A LED can only take a very limited reverse voltage. The number I once > learned was 5V, apply more and you might destroy it. The antiparallel > 1N4148 limits the reverse voltage to 0.7V. I thought they were well about 6V. Makes sense. > > The idea with the cap was not to stretch the cycle but to filter out > short voltage spikes (line noise). The value was a guess back then, > but if you omit it, your clock will be fast (that part was tested). That's my digital side peeking out. Never thought about line noise on the TTL. JIm Message was sent through the cbm-hackers mailing listReceived on 2012-02-23 02:00:05
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