B
Brian C.
- Jan 1, 1970
- 0
Hi, I am trying to toggle a +'ve edge triggered JK flipflop (74hc109) ,
it toggles fine when the clock input is driven by a 555timer but when I
try to drive the clock input from a phototransistor (which is being
pulsed by the 555 driving an emitter) then most of the time it will not
toggle, just stays at a high level. But if the emmiter and
phototransistor are placed directly in front of each other - then no
problem, even though the switching voltage levels at the clock are the
same no matter what the distance between them (good alignment is
mantained). I have tried buffering the phototransistor output to the
clock and this improves the situation a little (more so when I connect
the DVM to monitor the clock voltage!!), but even still it is not
consistent. Does anybody have an explaination for this? I would greatly
appreciate any assistance
Brian C.
it toggles fine when the clock input is driven by a 555timer but when I
try to drive the clock input from a phototransistor (which is being
pulsed by the 555 driving an emitter) then most of the time it will not
toggle, just stays at a high level. But if the emmiter and
phototransistor are placed directly in front of each other - then no
problem, even though the switching voltage levels at the clock are the
same no matter what the distance between them (good alignment is
mantained). I have tried buffering the phototransistor output to the
clock and this improves the situation a little (more so when I connect
the DVM to monitor the clock voltage!!), but even still it is not
consistent. Does anybody have an explaination for this? I would greatly
appreciate any assistance
Brian C.