O
[email protected]
- Jan 1, 1970
- 0
Hi all,
I made the foolish mistake in a recent instrumentation design of
routing a copper track from one board to another via a common 'mother'
board and associated edge connectors, straight into the input of a 4071
OR gate. The output of this gate clocks a 4015 4-bit shift register.
The circuit 'works' fine in the lab but the problem lies in the
equipment installation, where a number of noisy mains-powered solenoid
relays manage to falsely trigger the shift register for around one in
every ten actuations. I suspect that the long copper route is acting as
an ideal aerial for this noise, even though the entire circuit is
housed in a grounded metal box.
Are there any 4071 plug-in equivalents with schmitt-trigger inputs, or
other variants with better noise immunity? A less eloquent option would
be to insert two series connected schmitt-trigger NOT gates (of the
40106 variety), but space is already at a premium for such a
'piggy-back'. Any suggestions appreciated.
Thanks,
John.
I made the foolish mistake in a recent instrumentation design of
routing a copper track from one board to another via a common 'mother'
board and associated edge connectors, straight into the input of a 4071
OR gate. The output of this gate clocks a 4015 4-bit shift register.
The circuit 'works' fine in the lab but the problem lies in the
equipment installation, where a number of noisy mains-powered solenoid
relays manage to falsely trigger the shift register for around one in
every ten actuations. I suspect that the long copper route is acting as
an ideal aerial for this noise, even though the entire circuit is
housed in a grounded metal box.
Are there any 4071 plug-in equivalents with schmitt-trigger inputs, or
other variants with better noise immunity? A less eloquent option would
be to insert two series connected schmitt-trigger NOT gates (of the
40106 variety), but space is already at a premium for such a
'piggy-back'. Any suggestions appreciated.
Thanks,
John.