[ntp:questions] Trying to use Dimension 4 time keeper

unruh unruh at invalid.ca
Wed Sep 25 22:53:02 UTC 2013

On 2013-09-25, Dennis Ferguson <dennis.c.ferguson at gmail.com> wrote:
> On 25 Sep, 2013, at 12:04 , John Hasler <jhasler at newsguy.com> wrote:
>> I wrote:
>>> I'm suggesting adding an open-collector driver rather than adding a
>>> network of resistors and diodes.  Fewer parts and better results.
>> unruh writes:
>>> Probably. I'm a bit worried if the base voltage is higher than the
>>> collector.
>> A single transistor with a base current limiting resistor would work
>> fine but I had in mind an IC such as the 7407.
> If you are doing it with an IC a 3.3V buffer with overvoltage
> tolerant inputs would be better.  A 74HC4050 run at 3.3V would
> probably do it, if you don't need input protection (against >15V or
><0V inputs) it needs no additional external components.

Except a power supply, which can be a pain.

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