[time-nuts] WWVB remodulator for the Spectracom 8170...

Attila Kinali attila at kinali.ch
Tue Jun 18 21:21:25 UTC 2013


On Tue, 18 Jun 2013 10:52:24 -0400
paul swed <paulswedb at gmail.com> wrote:

> Interesting the HC will work all the way down to 2.2V so everything can be
> run from 3 Volts.

I don't have a spec sheet at hand, but are HC types speced down to 2.2V?
I thought it was something around 3V

> No idea as to the effect of the xtal oscillator maybe the 3.9 M R needs to
> be changed.

Probably not. the 3.9M resistor is to give the oscillator circuit 
(which is an unbuffered inverter) a DC bias. Its value is usually not
critical. 

> It also appears that the HC chip may doing the lions share of current
> consumption. Spec sheet says up to 20 Ma. Hard to believe actually.

As long as it's mA not MA, it is indeed believable ;-)
HC used quite a bit of current. Especially when toggling at high speed
(where as high speed is to be seen relative to the 70s when these chips
were designed).

> As for driving lengths of wire over distance it needs to be a buffer chip.
> 74hc244. But that seems like serious overkill it can drive 20 ma per port.

If it's just a single signal, why not use a pair of digital mosfets like
FDV302P/FDV303N? These can drive a big load (680mA speced, with good cooling)
and are can be interfaced with 3V logic.



			Attila Kinali
-- 
The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
		-- unknown



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