On Mon, Dec 08, 2003 at 06:29:19AM -0800, Martin McCormick enlightened us thusly
> As an electronics experimenter who is blind, I write down the
> pin-outs of chips I am working with in Braille in a notebook.
> Sometimes, I forget to write down crucial details that I just know
> I'll remember as well as I do my name, but my brain sometimes doesn't
> remember as well as I'd like.
>
> Are the Control lines for the 4 bilateral switches of a CD4016
> or a CD4066 active low or active high?
>
> I am going to be running one or two of these chips from a PIC,
> actually, via a 7405 open collector hex inverter to shift levels from
> +5V to +12v where the bilateral switches can switch a larger voltage
> range. The neat thing about the PIC is that I will just write the
> firmware to fit the polarity requirements.
>
> Those who have ever switched audio with a CD4016 or 66 know
> that when the switch is open, voltages that exceed VDD/2 will slip
> through anyway. With 12 volts, this raises the breakdown threshold to
> +-6 volts rather than +-2.5 volts.
>
My admiration for any blind electronics guy is sky high! How do you know
if you passed the 'smoke test'? How do you read a meter or 'scope, not
to mind email and all the bilge you have to read to do anything. Finding
a crack in the tracks must be a nightmare!
They are active high, Martin.
I built a crucial agc circuit with one at it's centre as nearly my first
job out on my own. I found a 6V offset was necessary to keep the
switched voltage central. You have that worked out I presume.
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
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