Subject: Re: How to get CMOS counter to drive a relay?
Date: Mon, 14 Oct 2002 18:39:56 -0700
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Thanks for the compliment.
Please educate me more.
A CD4020/40/60 counter is a cmos counter, yes?
The fet is driven by the same power that drives the CMOS
You can take out the 7 parts without removing the diode
on the relay coil.
It's all isolated by a relay and can be arbitrarily shielded
against external influence, yes? The FET won't require
any more isolation/shielding than is required for the rest
of the CMOS stuff.
If you'd said, "dont use cmos anywhere in the system," you
would have an arguable point.
In any practical application, additional protection may be required
to meet demands not indicated on the schematic.
There may be lots of issues, but if the two-transistor circuit
works, the FET will work with 7 fewer parts. And that's ALL I said.
I am proud to be a minimalist. That doesn't mean I don't know
what I'm doing. Minimalist design is not convenient; it's
VERY difficult to produce a low cost, reliable design. If you catch
an engineer before he gets set in his ways, you can train him out of
"brute force design mode".
Fred Bloggs wrote:
> mike wrote:
> > Or you could use a FET and take out 7 parts.
> This is not quite true because in the real world a stand-alone FET is
> inadequate and will require ESD and transient protection. The OP did
> mention some connection to HVAC and this means large electric/magnetic
> field strengths as well as destructive transients due to abrupt
> cut-outs. The various minimalist engineering types conveniently omit the
> fact that their experience does not extend beyond cheaply made, poorly
> designed, unreliable consumer products of no importance.
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