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Am 09.09.2012 17:42, schrieb John
Coffman:
On 09/08/2012 11:50 PM, Sergey wrote:
It must be some kind of conspiracy about switch debouncing, it looks
like 90% of the related pages on the Internet are referring to this
"research": http://www.ganssle.com/debouncing-pt2.htm . More exactly
to the circuit on Figure 3 (the circuit on Figure 1, which also
frequently referred everywhere, is mostly unusable, since nobody will
use a double throw switch just to overcome the contact bounce)
Simpler even than the circuit shown in Fig. 1 (see above) is the
attached circuit. Although it breaks all the rules about shorting
a gate output to GND, it operates well within the specs for
LS-TTL. Further, it minimizes components: only an SPDT switch
and a cheap IC are used.
The LS-TTL spec states that LS must not be harmed by a short
circuit to power or ground of duration less than 1 second. This
circuit shorts the output of a gate to ground for no more than
10ns, within the spec by a factor of 100,000.
In engineering a debounce circuit, using the absolute minimum of
components is generally the most economical approach. The LS00
solution of Fig. 1 above is good (the resistors to +5 can actually
be eliminated with LS-TTL), but the attached circuit is even
simpler.
I know of no more economical solution.
--John
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Hello John,
Sergeys circuit is absolute correct. Your circuit never works
correct. I watched my textbook about TTL-IC and there is Your
circuit out of standard.
Regards
Wolfgang
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Dr.-Ing. Wolfgang Kabatzke
Hansastrasse 9
DE - 21 502 Geesthacht
Deutschland / Germany
Phone: +49 4152 93 18 130 NEW!!!
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