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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