Re: Switch debouncing and related stuff (like CPU reset circuits)

[roman fulek <roman...@gmail.com>]

I did try using a 555 timer as single shot multivibrator for
> debouncing, but it has one problem - the 74x74 itself needs to be
> reset to a known state (so that by default, after connecting the
> power, ATX power supply will be off), otherwise it ends up being on or
> off randomly each time power is applied (well, maybe not randomly, but
> theoretically it could end up in any state). Since 74x74 doesn't have
> Schmitt triggers on /SET and /RESET inputs, it is not correct to
> connect an RC delay reset circuit directly to these inputs (while most
> likely it will work, sometimes it might not), so I needed to use an

no it'll not work :-(
I used this in my design recently and wondered why it does not work !!

> external Schmitt trigger for that anyway. So I ended up using a 74x14
> for that, and for power switch debouncing.