Re: [smartsockets] pull-mid resistors on Smart sockets
- On 15 Dec 2009, at 18:42, ckeiser10 wrote:
> I have just completed a 4 letter word clock using John Smout's pic.Charles,
> It works well but is noisy especially when all segments are on
> during a transition. I read an earlier entry from Chris about
> possibly adding pull-mid resistors to the smart socket. Has any
> tried this and gotten any results? I could cage the tubes in
> plastic but would prefer not to.
My tubes sing too when doing a fade or transition, it's the
transition frequency we hear. I am not sure there is much we can do
about this. Would a pull-mid help much?
- There is the possibility that pull-mids could help, because even though a fade is created by switching rapidly between two digit cathodes, each individual cathode is being switched between 0V and HV+ during that time. A pull mid will reduce the total switched potential by holding the cathode at a lower off state voltage than if no pull mid were used.
It is certainly worth trying as an option.
The noise,as far as I can tell, is a result of the small amount of movement which each cathode exhibits, when it is switched, as a result of electrostatic forces. The cathodes are not fixed rigidly, or clamped, to their supports and the sml amoint of fitting tolerance allows them to move slightly.
Has any tried this and gotten any results? I could cage the tubes in plastic but would prefer not to.