[time-nuts] Low noise power supply recommendations
paulswedb at gmail.com
Wed Jun 15 13:42:42 UTC 2011
Well a couple of thoughts.
As I said modern choppers do work and have big pluses these days.
But to the neon bulb.
I would use a led thats color more approximates neon. They make them.
I rebuilt a HP5360 counter /nixie with modern 7 seg leds that matched the
nixie color and it turned out very well. The photo resistors are touchy. The
older HP counters actually used neons and photo resistors in the decade
counters as the binary to decimal converters. The neon is not standard. Its
shorter, typical neons will not fit.
My O my has this drifted back to wwvb.
On Wed, Jun 15, 2011 at 7:49 AM, Will Matney <xformer at citynet.net> wrote:
> Correct, and by adding the series resistor for higher impedance, the
> voltage regulation at the zener value is raised from 10 volts to some value
> higher. I actually remember a variable bias control to a tube using a
> similar circuit, except the fixed resistor was a pot. He shows using this
> on a shunt regulator also on the following page. How much unstability this
> causes at the value given is unknown without actually building the circuit
> and testing it, but one shouldn't use a series resistor with a zener this
> way. I remember Rich Measures and myself speaking of this a few years back.
> One thing that's not mentioned in the article is that certain resistors can
> cause noise by themselves. Good articles on this are in some power supply
> and voltage reference App Notes from both Linear Tech., and National.
> *********** REPLY SEPARATOR ***********
> On 6/15/2011 at 6:59 PM Bruce Griffiths wrote:
> >Will Matney wrote:
> >> As far as the power supply is concerned, I think I am going to go with
> >> Ni-Cad batteries, and regulate the voltages. I think what they had was
> >> nothing more than four step voltages from the battery supply, going from
> >> 6 (7), 12, and 24 Vdc, or X2 of the other. From what I saw in the
> >> earlier, an easy zener with emotter follower regulator should do the
> >> by the comparison with batteries. They used some resistance in series
> >> the zener to reduce noise, but it did decrease the stability somewhat. I
> >> have seen this used in some old bias regulation circuits for tubes years
> >> ago.
> >A somewhat misguided idea, they really should have used an RC low pass
> >filter between the zener and the output transistor base.
> >The filtering effect is the same but without significantly decreased
> >stability over that of an unfiltered zener..
> >> As far as the noise, I also wondered about this, as ESI used a current
> >> limited DC power source to do the same thing, and it was ran off the AC
> >> line.
> >> Thanks,
> >> Will
> >> *********** REPLY SEPARATOR ***********
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