[Amps] Amps Digest, Vol 62, Issue 3

[d.cutter at ntlworld.com]

The relay will hold until about 20% or so of its nominal coil voltage.  After that it will take 10 to 20ms to drop out, perhaps longer, so, it depends on the brown out you expect.  Define "moment"

David
G3UNA
> 
> From: Sugiyama <ji3kdh at 2333.net>
> Date: 2008/02/04 Mon AM 10:35:39 GMT
> To: amps at contesting.com
> Subject: Re: [Amps] Amps Digest, Vol 62, Issue 3
> 
> 
> Hi all,
> 
>    I'd like to choose the circuit that has a
> timer to close the main contact. I wonder if the
> detected voltage falls down even in a moment,
> the contact will open in simple R circuit,
> unexpectedly.
> 
>    I've set a timer relay into the input of the filament
> transformer in some TL-922s as follows. The
> timer is set as 2 seconds in this case. It's
> poor circuit, but it runs better for filaments,
> I believe.
> 
> http://www.2333.net/~ji3kdh/weblog/pics/2007/070103-1.jpg
> 
> 73
> Sugi JI3KDH
> 
> 
> On Sun, 3 Feb 2008 11:35:14 -0500
> Gary Schafer wrote:
> 
> > As David said step starts circuits are simple. There is no need for a timer
> > etc. In a couple of supplies that I have I just place a low value resistor
> > in series with the mains and place the relay coil, of the relay that shorts
> > out the resistor, across the transformer primary. When the capacitors charge
> > up enough the voltage across the primary will also rise. When it gets high
> > enough to pull in the relay you are done. 
> > 
> > The only problem with doing this is that the relay will have some chatter
> > due to the rising pull in voltage. It would be better to use a DC relay here
> > and a diode from the transformer primary so that the relay pulls in
> > smoothly. 
> > 
> > This simple approach does the same thing as sensing the high voltage without
> > the associated problems. It also has built in delay too.
> > 
> > 73
> > Gary  K4FMX
> 
> 
> 
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