[Amps] Amps Digest, Vol 62, Issue 3

[Sugiyama]

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