Author: HammyDate: 09:16 24-08-07
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What is the best method for remote control of a PSU just to control
switching it on and off? I was looking at data sheets for relays DPDT
but they all seem to require a holding current in the coil. Is there a
relay that latches on for a single pulse and will stay latched until a
second pulse is delivered? No coil holding current required from the
battery operated control signal (see schematic).Or is there an
alternative solution?
This is the schematic. The transformers load is a 1.5W LM317
regulator.
http://i12.tinypic.com/5yx94q0.png
Thanks for any suggestions.
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On Aug 24, 9:16 am, Hammy <spa...@hotmail.com> wrote:
> What is the best method for remote control of a PSU just to control
> switching it on and off? I was looking at data sheets for relays DPDT
> but they all seem to require a holding current in the coil. Is there a
> relay that latches on for a single pulse and will stay latched until a
> second pulse is delivered? No coil holding current required from the
> battery operated control signal (see schematic).Or is there an
> alternative solution?
>
> This is the schematic. The transformers load is a 1.5W LM317
> regulator.
>
> http://i12.tinypic.com/5yx94q0.png
>
> Thanks for any suggestions.
Yes. They are called latching relays. Just about any large
electronics supplier sells these (see Newark Electronics, Digikey,
Mouser Electronics, etc.)
BRW
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Author: ehsjrDate: 09:46 24-08-07
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Hammy wrote:
> What is the best method for remote control of a PSU just to control
> switching it on and off? I was looking at data sheets for relays DPDT
> but they all seem to require a holding current in the coil. Is there a
> relay that latches on for a single pulse and will stay latched until a
> second pulse is delivered? No coil holding current required from the
> battery operated control signal (see schematic).Or is there an
> alternative solution?
>
> This is the schematic. The transformers load is a 1.5W LM317
> regulator.
>
> http://i12.tinypic.com/5yx94q0.png
>
> Thanks for any suggestions.
To begin with, eliminate NTC1, NTC2 and SW2.
You don't need a DPDT relay - single pole
is fine. And yes, there are latching relays
that are pulse operated and do not require
holding current.
Ed
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Author: Rich GriseDate: 18:05 24-08-07
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On Fri, 24 Aug 2007 13:16:47 +0000, Hammy wrote:
> What is the best method for remote control of a PSU just to control
> switching it on and off? I was looking at data sheets for relays DPDT
> but they all seem to require a holding current in the coil. Is there a
> relay that latches on for a single pulse and will stay latched until a
> second pulse is delivered? No coil holding current required from the
> battery operated control signal (see schematic).Or is there an
> alternative solution?
>
> This is the schematic. The transformers load is a 1.5W LM317
> regulator.
>
> http://i12.tinypic.com/5yx94q0.png
>
> Thanks for any suggestions.
Use the pulse to energize the relay, but then get power to hold
the relay in from whatever it is you're powering. You'd need a little
circuitry to turn it off, say a gate where if power is on, then when
a pulse comes in, it gets inverted and interrupts the power to the
relay, turning it off.
Good Luck!
Rich
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Author: HammyDate: 20:25 24-08-07
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Thanks all for your suggestions.
I think I may have found a suitable latching relay at Digikey (not
much selection). I've noticed that they must be derated 75% for
non-resistive loads. The largest current carrying capacity is two amps
resistive load and 0.5A non-resistive.
I have a 14VAC 4.4VA Transformer coming next week hopefully Monday; I
can take some measurements to see if 0.5A_rms is adequate for sure
with safety margin. The LM317 is for 12V @ 0.125A.
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