[Elecraft] The state of a latching relay

Fri Jan 24 22:26:03 2003

Hi

This some more of that firmware magic I was talking about. Notice one side
of all of the relays are connected together. The other side of each relay is
connected to an output pin on the IO controller. These pins can source or
sink current. Now if you make all of the pins low except the relay you want
to switch this will place a voltage in say, polarity + across the relay and
will set it. Now if you want to switch the relay to the reset condition then
you make all of the pins high except the relay you want to reset. Now you
have a - polarity across the relay and that relay resets. This sequence can
be repeated as many times as required and very quickly. Once the relays are
in the proper position they mechanically hold their condition so no further
power is needed to hold them and all of the pins can be set high or low.
Then no current will flow because there is not a difference of potential.
Only the relay that you want to switch will switch because all of the other
relay coils are in parallel so only a small amount(1/18 if you have the 160
module) of current flows in each coil except the one you want to switch and
it get the full current pulse.

Don Brown
KD5NDB

----- Original Message -----
From: "Sverre Holm - LA3ZA" <[email protected]>
To: <[email protected]>
Sent: Friday, January 24, 2003 3:44 PM
Subject: [Elecraft] The state of a latching relay

> If I understand right, the latching relays in the K1 and K2 change state
> every time you give them current for a short while, and then stay in the
> new position until the next impulse is given to them. To my mind this
> makes it impossible to figure out which position they are in, but I'm
> probably missing something here.
>
> So the question to the clever ones is: How does the firmware in the K's
> know the relay settings?
>
> 73
>
> Sverre Holm, LA3ZA
> ------------------
> www.qsl.net/la3za
>
>
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