[HomeBrew] Re: An RTS-DTS Reed relay question

[W1EOF]

> Message: 1
> Date: Tue, 1 Mar 2005 21:29:18 -0000
> From: "Philip Atchley" <beaconeer at sbcglobal.net>
> Subject: [HomeBrew] An RTS-DTS Reed relay question
> To: <homebrew at mailman.qth.net>
> Message-ID: <001201c51ea5$bb274fc0$d87ff504 at ko6bba1e64d2b6>
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> 	reply-type=original
>
<SNIP>

Phil - I wouldn't rely on the RS-232 port supplying ample current to
consistently operate those relays. Even if they seem to work OK now, I think
the design would be marginal. You could change computers in the future and
have a case where they would not work at all. You also run the risk of
premature relay problems because you are not driving them hard enough.
Typically reed relays like to have to have at least 40% overdrive.

There are websites on the net which contain schematics for interfacing the
RS-232 signal lines to a relay. Basically it takes two transistors. It
hardly seems worth it to skimp on four transistors, at least from my POV.

I hope when you are done you share your circuit with the rest of us. I've
been planning on building one for my shack for years now. Just never get
round-to-it. Two many tube based projects that keep me busy so I don't get
time for any new-millenium technology. :-)

73,

Mark W1EOF
N. Kingstown, R.I.
ARRL QCWA FISTS FP SOC QRPARCI
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