Thanks to everyone who responded, and special thanks to Joe, W4TV, for
enduring a series of questions. I thought others might find it useful
for me to document the outcome.
The solution, which Joe and several others suggested, is to use an
optoisolator with a MOSFET output stage. I chose two Panasonic AQW212
2PST (NO) "solid state relays" which can switch up to 60 volts at 500 mA
- plenty of headroom. I will try current limiting resistors on the
inputs, even though this part is rated at below 1 mA typical turn on
current, and a series diode on each output line to isolate it from the
manual switching. At Joe's suggestion, I'm going to use Position 1 of
the RCS-10's control box's 1 of 8 output to supply the 12 volts, because
in that position the BCD output is 000, eliminating any conflicts in
what gets sent to the relays.
I should have it running by the end of the week, and will report any
glitches, but it looks pretty straight-forward.
73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com
On 5/31/2010 9:25 AM, Alfred Frugoli wrote:
> Hi Pete,
>
> If you're looking to convert the BCD output from your lpt port to
> drive relays, why not just use the Unified Micro BCD-10 band decoder
> (http://www.unifiedmicro.com/decoder.html). I have 2 of them
> that interface my K3's to my ICE bandpass filters. Just make sure you
> hook them up right - there's no protection circuitry built into the
> boards so if you reverse the polarity, or some other dumb mistake, it
> fries one of the ICs.
>
> Good luck with your project.
>
> 73 de Al, KE1FO
>
> K3 #3055
> K3 #4094
> -----
> Check out my Amateur Radio Contesting blog at ke1fo.wordpress.com
> <http://ke1fo.wordpress.com>.
>
>
> On Sun, May 30, 2010 at 12:27 PM, Pete Smith <n4zr@contesting.com
> <mailto:n4zr@contesting.com>> wrote:
>
> I bought an Ameritron RCS-10 antenna switch at Dayton, particularly
> because of its BCD control protocol. My thought was to use the
> BCD band
> data output from my shack computer, running N1MM Logger, to
> control the
> remote relay box in parallel with the manual controller. But in order
> to do that, I will need 3 relay drivers to supply the needed current,
> and presumably, will also need a level shifter because the relays want
> 12 volts, while my LPT port is 5.
>
> Has anyone already been down this road, so I won't have to
> reinvent the
> wheel? Is there a way to use traditional PNP transistor source
> drivers,
> but with 5 volts on the base and 12 volts on the collector?
>
> 73, Pete N4ZR
>
> The World Contest Station Database, updated daily at
> www.conteststations.com <http://www.conteststations.com>
> The Reverse Beacon Network at http://reversebeacon.net, blog at
> reversebeacon.blogspot.com <http://reversebeacon.blogspot.com>
>
> _______________________________________________
>
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