In the Top Ten Devices band decoders, we use the CMOS version BCD to
decimal chip, the CD4028. It directly drives a ULN2003 which can drive a
lot of relays. The relays are connected to +12 and the ULN pulls them to
ground. If you prefer to ground the relays and send +12 to them from the
decoder, you can use a UDN 2580 with an inverter.
George
w2vjn@rosenet.net
----------
> From: george fremin iii <geoiii@bga.com>
> To: Doug Smith <desmith@Telalink.Net>
> Cc: reflector TRLog <trlog@contesting.com>
> Subject: Re: [TRLog] Switch box
> Date: Saturday, November 08, 1997 10:18 PM
>
> Doug Smith writes:
>
> >I've been thinking of working on a box like this myself, hopefully
> >incorporating a band decoder too..
> >
> >What's the coding for the band data port? I assume it's BCD, but the
> >cross-coding to bands isn't obvious.
>
> Yes it is BCD - you can use a BCD-to-Decimal decoder driver
> such as a 74145 or similar to decode it. I did this
> this evening now if I can figure out how to use the output
> of the decoder to drive something that will drive my relays.
>
> Anyway the encoding is output to
>
> pins 2 7 8 9
> bits 1 2 4 8
>
> Band incoding is:
>
> 160 01
> 80 20
> 40 21
> 30 40
> 20 41
> 17 60
> 15 61
> 12 80
> 10 81
>
> --
>
> George Fremin III
> Austin, Texas C.K.U. "Eight is enough."
> K5TR
> 512/416-7010
> geoiii@bga.com
> http://www.kkn.net/~k5tr
>
> --
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