[TRLog] Switch box

[George Cutsogeorge]

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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