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From: tom@syssoft.com (Rodentia)
Newsgroups: sci.electronics
Subject: Re: Design a bar graph
Message-ID: <1990Nov15.002806.328@syssoft.com>
Date: 15 Nov 90 00:28:06 GMT
References: <16307@s.ms.uky.edu> <10546@milton.u.washington.edu> <273510f4-521.3sci.electronics-1@vpnet.chi.il.us>
Reply-To: tom@ssi.UUCP (Rodentia)
Organization: Systems & Software, Inc., Irvine, CA
Lines: 52

In article <273510f4-521.3sci.electronics-1@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (Crash Gordon) writes:
>
>>Author: [Ken Tindle]
>>I have three binary lines, for eight possible states (yeah, oh wow).  How
>>can one light seven LED's from this, with zero having all LED's off and
>>seven lighting all seven of them, in bar graph fashion?
>
 [response deleted, it's just that the original article expired]
>
>>As a final touch, one should tax each digital
>>line with but one standard TTL load. 
>

   I finally worked this one out in a way I think Ken wanted,
it's one load each input, and each output may have one additional
load other than the LED, and there is an increasing prop delay.

   It uses eight OR gates, you can break the O0 LED and it's seven
LED's just like you said.  Also, I left off the decoder in this case, 
but just put it on I7..0.


GND-+
    |
I7___=D-+-------------------------------O7
        |
I6_______=D-+---------------------------O6
            |
I5___________=D-+-----------------------O5
                |
I4_______________=D-+-------------------O4
                    |
I3___________________=D-+---------------O3
                        |
I2_______________________=D-+-----------O2
                            |
I1___________________________=D-+-------O1
                                |
I0_______________________________=D-----O0

Legend:
=D-  or gate
+    dot (for connection)

   Hope this is close to what you wanted.  Three parts (decoder
and two quad OR gates).  A PAL might fit it all, or maybe a 
22V10.  As was stated, a PROM would definitely do it in one part.

-- 
Thomas Roden                            tom@syssoft.com
Systems and Software, Inc.              Voice:  (714) 833-1700
                                        FAX:    (714) 833-1900