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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: Design a bar graph
Message-ID: <10546@milton.u.washington.edu>
Date: 3 Nov 90 23:50:43 GMT
References: <16307@s.ms.uky.edu> <1990Nov3.185821.23815@julius.cs.uiuc.edu>
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Organization: University of Washington, Seattle
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In article <1990Nov3.185821.23815@julius.cs.uiuc.edu> totty@flute.cs.uiuc.edu (Brian Totty) writes:
>
>> 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? 

	If you can connect R/2R/4R resistors to the lines to make an
analog signal out of it, an LM3914 dot/bar display driver will do it.
It comes complete with a single resistor brightness control (fixed 1k ohm
will do for fixed LED current).
>
>	As a related question, are there any 4 bit -> 7-segment LED
>	decoder/driver chips that represent the 4 bits in Hexadecimal
>	rather than BCD with garbage for the top 6 values?
>
	I know of two; in CMOS, there's MC14495.  Made by Motorola, it
includes a four-bit latch, output buffers, and current limiting resistors.
In TTL, the old Fairchild F9368.  Straight TTL (1.6 mA input current),
these were the two WARM chips on the old 1802 ELF board (they drove the
address/data bus readout).  I don't think they have latches (and I
replaced mine with the CMOS as quickly as I could... lo those many years
ago).

		John Whitmore