Article View: sci.electronics
Article #8232Re: Design a bar graph
From: Brian E Rhodefer
Date: Thu, 08 Nov 1990 00:55
Date: Thu, 08 Nov 1990 00:55
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In article <1990Nov3.200047.11252@athena.mit.edu> chuck@mitlns.mit.edu writes: > (Tedious-to-enter circuit diagram deleted) > > Takes three chips 1 74xx138 and 2 quad and gates. How many did > it take you? > > > Chuck@mitlns.mit.edu One chip: A 7445 open-collector binary-to-decimal decoder/driver. The seven LEDs can be wired in series, with the cathode end of the string going to output 7 of the decoder, and successive cathode/anode node pairs going to outputs 6 through 1. Wire the anode end of the string to output 0, and apply a 20mA current source that has enough voltage compliance to push through all seven LEDs. Whichever output of the 7445 gets turned on will shunt the current to ground, preventing it from flowing through however many LEDs are "downstream" of that output. All the LEDs up to that output carry the current, and therefore light up. Brian Rhodefer
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arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!mit-eddie!uw-beaver!zephyr.ens.tek.com!tekig5!brianrReferences:
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Path: arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!mit-eddie!uw-beaver!zephyr.ens.tek.com!tekig5!brianr From: brianr@tekig5.PEN.TEK.COM (Brian E Rhodefer) Newsgroups: sci.electronics Subject: Re: Design a bar graph Message-ID: <7217@tekig5.PEN.TEK.COM> Date: 8 Nov 90 00:55:23 GMT References: <1990Nov3.200047.11252@athena.mit.edu> Reply-To: brianr@tekig5.PEN.TEK.COM (Brian E Rhodefer) Distribution: na Organization: Tektronix, Inc., Beaverton, OR. Lines: 23