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Old 24th July 2002, 04:12 PM   #1
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Default Making LED voltmeter

Does anyone has a schematic of voltmeter interfacing with 7-segment LEDs? I tried to do it with MAX7137 chip,but it seems doesn't working...
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Old 24th July 2002, 04:33 PM   #2
UrSv is offline UrSv  Sweden
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It is in the data sheet:

http://pdfserv.maxim-ic.com/arpdf/ICL7137.pdf

/UrSv
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Old 25th July 2002, 01:45 PM   #3
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Well,I make that circuit they sujjest,and it doesn't working.All I see is all segments are lighting,so I only see 888 digits...
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Old 25th July 2002, 05:47 PM   #4
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Default I had a bunch of these chips

these chips were very static sensitive -- when they were made by Intersil --

note -- the 7137 uses common anode display
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Old 3rd August 2002, 06:09 AM   #5
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I would use a microcontroller, three BCD to 7 segment IC, three 7 segment displays, and a 4-bit ADC converter.

OR

Use a three 7-segment chip controller.

Go to ePanorama.net to find other alternatives.
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Old 3rd August 2002, 01:11 PM   #6
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Default 4 bit ADC?

that's not very acurate (1/16). You need at least a 10 bit ADC and a quiet and acurate voltage reference.

Microchip (www.microchip.com) has several application notes on their website for the 10 bit incorporated ADC and multiplexing LED's. To get started programming PIC's is a little daunting, but once you get it, they become incorporated into more and more designs. <p>If you are just starting out in microprocessors, a chip with a built in BASIC compiler <b>AND</b> a 10bit ADC <b>AND</b> a routine for shifting data out serially to a LED controller (like the Maxim MAX7219) is the BX-24 from Netmedia (www.basicx.com). There is also a chipset from www.Embedsys.com which uses Sprint Basic -- and you can get Sprintbasic as freeware if the program doesn't go over a certain number of lines.

The Harris/Intersil chips were nice in their time, but I don't think they are particularly user friendly for DIY'rs. I fixed a piece of instrumentation a while back -- I traced the problem to one of their chips -- again common anode display --
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