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Seven Segment LED/LCD displays? Answered

Does anyone know a good tutorial on how to use these? Thanks!

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westfw (author)2007-06-03

Exactly what do you want to do? There's not a lot TO a 7-segment LED display until you want to connect a bunch of them to microcontroller or something. It's just 7 LEDs with one common connection, and you control what it looks like by which LEDs you light up.

Parallax's "What's a Microcontroller" has a pretty thorough discussion in chapter 6.

An LCD display is more complicated because it needs to be driven with an AC voltage, but the principles are similar...

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perkinsb1024 (author)westfw2007-06-03

I want to use two AAA to make it display a 5 It looks like they're attached in series inside, though, so I'm not sure how to do this with only 3 volts and without the chance blowing them out... Then I want to attach that to a 555 timer and make it blink about once a second. That's it. Nothing more, nothing less.

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LasVegas (author)perkinsb10242007-06-03

Then all you need to do is tie the positive (anode) lines of segments 1, 2, 4, 5 and 7 together. Then connect that to the positive output of your flash circuit and the Common line to the negitive output (or ground).

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perkinsb1024 (author)LasVegas2007-06-04

But wouldn't that only give 3/5 V to each segment? And how would I use a 555 with that? I'm not sure how they work... can someone draw a quick schematic? Thanks guys

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LasVegas (author)perkinsb10242007-06-04

No... It would give 3 volts to each segment, but split up the available current from the source. The LEDs are connected in parallel.

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perkinsb1024 (author)LasVegas2007-06-05

Well, I'm having trouble getting the 555 timer to work... can someone help me? I found a couple schematics, but they're pretty complex... I have a 220uF capacitor, two 3.3K Ohm resistors, and the timer... does anyone know where to go from here?

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LasVegas (author)perkinsb10242007-06-05

I found this circuit that should work fine with your 3v supply.

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perkinsb1024 (author)LasVegas2007-06-05

Well, I just tried this, and it didn't work, I'm not saying it's a bad schematic, I know it's my fault... would a picture of my circuit be of any help at all?

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LasVegas (author)perkinsb10242007-06-05

Have you verified if the display lights with 3v alone? Are you using a 555CP? The CP indicates a CMOS chip that will run on 3v. Some variants of the chip require at least 5v.

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perkinsb1024 (author)LasVegas2007-06-08

Actually I am using 5V now, well... I guess I'm not, I have a resistor to drop it to about 3V... I just got the only one RadioShack had...

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HamO (author)LasVegas2007-06-05

LasVegas, you might help him by telling him how you found that site. Nice link by the way.

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LasVegas (author)HamO2007-06-05

I simply did a Google search for "555 flasher circuit."

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NachoMahma (author)2007-06-03

. No complicated parts needed for what you describe: flash the number 5 at 1Hz. Wire the 7-seg LED as others have described (you may need a current limiting resistor). Between the battery and the display, put something that flashes (a flashing LED may work, but be careful of the current). If you want to get a little more complicated, use a 555.

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perkinsb1024 (author)2007-06-02

what if I want to do it without any microcontroller? I searched instructables for "numeric", "7 segment" and and "seven segment" and found nothing...

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LasVegas (author)perkinsb10242007-06-02

If all you want is to be able to turn each segment on or off, use a toggle switch for each segment. Each segment of a 7-segment LED is nothing more than an LED (plenty of instructables on how to drive them). LCD types require a bit more hardware to drive, but still can be toggles with a simple switch.

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trialex (author)2007-06-02

Check the maxim datasheet for the Max7219 or max7221. control up to 8 7segment displays using one chip. If you just want to use one or two segments, and you have heaps of spare microcontroller pins, there are planty of examples out there

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