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Seven Segment LED/LCD displays? Answered

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



11 years ago

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...

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.

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).

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

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

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?

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?

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.

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...

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

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

. 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.

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

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.

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