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Author Topic: How to light only some segments of a 7 led dysplay  (Read 2564 times)

bogdan_lupuro

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How to light only some segments of a 7 led dysplay
« on: February 18, 2006, 12:06:41 PM »

Is there ba way to light only some segments of a 7 led dysplay ? I am guesing you have to conect some of the pins but wich ?

Thanks
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wonko

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Re: How to light only some segments of a 7 led dysplay
« Reply #1 on: February 18, 2006, 12:34:42 PM »

Well, I'm no expert in the field, but if you can find a pin-out for the display you have it should answer your question.  You could alway take a multimeter to it and see what you get.
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Mikecx

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Re: How to light only some segments of a 7 led dysplay
« Reply #2 on: February 18, 2006, 01:13:43 PM »

http://www.aaroncake.net/circuits/counter.htm . Take a look at that, should be all you need like wonko said.
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bogdan_lupuro

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Re: How to light only some segments of a 7 led dysplay
« Reply #3 on: February 18, 2006, 01:15:50 PM »

Let's say that the pins arragament is like this.

If i connect a wire to 5V and another one to a1 and b1 , the a1 and b1 will light up ?

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Monster

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Re: How to light only some segments of a 7 led dysplay
« Reply #4 on: February 18, 2006, 02:33:36 PM »

Yes, ut don't you need to power the two 5V lines, and connect the grounds, not sure on this one so...
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viridius

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Re: How to light only some segments of a 7 led dysplay
« Reply #5 on: February 18, 2006, 04:05:31 PM »

Okay, looks like you got yourself a two-digit common-anode seven segment display.  That link that Mikecx posted has a good chart of which pins light up which segments.  To light up each individual segment, you would connect one (or both, it shouldn't matter) of the +5 volt pins to 5 volts, and connect the pin corresponding to the segment you want to light up to ground.  Now, the fact that a voltage is explicitly stated for the LEDs could mean that there are already current limiting resistors in there, but I would go out and get a few 180 ohm resistors and use those to connect the segment pins to ground.

If you want a decoder circuit that will automatically decode a BCD number and put it on the display for you, I'd recommend just scrapping that display and buying a new one (we're talking $3 here).  Then, you can use a 4511 or equivalent chip to drive the display.
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wonko

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Re: How to light only some segments of a 7 led dysplay
« Reply #6 on: February 18, 2006, 04:10:07 PM »

An easier way to look at it is as if you have 7 individule LED's.  All the segments that you want lit up need to have a pos and a neg (anode and cathode).  They will also need to have an appropriate resistor connected to the anode (pos) side so as not to roach your display.  It is possible to wire up all your anode (pos) pins together on a single 5v input, and all your neg together, but make sure you are using the correct resistor for the job.  It would help if you would explain what it is your trying to do.

Viridius is the one to listen too, he knows his s#*t  :D!
« Last Edit: February 18, 2006, 04:15:06 PM by wonko »
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Skylined

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Re: How to light only some segments of a 7 led dysplay
« Reply #7 on: February 18, 2006, 05:48:57 PM »

4543 is better than the 4511, because you can use common anode or cathode displays.

I wouldn't bother to take a look at pinouts, I would just take 5V and Ground, a resistor.
First of all, I would determine if it's a common anode or common cathode, and then I would write down the pins in a piece of paper. :)
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viridius

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Re: How to light only some segments of a 7 led dysplay
« Reply #8 on: February 18, 2006, 05:58:45 PM »

He already knows that it's common anode and has the pinout.  The 4543 is an acceptable substitute, but it can only source 10 mA at the output.
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bogdan_lupuro

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Re: How to light only some segments of a 7 led dysplay
« Reply #9 on: February 19, 2006, 04:42:29 AM »

Thanks you all for your answers

No that is not the pinout for my display i was talking teoretichaly. All i want to make is get the letter "OC".

The pinout looks pretty much the same as mein.

"First of all, I would determine if it's a common anode or common cathode, and then I would write down the pins in a piece of paper."

How would you do that ?

Thanks
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