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Author Topic: Seven segement display pin assignment.  (Read 2543 times)

TMM

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Seven segement display pin assignment.
« Reply #10 on: January 20, 2004, 07:45:39 PM »

Quote from: oldschoolnes
ok thanks skylined, thats wut i thought i was just checking, and then x24 kinda threw me off about that question.  havnt finished yet need new seven segment.  any advice, things to watch out for.


just make sure when you buy the display, get one with the right GND assignment, they come in anode(sp?) and cathode (+ and -)
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oldschoolnes

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Seven segement display pin assignment.
« Reply #11 on: January 21, 2004, 02:14:29 AM »

tnn: thanks for pointting that out again, i would prolly forgot to check for that.
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Skylined

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Seven segement display pin assignment.
« Reply #12 on: January 21, 2004, 06:28:43 AM »

I also did the anode version of this display.
I haven't posted about it because I haven't tested it yet but a friend of mine did it some days ago and it works.
Here's the schem if you would like to get anode displays.

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oldschoolnes

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Seven segement display pin assignment.
« Reply #13 on: January 21, 2004, 06:44:25 AM »

kool i ithnk i got a set of three anodes lying around somewhere maybe ill give that one a shot also
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TMM

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Seven segement display pin assignment.
« Reply #14 on: January 21, 2004, 09:54:13 PM »

Quote from: Skylined
I also did the anode version of this display.
I haven't posted about it because I haven't tested it yet but a friend of mine did it some days ago and it works.
Here's the schem if you would like to get anode displays.



you could have saved all those 150ohm resistors and just put one on each of the V+ for the displays :P
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oldschoolnes

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Seven segement display pin assignment.
« Reply #15 on: January 21, 2004, 11:40:38 PM »

if this observation is correct hte same can be done to the cathode version im working, correct?
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Skylined

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Seven segement display pin assignment.
« Reply #16 on: January 22, 2004, 08:41:51 AM »

TMM: Please if that was a joke don't ever do it again. Don't joke about electricity nor electronics, people may think you're telling the truth and they can blow up something because of that. This section isn't a section to make jokes, so please, don't do it again.

oldschoolnes: In one word, he is incorrect and what you see at the schemattic is the only way of doing it. Don't you think I would have used just one resistor if it was possible?
Do it as it's shown on the schemattic, if you want to know why, I can explain.
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oldschoolnes

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Seven segement display pin assignment.
« Reply #17 on: January 22, 2004, 10:32:12 AM »

skylined:  if you dont mind i would actualy enjoy to here your explanation on why tnn theory is incorrect.  i say this not because i have any doubt of you but because i want to learn as nuch as i can from this exoerience.
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Skylined

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Seven segement display pin assignment.
« Reply #18 on: January 22, 2004, 12:58:27 PM »

Each segment is a LED.
Number "8" uses 7 LEDs.
Number "1" uses only 2 LEDs.

Let's say each LED is 2V 0.02A.

When you want "8" to be displayed you need to supply 2V and 0.14A, this because they are 7 LEDs, 0.02 x 7 LEDs = 0.14.

When you want "1" to be displayed you need to supply 2V and 0.04A, this because they are 2 LEDs, 0.02 x 2 LEDs = 0.04A.

Now imagine you set a resistor for the "8" option.
When "1" wants to light up you'll burn up the LEDs because they only need 0.04A and you're giving them 0.14A.
Now the other option, ok, I don't wanna blow any LED, so I'm gonna set a resistor that is gonna be calculated taking in consideration the number that uses less LEDs, that's "1", only uses 2 LEDs.
Right, you set the resistor and it allows 2V and 0.04A to go to the LEDs.
Now "8" wants to show up, it requests 0.14A, but you're only supplying 0.04A, the LEDs will either be dim or they won't light up at all.
You don't want the display to show its brightness depending on the number that is shown.
This is why you have to use a resistor for each segment.

Hope it helps and hope it's clear to you.
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oldschoolnes

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Seven segement display pin assignment.
« Reply #19 on: January 22, 2004, 01:37:00 PM »

that makes sense thanks.  im trying to learn as much about electronics as i can at the moment thanks
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