LEDs: Connect 3 LEDs Without Microcontroller

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Discussion Overview

The discussion revolves around the possibility of connecting three LEDs in a circuit such that only one LED lights up at a time under specific conditions, without using a microcontroller. Participants explore various configurations and conditions for achieving this setup, including the use of multi-colored LEDs and switches.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about connecting three LEDs so that only one operates at a time, seeking clarification on the specific conditions required for this setup.
  • Several participants express confusion about the intended functionality and the specific cases in which each LED should operate.
  • Some participants suggest that using tri-color LEDs might be a solution, noting their typical configuration with multiple leads.
  • Another participant mentions the need for additional components, such as switches, to control the LEDs without a microcontroller.
  • One participant references a chip that can control multiple LEDs based on input voltage, suggesting it could be relevant to the discussion.
  • There is mention of powering bi-color LEDs with AC to achieve a third color, indicating a potential method for expanding the functionality of the LEDs.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific conditions or configurations for the LED setup. Multiple competing views and uncertainties about the requirements and possible solutions remain throughout the discussion.

Contextual Notes

Participants express limitations in understanding the exact conditions needed for the LED operation, which affects the ability to provide concrete solutions. The discussion also highlights the dependency on the specific types of LEDs and switches available.

Hassan Raafat
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Is there is a way to connect three LEDs so that there are three cases where one LED only is working in every case of the three without using micro controller ?
 
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What are the 3 cases?
 
cpscdave said:
What are the 3 cases?
Really I don't know what they are but I wonder it because there are two-color where are green is lighted in forward and red in reverse like that , so can I make the same for three LEDs ?
upload_2016-4-1_18-13-59.png
 
I'm still not sure exactly what you are trying to accomplish.
Do you want to have 3 multicoloured LED's each displaying a different colour??
 
cpscdave said:
I'm still not sure exactly what you are trying to accomplish.
Do you want to have 3 multicoloured LED's each displaying a different colour??
Not exactly , I want to have three LEDs in one circuit so each time I have a specific condition , there is only one LED working
 
What are the conditions then? Hard to tell you what you need to do if we don't know exactly what it is you are trying to accomplish :)
 
cpscdave said:
What are the conditions then? Hard to tell you what you need to do if we don't know exactly what it is you are trying to accomplish :)
Not for confusing you that is an idea not a real question in the picture up I have one LED working in the forward and the other is working in reverse bias where the first became off , now the question is Can I make a circuit which have three LEDs where there is one LED working in every case , But also I can't tell you the condition because I really don't know it .
 
Hassan Raafat said:
so can I make the same for three LEDs ?
Tri-color LEDs usually have 4 leads. One common (cathode), and 3 separate anode pins:

http://gcdn.indiabizclub.com/uploads05/30/H/5mm-Tri-color104258895.jpg
5mm-Tri-color104258895.jpg
 
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Please can you tell me how that works ?
 
  • #10
Your circuit showing two LEDs is incomplete. Something has to make the +V node to go both +ve and -ve with respect to the Earth node. That implies +ve and -ve supply voltages and a switch of some sort.

It's very easy to do what you want if you don't have any constraints. My house has at least 20 light bulbs and I can turn one (any one) on at a time without a microprocessor...but that's because I have 20 light switches.

We can't really answer your question without knowing the constraints. Can you use three switches? One multi position rotary switch?
 
  • #12
CWatters said:
Your circuit showing two LEDs is incomplete. Something has to make the +V node to go both +ve and -ve with respect to the Earth node. That implies +ve and -ve supply voltages and a switch of some sort.

It's very easy to do what you want if you don't have any constraints. My house has at least 20 light bulbs and I can turn one (any one) on at a time without a microprocessor...but that's because I have 20 light switches.

We can't really answer your question without knowing the constraints. Can you use three switches? One multi position rotary switch?
Thanks very much CWatters , So what you said I Can control these switches and control when to turn of the leds on , right :)
 
  • #14
Is three LEDs enough?...

Here is a chip that can be configured to turn on 1 of 10 LEDs depending on the voltage on a single input.

http://www.ti.com/lit/ds/symlink/lm3914.pdf

Can be used in "dot" or "bar graph" modes.

 
  • #15
CWatters said:
Is three LEDs enough?...

Here is a chip that can be configured to turn on 1 of 10 LEDs depending on the voltage on a single input.

http://www.ti.com/lit/ds/symlink/lm3914.pdf

Can be used in "dot" or "bar graph" modes.
Thanks a lot CWatters , I'll read it , you helped me a lot , Thanks again :)
 
  • #16
Hassan Raafat said:
Really I don't know what they are but I wonder it because there are two-color where are green is lighted in forward and red in reverse like that , so can I make the same for three LEDs ?
If you were to power this two-in-one with AC you could have both LEDs glowing 'simultaneously' to give (I'm guessing) a third color: violet.
EDIT: oops, seems that the third color for a R-G led could be yellowish orange, click on customer comments in this link: http://www.allelectronics.com/make-a-store/item/led-6/bi-color-led-2-legs/1.html
 
Last edited:
  • #17
NascentOxygen said:
If you were to power this two-in-one with AC you could have both LEDs glowing 'simultaneously' to give (I'm guessing) a third color: violet.
EDIT: oops, seems that the third color for a R-G led could be yellowish orange, click on customer comments in this link: http://www.allelectronics.com/make-a-store/item/led-6/bi-color-led-2-legs/1.html
That's great :) , big thanks NascentOxygen :smile:
 
  • #19
CWatters said:
Is three LEDs enough?...

Here is a chip that can be configured to turn on 1 of 10 LEDs depending on the voltage on a single input.

http://www.ti.com/lit/ds/symlink/lm3914.pdf

Can be used in "dot" or "bar graph" modes.


Great Video , CWatters , Really thnak you for your effort :smile:
 

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