LED open and short detection

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Can someone tell me on what how to detect a short circuit and LED open circuit for the below circuit?

Is it possible to detect which LED?

Could someone provide a circuit which would help to detect an LED short circuit or LED open circuit if all the below LEDs are connected in series as a single string?

I just require a circuit which will detect LED Failure (LED open or LED Short) when the LEDs are working during its normal operation.

voltageledcurrentresistorsdiodesShareCiteEditFollowFlagedited 8 hours agoasked 11 hours agoNewbie1,00044 silver badges2424 bronze badges

• My first thought is to use the following: 74HC244; 74HCT244 Octal buffer/line driver; 3-state:assets.nexperia.com/documents/data-sheet/74HC_HCT244.pdf.TIP30x can be inputs to the buffer. – tlfong01 11 hours ago   
• 1@tlfong01 , the link is not working. Could you tell me how to use this IC and how will it help to detect the open and short condition? – Newbie 10 hours ago
• What does “help to detect” mean here? How do you expect the “circuit” is going to inform you that an LED has failed? Exactly what information do you expect the circuit to provide, and in what form? – Elliot Alderson 8 hours ago
• You didnt mention what is desired output of watch circuit (0V ok and 5V fail, some Led visualization?) Simplest open Led detection is cross the Led with D+Led, or cross with blue. – Michal Podmanický 8 hours ago 
• I just need some indication. Like assume I have some microcontroller pins according to the number of LEDs. So, I need a circuit that will convey the Open or short to the Microcontroller – Newbie 8 hours ago
• Add all of these details to your question. Don’t make the reader sift through all of the comments for important information. Do you want to know if an LED is open or short, or just if it has failed? – Elliot Alderson 8 hours ago
• If you have uC, just measure with ADconverter BG_SUPPLY and anode voltage. If BG_SUPPLY is 5V and anode also 5V, the Led is open. Of course apply some tolerances. – Michal Podmanický 8 hours ago
• The same for short. If BG_SUPPLY is 5V and anode less than 1V the Led is shorted. – Michal Podmanický 7 hours ago
• #Newbie, Welcome and nice to meet you. First thing first: My apology for the bad link. Your following question: “Could you tell me how to use this IC and how will it help to detect the open and short condition? sounds like a newbie problem. I think I need to think a bit thoroughly before I can write up a question at newbie level. Luckily It is locking down holiday today. So let me take it easy and give an answer that even newbies can easily understand. Stay tuned. Cheers. – tlfong01 just now   Edit   

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Connect the black (COM) lead of your voltmeter to ground. Now, connect the red (+V) lead to each of the test points, TP7301 through TP7303, in turn. If the voltage you read is equal to BG_SUPPLY then the LED is open, if the voltage you read is zero then the LED is shorted. Since each test point corresponds to a single LED, it is clear which of the LEDs has failed.ShareCiteEditFollowFlaganswered 11 hours agoElliot Alderson23.5k44 gold badges2020 silver badges4949 bronze badges

• @Newbie “detect […] if all the belpw LEDs are connected in series” – the same should work if the LEDs are connected in series, so you would read BG_SUPPLY on open and 0V on closed LEDs. You have to place TPs between all the LEDs. – Sim Son 11 hours ago
• @Elliot Alderson, No, I am asking like, is there a circuit which can detect the LED OPEN OR SHORT during the circuit working conditions. – Newbie 11 hours ago
• 1@Newbie You need to edit your question to clarify what you want. How exactly is this “circuit” supposed to let you know if an LED has failed? – Elliot Alderson 8 hours ago
• Sure, sorry, let me edit my question – Newbie 8 hours ago
• I’ve edited my question – Newbie 8 hours ago

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