I'm using bunch of LEDs with red, blue and yellow colors in a product for sign indication. the product has total around 150 LEDs of all three different colors.
As these LEDs are purchased in bulk, there are some faulty LEDs which are sorted on either side or both side. Currently, I check each LED with multimeter in forward bias and reverse bias mode. If LED is OK, then I solder it to PCB. These method works but it is time consuming. is there any fast method to check bunch of LEDs?
Another question is, there are some LEDs on PCB, which become faulty after some use. Some are sorted on either one side or both side. So, is there any circuit that I could integrate in my PCB which will detect LED failure?
Below image is the LED driving part of circuit. Is there any problem in my circuit to cause some LEDs to become faulty after I install them on PCB?
The L1, L2, L3 are connected to AVR microcontroller with 3.3V operating voltage. 74HC595 is supplied with +5V and controlled by AVR. Circuit shows only three LEDs, but there are a bunch of LEDs in column not shown in circuit for sake of clarity. Does this circuit have any problems?
I want to mention that only one LED will glow at time out of all 150 LEDs. So, No over-current problem in this case. I have tested voltage drops for each color type and according to that resistor R1 is set to 200 ohms which is maximum resistor value required by three color types(The brightness level may be low for 2 out of 3 color types, but that is OK for me). I am thinking to create a test program that will run on on-board AVR microcontroller and test each LED. is it possible to test LED from its current and applied voltage value by program ? Any idea how it can be possible ?
Suppose if any channel (guess here QA) is off(at 0V) in 74HC595 IC and L1 is at 0V then, LED D1 gets 5V at cathode side and 0V at anode side. Is it cause failure due to reverse breakdown of LED? Can i omit R62, R65 and R68 pull-up resistors ?