LED circuit problem

[captainjackS]

When you use the power supply and LEDs light up, have you measured the current being drawn by the LED circuit?  If your DC power supply is fancy enough, it should show on the display.  Otherwise, use your DMM in series to measure DC current.  Is it possible that your your fully assembled configuration is starved for current and not lighting up?  Perhaps some component in your full configuration is not capable of suppying sufficient current to light up so many LEDs at the same time.

[pizzachang]

On 5/14/2021 at 10:26 PM, captainjackS said:

When you use the power supply and LEDs light up, have you measured the current being drawn by the LED circuit?  If your DC power supply is fancy enough, it should show on the display.  Otherwise, use your DMM in series to measure DC current.  Is it possible that your your fully assembled configuration is starved for current and not lighting up?  Perhaps some component in your full configuration is not capable of suppying sufficient current to light up so many LEDs at the same time.

Thanks for your reply. Enclosing 2 schematics The one using the ULN 2003 and no capacitor was designed using incandescent, single bulbs. I used the common available 12 volt LED, multiple car lights and have 100% success, in function on my breadboard, so if my soldering is good, should  work on the 9 x 15, double-sided pcb.  The schematic using the ULN 2803 and 4, 48 LED arrays, has been my problem. As I said, I can make the arrays light in tests, but as soon as the ULN and capacitor are in the circuit - zip. So, you might well be correct in suspecting too low current, somewhere. Or my solder job - other than the arrays/resistors pcb's has a fault.

8 x 6 led array (5).pdf