Tuesday, 6 May 2014

LED Desk Light – 4 x 5 Matrix – PCB – Part 2

I’ve completed the etch of my 4 x 5 LED Matrix PCB and there are two gaps in the circuit.
The trace gaps are marked with red boxes. The gap in the negative trace was found using my multimeter using the continuity test function and verified visually. The gap in the connection from the LED cathode to the resistor can be plainly seen. This gap was where there was a missing trace in the laser printout that I “fixed” using the permanent marker, clearly, the marker wasn’t permanent enough. I think that it would have been OK if I had gone over that resist line a couple of times. Well, that’s a good lesson for me.
To fix the break, I intend to over-solder the negative trace gap and to solder in a jumper on LED 8.
PCB_Etched with LED numbers
My next task will be to drill and solder in the power at the bottom right of the PCB and then connect LED 1 along with it’s resistor. That should be proof enough that the trace is working.
After that, it will be a matter of plodding on with the remaining LED and resistors.
Now that I’ve populated the PCB and given it power … I can see that there were some other problems with the traces. LED 11 and 16 are non-responsive. When I test them with the multimeter, they respond, but not when the board is powered. Oh well … it’s a prototype.
Picture 39
Picture 38
With that done … I’m going to try another board and see if I can work out the bugs in the traces before I populate it. What a pain in the butt.
I’m going to order some SMD resistors and LED and get on to the SMD version of the 4 x 5 LED Light.

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