Remember in my last few post, I asked, ‘What can go wrong?‘ and then I approved the design with JLCPCB?
Yeah, I found a much better circuit solution.
I AM SO SMART, DUH
I always use the ULN2003 Chips or its variaton to drive the LEDs. It is basically a driver for higher current components, controlled from a microcontroller. It is a need and if you do not want that, you can replace them with transistors and, or MOSFETS. Unfortunately, when it comes to compact design, these replacements would create more issues where component count (read: SMD soldering) and PCB real estates are concerned.
The ULN2003 is capable of driving 7 channels, which is great for motors and LEDs. However, my downfall is that I am limited to this chip and its 7 inputs.
So, right after my dinner last night, I discovered the ULN2803 which has 8 inputs. Which means, I can remove the second ULN2003 chip from the board and replace it with this new-found solution!
is much bigger than the ULN2003 (left)
GODAMMIT, WAKE UP!
Then this morning, the bulb above my head turned into a 1 ton slab of concrete.
The ULN2803 was NOT the solution I was looking for. And I still could use only one ULN2003 instead of two. This is still a theory and I would need to get some components to try it out. In the original design, I paralleled the signals into the ULN2003 pair and then use a relay to switch either one via the power rail. But now, what if, I paralleled the LEDs instead?
See what happened there?
Being so engrossed and impatient into getting this decades old project done, I could not see the solution right in front of me. Not only that, because this is a niche Hobby, I could not really discuss it with like-minded friends, not that I have any.
OH, MY GOD! THE HORSES ARE TRAMPLING BACK!
Um what the heck did I just typed? I really need some coffee first.
[30 minutes later…]
This coffee is good. Maybe I need more….
OK, that brief epiphany turned out to be a dud. Electrically speaking, even when I switched the power rails, to the circuit, it is the same. So, I’d still have to use two ULN2003 chips. There is another solution which is to use a microcontroller, my original concept so many years ago. Ultimately, I changed to the 555/4017 circuit because well, it was more fun. Now, it actually might be a better idea after all.
