After more than about 10 days, the newly re-deisigned (and I hope, the final version) of the Razor Crest’s main board has arrived. The circuit is the same except that it has been re-wired slightly to fit into the new screw terminals. To make or rather, allow for last-minute re-soldering, I have moved the components. Since the new screw terminals takes up lass space, I now have the luxury to label each lighting pin.
ALL FROM ONE LITTLE CHIP
Like all Star Wars Spacecrafts (except for Tydirium Shuttle) their lighting is quite simple, with with no flashing sequences. And the Razor Crest is no different. However, throughout the two seasons, the lighting of the spacecraft changes depending on whether it has landed or in flight. And so, I create as close as I could to mimic these changes. It was done with an 8-pin microcontroller, with only five usable outputs for LED lighting. The other three were for power and switch inputs. Yeah, I wished there were more outputs but working within constraint sometimes can be fun. And all of these must run from a 5 volt DC source.
NEW CIRCUIT BOARDS
The Razor Crest model was being sold from two companies, namely AMT and Revell.de and each has their pros and cons. It was the Revell.de copy which pushed me to try other ideas. Lighting up their interior cargo bay without extensive drilling and grinding of plastics can be quite a mess for normal modellers who are not used to soldering tiny SMD LEDs. But I am thankful the idea worked albeit at a great sacrifice of my wallet.
Calling it The Razor Crest Lighting System is much easier but hey, an ex-Engineer like me have naming issues.
The only issue would be that the screws in the contact terminal might come loose with vibration?
20250225 Okay, Houston, we’ve had a problem here
It took me quite some time to populate this board as I was too tired from Work. But right after I did that. I noticed the four ceiling lights were not lighting up when in Standby Mode. So today, I de-soldered and re-soldered some components to check out what the issue was. The conclusion at this point in time is that either I used the older program, there is a short, or, the transistor Q8 is the main suspect. This transistor powers about 15 LED or, passes a potentially equivalent 300mA of current through it.
Troubleshooting #1 – Not the Microcontroller
The first thing that came up to my mind was that I could be using the previous program where the lights did not come on during Standby Mode. So I programmed another microcontroller and verified that the port (Port 06) is working. After replacing the microcontroller, I discovered that the first microcontroller DID have output at Port 06. So, this means, the microcontroller is working.
Troubleshooting #2 – Not the Base Resistor
But there is still no voltage between the microcontroller Port 06 and the 10K resistor, R9. This is the resistor which is used to control the SMD version of the 2N222A transistor, Q8. And once I have de-soldered that resistor, the voltage is there. And so, I re-soldered it again, only to have the same unresolved issue.
Troubleshooting #3 – The Short
So, yeah, there is a short in the design. This is one frustrating problem with EaglePCB as there is no option to select any one trace and widen it. I have to do that manually segment by segment. How I wished I can tell the software to widen its trace for Power and Ground during the autorouting process. When I was manually rearranging the traces and text, I forgot about the overlapping error. I am not sure if this does show up in the software because I have no idea how to look for it in the first place.
Version 5A?
Sigh, Well I suppose it will have to be. For the time being, I can just correct the shorting with some soldering and all but it would not look great.
