This is the fifth chapter in the odyssey of constructing the SRS Imagination, a John-Henry class rocketship. Be sure to read chapters one, two, three, and four to know the whole story up to this point.
Designing the Electrical Circuit
Ever since I first dreamed of making this epic rocketship, I knew that it needed to light up. While I have accrued a rudimentary understanding of electronics from years of soldering kits together and general hacking, I know that following instructions is one thing, and designing your own circuits is another. I wanted the ship to be powered with batteries, as well as the option of being discreetly plugged into a wall outlet. My client requested it could be controlled with his smartphone, which made things a bit more challenging. A couple of winters back, I made some custom adjustable pin-spot lights for my studio with a lot of guidance from the weekly ‘Circuit Hacking Night’ at the E&R department at the Artisan’s Asylum, which helped me gain knowledge of the humble yet powerful LED. The crew in E&R was instrumental in helping me figure out a solution to the phone-controller for this rocketship.
The Circuit Hacking night at the Asylum happens every Wednesday from 6-8pm EST. They’re a welcoming and friendly bunch, and I encourage anyone who’s curious about electronics or has a problem to solve. Don’t be fooled by the date mentioned on this page, it’s still happening.
As you can see in the above image, the circuit underwent many revisions before a working solution presented itself.
Connecting the Rocket to the Internet of Things
The Internet switch is a Sonoff Dual R2, which is two relayed switches that can be controlled with an app. The output is 110v AC. This was a problem for the rocket, the LEDs were wired up to require 12v DC. Early circuit iterations used two separate wall-wart voltage adapters to convert each line separately, but the Asylum’s E&R folks suggested I modify the board to disconnect the power from the relays, which made routing power through the switches much simpler. The magenta outline box in the above photo points out where I cut the circuit: I wanted to be 100% certain there was no leftover trace, so I used a Dremel bit to cut right through the board. This was exciting to do! It worked, but I inadvertently cut AC power to the board, and needed to add a jumper to reconnect.
Here’s a shot of the underside of the board, with the heavy-duty jumper in place, as well as the 12v+ used to send to the LEDs.
Planning and Testing
Here is the final wiring diagram for the SRS Imagination. Things got a lot simpler once I modified that internet switch, and I no longer needed to worry about sending household current to alkaline batteries, which is a big no-no.
LED Choices and Soldering
I needed to check to see if I was using a sound method to power the LEDs. It was a perfect excuse for me to get myself a regulated bench-top power supply.
After trying both cool white and warm white LEDs, I chose to use the warm white ones, which are more reminiscent of the old-school vibe of the rocketship, and of the incandescent lights that were originally used to illuminate the vintage panel lamp covers.
My soldering has improved as a result of my pursuits to be a better TIG welder. Things also clicked for me when a friend of mine said in regards to soldering, “It’s all about heat transfer!” It’s immensely satisfying to watch the solder flow through the joint from one side to the other when the conditions are right.
Unfortunately I know now in retrospect that putting the resistors near the LEDs like this makes for an ‘Achilles heel’, since the resistor wire isn’t very strong. If I had to do it all over again, I’d put the resistors somewhere in the circuit that would be less likely to be bent around. That being said, once installed the circuit is well protected in a very thick steel vessel, and is unlikely to be stressed to a breaking point. Besides, I guarantee my work: if it fails, I will fix it.
I needed to convert 110v AC household current to 12v DC: I yanked the plug tabs out of this used wall wart voltage adapter, and soldered wires to it instead. Then I taped the holes closed.
It probably goes without saying that these vintage panel lights weren’t designed to fit LED’s, but rather some highly inefficient bayonet-style incandescent bulbs. Making good use of Occam’s razor, I cut the back side of the housing off, and used a coil of high-grade electrical tape to create a nice press-fit connection. The simplest solution is usually the best solution.
The crown jewel of the rocket is this mechanically adjustable dimmer switch. I nicknamed it ‘the radlight’, as it’s reminiscent of a radiation symbol, and its RAD!
The Interior Lighting Fixture
I took some precise measurements of the LED’s with a pair of dial calipers and designed a lighting fixture using Adobe Illustrator. Once I was happy with a pattern I printed a template for cutting up a piece of polycarbonate. It’s amazing that I can use tin snips to make a circle like this. I drilled holes at a precise diameter for a press-fit.
For the outer housing, I used the flange from a coaster brake hub from a kid’s bicycle. Experience tells me they pop right off the hub with a good whack of a mallet.
These are seriously vintage machine screws! I think the ‘So-Hard’ name refers to the difficulty in finding nuts small enough to fit them. Once I had four of screws and nuts installed, I realized it would look a lot more sc-fi if I put a bolt in every spoke hole. I don’t know if anyone would ever notice that I was very careful about radial screw slot orientation, but if anyone does notice it will hopefully be a delight for them. Artists like to hide details like this so viewers can find joy in the discovery.
Fortunately, the eight LEDs seemed to produce just the right amount of light for the command module to illuminate in a way that had the right mood. The pilot looks right at home.
The Switchplate
This is one of the alters at which I worship: A vise, a hacksaw, and a file. I take great pleasure in working metal by hand. Copper is so soft, it’s very easy to work.
Copper is also easy to screw up. It took me three attempts to get the holes in the correct place. The method that finally worked was to drill the center hole, bolt it onto the steel control panel plate, scribe the other two hole locations, remove the plate, drill small holes, reinstall the plate, and use a round file to make the holes the correct size and in the correct place. In retrospect I would drill the holes in the copper the same time I drilled through the steel underneath, but as my father used to say, hindsight is 20-20.
The extra pieces allowed me to experiment with stamping, which I was very nervous about messing up. The panel is small, and the letters are tiny, so tolerances were particularly tight – and I really didn’t want to have to make a fourth plate! Once I had a plan as to what I was stamping on the plate and where, I carefully proceeded. I took my sweet time, and checked three times before committing with the hammer for each stamp.
Success! The ‘HOME’ setting is for AC power, the ‘SPACE’ setting is for the battery. ‘RMT’ means internet controlled switch, ‘ON’ is always on, and ‘-‘ is always off, no matter what the Internet switches are telling the rocket to do.
Final Wiring
The AC power cord needed to be discreetly stashed when not in use. Vacuum cleaner cord is an excellent choice, as it’s designed to be handled roughly, and the cord needs to be tough, like the rocket. The plug has a extra part that allows it to clamp to it’s own cord, but I use it to clamp onto a bolt next to the hole, as outlined in blue in the above photo.
The exciting last steps of wiring the ship are reminiscent of the kraken’s tentacles reaching out to take down a sailing vessel. I’m very proud to say that even in my excited state, I wired things correctly on the fist attempt.
Everything is assembled and almost ready for blast-off!
I was concerned that the Internet switch wouldn’t work inside the rocket, since it was similar to a Faraday cage, but even in the basement, far way from the WIFI router, it works fine.
The final chapter in the story of the SRS imagination is coming up next!
Related Posts
Constructing a John-Henry Class Rocketship: Stage One
Constructing a John-Henry Class Rocketship: Stage Two
Constructing a John-Henry Class Rocketship: Stage Three