Printing A Moon
This lockdown has given me an opportunity to learn about 3D printing like never before. The expertise gained in last couple of months is far more than previous 6 months combined! I spent previous months looking for things to fix around the house ( like the wifi coverage inside house, a clamp for the spring chair that gave up!). This time however, I was looking for a night lamp when I read that you could 3D print surface of the moon.
Moon as a nightlamp, I was sold at that very moment! A quick search through thingiverse gave me an appropriate moon map to print.
After printing the moon model ( I used the 3inch one), I gathered all the LEDs ( turns out I only had 5mm ones :/), and soldered them onto the PCB. A typical 5mm LED delivers peak luminescence at about 20mA forward bias current. Connecting them directly to 5V supply will result in LED damage. I also wanted to have the ability to dim/brighten the lamp. For power I plan to use mobile adapter/ mobile power bank. The catch with mobile power banks is that if the current drawn from them is below certain threshold, they automatically shut down! By hit and trial I found that if I draw 50mA of current constantly, the power bank does not shut down.
So based on these requirements, a devised a simple using a single NPN transistor, and a switch, shown below:
The 2.2K resistor limits the current to the base ( the transistor can have at max 5mA as base current), the pot connected on the collector acts as a current limiter. Increasing the value of the resistance dims the LED. Instead of single LED, I added 4 LEDs in parallel to increase brightness.
A switch is attached to turn the lamp on/off. I originally intended switch for 2 color LEDs, but more on that later.
Having designed the PCB, it was now time for designing the box. Fusion360 offers great ease in designing model ground open. after a few hit and trials I was able to get the base which could fit the PCB. Several things went wrong, like I mistakenly put the USB port too inside the base, that I was not able to connect to it :P
I printed the base and top separately, once the PCB sets in, all can be sealed off with some glue. I do need to work on adding screws for later versions. Not having screws did bite me, when in one of the prototypes I broke the USB jack, and had to tear apart the whole base, just to fix the jack :/.
Here are few images which I clicked during development.
And some while experimenting with colors
And finally on completion:
The current project details are uploaded at thingiverse, at the following link: https://www.thingiverse.com/thing:4413946
For this project I did PCB design for the first time, Fusion 360 provides a good PCB design, layout tool as part of their electrical library. Learning and PCB layout was pretty easy, and I was able to get a decent enough PCB in 1 day. THe tool exports the gerber, which can directly be uploaded to the PCB manufacturer sites. Whats really nice is you can generate 3D view of the PCB, and integrate it with your mechanical design, to visualize how your PCB fits in the mechanical package!
Folks in India, can try LionCircuits for getting their PCBs printed, as there charges are pretty reasonable, (for the following PCB I had to pay INR 650 for upto 9 pieces!
This has been a good design project, I have already ordered some high wattage LEDs, and some more features to add. Stay tuned for V2.0!
-Nishant