Introduction: Nebula With Glowing LED Stars at Night
This project was largely inspired by Auroris galaxy painting. I was originally planning on doing a custom painting like the instructable demonstrated but I remembered there is an awesome collection of Hubble Space Telescope images on the NASA website. Because it is fairly easy to get photos printed on canvas, I decided to use one of those images instead of painting my own. I also wanted to take it a step further by not having to manually switch the LEDs on and off but rather use ambient light as a switch.
My goals for this project included:
- Be able to hang this picture on a wall
- Battery powered (to avoid ugly cables from a hanging picture)
- Use a photoresistor as a switch to turn LEDs off during the daylight and turn LEDs on during the night.
Step 1: Pick an Image to Print on Canvas
As I mentioned above I chose an image from the collection of Hubble Space Telescope photographs. I chose the Melotte 15: In the Heart because of the cool colors and it was populated with a good number of bright stars. Here is a short description of the nebula:
Cosmic clouds form fantastic shapes in the central regions of emission nebula IC 1805. The clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are toward the right in this colorful skyscape, along with dark dust clouds in silhouette against glowing atomic gas. A composite of narrowband and broadband telescopic images, the view spans about 30 light-years and includes emission from ionized hydrogen, sulfur, and oxygen atoms mapped to green, red, and blue hues in the popular Hubble Palette. Credit: Ivan Eder.
The next step is to upload your image to Mpix or any other canvas printing service. It is important that your image is printed on canvas as the material will let the light from the LEDs shine through.
Step 2: The Light Dependent Switch
I wanted battery powered LEDs and found these for a good price. I decided to use two different colors, white (for the stars) and blue (for the background). Your color choice will depend on the colors in your image. I only used two different colors but you can definitely adapt the circuit to use more or less.
The schematic above shows how I wired both sets of LEDs with the transistor and photoresistor. A photoresistor works by decreasing the resistance (allowing more current to flow) with increased intensity of light. We can use this property for our project. The problem is that we want to current to flow (switched turn on) with decreasing intensity of light. This is where the transistor comes into play and acts as an inverter of sorts. Additionally, the resistance in the photoresistor is proportional to the intensity of the light. This creates a cool effect in that as it slowly gets darker outside, the stars and nebula will slowly glow brighter like a real night sky.
I used a small piece of perf board to solder all of the components together.
Step 3: Assembly
Fit the Canvas into the frame. Once I received my printed image I had to trim the excess border of canvas around the image. Then, I was able to lay it flat into the shadow box frame.
Decide which stars will glow. There were 20 white LED's on the string so I chose 20 stars on the image that I wanted to glow. I tried to evenly space them out but you will be limited by the length of wire in between each LED so you have to be strategic about which stars you pick. I then made light pencil marks on the back of the canvas to mark the stars. I then worked my way around the canvas hot glueing each LED down the the canvas where I made a pencil mark.
Arrange the background LEDs. This will take a bit of trial and error. Based on the image I chose, I wanted to concentrate the blue light over the blue part of the image. The shadow box has a soft back with push pins that I was able to use to tack down the LEDs. I would recommend using this method until you are happy with the placement. These blue LEDs are creating a background glow so you want to keep them as far back from the canvas as possible.
Cutout for the photoresistor. The photoresistor needs to be facing the front of the image to detect the light. I made a small hole in the bottom of the canvas and hot glued it into place. It is barely noticeable even up close.
Glue the rest of the components. I then glued the circuit to the bottom of the frame. I glued the battery packs to the bottom and as far back from the canvas as possible. I took the battery covers off before gluing so that the batteries can easily be replaced.
Step 4: Watch It Glow!
Add the batteries, push the back of the frame on, and you're finished! Find a nice bright spot on the wall and enjoy a colorful nebula print during the day and glowing stars at night.
You can see in the images above how the nebula glows brighter in darker light.
One final recommendation is to get rechargeable AA batteries. Because there is no true off switch (unless you turn off the LEDs from the battery pack) the batteries will eventually die and need to be replaced to keep the canvas glowing. The AA's that I use keep the nebula glowing for a little over a month until they need recharged.
Participated in the