My wife and son recently went to a science and space convention and my boy brought back a planetarium kit. It consisted of a base and a thin carton sphere with all the star constellations printed on it. At first we all were exited to get this thing up and running but then ran in to a few problems. The sphere came in four parts and you have to put it together without loosing your patience.
After a few nail biting attempts we succeeded in the completion of the sphere with a lot of sticky tape but it still was not strong enough for a child to play with.
This is were this instructable comes in. I had to figure out a way to make it a bit stronger so that my son can actually touch it without it falling apart.
I want to give a special thanx to -Ranger on his instructable on making a sphere. please checkout the link
If you like what you see or have any questions, please don't hesitate to leave a comment and I will get back to you. If you decide to make this you can post a picture of it or post a link to you instructable in the comment section. I would like to see someone else's point of view. Also please check for what contests its registired for in the top and vote.
Step 1: What Will You Need?
- A map of the star constellations. (part of the kit)
- Black paint. Any will do. (optional)
- Brass tube
- Copper wire
- Some Quick dry putty
- Blue LED and a 100 ohm resistor
- A lamp for inside the sphere (part of the kit)
- Thin wires
- Sanding paper
- On/off switch (part of the kit)
- Battery holder (part of the kit)
- Drill and drill bits
- Scroll saw
- Soldering iron with solder
- Glue gun with glue
- Dremel rotary tool
Step 2: The Sphere
I started with the sphere because this was the most difficult part of this project
Cation: The scroll saw is a power tool with moving parts. please wear the necessary personal protective equipment to avoid any harm
First I decided on the size of the sphere. The wooden plank I had available was the size I wanted the sphere to be so I measured the width(15cm) of the plank and and determined the middle. This will be my starting point.
By finding the middle of the plank I now have the radius of the sphere.
- Draw the radius you determined from the plank width and draw it on a paper with a compass. My plank width is around 15.2cm
- Find the center of the circle and draw a line through it on the same paper as seen in image 1
- Measure the thickness on the wood plank you'll use for the sphere
- Transfer the thickness of the plank to the drawn circle as seen in image 2 from the center of the circle to the outer line.
- Image 2 will be the reference for the amount of circles you have to cut and the radius for each one for one half of the sphere. To make a full sphere with both halves, two of each circle will be needed.
- Mark the outer radius for each circle gathered from the drawing on the plank with a compass.
- With a scroll saw, cut along the outer radius of each circle until all segments are complete.
- Now draw a new circle on the paper over the existing sphere segment diagram using the same center point. This circle should be about 6 to 7 mm smaller
- After determining the inner circle radius for each segment you can transfer the circle dimension to its respective segment.See Image 2
- After transferring all the inner circle radius to its respective segment you can make a small hole close to the inner circle, big enough for the scroll saw blade to fit through. See image 5
- Cut along the inner circle line for all except the last two.(the two smallest ones)
- After this is done you should have the result as seen in image 6
Note: above steps has to be done twice to make a full sphere.
Step 3: Sphere Construction
Once all the segments is done you can just sand off all the rough edges with a piece of sanding paper.
Pile the segment on-top of each other from big to small one by one and glue each one to the next. make sure you center each ring with the previous one because this will make the sanding a bit easier. Let the glue dry for at least a day and make sure a you use proper wood glue.
OK, I'm not proud of what i have done next but I had to use the tools I had in hand to complete the sanding of the sphere. I do advise you to seek help from someone with a wood lathe or if you have one that will be perfect.
- Make a hole of 6 mm in the top of each half of the sphere.
- Insert a 6 mm bolt through the hole from the inside of the dome to the outside and secure the bolt on the outside with a lock nut. See image 3
- I needed to rotate the done at a moderately high speed so I secured my drill to a table with a clamp and used another clamp on the power button to variate the speed. See image 4
- Secure the dome with the bolt to the machine spindle.
- Increase the speed to were you feel comfortable. Again!!! use your PPE. If you feel in any way uncomfortable to do this please do not hesitate to ask a experienced wood craftsman to help
- While the machine is rotating the half sphere, sand down the dome until all the segments merge into one complete half sphere. Its all up to you how smooth you want the surface to be.
- To the same with the second half
- With the help of a dremel, sand down the inside of the dome.See image 5 and 6
- Do the same for the other half
- Once done you should have a similar or better result as seen in image 7
- Cut four small pieces of wood and stick them on the inside of the dome.Please see image 6.This will help to keep the dome intact.
Step 4: Star Constellations
I combined the two domes to make a complete sphere and marked it on the side to make it easier to line-up the two pieces later. See image 1
You will see in image 2 I painted the inside of the sphere black but you can leave it as is.
I was lucky to have the constellations on a piece of carton shaped as a sphere but I think the constellation map is available on the internet.
I placed the constellation map over the dome and started to burn the star locations onto the dome through the constellation map with a soldering iron. After all this I linked the stars with a pen and written the constellation name close to it and then again burned the names and lines in with the soldering iron.
I drilled a hole through each Star. Try to keep the drill 90 degreed with the surface of the sphere.
Step 5: Sphere Lamp
I used a lamp that was part of the Planetarium kit.
The lamp was attached to the base of the planetarium kit so I carefully removed it so not to damage the lamp or the lamp socket. You can use a LED lamp but just keep in mind what voltage your battery supply and what resistor to use.
I used Brass pipe to secure the lamp inside the sphere. Please refer to the images for reference on bending the pipe. There is no drawing or measurement for this. I just wanted the lamp to be in the center of the sphere. This means I had to bend the pipe by hand until I was satisfied with the location of the lamp.
As seen in the images I removed the lamp from its socket and removed the existing wires and soldered in longer wires. If you use the same color wires like I have for the extension then you just have to mark one of the wires somehow so you will know positive from negative.
I made a small hole in the pipe where I wanted the lamp to be and pushed the extension wires through the hole and all the way to the pipe opening.
After determining the polarity, I made a knot on the Positive wire.
After i was happy with the location of the lamp I secured the lamp in place with some fast drying putty and left it for about an hour to dry..
Step 6: Lamp Base
The base consists of 4 square planks and one acrylic sheet. The bottom plank I traced out the battery holder and cut that piece out with the scroll saw. The second plank I measured about 10mm from each side and drawn a straight line through each mark to get a smaller square shape inside the square plank. This smaller square was then cut out. This will allow you some space for the wiring. I glued the two together
The third, fourth and thith layers were then combined with the acrylic sheet as the middle (fourth layer) layer
After combining all the layers I drilled a 4mm hole in each corner, all the way from the top of the base to the second last layer. Note: Mark the base with a pencil after drilling the holes to insure the orientation remains the same throughout the build.
Screw the top three layers together with either self-tapping screws or a 4mm bolt. If the screw protrudes through the third layer of wood you can cut it off with the dremel tool and a cutting disk.
Drill one 6mm hole in the center of the part with the 3 layers up to the acrylic (middle layer). Do not go all the way through.
These two parts, the bottom two layers and the top 3 layers, should not be joined at this stage because the wiring still remains.
Step 7: Wiring
Solder a 100 ohm resistor to the LEDs positive leg (my power supply is 5 volts).Remember to use some shrink sleeves on the solder joints. Install the led in the hole that was drilled in the previous step. See image 2, 3 and 4. I used Hot glue to secure the LED in place
With the dremel I made small hole on the side on the second layer of the bottom segment for the power switch. Hot glue was used to secure the switch in place. Before installing the switch I soldered two extension wires to the connections of the switch and fed the wires through the hole. See image 6, 7 and 8
On image 5 you will see I made a 6 mm (same size as the brass tubing) hole on the top segment of the base. This is where I will insert the Brass tube that holds the lamp and sphere. The hole has to be drilled through all four to layers and not the bottom two.
Insert the wires for the lamp and tube through the hole
- Solder Positive side of the battery holder to the common contact of the switch
- Solder the normaly closed NC or normaly open NO (in my case it does not matter) to the posative leg of the LED
- Solder the posative wire of the sphere lamp to the posative side of the LED
- Solder the negative side of the sphere lamp to the negative leg of the LED
- Solder the negative leg of the LED to the negative side of the battery holder.
Install the batteries into the battery holder and switch on the lamp. If the lamps do not work you have to make sure about your polarity.
Step 8: Finishing Touches
After you have tested the Lamp and LED you can glue the top and bottom segments of the base together and let it dry for about 3 to 4 hours.
In Image 1 you will see wrapped copper wire around the brass tubing. This was done to keep the sphere from sliding down when you rotate the sphere.
In image 2 you will see two screws on the side of the sphere. This was done to keep the dome closed. I didn't want to glue the two half spheres together because I might change the Lamp later to an LED. I wrapped a very thin copper wire around the two screws. Right across on the other side of the sphere I done the same.