Introduction: LED Star Constellation Light or Night Light

This instructable was a small after school project that I created for some STEM Club students to make as part of our astronomy sessions. Learn about astronomy and electronics at the same time!

Materials and equipment
small cardboard box (shoe box)
Red electronics wire
Black electronics wire
5 mm White LEDs
100 ohm resistors
Small matrix circuit board
Printed picture of star constellation
Soldering iron, solder, flux
Heat/shrink wrap (optional)
9v  Switched battery holder/box
Mounting tape

Step 1: Prepare the Box

Take the box and glue the picture of your chosen constellation to the bottom of the box. You may need to reprint the picture so the constellation fits nicely within the area of the bottom of the box.


Following this you need to make approx 4mm holes in the bottom of the box where the stars of your chosen constellation are located. Some constellations have only a few stars. Others have many more. I recommend a constellation with about 8 - 12 stars, but this is up to you. A 9v battery should easily power up to 20 LEDs though you may need to choose the correct resisters for your LEDs.

Step 2: Cut Some Wire to Size

Cut a 200mm length of red wire and black wire.

Repeat this for every  LED you are going to use in your chosen constellation. I use The Big Dipper in this instructable which has 7 main stars. So I need 7 lengths of red and 7 lengths of black.

When you have done this strip approx 5 - 10mm of insulation from the wires and twist the ends to keep the strands tidy.

Step 3: Tinning the Wires

WARNING
PLEASE BE CAREFUL WHEN SOLDERING. BURNING YOURSELF IS POSSIBLE IF YOU DO NOT TAKE DUE CARE.

Next we need to tin the wires. This means we are going to coat the ends of the wires with some solder. This makes it easier to solder the wires to the LEDs and circuit board and also keeps the wire strands tidy.

To do this coat the bare ends of the wire with some flux. Then with a hot soldering iron pick up some solder and then draw the melted solder along the bare wire. Repeat this on all wires.

If you have not done any soldering before, you may need to check out a good guide.  There are a few on instructables. Try this one: https://www.instructables.com/id/How-to-solder/

Step 4: Solder the Wires to LEDs

Before we solder the wires, you need to know which wires, red or black are soldered to the correct part of the LED. Anode (+) or cathode (-). You can determine this by looking for the flat edge of the LED. This is the  negative terminal. It is also the shorter of the two terminals.

cathode (-) = black.
Anode (+) = red.

Solder the black wire to the cathode (-) and the red wire two the anode (+). You may want to shorten the LED  terminals to about 10mm to match the wires ends


Try to make the soldering as neat as possible so that you can slip some shrink wrap over the soldered connections. Once heated with the soldering iron it will shrink to insulate and hold the connection together. This is optional, though you must make sure the + or - do not touch.


Repeat
You will need to repeat the tinning and soldering for the number of LEDs your chosen constellation has.  I have chosen Ursa Major (The Big Dipper) which had 7 major stars. Therefore I need 7 pairs of tinned red/black wires.

Solder the wires to the Remaining LEDs and shrink wrap soldered connections if desired.

Step 5: Create the Circuit Board

The circuit board is used to connect the LEDs to the power source. It is good practice to use resistors to maintain the correct amount of power to the LEDs. Otherwise the LEDs might blow. It is not advisable to do this project without resistors.

This circuit diagram shows 7 LEDs.  The LEDs are in parallel layout with a resistor of 100ohms. The LEDs wil be quite bright with 100ohms.

Take your piece of circuit board and place the resistors like this image. It does not matter which way you place the resistors.  All components are placed on the non copper side. All soldering is done on the copper side. The copper helps the solder adhere to the circuit board.

Solder these on the reverse side being careful to solder to that copper strip only.
Trim any excess off of the resistors leaving a nice clean soldered join.


In this picture you can see I've added some additional wire to connect the resistors in parallel.

Step 6: Solder LEDs to Circuit Board

Next we want to solder the  LED wires to the circuit board.

Place the black wire from one of the LEDs in the hole next to a resistor. Solder this in place so that it is connected to the resistor.

Place the red wire a few rows up from where the black wire is. Solder this in place

Repeat with the remaining LED wires making sure that the red wires are all in the same row and the black wires are soldered to the resistors.

You may also need to solder  joins in the row of red wires to make them parallel.

Step 7: Add the Switched Battery Box

Solder the red wire from the battery box to the row of red wires or the positive terminal.

Solder the black wire from the battery box to the bottom row by the resistors or the negative terminal.

Put a 9v battery in and test it works.

Step 8: Insert LEDs

Gently insert the LEDs into the holes from the inside of the box until you can bed or wedge the LED into the box. Do this for all LEDs.


Finally, use some double-sided mounting tape to secure battery pack and the circuit board to the box.

Comments

author
VesaB (author)2017-04-27

would insulating tape work instead of mounting tape?

author
Paulbacca (author)VesaB2017-04-28

You can use whatever adhesive you want to though insulating tape might not be as strong.

author
VesaB (author)2017-04-27

where can I find the red and black electronics wire?

and could I use a arduino board instead of the matrix circuit board?

author
Paulbacca (author)VesaB2017-04-28

The wire should be available to buy in any good electronics shop or ebay.

author
AliceFromNEVERLAND (author)2016-11-28

Can you tell me what code was used?

author

Hi! No coding was necessary for this project. Just some electronic components and some soldering.

author
randofo (author)2012-08-28

Cool. I like the big dipper. It is one of the few constellations I can always pick out for certain.

author
kevinlc77 (author)randofo2012-09-05

my fave is Orion.
the star Sirius is in his belt !!

author
Paulbacca (author)kevinlc772012-09-05

Orion is one of my favourites too! I did make an Orion light but I had to leave this at my last job.

author
Treknology (author)2012-09-02

You've missed an opportunity to be economical. Instead of using one LED and Resistor combination repeated in parallel, try lowering the Resistance and running some LEDs in series.

With a 9V supply rail, you should be able to get up to three LEDs in one string with a much smaller resistor, such that the 3 LEDs are using the same current as a single LED in the existing circuit.

author
Paulbacca (author)Treknology2012-09-03

Thanks for your feedback.

Even in parallel I'm still getting variations in the brightness of the LEDs that seems to be because of the resistors. It's a great effect.

I've never been to the southern hemisphere. So I'm in a similar position to you. Fortunately with this project you can simply turn the box up-side-down to align for northern or southern hemisphere.

author
Treknology (author)Paulbacca2012-09-03

What is the tolerance of your Resistors? If they're average 20%, then each could vary in value from 80 - 120R which, on high-bright LEDs, would make a distinctly visible variation in the light output. If you want higher consistency, look at better tolerance Resistors such as 5% or better. Unless you go to the ultimate extreme of 1% tolerance, there will still be noticeable variance, and I suggest you re-arrange the LEDs according to the magnitudes of the stars they are representing (as it looks to me in the photo).

As NitroRustlerDriver points out, when a LED fails it is usually a short circuit rather than open circuit.

<03:00 rant>I am working on my own LED lighting design to get the optimum wattage:efficiency ratio. On the last batch of LEDs my calculation was 80 minimum in a single string to handle 260V peaks in Oz at a rating of about 5W. I don't want lower power using chopper supplies because of RFI health risks, and I definitely don't want to use Luxeons because they are really pushed to the limit and with those whopping great heatsinks on them, where's the so-called efficiency improvement? So I'm looking for a comfortable balance which will probably be a 10*10 square to allow for higher spikes, and hopefully enough buffer, so that if one LED shorts it won't overload others. I'm also trying to come up with a design that is extremely easy to unplug so that defective LEDs can be replaced without excessive diagnosis. That safety barrier probably means it will only operate at about 4W (over-engineering rears its ugly head again). I'm designing it to plug directly into the wall, in such a way as it MUST be physically removed to replace any defective LEDs which, if I get it right, should be a fairly quick process.

If you want a challenge, mount 5mm multicolor LEDs in a practice golf-ball---works fine until you want to fit a battery inside. As this was part of a movie prop, I'll put both related projects up at some later stage. I'm not going to get photos together in time to get an entry this time.

I love to support simple starter projects like this, because this is the learning field before you move on to sticking your fingers inside live mains equipment and taking your life into your own hands. I was lucky. My Father was an electrician and Installation Inspector. From very junior ages (5-6), I was allowed to wire up mains equipment, provided that he inspected it before it was plugged in, so by my early teens 240V zaps were a way of life. Sadly I grew up in old 3-phase territory where Red Yellow and Blue were the primary (colors) phases, Black was Neutral, and Green was Ground. Changing over to the new ISO standard was annoying, but when I look back on it, it was designed with two major factors in mind.
One, Red-Green Color-blindness (the most common, leading to Active/Earth swaps).
Two: Such color-blindness is prevalent in males who predominated the industry at the time.

author

This will work, but you will get much more even lighting from the LED's by putting a resistor on each one. Manufacturing variations in them cause them to draw different amounts of current, so when wired in series, some will draw less current and be dimmer then others. Also, when wired in series, if one burns out, that will increase the current draw on the other LED's, possibly causing them to burn out as well.

All in all, it is much better practice to wire them in parallel, each with their own resistor.

author

I get your point but, are not these LEDs meant to be of varying brightness to represent star magnitude? Or is that just the way it happens in the photography? Being in the Southern Hemisphere means I've only seen representations of the "Big Dipper" and never the real thing.

I would expect that if a LED were to fail, it would happen within the first week. It is only because of over-driving illumination LEDs that there is even a quoted life-span on LED products.

I'm also very prone to over-engineering, meaning that I would be running the LEDs below their peak values and seeking to make that 9V battery last to the bitter end. If using a potentially spiky power supply from the mains, then, yes, I would defer to your preference for individual resistors.

author

LEDs don't get short-circuited when they burn out; they only get dimmer, or open-circuit in catastrophic cases.
I would follow Treknologys design advice :) , not too difficult to test both designs before committing yourself either.

author
wilgubeast (author)2012-08-29

Nice. Oh man, there are so many more constellations that could use the night light treatment. Somebody's got to get their scout troop or physics class to make a full night sky's worth of these. Start with the northern hemisphere, then later... the world!

author
Treknology (author)wilgubeast2012-09-02

Remember that the those constellations that can be seen in both hemispheres are upside-down to each other.

author
Paulbacca (author)wilgubeast2012-08-30

Thanks. Actually I did a large version with a large paper mâché dome and Christmas lights. It worked great but I did not take any photos record the build. That would be an awesome next project for me to do again for instructables.

author
Insonicbloom (author)2012-09-02


I love LED projects - this one is pretty nice dude.

there is a few on my site, one popular one is the knightrider/cylon LED scanner on stripboard HERE

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