Ballet Bling

LED Illuminated Ballet Dress

Andrew Pullin

Issue 26, September 2019

What does a maker do when their daughter wants a ballet dress with flashy LED lights? They get out the soldering iron, LED striplight and common components to DIY.

It seems no matter the after-school sport or classes children take up, the fees just seem to be never-ending. Equipment, membership fees, performances, uniforms, costumes, etc, just to name a few.

When Andrew’s daughter Katy asked for a ballet dress with lights, instead of buying a new dress that can cost up to $300, Andrew decided to make one. We caught up with Andrew to find out more.

What inspired you to DIY lights into a Ballet Dress?

My daughter is a Ballet Dancer doing Level 5 and has performed in the local Eisteddfod last year for the first time. This year she wanted to perform again and was excited to be given a very pretty dress for Christmas from her Auntie with battery powered LED lights. Great idea! Except she is 10 and growing like a weed and she has grown out of the dress. So – what to do? Well obviously make a new dress, but she wants the flashy LED lights, and by the way “dad could we have some coloured ones too?”. The things we do for our little Cherubs!

Nothing like a challenge set by a loved one! How did you go about choosing the LEDs for the job?

The lights were simply 1m RGB light strips from Jaycar that just plugged into a USB port Catalogue ZD-0571. The lights come with a small controller that has several pre-programmed settings and you can trim the strips down from 30 LEDs to whatever. I also ended up adding another set of “Christmas” lights.

Fantastic! How did you go about attaching them to the dress?

One set was Hot Glued and the other sewn in and we strategically hid the battery pack.

You mention a battery pack, but the Jaycar lights are designed to go into a USB port? How did you end up powering the LEDs?

I just needed a small portable power supply for it. Hmmm, not so easy, so I built one. After popping on my Google Goggles, a few minutes later I had the following circuit based around a standard LM7805 Voltage Regulator. I also found some great tutorials on the Electronics Hub website.

7805 Voltage Regulator IC Basic Circuit. DIAGRAM CREDIT: Electronics Hub

These devices are a family of devices that regulate the output voltage to a set value depending on the device used. The last two numbers denote the voltage; e.g. LM78xx. In our case an LM7805 will supply +5V. The circuit above will basically work with any of these devices unchanged. The input voltage just needs to be at least 2.5 volts higher then the regulated output. The LM7805 can operate with an input voltage of 35V and still output 5V but as you can imagine the device has to get rid of that energy somewhere so it dissipates the “waste” energy as heat. With an input of 35V you will need a good heatsink because the component can get very hot.

We’re sure our readers who are unfamiliar with voltage regulators would have enjoyed that brief tutorial. How did you choose which battery to use?

I used a 9V battery because I only needed a short amount of time for the circuit to work and in relative terms 9V batteries are cheap.

Using 9V batteries would be much more practical than trying to dance with a heavy USB powerbank. How long do you expect the 9V battery to run for?

I only needed it to work for a 4 minute dance routine. A fully charged 9V battery should supply about 600mAh but the data sheet for the LED didn’t give me its power draw data. Having a spare battery in my pocket solved any problems.

Top side of the board with USB sockets.
Underneath the board with wires soldered directly.

Good idea. Tell us more about the circuit and anything our readers should know if they plan to build their own?

The small board I built was simply a 9V battery connection to the LM7805, connected to a PCB mount USB port with a two decoupling capacitors to filter* the power source. The USB connectors made it easy to connect the LED strip.

*EDITOR'S NOTE: The two decoupling capacitors are intended to prevent the regulator from oscillating if there are varying signals present. Seeing that this circuit works from a battery (pure DC) they are not mandatory, however, it is still good practice to include them.

To build this circuit I needed a few other things so off to the local Jaycar store in Albury for the following parts (Around $30 in total):

Parts USED:Jaycar
1 × 9V Battery Snap - High QualityPH9232
1 × USB Type A PC Mount SocketPS0916
1 × 220nF 100VDC Polyester CapacitorRG5145
1 × 100nF 100VDC Polyester CapacitorRG5125
1 × 7805 +5V 1A Voltage Regulator TO-220 caseZV1505
1 × Ultra Mini Experimenters BoardHP9556
1m USB Powered Trimmable RGB LED Strip LightZD0571

Parts USED:

1 × 9V Battery Snap - High QualityPH9232
1 × USB Type A PC Mount SocketPS0916
1 × 220nF 100VDC Polyester CapacitorRG5145
1 × 100nF 100VDC Polyester CapacitorRG5125
1 × 7805 +5V 1A Voltage Regulator TO-220 caseZV1505
1 × Ultra Mini Experimenters BoardHP9556
1m USB Powered Trimmable RGB LED Strip LightZD0571

Using USB connectors does add extra cost, but it does make the LED strip easier to connect and disconnect. Please explain to our readers how you put it all together.

First, I needed to find out the pin out for USB connectors. According to the lammertbies.nl website, the pinouts are as follows in the table I made below. It includes a +5V power and a 0V or Ground, just what we want to power our LED string.

1 Vcc Red +5V supply voltage
2 D- White Data- signal line
3 D+ Green Data+ signal line
4 GND Black Supply ground

The USB Socket has four Pins and two “Legs”. I only need to solder the Pin 1 to my +5V supply and my Pin 4 to the 0V or GROUND but it is tricky to do that directly, so I solder the pins to the separate sets of Holes on the board and then connect these to my Power and Ground Rails with hook-up wire. It is a good idea to also solder the Legs to the board to help support the Power pins.

Solder the LM7805. ALWAYS check the markings of components when you are purchasing components and building your project because getting the wrong component in a circuit can be disastrous. It is a good idea to check the Manufacturers Data Sheet to get the correct Pins. There may only be three pins but there are SIX combinations that those three pins could be in. Checking my Data Sheet, I find that Pin 1 is my Input Voltage, Pin 2 is my Ground and Pin 3 is my Output Voltage so I put these pins into appropriate holes on the board, using the board rails, and solder them up. A little hook-up wire to complete my circuit and I am ready for testing.

What advice do you have for someone who is soldering for the first time?

A good solder joint will usually look slightly shiny and appear to blend between the part and track. If a joint is dull or it does not look like there is a nice blended connection then usually a quick touch of the soldering iron to re-melt the solder will fix it. A “dry” joint on the surface looks like there is a connection but underneath there may be no connection or an intermittent connection. Also, sloppy soldering can cause short circuits between parts or tracks on the board. While a bad joint may make the project not work, the tiniest sliver of solder between two tracks CAN cause spectacular results. Thankfully with a simple circuit and only a 9V supply we will be safe from this.

That’s sound advice, Andrew. It would be terrible for the lights to fail while the performance was underway! What should readers do before they connect their 9V battery?

It is very important after completing the circuit to visually inspect everything to check that it is the actual circuit that we wanted to build. It is far easier to correct a mistake from a misplaced component BEFORE you apply power to it and smoke starts coming out.

True, you can never put the smoke back in once it comes out. Do you just connect the battery next?

Connect up the Battery and make sure nothing gets very hot or starts smoking. When you are happy everything seems to be working – plug the LED string in. If ANYTHING happens that shouldn’t – disconnect and re-check. If all goes well you should now have a working LED light strip powered from a 9V battery.

Awesome! Any tips and tricks for sewing the lights into the dress?

Don’t get your fingers when hand sewing ha ha. Otherwise not really, was pretty simple and straight forward. The battery was a case that fits into a small pocket in the dress. I used very basic electrical tape to cover the PCB as it was not meant to be robust or long term.

Perfect! What have you learned from the experience that you would like our readers to know about?

I would say the importance of checking data sheets and using Standards to make sure your design will work on paper before building it, and to carefully check your creations for common issues.

Have you had any thoughts about extending your electronics skills to other costumes?

The circuit is so basic that it would be easily adaptable to any Cosplay costume. It should run longer on a LiPo battery but I had size and weight constraints that are maybe not an issue for a Cosplay but are an issue when dancing in a competition. Size is not really an issue, just the final weight. The whole thing weighs only 120g. A LiPo is bigger and maybe a bit heavier but could be more easily hidden and supported in a Cosplay costume situation. There is not much room to manoeuvre with a Ballet Tutu.

Thank you for taking us through your handy work. We wonder what project your daughter will request next.

Andrew Pullin

Andrew Pullin

Father of the Year!