High Power Rotating LED Disco/Band Light

The problem

I had two no name inexpensive but very effective revolving 'disco' lights that I used for the band I was in a few years back. One is shown in the second image.

We had some American DJ pro lights too (third image) which were also very good.

But the cheap lights filled any size gig space we played with hundreds of impressive light beams.

I also noticed a few times that its effect was more admired by an audience than the two ADJ ‘jellydome’ lights (the bluish one in the images above) which cost a whole lot more. The jellydomes lights looked basic in comparison.

Each beam of light from the LED's is focused by lenses moulded into the plastic domes. Its a system that works brilliantly.

We used these lights because they are easily portable fixed down in a box with a removable lid. They could be placed on the floor turned on and you were good to go.

Domed and Doomed

So one of the two cheaper LED lights eventually stopped working.

When I looked inside I could see why.

The revolving head with the 6 LED’s on it was powered by wires simply soldered to the head. This meant that as they were constantly moving they were doomed to fail at some point.

This could be by the soldered joint failing or the copper wire breaking (copper 'work hardens' as it bends).

Eventually the second light died too. I missed the excellent effect that they made.

These are no longer for sale, I guess because they had so many sent back broken. You can get smaller ones now but I wanted to bring these larger versions back to life.

I did try soldering more flexible wires back on the LED pad but this didn't work. I guess that they took a few components with them when they died. I tried bypassing the power supply as I know these also fail due to low quality capacitors and overheating inductors. The supply is on its own board with convenient screw connectors to connect my own supply. It even showed the polarity. I didn't know what voltage to apply so I used a variable supply and went up to twelve volts at one point. This didn't really work to fix the lights. The LED's lit but the motor wouldn't turn, or the other way around. I gave up as my electrical knowledge is very limited.

The solution

The ADJ ‘jellydome’ lights rotate the dome itself while the LED lights stay in a fixed position.

This is a far better idea but more complicated to make and therefore would cost more to do.

So my task was to reproduce a similar action using whatever I could find or make myself. 

Interestingly the cheap lights dome has a lot more lenses cast into it than the pro lights as you can see in the image.

More lenses produces a much better effect.

I have tried to keep these old lens domes safe until I got around to using them once again.

Design Idea

I needed something that would rotate and support the lens and allow some method driving it around.

I eventually sourced a 'Revolving chair/lazy Susan bearing' with a hole in the centre big enough for the lights to go through.

On this I would mount a large cog/gear and I would need a slow speed geared motor strong enough to propel it around.

It would then need a method of retaining the dome in position over the cog.

This mechanism would need mounting on a suitable box.

Improvements from the original

Both the cheap and pro dome lights had limited colours.

As I am building my own I could look to see what other colours are out there.

I could also use more powerful LED’s.

I could use more LED’s than the other designs.

A bigger fan would extend the life of the LED’s. It would also be needed if the light were more powerful = more heat.

Shopping

1. ·      6 inch ‘Lazy Susan’ bearing 
2. ·      10 x 3watt LEDs in 10 colours with mounted heat sinks
3. ·      60 revs per minute geared motor 12 volt
4. ·      Heat sink that will fit in the centre bearing hole
5. ·      LED driver suitable for all the 3 watt LED’s (from the same place as the LED's in my case)
6. ·      12 volt Motor speed controller
7. ·      4mm plywood for laser cutting parts
8. ·      Suitable gauge wire
9. ·      Silicon Heat transfer pads for the LEDS
10. ·      12 Volt computer cooling fan
11. Small 12 volt power supply for the fan and motor

And various screws, hot glue gun, drill, laser cutter if you have access to one, etc

All of these apart from the plywood are easy to find on Bay in the UK

Making

The gear/cogs were going to be a major problem. You can’t just draw them out and guess how the teeth mesh together.

I could have used a belt system to turn the dome but I thought that a cog would be more interesting. Besides, the bearing didn’t like to be pulled under tension because it would unseat from its bearing surface. A cog would be less likely to cause a problem.

Luckily I found a really helpful site (shown above) where I could customise and download for free a suitable set of gears in DXF format. I could rescale these in SerifDraw to what I wanted afterwards.

I used a Sculpfun S9 laser cutter. The cogs came out better than I expected. I only use cheap ply from a local wood yard. The ply on eBay is very expensive in comparison. If a cog was to have a weak tooth due to a gap/void in the wood I would just cut another and another until I got a good one. The first version was fine.

The second time I added some screwdriver access holes for the screws that hold down the bearing.

The gears mesh well, although there is a bit of friction. Exterior wood glue on the teeth improved the friction and made them a bit more resilient.

I will eventually make the smaller gear out of acrylic and this will reduce friction and the size of motor needed to drive it.

I also cut out the hole for the motor in the smaller cog at the same time making sure that the ‘D’ shaped profile was included so that it would be a friction fit and would not slip around. I cut two and joined them together to make it easier to align the cogs and compensate for any wandering as the bearing is not that perfect.

Next the outer ring was cut out that would hold and support the old dome lens. I could hot glue gun the dome in position later when its complete.

There is also a wide ring underneath to allow more wood depth for the screws to hold onto.

Ive attached some DXF files I used as examples if your interested.

LED's and Heat

The heat sink was marked out for 9 LED’s. I couldn’t fit a tenth on.

I drilled through the heat sink to allow the wires to go through.

Be prepared to break a few drills, aluminium is tough stuff. Wear safety glasses.

The LED’s were attached to colour coded wires so I knew which was the positive and negative connections.

I used silicon heat transfer pads cut to size to glue down the LED's onto the aluminium heatsink.

I then joined the LED's in ‘series’ ready for the power supply which would accept 8-10 bulbs and give them the correct voltage and limit the current. There are lots of YouTube tutorials showing what series connections are and why they are used. This guy does a demonstration of what happens which is really practical compared to those that just like the sound of their own voice! (if you know what I mean)

https://www.youtube.com/watch?v=VrL_WN3Xcho (screenshot shown above)

• Don’t just connect any LED to its voltage rating without using the correct current limiting resistor or regulated supply, it will not last long.

The Motor (see video)

I cut out 3 supports in ply for the geared motor and glued them together in a stack. The hole had 0.3 mm clearance (oversize) to allow the motor to fit snugly.

I hot glued on some supports to keep the motor at 90 degrees to the top surface.

An elongated slot one side allows for sideways adjustment so I could control how much of the teeth meshed.

I didn’t mesh the gears tightly, doesn’t need it.    

The supports were added oversize so that they could be trimmed later when I had made up my mind how strong they looked to be.

The Heatsink

The heatsink needed the corners removing in order to sit in the bearing hole with some clearance.

I used a belt sander for this.

It got suprisingly hot doing this so I had to do it in stages.

The heatsink is attached to 4 'body washers' by screws so that it is not directly mounted on a flammable surface, just in case. 

Anything metal will do its just that I already had these from other projects.

Some screws go though the body washers and are trapped in between the cooling fins. It took a few attempts to find the right size screws. The fins are quite tough so they seem ok with this primitive method.

The Box

I laser cut a box out of 4mm ply. This has lots of venting and a mounting for the cooling fan.

It fixed together with hot glue.

There are 2cm feet underneath to allow for air flow.

I made an additional recessed mounting for the mains connection, switch and the motor speed controller.

The speed controller is called 'PWM DC Motor Reversible Variable Switch Speed Controller Driver 3A 6V 12V 24V'

My circuit board was clearly labelled for the motor connection and voltage supply.

The lights work off a mains 230v supply unit that used to being to a laptop. The small cog motor and the cooling fan both use a small mains AC voltage to 12v DC supply that fits in the box.

In Practice

It need some more development but it works really well.

The extra colours make a big difference.

The colours I used are:

1.     Royal blue (more towards purple on the colour wheel)

2.     Deep blue

3.     Cyan (greenish blue)

4.     Orange

5.     Yellow

6.     Deep red (more towards crimson)

7.     Red (its more towards scarlet)

8.     Pink (it’s a plant grow light but who cares, it’s a great colour)

9.     Green

The motor is noisier than I expected. But when reduced to a slow pace its not really a problem.

I think that the lights look best at a slow pace.

I think that the motor would be better geared even slower to 10 RPM.

An improvement would be 'sound to light' feature but I like it as it is.

When it works along with the ADJ jellydomes they do they do that sound function so they end up contrasting with each other which works fine.

Ive attached a short video of it working. Its much better in a big venue.