The Amazing Rave-O-Matic Laser Disco Music Machine

Construction Diary

June 24, 2005

IT'S DONE


Nine hours of construction later, I have a finished rave-o-matic.


There is a great deal of wiring. I love the way the switches look.


The big pair of terminals supply power to the laser; the smaller pair each power one of the blacklights.


The wires are all anchored to the ceiling so they keep out of the battery's way.


The laser box is securely mounted onto its platform.


I'm powering the laser with a converter designed for a cigarette lighter socket; instead of building such a socket, I just soldered the leads directly on.


There's room for expansion: one of the switches is unused and there are a couple of spare power terminals.


Two blue lights give the interior a high-tech look, and the stereo power switch glows red.


All plugged together and running: the purple tubes are the blacklights on the wheel outriggers, and the red blur is the laser, responding to the music.



Another look at the power terminals, with their plugs installed.


The silver paint was a pain, but it's actually kind of convenient since the light reflects off the walls and these two little bulbs illuminate the whole electronics compartment.


I am very pleased.

June 23, 2005

I made a really big push today and got all of the stereo wiring done. The speakers are installed, the amplifier is connected, the audio wiring is routed, and the power system is set up. It feels really good to be actually installing components: cutting wires, designing circuits, soldering things together. The finish work turned out beautifully - the silver gleams, and the acrylic finish is smooth and shiny - but I am very happy to be done with it and on to some more of the actual building.

I had never actually tested the amplifier, so there had always been a little fear in the back of my head worrying that I would get everything finished, flip the switch, and nothing would happen. Then it would turn out that the amp was completely shot, and there was nothing for it but to buy a new one and modify the mostly-built machine to fit. So imagine my astonishment when I got everything finished, flipped the switch, and... nothing happened!

Well, not only had I never tested the amplifier, but I'd never actually worked with car stereo components before, and as this was a second-hand amp I had no instruction manual. Not to worry: a few minutes of web crawling revealed that the cryptically named "P.CON(REMOTE)" terminal is sort of a power switch, so that the amp only turns itself on when the car stereo itself is on. Not knowing what this terminal did, I had ignored it - but that was easily solved. One wire jumper later, out came the music!

This is definitely the loudest, bassiest, most dance-worthy stereo I have ever owned. It was getting pretty late by the time I finished the wiring, so I couldn't really give the machine a proper test, but I like what I hear so far. I'm sure it will sound less overwhelming once I get it out of doors, but it should still be respectably energetic.

The weight is not as big a problem as I had feared. The speakers and amp do add some heft, but I can still pick the body up and move it around without trouble. Of course, I have to remove the battery first: I think the battery weighs as much as the rest of the machine altogether.


Time to install the speakers.


Are we ready to rock, or what?


The stereo is all wired up. One switch controls the amp, the other will control the lights.


The battery clamps are connected to a pair of screw-terminal buses, so I can easily connect additional devices.


Now that the finish is done, the wheels can go back in their frames.

June 22, 2005


Finally, done with the paint! Time to build the battery mount.


A pair of u-bolts in the back hold the rubber straps in place. They stretch over the top of the battery and hook into the eye-bolts at the front.


It works! The battery is snug and secure. I'm so happy.


Let's drill some more holes in that gleaming fresh paint.


The silver box labelled “Kenwood” is the amplifier. The red thing on top with the handle is an inverter, which converts 12VDC battery power into the 120VAC ordinary appliances use. It'll drive the disco light, since nobody makes disco lights that run on 12VDC.

June 21, 2005

The paint situation is improving, slowly but steadily. The main body looks good now - especially the top surface, which gleams - but I may wrap another coat around the front face to really, truly cover up the last traces of white. The outriggers are kind of a mess; they are such a complex set of surfaces that I lack the patience required to paint them carefully enough to avoid drips. There are, therefore, drips. The white underlayer is almost gone; I'm sure I will need another full coat before the outriggers are done, but the end is within sight. The pole top bracket has only two coats but already looks great, especially considering the fact that it is going to be way up in the air where nobody can really see it anyway.

The lesson, children, is never to paint anything silver. If your muse descends upon you in the paint aisle, throws a screaming, kicking, name-calling hissy fit, and refuses to lay off until you pick up that can of silver paint, then at least make sure to use grey primer instead of white.

I bought the last of the expensive components for this project today: an Exide Pro Comp Super HDX Off-Road/Deep Cycle Battery (whew!). It's forty-five pounds of high-tech battery goodness, and I was relieved to find that it fit perfectly into the space I had reserved for it. I have been waiting to finish mapping out the electronics bay until I had this battery, since it's big and heavy and can only go in one place. I had thought I might have to build a tray to hold the battery in place, but now I think I can just use some eye-bolts and heavy-duty rubber bungee straps. The amp will have to be mounted on the outside after all; I had thought there might be room inside, but it's clear now that it would be too tight a squeeze. That's OK; I'll just bolt in onto the side panel that partially encloses the electronics compartment.

My friend Michael and I did some beer-enabled brainstorming last night and came up with a rigid-but-swivelling hitch design that will allow me to steer the trailer more effectively, eliminating the shimmy problem, and will let me use my brakes to slow down both bike and trailer. It's really quite a simple design, so I'm confident that it will work, and it should make the whole experience rather less stressful than it would have been had I tried to use a length of rope.

The disco ball light I ordered turned out to require 12V AC power, not DC, so I cancelled the order. This leaves me a rather skimpy lighting situation for this weekend, since it's too late to mail-order anything else in time; but I'll make do with what I have. There really don't seem to be many battery or 12VDC-powered options for disco balls, so I may end up buying an inverter anyway (ugh).

June 19, 2005

Slapped on another coat of silver paint today. It's still not looking great, but it's slowly improving. Another six or seven coats and it should be quite pretty; alas, I think my forearm will have seized up by then and I'll be painting with my teeth. I also ordered two twelve-inch blacklight tubes and a disco colorball light, already set up to run on twelve-volt power. I still want to get a few more blinky things, but I think I've got the rave lighting situation pretty well covered.

I'm still hoping to have this thing finished in time for Critical Massive next weekend. It will be a lot of work, and there are still a bunch of parts to buy (including, most critically, the battery), but I think I can pull it off. The pressure is kind of fun, actually.

June 18, 2005


Two coats of silver. Not looking too well yet, but I think another couple of coats should help smooth out the streaks.


I'm still tired of paint. The outriggers take a lot of time because they have so many little angles and hidden surfaces.

June 16, 2005

I put the second base coat on the body today, and a first coat on the wheel outriggers. Now I am covered in flecks of paint and my right wrist aches. The carpentry was fun, and the wiring will be fun, but this part is just work and I am ready to be done with it. Perhaps I will feel more enthused once I start painting on the silver finish coat: this white primer stuff is boring.

I hung the outriggers from the overhead rafter on bungee cords, so that I could paint all sides at once and let it all dry instead of having to take two passes. I hope nobody walks in there in the next day or two, because the scene is a little ominous: suspended right at eye level as you walk in is this row of things, pure white hunks of bolted-together wood without apparent function; it reminds me a little of one of those walk-in meat freezers you see in horror movies.

Nobody has yet walked in while I am working, and so far as I can tell nobody else has visited the basement at all since I began my project. I was a little nervous at first, because I didn't exactly ask anyone's permission to use the work space, and I had worried that someone would walk in on me, take offense, and complain to the managers. But I seem to be the only person in the building who is using my storage locker for anything but long-term stowage, so I pretty much have the basement to myself.

June 15, 2005


These brackets will hold the laser projector onto the top platform


The beam will project at around 45° from the pole, which makes about 18 feet to the ground, so the image should be around 6-8 feet wide


Primer base coat is finished

June 13, 2005

The laser projector arrived today, and of course I plugged it in immediately. It works pretty well. The laser is very responsive to the audio; it's kind of like watching a laser version of an MP3 player's visualizer mode. The only settings are a pair of knobs adjusting the projector's sensitivity to each audio channel, which is just fine with me; I want something I can stick on the end of a pole and forget about. The image is a bit small, but the size of the picture fluctuates according to the audio volume, so it could be that I just need to fix the levels so the gadget gets a hotter signal.

Now that the construction is finished, I'm starting to think more about lighting. I'm going to mount blacklights along the two rear outriggers, a strobe light and a colorball underneath the laser platform, and various other blinky things sitting on the top platform. I need to put enough gadgets on top of the stereo that people don't think it's somewhere to sit, at least; and I don't think it will take too much to make this contraption visible at quite a distance.

Here's an interesting microphone preamplifier circuit; it's a bit more complex than I would need, since it supports either an electret or a dynamic mic element, but it looks like it might not be that hard to modify.

June 12, 2005

I spent a couple more hours working on the rave-o-matic this afternoon. The wheel adjustment involved a little bashing about with a hammer, but it really wasn't as bad as it could have been, and now the chassis rolls straight and smooth. I took the machine out for its first road-test, and it actually rolls a bit too well - I had some trouble keeping it from running away down the hill and crashing into parked cars. It exhibits a fair bit of nose-wheel shimmy, so I will need to rig up some kind of damper, but overall I am quite pleased with its performance.

It's a little weird not being able to see the machine as I tow it. As I've been designing this project I've been imagining what it would look like to an observer following behind; it never occured to me that I wouldn't be able to watch the show as I rode. Oh, well, I guess I can always stop my bike and join the party anytime I want.


The big round holes are for the speakers; the peg on top will pin the laser pole in place.


The assorted batteries, power supplies, stereo components, and other electronic gadgets will fit inside this compartment.


The bearing warped a little under the pressure, so the swivel plate is closer to the mounting plate at the back than the front. I think this will be OK but need to keep an eye on it. Perhaps a small support roller would help.

June 11, 2005


Most of the carpentry is finished now, though I need to adjust the left wheel - seems I mounted it ten degrees off true. Oops.


The front wheel swivels, using a lazy-susan bearing, and it weathercocks as well as I'd hoped (whew!).


Close-up of the swivel bearing mechanism


The swivel at rest...


...and in action.


The two back wheels are mounted directly to their outrigger plates.


The completed machine is about six feet wide, which is too big to fit through doorways or into the back of my car. I modified these joist hanger brackets so I can slide the outriggers into them and pin them in place with hex bolts. All the weight is supported by the hanger brackets, so the pin bolts only need to be finger-tight, which means assembly and disassembly do not require any tools.

June 10, 2005


I went over to West Marine and checked out their deep-cycle batteries. The prices weren't bad, but I think I can get an Optima for fifty bucks less than one of their AGMs, with equivalent power and weight. Lead-acid is a lot cheaper (half the price, roughly), but I am worried about vibration damage and the risk of acid leakage if the battery tips over.

June 9, 2005


The speaker enclosure is finished. (This is the center part of the
rave machine, minus the outriggers.)

June 8, 2005

Here's a 12V DC voltage converter for $3.95; like one of those universal wall warts, except it's designed to work on DC power. This will be useful; the amplifier needs 12 volts, the laser needs 9 volts, the strobe and other lights use 6 volts, and the MP3 player expects 5 volts... instead of wiring up a separate battery pack for each device, I'll just get a bunch of these converters and run them all on the 12V main battery.

I've been working hard on the rave machine over the last few days, though progress has not been as visible as I would usually like. There are a number of tricky design problems involved, relating to various limits of space, time, volume, power, and money, pushing against my desire to make the finished product as exciting, noisy, and visually impressive as possible. I finished the laser platform and its collapsible pole last night, and built about half of the speaker enclosure. I've solved the wheels problem - I'm going to use ten-inch pneumatic hand-truck tires - but I still need to actually build the swivels and mounting brackets, and I'm still trying to figure out what the electronics box is going to look like.

June 4, 2005

I spent the afternoon building the frame for my portable rave machine. This is a trailer I will tow behind my bike, containing a stereo and a laser projector. This would be pretty simple, except that the laser will sit on top of a sixteen foot pole, and a trailer wide enough to securely anchor such a pole would be difficult to store and transport. What's more, I want it to look cool - a little otherworldly - something more than just a boom box on wheels. My solution is a circular central platform with three removable outriggers. All of the audio hardware will be bolted onto the central platform, while each outrigger will have one large wheel and an eye-bolt for anchoring the laser pole. I like the look so far, though it desperately needs paint; it reminds me a bit of crop circles or lunar landers, sort of a miniature UFO.