I “test fitted” the sensor circuits to the gantry tonight and I’m pleased to say that they work with a surprising degree of accuracy.

The sensors are wired to input pins 11 (X), 12 (Y) and 15 (Z). I used the Mach 3 “auto set” feature to configure the pins as home for M1, M2 and M3.

A neat feature of the homing functions (Ref) in Mach 3 is that it homes past the switch limit, then backs up to the on position, so the home is always referenced from the same position.

UPDATE : After giving this some thought it occurred to me that the home position doesn’t really have to be at the origin at all. It just needs to be a fixed reference point, so that the machine can “pick up where it left off” from a known location. Changing the tool on the router will typically nudge the motors and cause the software to get out of sync with current position.

I believe it is possible to script Mach3 to move to a fixed offset away from the “home” position, and use this to set the start point for the cut.

I’ll have to put together a movie that shows how Mach3 is configured too.

One thing missing from our CNC routers is an automatic axis home circuit. This is something that signals the control software that the gantry is in a known position (usually at the origin). A lot of CNC hobbyists like to use the end mill as part of the homing circuit – this is OK, but does not take into account different sizes of bit diameter. A better solution is to have the X/Y home switches attached to the linear axis. Then the home position will be the same regardless of bit diameter.

Initially I wanted to use Hall Effect sensors, but the detectors themselves proved difficult to get. I’ve had some QRD1114 reflection sensors for some time, so I thought it was about time I put them to good use.

Initially I used a PNP transistor to amplify the switching signal from the sensor, but this proved to be way too analog. The resulting signals were not very clean. So instead I used an LM324 opamp configured as a comparator, with a simple potentiometer providing the reference voltage. A 1M resistor is used for feedback, providing some hysteresis around the switching point. Eliminating any potential chatter that can occur.

Once we have the system fitted and working – I’ll be publishing a howto guide.

This switch will be used to home the X and Y axes, the Z axis will be using a touch plate.

For many years Manuel Schulz maintained The Laser Harp Pages. This site was a major influence on me, and offered some wonderful technical information on how a laser harp could be constructed.

In early in 2010 he decided to close the site. Later the same year he asked me if I would be interested in hosting the site content. I firmly believe that all the great information he collected should be preserved, so I very quickly agreed…

Click Here for the Archive

I’ve been asked a couple of times for the source code to the World Mood Light I ported to use the WiShield.

I put it all in a RAR archive file and you can download it here.

Lightwave International rolled out the big guns for Little Boots at Coachella Music Festival 2010…

They used the 46Watt RGB projector to give over 100W of luvly laser light ™ on stage. My laser harp was right in the mddle. (Yay!)

Set your faces to stunned…

http://www.youtube.com/watch?v=dtN0SFihTac

From the Lightwave International news page:

“Lightwave International was present on 4 simultaneous stages at Coachella 2010.   Laser were featured at the Main Coachella Stage, Sahara Dance Tent, Gobi Tent, and the Mojave Tent.

Lasers were provided for Tiesto, Pretty Lights, Erol Alkan, Benny Banassi, Fever Ray, David Guetta, Z-Trip, Infected Mushroom, and Orbital.

Closing out the last day of the festival, Little Boots performed ‘Earthquake’ on a Laser Harp using the world’s largest full-color RGB laser, a 46 Watt monster system — and a total of nearly 100 Watts of full color lasers on stage.”

[http://www.lasershows.net/content/blogsection/10/89/]

http://www.youtube.com/watch?v=vhecLQl66TU

From GeekWeek [http://www.geekweek.com/2010/04/top-5-best-acts-of-coachella-2010.html]

“The expansive Gobi tent was the perfect venue to her traveling laser show which closed with the laser harp intro of “Earthquake”.  Hesketh even called out Ke$ha for stealing the laser harp act on her Saturday Night Live performance that same weekend.   This is the second time I’ve seen Little Boots and she gets better with every performance.”

Go Boots!

I’ve just been doing some work on my box of mystery. It’s a PC in the middle but surrounded by 3 mystery components – would anyone like to have a guess what the extra bits do…?

Wow – I’ve been working with lasershows.net to provide a dazzling performance for the Little Boots US tour – the photos from the LA gig at El Ray are just in, and the view from the lighting desk is truly spectacular…

George (Mr Laser) Dodworth from lasershows.net provided some serious wattage (30 – count ‘em I know you will) and cool visuals for this…

Wow I knew these guys were working on “some add-ons” for the 9700, but they’ve just come out with a bumper crop…

I think these modules just about cover all the limitations I found when using my 9700 – pretty cool.

Click here for more info

I think I’ll be getting the new noise source, the CV attenuator, the mixer, and the patch bay…

Or more precisely – how to build a ring mod and light flasher.

[If you are wondering what a Dalek sounds like, take a look/listen here]

The first step I took was to download the manual for the MoogerFooger and find out what all the knobs do. It looks to me like Nick Briggs uses a “secret Dalek factor” as the carrier and feeds this through a traditional ring modulator constructed from 4 diodes and 2 audio transformers.

Luckily there’s a great website that shows you how to build a passive analog ring mod here:

http://www.asciipr0n…gmod/index.html

Follow the directions on the page and wire up the audio transformers:

Audio Transformers

and the germanium diodes

Germanium Diodes

in the characteristic ring arrangement:

Lovely.

Your voice goes in on the red wires, the secret Dalek factor goes in on the green, and Dalek magic comes out of the yellow. (Actually connecting up in any order will make the RM work)

OK now to add the secret Dalek factor.

I don’t like to re-invent the wheel, so if there’s something out there that can *almost* do the job, I will hack away at that rather than design something from scratch.

The secret Dalek factor (as most of you know) is a 30Hz sine wave. So we need to find an audio oscillator that can provide what we need. Fortunately for us, (and Mr Hewlett, *and* Mr Packard), there’s such a thing as a WIEN-BRIDGE oscillator. Rainbow Kits sells a nice one for $not-very-much-at-all.

However, out of the box this kit does not do what we want. It oscillates at a fixed frequency that is too fast. After a bit of RC [1/2PiRC] math it turns out that we need to replace capacitors C1 and C2 with 0.1uF ceramic caps, and resistors C5 and C6 with approx 53.1KOhm.

Alternatively you can do as I did and get a dual gang pot (200KOhm) and turn this till the output reads close to 30Hz.

Great, so we’ve added the secret Dalek factor on the green wires, now we need to add the voice. For this we’ll need a microphone and a pre-amp. Velleman to the rescue here:

This tiny kit goes straight in unmodded.

All that remains is to add the speakers – for this I hooked up to 12v PC speakers to the red wires. Plug it in and hey presto – instant Dalek.

The sound can be improved greatly by feeding the microphone through an EQ effect pedal, boosting the mid-range and cutting the high and low.

Next stop – the light flashers…

-+-+-+-+-+-+

This was tricky. The standard Schmitt trigger that’s on Dalek City is OK, but the lights can get stuck in the “on” position and you have to cough to toggle them off. Also inside the cockpit there’s no visual feedback to what the dome lights are doing. Also the current requirement to flash 2 x 20W halogen lights on 12V is pretty darned high.

Again, I’m just going to mod some existing cheap kits that are readily available. The first kit is the well-known Velleman MK103 sound to LED light flasher:

This works at a mic level input – great for us – and has high impedance so the signal is not really affected. It only light 4 LEDs though which is no where near what we want to power 40 watts of halogen grooviness.

Here’s a picture showing the basic mod:

I replaced the built in mic with two wires which is connected to the mic socket, and the last LED (4) has been removed. You can simply wire this output into an optoisolator (4n29) through a 1K resistor, then use a big power resistor to switch the lights (TIP142, or a Mosfet)

OR…. you can take the Rolls Royce approach and wire the output directly into this little beauty:

The fantabulous Velleman MK114 12v sound to light kit, rated at up to 50 watts at 12v and a brain tingling 100 watts at 24v!

You just plug it straight in and away you go…

Note – the MK103 really likes to be run at 9v, not 12 – so I added a 9v regulator to run it where it wants to be.

I like this solution, there are two parallel transistors and a nice big fuse. It really *looks* like it can handle the power.

So that’s it, your voice mod, light flashing device is ready to be installed in your favourite MkIII travel machine. The lamps I have plugged in are low power, as my PSU cannot put out enough current to drive the two 20w halogen bulbs I just bought. So I need a bigger PSU…

Of course, this is only half of the story.

To really sound like a Dalek you have to adopt the harsh staccato tone, and do a bit of acting…

Pew! Pew! Pew! Lasers

This is a pretty cool review of Little Boots recent gig at the Highline Ballroom in New York City.

“There’s not much you can say against the laser harp. At the Highline Ballroom on Tuesday night a beam of green light shot up from the floor, then fanned out into eight individual rays. The tiny synth-pop singer Little Boots, wearing a gold lamé gown and face mask, played the melody of her song “Earthquake” by moving her hand among the streams of light; each time she blocked one, it triggered a synthesizer pitch, and she could alter its tone by lowering or raising her hand on each beam…”

Read More at NYT…

It’s been great to finally put the laser harp into the hands of a creative artist. Victoria’s going to take her band to the Ultra festival this month, and then on to Coachella next month. We’ve been working on something very special for that gig…