This week, I have been mostly working on... » Electronics

…infringing patents (probably)

Stephen Hobley — Wed, 23 Nov 2011 18:12:09 +0000

I’ve been meaning to build one of these for ages.
Can anyone guess what it is?

It’s not a Taser, or one of those shocking buzzer things – the clue is that the coils are well “potted” and have very different gauges of wire.

Answers on a postcard please, or in the comments…

UPDATE : Correctly identified as a “guitar sustainerizer” otherwise known as an Ebow.

The circuit is a simple audio amplifier based on the LM386 (or in my case the NTE823) IC.

The two coils are taken from old telephone pickups – one (input) has a small rare earth magnet on the back, the other (output) was unwound and rewound with about 300 turns of #32 wire – this coil now has a resistance of just under 8 ohms. I tried a 4 ohm output coil, but the IC got too hot so I doubled the turns.

Note – I recently found a better candidate to make the coils with – tiny PC speakers.

The input coil has a resistance of 250 ohms – this is probably too high – I read somewhere that 50 ohms is probably better – so I may remove some of the turns on the coil.

Tomorrow I’ll publish the circuit and the etch mask, along with a video of the device in action.

…and here’s the patent

UPDATE2 : Here’s the schematic, placement and etch mask – click to enlarge

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…Treasure Finder for MAKE:Projects

Stephen Hobley — Sat, 19 Nov 2011 20:51:41 +0000

This was my favo[u]rite of all the MAKE projects I’ve been working on.

This project uses 2 oscillators in a configuration very much like a Theremin to create a beat frequency (BFO) metal detector.

Range is a few inches for the smaller detection coil, but the detection range can be increased by adding a larger coil.

What I really liked about this project was how the oscillator coil is tuned – using a brass nut on a PVC sleeve.

Full build instructions can be found here…

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…Fritz Lang’s Theremin Stand

Stephen Hobley — Sun, 06 Nov 2011 20:13:27 +0000

(Sounds like something you’d find in Warehouse 13)

For many weeks I’ve been trying to come up with a cabinet design for the vacuüm tube Theremin I built a while ago.

I decided that the electronics were far too marvelous to hide away in the classic RCA “drinks cabinet” – and that something more radical was required. (Electronic design by Mark Keppinger – more information is available here)

…and it had to have *lots* of elliptical curves. (‘Cos nothing says CNC like ellipses)

What I wanted was something that would be open enough on the front, back and sides so that the coils and tubes would be visible. It was routed from 3/4″ MDF and then the beveled edge was created using a small table router and “tracing” bit.

I still need to figure out a way to attach the antenna – and replace the 1/2″ copper tubing with some stainless steel, or brass. The front panel will eventually house the pitch tracker and midi interface I designed.

(Yeah… it’s dusty)

The speaker is not in the ‘ideal’ place for performance – it should really be behind the player’s head. This position does allow the speaker to be placed facing forwards or backwards, and it can be removed completely and placed on another stand if required.

I’ve been experimenting with different paint finishes – and I think that black satin is probably the best. High gloss would be nice, but requires more maintenance. Unfortunately the seasonal window on spray painting is starting to close, so it might be spring next year before I can finish the project.

…and even though the Fritz Lang thing was a joke – it does remind me of this scene from Metropolis.

Update:

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Fry’s – now dealin ‘duinos…

Stephen Hobley — Sun, 06 Nov 2011 13:53:02 +0000

Wow, didn’t expect that. I was lurkin’ in my local Fry’s and found a section full of Arduino clones…

They seem to have a range (from Megas to Nanos) of them – prices are pretty good too.Similar Posts:

Air Guitar? …meet Air Piano

Stephen Hobley — Sat, 05 Nov 2011 18:17:21 +0000

My buddy John Claeys sent me a link to this video of the AirPiano device being demonstrated by Jo Hamilton.

I’ve not been able to find out too much about the design or origins of the instrument. It seems to use optical proximity sensing to detect the player’s hands.

A neat idea, and a slick implementation. Guardian article here…

I do feel that a lot of these devices (yes, the laser harp included) miss out on the important element of “feel” in their design. Although the laser harp project was fun, and visually very dramatic – it’s not really an expressive musical instrument.

I’ve worked on several new instrument controller designs since the laser harp, based on a variety of physical principles – and always the most successful derive their playability from some kind of electro/acoustic interaction – striking metal plates, blowing into hollow tubes, even “stroking” custom sensors (like wine glasses). The response of these sensors was then analyzed and mapped to various expression ‘dimensions’ within the tone generator. Unfortunately, moving your hands in the air has only ever been a novelty.

For that reason, I think I would trade an AirPiano – for one of these:

…and definitely for one of these:

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DIY CO2 Laser Cutter – more test cuts…

Stephen Hobley — Wed, 12 Oct 2011 03:13:07 +0000

I re-aligned the bounce mirrors, added an air-assist, and did some test cuts on acrylic, plywood and hardwood. Slowing the feedrate seems more effective than increasing the power.

Need to spend some time with different materials, figuring out the cut parameters for each one.

Oooh shiny!
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…555 timer “Ball Whacker”

Stephen Hobley — Mon, 10 Oct 2011 18:58:13 +0000

As another Radio Shack “Great Create” challenge I put together this fun project. A 555 timer and simple optical feedback loop creates a simple cybernetic control system.

The photocell in the tip of the arm responds to the light pattern falling across it – this in turn controls the position of the arm. Resulting in some amusing, and very human-like behaviour.

Check out the project details on the MAKE: Projects page:
http://makeprojects.com/Project/555-Timer-Ball-Whacker/1061/1Similar Posts:

…making some initial cuts with the CO2 Laser

Stephen Hobley — Tue, 04 Oct 2011 20:13:26 +0000

Yes! Finally, after several iterations we have the installed, aligned and focused CO2 laser wreaking some serious havoc on a piece of MDO.

There are still many tests to run and various safety mechanisms to install, but the system works, and is aligned over a 24″ x 24″ area (at least).

I can think of at least half a dozen improvements to make right now, but they’ll have to wait – for a day or two anyway.

Again – safety glasses are *mandatory* for this kind of work.

The first part of the movie covers some tips for beam alignment, the cutting is right at the end.

…almost forgot about the air-assist nozzle…

…for making nice clean cuts in acrylic.

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…building my Destructor(tm) beam

Stephen Hobley — Sun, 25 Sep 2011 13:54:59 +0000

More progress in the laser/CNC saga.

I built a cage from steel and MDO for the laser tube – fits really nicely. Next step is to add the first bounce mirror which will turn the beam straight up – into a PVC tube attached with plumbing flanges (The sales assistant at Menard’s asked me what I wanted it for – I’m pretty sure he wasn’t expecting the answer he got).

www.stephenhobley.com I moved the CO2 laser tube out of its box and into a steel and MDO cage. Now I'm ready to install it in the BlackToe CNC gantry." longdesc="" />

All the parts are in – I was able to repurpose some Laser Harp spares for the mirror mounts, and found a 25mm Silicon/Gold mirror on eBay for under $30 – a bargain.

www.stephenhobley.com Ready to be installed in the BlackToe CNC gantry. (This is the business end)." longdesc="" />

I finished the last of the designs today – now all I need to do is cut it out and assemble it.

Pete came over on Thursday night and we tested the ‘volatility’ of the unfocused beam on a variety of building materials…

“Impressive. Most impressive…”

New update here.Similar Posts:

…fixing up a Roland Juno 60 synthesizer

Stephen Hobley — Sun, 18 Sep 2011 13:59:42 +0000

A couple of years ago I bought a Roland Juno 60 from eBay. It was in “fairly good” condition but was very dirty and the faders did not work properly. There also seemed to be a sticky (beer?) substance on all the keys that was less than attractive. Additionally the programs weren’t being saved correctly – probably the internal lithium battery was just about done.

So I thought it was about time I opened it up and cleaned out all the gunk, and fixed the battery at the same time.

The top section is hinged, and pretty easy to open.

7 screws hold down the keyboard. Once these were removed I could remove the whole unit. Each key is held in with a tension spring – carefully unhooking these allows each key to slide out.

A quick go in the dishwasher got rid of the gunk. When you put them back check the underside, they are labelled with the correct note position for each key.

Next up were the faders, I used some Deoxit “Fader Lube” on these and got them working smoothly again.

When I replaced the keyboard, I noticed that two keys were not triggering consistently – I used Isopropyl alcohol to clean the contacts and that seemed to fix it up.

Finally I de-soldered the old Lithium battery, and tacked in a regular 3.3V button cell. The negative terminal is on top (black wire), and the positive below (green wire)

The last step was to reload the programs back to the factory defaults. There are SAVE and LOAD audio jacks on the back of the JUNO-60. Originally you hooked up a tape recorder to save program data (yes, computers used to work like that). I found wave files of the original program data online, and transferred them out through the earphone jack of my laptop into the LOAD jack on the synth. You have to fiddle with the levels but it does work (eventually).

All done! Time to take it for test drive:

The delay effect in this video was provided by a Tascam 32 reel to reel tape recorder – looping the signal from the playback head back to the record head. – It doesn’t get more analog than this!

You can get the service manual, user manual, and default programs from here.

There’s also an online version of the manual here

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