Archive for August 6th, 2012


The UFO and the Shuttlecraft

The UFO is a simple device for controlling instruments with light-dependent resistor (LDR) controls, for example the Opto-Theremin described in an earlier post.

It started life as one of those battery-operated lights where you push on the top to switch it on and off:

I painted it silver, and added bits to make it more flying saucer-like, some LEDs that change colour slowly, and a 5-LED goose-neck lamp that I found in a local Poundshop.

The colour-change LEDs have no important function, but the brightness of the goose-neck lamp can be controlled with a potentiometer, and can thus be pointed at an LDR and used to vary – in the case of the Opto-Theremin – volume, pitch or filter cut-off frequency.  Here you can see the lamp and the potentiometer: I didn’t attach a knob as I couldn’t find one that looked more UFO-like than the knurled shaft:

UFO High Angle DSCF0029

The goose-neck lamp is meant to operate from a computer USB port, so plugs into a USB socket, with only pins 1 and 4 (5v and 0v) connected.  The battery holder in the lamp is designed for 6v, and therefore had space for 4 AA batteries, but I mostly use 9v, so I adapted it to take a PP3.  I restricted the potentiometer from putting the full 9v through the LEDs, in case it was too much for them.

The maximum voltage allowed for the color-change LEDs was 4.5v; there are 4 of them, so I connected two in series on one side of the dome, in parallel with two in  series on the other side.

UFO Back DSCF0032

I also added some extra 3.5mm mono sockets, as can be seen in the picture, as this is a system I use for distributing power.  When the Opto-Theremin is used in conjunction with the UFO, it can receive its power from there, rather than from a separate battery.

This picture shows the two being used together:

UFO and Optical Theremin DSCF0022

These pictures illustrates the soothing effect of the constantly changing colors:

UFO Colours

The ‘Shuttlecraft’ isn’t really an invention of my own: in fact, it’s just a multi-LED lamp on a headband, as worn by cyclists.  It appears here only because it’s an aid to playing the Opto-Theremin.  Because light levels are often too low to get the maximum variation in parameters controlled by LDRs, it can be useful to have extra light to hand: but when your hands are occupied playing the instrument, the next best place is on your forehead.

Shuttle DSCF0035

Although the UFO and the Shuttlecraft were created with the Opto-Theremin in mind, they could be used with any instrument (or effect) that uses an LDR – for example, my first Stylophone mod, the ‘Alien’, or the Stylophone 350S.


August 2012

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