Romancing the (Light) Stone

31 10 2014

This is a hardware hack idea for the Wild Divine Lightstone in order to detect (REM) eye-movements via a light-dependent resistor or photoresistor.

Wild Divine Lightstone

Image courtesy of Wild Divine. com

 

Background

The Wild Divine Lightstone is basically a biofeedback, or more correctly, a human/computer interface for reading biosignals, etc.

The Lightstone hardware is bundled with The Journey to Wild Divine package for use on your home computer along with the manual, music and software disks.

It also features Deepak Chopra.

3 electrodes are worn on the middle fingers of the hand. This enables Galvanic Skin Resistance (GSR,) and the person’s heart rate to be measured in real-time.

Interactive exercises in your game journey give you the chance to practice your breathing and meditation exercises, as well as to complete tasks and learn new skills whilst in a mystical simulated game-type environment.

The down side however is that the interface cannot be used as an EEG, nor can it read brain states.

 

Design overview

The short and flimsy sensor leads merge in one long cable which is approximately 1 metre long which is terminated by a PS/2-type Mini-DIN plug.

The main (middle) sensor from what I can make out seems to be some form of photo-transistor or diode-type device which has 3 pins just visible in the square opaque window which is used for optical detection or measurement.

The two other electrodes are fairly standard metallic-type small disks used for measurement and changes in skin resistance.

The Lightstone case is made of a fairly dark blue plastic and is of solid, sound construction.

 

I could not find a schematic, circuit diagram, or any technical information on the actual Lightstone interface itself.

I would expect it to have the usual op-amp front end stages, analogue to digital conversion, etc. however.

I do know that it is illuminated by a pretty blue LED to give it that ‘special’ spiritual glow for your personal quest and to balance the energies in your room space.

Connection of the hardware to the computer and power is via a standard USB to printer-type cable.

 

I would expect loose connectors along with associated dry joints on the pins over time, especially if you constantly kept changing or unplugging the leads from the main unit for example.

Bent connector pins (like PS/2 devices) on the plug could also be one to look out for when troubleshooting.

The electrodes themselves too would have weak points at the exit and the main junction worsening over time due to movement and sheer weight. However there are strain relievers fitted on the cables which themselves are thin and flimsy, especially the GSR pair wiring which could break internally and go open circuit in a similar way that Walkman-style headphones tended to do.

The electrodes I found do not work very well if you have poor hand circulation due to the cold.

This usually manifests in no heart rate being displayed!

 

Pinouts

I have provided a diagram which shows the relevant pin information that I have gleaned during my investigation and testing.

It is not completely concise due to not having any technical information to hand, where I didn’t want to just ‘assume’ what did what, etc. and possibly come to the wrong conclusion or mislead.

Lightstone socket pinout

Wild Divine Lightstone Mini-DIN socket pinouts

 

I tried connecting a standard two-legged ‘old skool’ cadmium sulphide type photoresistor via ground (pin 3) and pin 1 as shown in the diagram.

It might be prudent to add a small value resistor in series with the LDR, especially if the value of the component you use swings low, close to single figures when you shine a strong light on it for example, although mine didn’t.

Photo-resistor connection

Photo-resistor connection

 

For example measuring out of circuit:

Resistor completely covered > 10 MΩ

Semi-darkness 1 MΩ

General daylight 3 KΩ

Outside bright sun 1 KΩ

Lightstone interface with photo-resistor connected

Lightstone interface with photo-resistor connected

 

Preliminary results

These are actual screenshots taken on my computer using the Lightstone Monitor (Version 7) program by Bryan Ingram.

For example, simply ‘waving’ my finger back and forth near, across my photosensor produced the following trace below (shown in red.)

Lightstone Monitor v7 finger trace

 

Lining up and placing the sensor carefully in the aperture or space of my right eye-cup and blinking 4 times produced the following trace (below.)

Lightstone Monitor v7 eye blink trace

 

Next, with the same set-up I carried out a ‘Left, Right, Up and Down’ (L, R, U, D,) eye-movement test in relatively short succession.

Lightstone Monitor v7 trace. Eye movements

 

Finally I completely covered the front aperture of the sensor face with the tip of my left index finger so no external light could reach it whatsoever.

The result to my surprise (after ruling out mains noise) is a very weak amplitude trace of my actual heart beat peaks, albeit distorted rather than classic QRS.

Lightstone Monitor v7 trace. Fingertip heartbeat

 

All the above tests were carried out in a dim room, late evening.

I did not use the skin conductivity channel shown on the graphs in the yellow trace as no GSR electrodes were connected or used on the Lightstone during the test itself.

In all the screen shots, the heart trace shown in red was utilised to record ‘events’, so the pulse rate (BPM) shown is academic, except maybe the last one.

 

(Disclaimer: The author ‘Lucid Dream Art’ assumes no responsibility for any possible loss or damage to associated equipment caused when undertaking this experiment.)

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