I bought a selection of brass tubing from my local model shop for about 60p for a 12 inch piece. I used an inch of 1/8 inch bore for the larger walker and half an inch of 1/16 inch bore for the smaller photovores.

 

It took some time but I found various sizes of cable sleeving to make up the thickness between the brass and the guitar string. They want to be quite a tight fit so that the string is held in the centre of the tube.

 

The guitar string was from my local music shop and cost about £1 for about a meter.

Slide the sleeving onto the string using as many pieces as necessary to make up the thickness. If they are a bit tight “spit” makes a good lubricant!

If they are a little loose once put together, a dab of super glue on the end will hold them in place. Don’t get any on the tube as you may want to slide the whole assembly in or out of the tube to adjust sensitivity.

 

Make sure that you have enough guitar string hanging out the back for your connections.

The connections will vary from bot to bot, in my case for the walker using the Almost Complete Walker Circuit, I put the string to pin 19 of the 74HC240 and the tube to ground.

 

For my photovore using the 1381 based circuit, I put the string via a 680k resistor to the ground loop and the tube to the 1381 side of the 224 caps.

 

It doesn't really matter which way round the two connections go as long as they go to the right place.

You will usually find that component placing dictates which way round is the easiest.

 

To mount the sensors on the walker I used a cable connector cut in half and soldered to the frame.

On the photovore I simply superglued it to the bottom of the pot and PD assembly.

Drawn with Design Cad Pro 2000