Never being one to understate anything or avoid unnecessary complication, and, also being in possession of more guitars than sense, I decided that I would like to use 6 different guitars during the course of our gigs.
This presented me with a problem. I already had a 4 guitar selector comprising of three switches. 2 switches each select between a pair of guitars, the third switch selects between pairs. Adding extra guitars to this would end up being very complicated!
I decided on a re-design (having first scoured the inter-web to find if anything suitable was already available).
I realised that there are readily available chips that will count the number of pulses and light LEDs accordingly. I thought that if I used a 4017 chip I could step through a sequence of six LEDs every time I pressed a single foot switch. if I could use the current flowing through the LEDs to operate a relay then I would be able to sequence through each of six guitars at the press of a switch.
I looked up on the internet for a suitable circuit and in the process discovered that I would not be able to just use a foot switch but would need something to smooth or de-bounce the action of the switch.
Finally I selected the following circuit for the switch de-bounce using a 555 timer IC (thanks to The Free Information Society).
Then I made a simple circuit as follows using the 4017 IC (which needs no additional capacitors of resistors, only the LEDs)
The pulse for the output of the 555 drives an LED (shown in red (so I know I've pressed the switch!)) and goes the the input of the 4017. The outputs of the 4017 drive the LEDs and also a pair of mini relays (the coil of one is shown in red) to switch the ground and signal from each of the jack sockets (that way there should be no earth loops as the ground is disconnected when the input is not selected).
The whole thing together with the relays, 6 in and 1 out jacks, 9V in and a couple of 9V out sockets (so I can supply power to other pedals) just fits into the aluminium box!