Circuit Improvement and V2.1

The main focus of playable streets' installations are human interactions - with other human. The previous demo shows the system will strongly affected by induction, however the data have small changes when the contact is made. This means even human interaction is made between each other, the sound will change dramatically before a contact is made but the sound will almost be steady when two people touch each other.

A second version of the circuit was designed to have the system more sensitive to contact instead of induction. Also trimpots were used to adjust the sensitivity depends on different environments and activities. The improvement hopefully can solve the multi-channel issue - when the second sensor being activated the previous one seems not functional. The idea here is to buffer the 5v reference voltage which hopefully can isolate two channels. The improved circuit is shown below.

The improved circuit is more responsible to direct touch, and more accurate controls can be done when interacting. The demo below shows me playing jazz saxophone with the prototype V2.1.

Since the sensor data have a sharp increase when touching and only behaviors a small amount of change when contact interactions are made with previous mapping. The idea is to have an exponential respond of the data. When contact just made, the gradient of the data will decrease and the changes in contact interactions will be increased. The percentage of sharp increase in the data is too large among the overall signal, it's hard to fix it with single exponential equation, instead a piecewise function was used. The sharp increase below a certain threshold will be divided by 4, which fix the gradients of the data to a similar level. Most of the contact interaction can be achieved, in this case the device won't be activated when no interaction is made. The demo above shows the wide range of pitch control through contact interactions and the free hand control while one hand is on the sensor electrode.

However, the multichannel issue haven't been solved, serval separate chips running single sensor is needed to achieve this function. The prototype V2.1 was fully soldered to a prototype board as shown below.