The problems

So it has been a few weeks since we decided the final hardware for the collabrative touch idea. This is to use the combination of Arduino and AD9850 DDS as the frequency generator and the Pico Oscilloscope as the signal detector. The project seems going well as we are able to generate and detect he desire frequencies we want. However, I think it is worth mention that are the problems we are facing and the propose solutions.

Problem 1 - USB Power (Dedicated to all Mac Haters): After many times couldn't get the signal from the AD9850 DDS, we figured out that the usb power or the current supply of the Macbook are not enough for the Aruino and AD9850 DDS function properly. It turn out that the Macbook power management is so "advanced" so that I can control the current out of the each of the USB port depends on the device plug in to that port.  This problem has caused alot of troubles for us in the last week. The current solution is to move to use the PC usb port with laptop hooked to the socket all the time.

Problem 2 - Contact to the skins: It is hard to connect the signal generator to human skin and even we can do that, the contact between the signal generator wire to the skin is not very good. It also painful to stick the shart "ugly" wire to our skin to test. We decided to bought the reusable electrodes (as shown in Figure 1) which we believe that is best adhesive for optimal conductivity and skin adherence. This has solved the problem completely. The pad is easy to use and can be reuse. The signal pass through our body is good and the Pico Oscolliscope can detect it accurately.

Figure 1: The Reusable Electrodes.

Problem 3 - Switching to battery: After successfully tested using the usb power supply, We wanted to switch to battery so that the device can be portable. We bought the 2.1mm DC Jack to use the battery as the power suppyl for the Arduino ( as shown in Figure 2). The problem is that the signal received from the battery power is not as good as the one fromt he USB power supply. The signal is just 50% clear compare to the one from the USB power signal. The reason is the current from the 9V battery is much less than the current directly from the USB and hence, the signal is not as good. We are currently working on this problem and will find a solution soon as this is the neccessary step to increase the detect arruracy and to cutting wire.

Figure 2: 2.1mm DC Jack Plug Arduino