Psigasm 2.0 PCB designon February 19th, 2011 at 6:15 am
With the prototype Psigasm up and running, I can’t help but get excited about how much better it could be. The next version is planned out pretty well in my head. I’ll be posting each step of turning those ideas into drawings and CAD files, and those into a physical device.
I just finished a draft of a PCB with measurement electronics for the Psigasm 2.0. It supports a pressure sensor, an accelerometer, three thermometers, a heater, a measurement of skin resistance, and an optical measurement of the skin reflectivity. If all of these sensors work properly, it will be capable of monitoring muscle contractions, heartrate, blood volume, blood volume pulse, moisture, heat capacity, and temperature of the external genital skin. All of these have been shown to link with the arousal cycle in interesting ways.
The board is designed to interface with the Arduino Fio. In case you are unfamiliar with Arduino, they are the state of the art in hobbyist microcontroller boards, highly celebrated in many an Engadget nerd porn post. The Fio is designed for wireless communication, so this board will be totally cord-free (one of the first thing I noticed about using the prototype is that it’s really annoying when the USB cable pops loose in the middle of the action). The new one will run off of a battery that charges by USB, and will communicate only with it’s zigbee wireless chip.
Check out the PCB! A schematic, bill of materials, and links to datasheets will follow when I get around to it.
These are mostly four wire resistance measurements. Each measurement channel is amplified and filtered before being read by the ADCs on the MPC. Signal lines are short and shielded. Ground planes and decoupling capacitors abound. Low noise measurements get me hot.