SRAM and Negative Power Supply
The ADM660 chips arrived today, so I decided to test their performance against the ICL7660. If you read my previous post, then you'll recall that the negative output voltage of the ICL7660 dropped almost 12% under the load of the Muscle Sensor. I repeated the same test with the ADM660 and it performed much better... only dropping about 3% under load. This should be good enough for a single battery solution.
As an added bonus, I was able to get an SRAM chip (Microchip 23LC1024) working with the Arduino. It runs on the SPI bus and provides 128KB of RAM, in addition to the Arduino's 2KB. This will allow me to capture more data for the alarm algorithm. It depends on the final sampling rate, but I should be able to keep hours of data in memory.
Next up... the analog to digital converter.