10
edits
Changes
From Pumping Station One
→EKG Circuit Update (element14 post)
When your heart beats, it generates an electrical current, or signal. The range of that signal can vary from .05 Hz to 150 Hz. Anything outside of that range isn't coming from your body, so to the first step in building our EKG sensor is to filter out all signals that outside of that range. We're doing that using two second order Butterworth filters (one high-pass and one low-). I used this hand dandy online filter calculator to figure out what components I would need.
When your heart beats, it generates an electrical current, or signal. The range of that signal can vary from .05 Hz to 150 Hz. Anything outside of that range isn't coming from your body, so to the first step in building our EKG sensor is to filter out all signals that outside of that range. We're doing that using two second order Butterworth filters (one high-pass and one low-). I used this hand dandy online filter calculator to figure out what components I would need.
[[File:EEG-EKG-Amplifier.JPG|thumb|EEG-EKG-Amplifier.JPG|text| EEG EKG Amplifier based on Open EEG Design]]
[[File:SallenKeyLP.gif|thumb|alt=SallenKeyLP.gif|text|The low pass filter diagram.]]
[[File:SallenKeyLP.gif|thumb|alt=SallenKeyLP.gif|text|The low pass filter diagram.]]
After amplifying the signal and filtering it to remove the power line signal of 60 Hz, we may amplify the signal again and pass it into the main Arduino for some processing before it gets sent to the Master Controller that's sending all the data off of the sensor array.
After amplifying the signal and filtering it to remove the power line signal of 60 Hz, we may amplify the signal again and pass it into the main Arduino for some processing before it gets sent to the Master Controller that's sending all the data off of the sensor array.
But we'll have to build the signal amplifier first. We will use a design close to the reference design from the INA114 instrumentation amplifier datasheet, design also based on the Open EEG project design. I'll post an update after my build this weekend.
But we'll have to build the signal amplifier first. We will use a design close to the reference design from the INA114 instrumentation amplifier datasheet, design also based on the Open EEG project design. I'll post an update after my build this weekend.
