Semester Project Log

Circuit Iterations 1, 2, and 3 do not give desired results. Nothing useable attained.

Met with Jason Huang, Biomedical engineer undergraduate. He lended me an Analog Discovery device and I am using Waveform to view my signal with its oscilloscope function.

Documentation of components and voltage as I build the circuit once again from scratch, checking each component's voltage as I move along.

1. 12 V wall-plug transformer to barrel plug power supply.
   Transforms household 120v to 12v.
   Multimeter is actually reading at 18.46v.
   Barrel plug reads 18.46v.
   Changed to a different "12v" 1A adapter aaaannnnd.....reading at 6.07v. This won't work either...goes to show checking your equipment with a multimeter is extremely valuable.
   Luckily...had a third "12v" AC/DC transformer and finally 12(ish)v!
2.  7805 Voltage regulator (2)
   Both regulators read out at 0.054v from 18.46v input.
   After switching to the actual 12v adapter I get 0.23v which is a very significant difference.
3. All gold-cup electrodes have about 1.5ohm resistance from cup to terminal.
   Left and Right electrodes tested positive for continuity to pins 2 and 3 to INA118.
   Through Analog Discovery + Waveforms successfully got a signal but currently is too noisey -- which is the point of the filters. At this point I only have the 12v supply running through the regulators and into the INA118. I get a readout that fluctuates between just under +5v and a little bit over -5v which is pretty ideal from what I understand.
4. Found a bad resistor in the Notch Filter circuit. a 3.3k ohm resistor was reading at nearly nothing...0.03 ohm. Signal read on WaveForms from LM358 filter are low and inconsistent. Uncertain if this is "normal" before the LM741 IC integration.
5. Signal unusable after LM741 integration. Reverting back to sampling the INA118 with the rest of the circuit built also yields significantly different results at before.
6. Arduino Paul Uno is no longer responding to any serial input/output after swapping things around trying to get a sensible value. RIP Paul.

5th Attempt:
I feel I understand the circuit significantly better now, and as such I am attempting the 5th build from this schematic:
http://onloop.net/hairyplotter/images/final_eog_ckt.png

This schematic is more intended for Arduino Uno. I didn't understand this person's schematic at first so I avoided it but now it makes more sense to me having built the very similar one presented in the MAKE Magazine article.

1. Power Supply to Regulators
   12v DC power confirmed from power supply. 7805 regulators confirmed connected by the right gates,
   7805 (a) 1 --- connected to 7805 (b) confirmed
   7805 (a) 2 --- to Power Supply GND confirmed
   7805 (a) 3 --- to 7805 (b) 2 (GND) confirmed
   7805 (b) 1 --- connected to 7805 (a) confirmed
   7805 (b) 2 --- to 7805(a) 3 confirmed
   7805 (b) 3 --- V+ out to INA118 pin7 confirmed
2. INA118 InstrumentationAmp (+500 gain)
   11.2v between pin4(GND) and pin7(V+ input)
   pin1 to pin8 connected by 100ohm resistor (+500 gain)
   pin7 V+ output to LM358 pin8 Notch Filter
   pin6 passes through parallel cut-off circuit to filter out high frequencies; this parallel reconnects to pins 2 and 3 of LM358 as positive and negative voltages.
3. LM358
   Filters noise from the amplified V+, V- signal and outputs it through pin6 toward the final amplification circuit LM741
   Cut-off circuit connection test:
   R2 connected to C1, C2, C3, and R3
   R3 connected to C1, C2, C4, and R2
   R4 connected C1, C2, C3, C4
   pin2 of LM358 connected C1, C2, and R4
   pin3 connected to R2, R3, C3, and C4
   pin6 to resistor, capcitor(to GND), and onward to LM741 pin3 as V+
4. LM741 final amplification IC
   V+ signal from pin6 of LM358 with a difference of the virtual GND
   Output voltage follows the input by connecting V- (pin2) to Vo giving the analog signal.
   
   When I hook up the Arduino Analog 0 to pin 6 of 741 I get the same arbitrary drifting of values as before.
   
   Received an e-mail from Luis Cruz himself this morning, giving me access to the Google Drive Eyeboard documents. After several more builds from this guide I came to a temporary solution. I bypassed the notch and opamp, getting the signal from the instrumental amp (118P) alone and I have a useable signal for the purposes of this project. It is still cluttered and takes a strong eye movement to detect but the values do indeed rise with right eye movement, drop with left eye movement, and stay relatively steady when stationary.