Semester Project Process Videos

I 3D printed a great case for the Arduino but the Uno friend and I used the Leonardo (which was pretty anyway since I was doing keyboard commands).

EOG Amplification Circuit Fritzing Diagram

Ultimately, the Notch and OpAmp circuits never worked correctly. For this semester I will be working with the EOG circuit amplified through the Instrumental Amp IC INA118P. This signal is a bit noisey but does still distinguish left eye movement from right eye movement.

This circuit is not sensitive enough to detect something as small as REM, but is a great starting point for exploring EOG Arduino interface because IT WORKS.

The power supply should be 12V 1A for the L7805s I am using, but the only adapter I have that works with the circuit correctly is 2A. Ideally, the L7805s would also be a different variation of the same regulator, LM7805. Theoretically there is no difference, but in reality I do get an output voltage of 8.6V when it is supposed to give me 5V from one regulator, and a 3.3V from the other. Something here isn't working correctly, but I've studied the circuit intensely and following the instructions for it soundly so my suspicion is either the 12V 2A adapter is effecting it, or the difference between LM7805 and L7805.

The L7805 circuit takes the 12V power supply and regulates it down to a smooth 5V. The reason we are using two supplies is to drive the differential amplification between the two electrode inputs. Thus a power supply ground is created from the 12V supply, and a second, virtual ground, is made from the output voltage of the second regulator.

The INA118P takes the signal input and amplifies it with a gain of +500 (giving us a net gain of +501 to the signal). We use a 100ohm resistor to set the gain. There is a chart on the INA118P's datasheet that shows how to set the gain with different resistors.

When we move our eyes the electrical signal from the skin polarizes the corresponding electrode and raises or lowers the voltage. A GND electrode is connected to the forehead and to the virtual ground of the 7805 series. This signal is output as a single voltage to the Arduino's Analog 0 input and the ATMEGA328P converts it into a digital value we can then use in programming (ADC).

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.

semester project process

I still have challenge to find a good material and making a good form to show my idea. I experiment several materials to find the best one to display different thing ( different words or sentences). I m thinking about making some notebook or overlapping two paper with different languages.
The main problem of this project is finding the good form and working on light of LED that how they have to be placed and how are the light to read or showing the words clear.