I started building the circuit!

The circuit via the Instructable is chunked into six parts, and as of now, I’ve completed almost three of them (more on that later), so I’m almost halfway there. This is my first real attempt at circuitry, save the Arduino workshop I got to do with Krista and Jarah last year. The author of the circuit included a diagram and a proposed photo layout, and I’ve been using both to build it. I’ve been using the photo layout as a guide to how the components should look spread out on the breadboard, and the circuit diagram as a tool to double-check his layout and to understand why the pieces are being placed where they go. I’ve made it a rule for myself that I’m not allowed to place a piece until I understand exactly where it goes and why, and it’s worked out really well so far. The photo layout is really messy and has odd overlaps that don’t make sense, but it’s really helped me visualize how the circuit should look. The diagram has been a counterbalance for understanding discrepancies in the photo layout and in making sure my connections are true to the circuit.

The circuit diagram.
The photo layout – slightly messy.


So, I’ve almost completed three of the chunks of the circuit. Why not more? And why almost three?

Stage 3 of the circuit.
Stage 3 of the circuit

I started the third section by adding in C6, C7, and C8, all 220nF capacitors. The next to add in was R7, a 47kΩ resistor, but when I looked through my parts bags, I couldn’t find it. After going back and checking my parts order, and checking the parts list the Instructable creator provided, I realized that I hadn’t ordered any 47kΩ resistors because the list didn’t say I needed any.

I don’t know why I didn’t double-check and cross-reference the schematic with the provided parts list, but I didn’t, and this was completely and utterly my fault.

So, I placed another order for parts (which worked out, because I was able to order my parts for my next two circuits along with the parts I needed for this circuit) after thoroughly checking and re-checking the schematic. It should arrive shortly, so it’s not setting me too far back on time.

I decided to purchase touchproof electrode adapters to facilitate adding the electrodes into the circuit. My initial idea was to just cut the DIN plugs off the ends of the electrodes and strip the wire so that I could fit it into my breadboard, but I decided it’d be safer and more secure if I used adapters. I ordered those at the same time as my other parts, so they should be arriving this week. I’m hoping they come quickly so I can keep working on my circuit in order to move onto creating the EEG reading code.

As I mentioned before, I’m planning on creating two more identical circuits in order to add more electrodes to my build. Each circuit provides two electrodes and a ground electrode, although I think I’m only going to use one ground electrode as a reference. Basically, I’ll have a total of six electrodes and one reference, which is what I originally planned to have. All three circuits will be plugged into the analog inputs of my Arduino Uno, and then fed into my computer via USB 2.0 for the final product.

But, for the time being, I’m sticking with the original circuit design, which uses an audio cable to send the signals into a laptop via the sound card. Once I get comfortable with this one, I’ll move onto building the other two.

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