@himanivishwa68

okay so for today i decided to simulate my circuit in ltspice, i wanted to know about two things:

• a well prepped mastoid electrodes, has an impedance of 2k ohm, but this range can go to well above 10s of thousands of ohms, if skin in not well prepped or not prepared. i wanted to find out how much current my circuit would be able to deliver in these different conditions, i also wanted to know what would happen if there was no resistance
• what supply voltage should i use for my opamps, as if i choose too low the current would sag under load and wouldnt be able to deliver the necessary current

findings:
-so i started simulating by circuit with +- 12v as the power supply here are the results :
-0.1 ohm = 2.999mA
-2k ohm = 2.999mA
-3k ohm = 2.54mA
-5k ohm = 1.72mA
-7k ohm = 1.28mA
-10k ohm = 930 µA

• after that i decided to increase my supply voltage to -+15v for more head room,im too lazy to type all the values out right now but here are the top 4:
  -0.1 ohm = 2.99mA
  -2k ohm = 2.99mA
  -3k ohm = 2.99mA
  • 5k ohm = 2.21mA

so as you can see the later one performed much better, i simulated +-24v too which gave me really good results, since tl082 has only a max supply voltage of +-18v, so im going to operate it wtih +-15v

hello there!, so im making a pcb called HACK_GVS , which will essentially be able to control human balance!!! isnt that crazy??

• So to understand how we will do that we need to know about GVS (galvanic vestibular stimulation), inshort when you apply a controlled amount of current (0-3mA) to your mastiods, itll stimulate your vestibular system, and your brain will think your head is not aligned with your body so in order to compensate your body will lean on one side, and if you reverse the current the opposite will happen

-so how will we design this?

• we basically the pcb will be sectioned into two main parts, a unity buffer which will output low impedance 1.65v, and an opamp in non inverting configuration which will act as the solver

-why do we need the solver?
-so the mastoids will have a variable resistance due different positions of electrodes each time, sweat, oils, humidity,etc but we need to put a constant current through our mastoids, that’s why we need a solver that will calculate the voltage based on skin’s resistance and supply constant current!

okay so after so much searching around i finally designed my first stage of my brain-computer interface, this isn’t something really special, but here’s how it will work:

• this is just an input buffer, which will take in biosignals from the brain which are high impedance and you cant do any filtering stuff with it cuz it will distort the signal, and it will convert them into low impedance
• the non inverting input also sits are half of vcc, therefore the output will also sit at half, this is useful as op amps are usually supplies power like +9 and -9 but since we will power this from a microcontroller it will only have a single supply power, if we just it hooked up without dividing voltage the negative signals will be lost so we make a virtual gnd , so we can see positive and neg signals with ADC

okay so i used a kicad plugin called pcb2blender so i can export my kicad pcb to blender without having to add materials and stuff myself which makes the workflow sooo much smoother, after i imported them into blender i just setup camera with some point and area lights are just made these pretty renders with eevee!!!

today i made the schematic for connecting the IP5306 charger module, the thing is i couldve used the ip5306 ic on my pcb itself and integrated the charger on the pcb itself and made the end product look neater but i didnt as i wanted my project to be as easily replicatable as possible so if someone else wants to build it they dont have to have hotplate and solder smd components, also the module is really good as it has every feature you’d need like charging while using the music player, power indicator, built in 5v boost converter

so i have almost completed my design today:

-the drc error for annular length i was getting was fixed by just adjusting the pad to hole ratio by editing my audio jack footprint

-i also forgot to add mounting holes as im intending it to be used as a keychain so you can carry it around easily, so i added m2 mounting pads, to accomodate the holes on the pcb i had to increase the pcb area a bit

• the most work done was on making the silkscreen look prettier, some drawings are handmade by me and some are from internet, i also added power value indicators on the silkscreen as well!, i used a plugin called transform it which made scaling and mirroring stuff so much easier

so for today it was kinda difficult for me cuz i didnt know how to setup constraints for the board inorder to avoid problems in fab so i just put the factory’s manufacturing capabilities in claude and just filled the constraints in kicad, also i completed the routing for my board which went smoother than i expected as i was expecting ton of trc errors, but my routes were good enough i think, but the remaining thing is this annular drc error which i kinda have idea of but not sure so i have to watch some tutorials about it and fix it!, now the only thing remains is to make the board prettier!!

okay so most of my time was spent on finding out tutorials and researching parts cuz i had no clue on how this stuff works, so after some hours i came to use ESP32-C3 Supermini as the brain, a DFPlayer Mini for the actual MP3 playback, a 1.3” OLED for a UI, three push buttons, a slide switch, and a 3.5mm audio jack for output

after deciding what to use i had no clue how to import and use footprint exertnally so i had to watch 2-3 videos related to that and also for 3d models too!

current state: schematic is roughly done , footprints are assigned and i have made the basic component layout, im pretty unsure about my schematic as cuz for battery im thinking of using a separate off the shelf lipo charger +boost module for easier assembling and lower costs if someone wants to replicate it