I wrote the README for the github repo and added the files. I found a coupon so now the price got reduced! I also had to update a component to a bigger package for availability purposes on JLCPCB.
I went on JLCPCB to see the estimated cost of the project. It ended up being approx. 35$ with shipping. Now I just need to polish some details in the board like the components silkscreen which is a bit ugly and it’s ready to ship!
I graphic designed the pcb business card!
Math, physics, learning and LEDs. Literally. I learned a lot about formulas, current and voltage, how everything works, etc. My brain power is lost right now so I will paste the document I made summarizing everything I learned. I also added the LED, finally. Coil to LA/LB, GND to ground, FD left open or wired to an MCU/LED if the field-detect feature is wanted, and EP (exposed pad) left open/floating per the datasheet.
No pours, no wires, no NOTHING near the coil and chip.
The chip can be near the coil.
LA/LB can be wired freely to the chip.
nfc is interesting
The basic LED resistor formula:
R = (V_supply - V_LED) / I_desired
Vf - The forward voltage is the voltage it needs for a given current.
If - The forward current is the current actually flowing through the LED. Controls brightness. This is the value you target. Everything else in the calculation exists to make sure this number ends up where you want it.
They are related to each other. When more current flows through, Vf goes up as well.
The current is the same in every part of the circuit.
The total available voltage HAS to be spent between the resistor and the LED.
Formula: R = (V_supply − V_LED) / I_desired
V_supply: the total voltage available from the source (VOUT, ~2V in this case)
V_LED (Vf): the voltage the LED itself consumes at YOUR CHOSEN CURRENT!!
(V_supply − V_LED): whatever voltage is “left over” after the LED takes its share, this is the voltage the resistor needs to drop
I_desired (If): the current you want flowing through the LED (and therefore through the resistor too, since they’re in series)
R: the resistance needed so that this leftover voltage, divided by this resistance, produces exactly the target current, this comes directly from Ohm’s Law (V = I × R, rearranged to R = V / I)
Finished Formula: R = (2 − 1.7) / 0.002A = 150 ——> R = 150 Ohms
“mA” MUST BE CONVERTED TO “A”
If Vf (toll) was 1.65: (LED needs 1.65V at 2mA)
R = 175 Ohms
If Vf was 1.75: (LED needs 1.75V at 2mA)
R = 125 Ohms
If Vf was 1.8: (LED needs 1.8V at 2mA)
R = 100 Ohms
If the LED consumes more voltage, the resistor needs a smaller value, and if the LED consumes less voltage, the resistor needs a higher value
PART THAT WILL BE USED::
TLMS1000
COLOR: RED
LOW CURRENT
Vf for 2mA = approx. 1.75, so R = 125 Ohms
In this session, I researched and found a nfc chip and coil that would work together and wired them. It was my first time using nfc so I had to learn it from scratch and it was fun. Later I found a better chip, the NXP NT3H2111W0FHKH, a NTAG I2C plus, that allows me to connect an LED to it without using an external power supply and only using the power generated by the phone to the coil! There were a lot of issues with file formats and I had to use some techniques to convert them to the right file formart. I also used the python script from the flight controller guide to import the easyEDA footprint and schematic from lcsc.
