Stylus

title: Stylus author: GeorgeKosmas description: A smart pen for everyone created: 4/6/25

• Before sign in the contest i already bein working on this project fo 10 hours.in hours one and two i researched and picked the components that i will use after that in the hours 3 and 4 i studied the datasheet of every component and for the remaining hours i started creating the firs version of the schematics
• 4/6/25 20:07-21:00 Created git hub repository and readme file also uploaded my previous work on the project
• 4/6/25 21:07-22:00 started working on the pcb of the version one of the board and finished it
• 5/6/25 11:30-13:30 started working on a more simplified version (v2) of the schematic and also the PCb because the previous one was very bulky. I had to make a lot of chanches such as removing the 3.3V regulator and also removing the connectors thaty meant that i have to reroute the circuit and also find a way to connect the boards together.I came to the conclusion that the best way to connct the boards together is with simple wires and holes. The PCB design was a little bit chalenging because. First of all i had to to squize a lot of the components together and that meant a small space for a lot of connections, i solved it by introducing two more layers to the pcb so the connctions are more organized and have more space betwwen them . Also i had a problem with conncting the components from the top layer to the bottom but i figured it out by using VIA for this type of connctions.All in all it was a chalenging design but i managed to come through the problems and finished it
• 5/4/25 16:05-18:00 designing the schematic and pcb of the power distribusion sytem and adding it into a pcb with the other components that i previously removed from the version of one the schematic also mid jerney of the designing i figured a problem with the output of the 3.3V regulator that i later fixed. Also started working on the charching board by researching components and readings datasheets to find the most suitable for board
• 6/4/25 13:31-14:45 i worked to he charging station by first of all picking the parts and starting designing the first version of the schematic
• 6/4/25 15:15-17:15 In this hour i finished the charging station schematic and PCB that possed a challenge as i had to find a way to limit the voltage curent that was coming from the usb-c connentor i solved this problem by inplimenting a p-fet and a control source resistor in the v-bus of the usb-c input. Also i made some changes in the power schematic of the pen more specificly i changed the previous regulator with a more smaller and more efficient one as a consequence of this i had to redisigne the pcb.In the end i deleted the previous version of the power-etc file , uiploaded the new one and the charching station schematics and pcb.
• 9/6/25 12:20-15:20 started working on the 3d printables that presented to number of chalenges.Firt of all the 3d models were incorect and spend some time to solve this problem after that i had two main problems the dimensions and the layout of the pcbs inside the device. For the first problem i used my digital caliper and take some measurments of a regualr pen and i started designing from this, for the second problem i decided to a layout with the microcontroler and gyro on the top of the device the battery in the midle and the power/etc circuit on close to the bottom of the device so the button is more accesible.Last but not least i had a proble on how i am going to fit the pcbs on the device so i ended up spliting the case and making some insertrs so the microcontroler and gyro can slide in and after that the case can be closed with some screws. ,
• 9/6/25 16:05-17:00 a simple circuit simular to the design so i can ensure that evreythink is conected properly on my PCBS https://wokwi.com/projects/433297580970426369
• 9/6/25 19-19:50 i realized that i have not added a flash memory and a way so the microcontroller can boot so i starter researching for the flash memmory and the way to connect everything together ,
• 9/6/25 21:00-22:22 After some thinking i decided that was more efective to change the microcontroler than insert flash memory into the sysyem so i ended up researching and replacing the ESP32-D0WD-V3 with ESP32-PICO-V3-02 that has interegeted flash memory
• 11/6/25 9:20-10:11 today i studied the datasheets of the new microcontroler and take some notes about pins and bootmode so the process of the design is easier
• 12/6/25 21:14-23:12 i started designing the Schematic and Pcb of V3 of the main board (i delayed updating the journal because i had no internet)
• 14/6/25 16:02-17:34 I changed the design of the charching station and charging circuit of the main device .Fot instance in removed the pogo pins from the charging circuit of the main device and replaced them with condactive pads so the PCB is more compact .Also i removed the the pads from the charging station and replaced them with pogo pins.In the end i deleted the previous version of the boards on the github page and uploaded the new ones as version 1
• 14/6/25 12:10-1:29 I started working on the printables by first deleting the previous design as the pcb dimensions have changed and i built a new design simular to the previous one with inserts for the Gyro and microcontroler PCB
• 20/06/25 12:09-1:32 today i added some things on the 3d model .Firts of all i choosed an oriantation for the Pcbs i also added the base of where the threads for the two pices of the main body will be
• 21/06/25 12:19-13:47 Today i finished the 3d printables of the project and uploaded them .I ended up with a case that splits in to two part (Case1,Case2) and is held together with six screws