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###Week10: Output Devices
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### Li-Po Charger
Nathan held a workshop about building Li-Po charger and SD card storage, a minimal network of boards that could be used for logging data to a rechargeable device for later purpose.
For more details <a href="http://fab.cba.mit.edu/classes/863.21/Harvard/people/harvard-group-work/data-logger/">Recharger & Data Rogger</a>. A more detailed <a href="https://www.robotics.org.za/MH-CD42">Li-Po Charger</a> datesheet can be found here.
Thanks to Nathan and Iulian's accompany, I gained some sense of charging system, and this is how I understand:
<img src="01_LiPoCharger/Schematic1.jpg" alt="strandbeest" width="500"/> <img src="01_LiPoCharger/Schematic2.JPG" alt="strandbeest" width="500"/>
Basically there are three components that connect to Li-Po charger:
1)output devices
2)rechargeable Li-Po battery
3)USB-Wall charger
<img src="01_LiPoCharger/AllComponents" alt="strandbeest" width="1000"/>
We built a breadboard prototype to figure out the relationship between all components. We also used an <a href="https://www.arrow.com/en/research-and-events/articles/types-of-oscillators-oscillator-uses-in-microcontrollers">oscillator</a> to monitor the voltage change in real-time while charging and discharging.
Starting from using a 5V LED, we then pivoted to using a bigger motor to consume voltage faster so that we can discharge the battery faster. Pretty interesting to see how voltage vibrates when we tried to add more resistance to the motor nob (see video below).
<img src="01_LiPoCharger/AllBreadboard.jpg" alt="strandbeest" width="1000"/>
<iframe width="1000" height="600" src="https://www.youtube.com/embed/HrU2cqlqTBg" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
The final goal of the charging module is to make a standalone charger so that we don't need to connect to the PC for powering the device after the chip is programmed.
The reference from <a href="https://fabacademy.org/2019/labs/barcelona/students/gustavo-deabreu/projects/usb_lipo_battery_charger/">gustavo-deabreu</a> is very helpful.
Right now I'm just using a PCB board to test the orientation of all pins, eventually we will mill a board and share the trace file to the class so people can fabricate their own standalone charger!
<img src="01_LiPoCharger/AllStandalone.jpg" alt="strandbeest" width="1000"/>
### ESP32
With the default MODs 1/64' setting, I was not able to cut through the tiny distance around the pads of ESP32. Fortunately, Takeo had experienced with this issue, and suggested that I change the cut diameter.
I also modified the file to only cut the middle pads to reduce the milling time. The moment that we used the vacuum machine to clean the dust, and yessssss it worked! (Monday 3am in Science Center)
Trying the same MODs setting as last night to mill the board in one step, the result was unfortunately not ideal. Since the traces were too tiny, some copper just fell off.
After consulting with Nathan, he suggested two routes:
1) increase the width of the trace, or 2)decrease the pad size of EPS32.
<img src="02_ESP32/ESP-01.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/ESP-02.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/pad1.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/pad2.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/pad3.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/ESP-03.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/ESP-04.jpg" alt="strandbeest" width="1000"/>
<img src="02_ESP32/ESP-05.jpg" alt="strandbeest" width="1000"/>
### Design ideas
I want to connect the pressure sensors to lighting and music, but didn't manage to do that due to some glitches in my ESP32 board. The initial reason why I pivoted to use ESP32 is because that I need a lot of input pins for a multi-touch pressure sensor for my shoe.
It's also for wireless communication for next week.
<img src="03_Design/Moodboard.jpg" alt="strandbeest" width="1000"/>
<img src="03_Design/Process.jpg" alt="strandbeest" width="1000"/>
]]>