2020-09-03 14:10:52 +02:00
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Components
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==========
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https://lcsc.com/
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- ESP32-WROVER-E (has PSRAM compared to wroom, the IE version doesn't have pcb antenna)
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https://www.mouser.de/ProductDetail/Espressif-Systems/ESP32-WROVER-EM213EH2864PH3Q0?qs=sGAEpiMZZMu3sxpa5v1qrgqRbH4gaXhhyqOoBsYWKak%3D
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- HX711 ADC for weight scale
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mouser doesn't have it?
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Tools
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=====
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- easyeda has lcsc library, to import in kicad use:
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https://wokwi.com/easyeda2kicad
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2021-05-15 12:19:44 +02:00
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Capacitor List
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--------------
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- 22u 3x (2x esp32 power + 1x ESP_VDD)
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- options: CL21A226MAQNNNE 25V $0.05 (basic part)
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CL10A226MQ8NRNC 6.3V $0.02 (basic part)
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- 10u 2x (1xHX_VDD + 1xHX signal)
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- options:
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CL21A106KAYNNNE 25V $0.03
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CL10A106KP8NNNC 10V $0.0185
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- 0.1u 9x (2x programmer button + 1x ESP_EN + 1xESP_VDD + 2xHX_VDD + 3xHX_SIGNAL )
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- options C1005X7R1H104KT000F 50V $0.012 (extended part, but huge stock)
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Resistor List
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-------------
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- 100
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0603WAF1000T5E
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- 200 ( 2x HX_SIGNAL)
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0603WAF2000T5E
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- 8.2k (1x HX_SIGNAL)
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- 0603WAF8201T5E
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- 20k (1x HX_SIGNAL)
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- 0603WAF2002T5E 1% 1/10W $0.0022
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- 10k (1x ESP_VDD)
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- 0603WAF1002T5E 1% 1/10W $0.0025
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2020-09-03 14:10:52 +02:00
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Related open source PCBs
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========================
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2021-05-15 12:19:44 +02:00
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ESP32 Circuit
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=============
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- based on
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https://www.espressif.com/sites/default/files/documentation/esp32-wrover_datasheet_en.pdf
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and
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https://dl.espressif.com/dl/schematics/esp32_devkitc_v4-sch.pdf
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- further resource https://github.com/adafruit/adafruit-HUZZAH32-ESP32-Feather-PCB
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- removed the USB programmer (connected externally once then OTA)
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- Delay power up circuit:
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data sheet example is 10k and 0.1u with tau=0.001s
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to use same resistor multiple times, changed to 20k
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2020-09-03 14:10:52 +02:00
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Requirements HX711
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==================
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2021-05-15 12:19:44 +02:00
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-
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Power Circuit Design
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====================
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- Goal: power by typical outdoor power supply
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- googled around and found Texas Instruments LM2596SX
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- they have a tool here to design circuit
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- https://webench.ti.com/power-designer
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- Selected Parameters
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- Input 12V - 25V
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- Output 5V at 0.8A
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(0.8A because for higher currents I couldn't find the suggested components on JLCPCB)
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- Temp 30
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- From the tool selected components that JLCPB offers
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- Input Cin: UUD1H221MNL1GS (Nichicon)
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- Diode D1: SS26FL (Fairchild Semiconductors)
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- Inductor: SLF12575T-151M1R5-PF (TDK)
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- Outout Cout: 2x TPSA105K035R3000 (AVX)
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- Open Questions
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- ESP32 datasheet mentions 0.5A, so 0.8A design should be enough?
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- to be safe I convert from 24V -> 5V using switching power supply
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and later 5V -> 3.3V using linear regulator
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that way I can also optionally connect 5V USB
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is it better to directly go to 3.3V ?
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