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• Maximum ON time for each charlieplexed LED

  Clovis Fritzen • 05/13/2024 at 00:49 • 0 comments

  For a 70Hz refresh rate (for which the human eye cannot see LEDs as blinking anymore), the total time for all 36 charlieplexed LEDs to remain on is 14.3mS. Dividing this by 36 I obtain 397uS.

  This is the maximum time each LED can remain ON. I will probably start my testing with 400uS.

  Also on a separate note: I have decided to program the Raspberry Pi Pico with the Arduino IDE instead of microPython. This is mainly due to speed concerns, having seen I need 400uS slots for the LEDs only.

• Costs so far

  Clovis Fritzen • 05/11/2024 at 22:57 • 0 comments

  I live in Brazil, so will post the project cost in Reais and also in Dollars (converted). It goes like this:

  - PCB x5 R$65.78 (US$12.79) so US$2.56 each

  - Raspberry Pi Pico W R$69.9 so US$13.60

  - 0.96 OLED display R$29.90 so US$5.81

  - 36x White 0805 LED R$17.28 so US$3.36 

  So far the cost of the project (each unity) is US$25.33, a bit too high if you ask me. This is mainly due to the cost of the Pi Pico W in Brazil. For comparison the same product in the USA costs US$6 (https://www.pishop.us/product/raspberry-pi-pico-w/), so half the price.

  I have not bought nor calculated the cost of the push button and 7-9 0805 SMD resistors, should be very low.

• Charlieplexing code examples

  Clovis Fritzen • 05/10/2024 at 18:38 • 0 comments

  I got some charlieplexing code examples from here: https://goodarduinocode.com/guides/charlieplexing 

• Capacitive touch button

  Clovis Fritzen • 05/10/2024 at 12:11 • 0 comments

  The project will need a button to "wake up" from showing time and temperature to showing user's contact information. I will add a button footprint but the primary method I want to tackle is a capacitive button, made on the PCB.

  https://electronics.stackexchange.com/questions/321669/capacitive-sensing-pcb-overlay
  

• Considering different HMI displays

  Clovis Fritzen • 05/09/2024 at 12:19 • 0 comments

  I am considering the possibility of implementing a 0.96" OLED display footprint alongside the 36 (6x6) charlieplexed LEDs. So that one can choose which HMI (human machine interface) to use.

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