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skot / bitaxe

Open source ASIC Bitcoin miner hardware
GNU General Public License v3.0
901 stars 136 forks source link

Fan PWM speed control should be pulled up to 5V instead of 3.3V #124

Closed skot closed 5 months ago

skot commented 8 months ago

From K1 in the discord;

PWM fan control is open drain those fans typically have internal pull-ups to 5V the EMC23xx series controllers are 5V tolerant for open drain applications, otherwise do 3V3 push pull the fan controller is switching ON 3V3 into a 5V circuit and then OFF to GND (sinking it low) - the sinking action is what theoretically controls the fan some things absolutely demand a 5V driver though if you are designing a new board, it needs to be pulled to 5V or driven push/pull to 5V with a capable complementary level FET pair or level shifter or MCU

existing circuit:

image
skot commented 7 months ago

the BM1368 supposedly has digital, internal temp sensor. if this is true and we can use it, we might not need the EMC2101 at all.. just drive the fan from the ESP32

skot commented 7 months ago

EMC23xx series controllers are 5V tolerant

But what about the EMC2101 on the bitaxe. need to check this out

skot commented 7 months ago

it looks like the EMC2101 PWM pins are 5V tolerant too.

image

https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/EMC2101-Data-Sheet-DS20006703.pdf

skot commented 6 months ago

added in 9afeb2c