Tach connection may damage 24V fans.
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Description
Your EBB SB2209 CAN (RP2040) design allows for selecting 5, 12, or 24V for the 4-wire fan. When 24V is selected this pulls up the tach pin to ~24V.
With the 1K resistor on that line, that will result in a current flow of ~24mA through the fan when the tach signal is pulled low.
All of the datasheets for 24V fans that I have seen have suggested limiting the current and voltage on the tach line so that no more than 2-5mA go through the fan. Has this been tested? Can you change the signal conditioning on the tach signal to a larger pull-up resistor and switch the pull up voltage to 5V?
Noctua
Sunon
Same sky
NMB
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Research direction
Start by reviewing the EBB SB2209 CAN (RP2040) fan tach signal conditioning and the attached Noctua, Sunon, Same Sky, and NMB datasheets. No file or test is named in the issue; done means validating the tach connection against the cited fan limits and determining whether the proposed conditioning change is appropriate.
Written by the indexing model from the issue text.
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- embedded-iot
- Issue type
- Bug
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- 4/5
- Estimated time
- 3-5 days
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