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pyr0ball / pyr0piezo

An AVR/ARM based piezoelectric sensor for use in ultra-precise applications
https://docs.pyroballpcbs.com/
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Current LDO on standalone does not supply enough power when only getting 5v input #13

Closed pyr0ball closed 5 years ago

pyr0ball commented 5 years ago

When the standalone unit is supplied 5v on it's main input, the AVR does not get activated due to low voltage dropout. LDO appears to be responsible, as it requires 6v or more to work properly

79L05 Datasheet

pyr0ball commented 5 years ago

Options for fixing this issue:

  1. Add a bypass jumper pad which will allow the end user to solder a bridge, bypassing the voltage regulator and allowing the control board's 5v to power the sensor
  2. Replace the regulator with an LDO regulator at the same current value (max theoretical for the circuit @ 100mA), that can handle 5v input as well as higher (costs 5x as much as the current one)
  3. Replace the regulator with an LDO with lower current output, possibly risking dropout
pyr0ball commented 5 years ago

Added bypass jumper for now.

https://github.com/pyr0ball/pyr0piezo/commit/0b4e0d56df621e5de7ac43b4e4eb7d8816ab22f7

Additional testing required to determine circuit's overall current draw

pyr0ball commented 5 years ago

After building more units and setting the "brown-out-detection" fuses to 2.7v, this issue has disappeared. Apparently I goofed and set the brownout detection to 4.5v which was the source of the problem