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QT PY 5V input diode requirement
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QT PY 5V input diode requirement

by yzfoot on Wed Jan 26, 2022 10:59 pm

Pinout blurb says it's important to place a diode between external power and 5V input pin. What is the purpose of this ? Backfeed protector ? Voltage drop ? Other ?

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Re: QT PY 5V input diode requirement

by rpiloverbd on Thu Jan 27, 2022 8:25 am

To protect the board from sudden spikes maybe?

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Re: QT PY 5V input diode requirement

by dastels on Thu Jan 27, 2022 8:47 am

The reason for the diode is to protect against the problem of having an external supply connected when you plug in USB. There's a diode onboard between the 5v line on the USB connector and the 5v pin. By putting one on an external supply you guarantee that only one is providing 5v to the board: whichever is higher.

Dave

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Re: QT PY 5V input diode requirement

by yzfoot on Thu Jan 27, 2022 10:26 am

Dave
Thank you. That explanation of why would be welcomed by many along with the statement that the diode is needed.

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Please be positive and constructive with your questions and comments.