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Topic: Vin not the same as input voltage (Read 459 times) previous topic - next topic

Boopidoo

Shouldn't Vin be directly routed from the input voltage +pin? When I measure the input voltage it varies greatly if I measure using Vin or directly from the input pin on the power connector.

Shouldn't Vin be directly routed from the input pin?

V = 12.37V (actual voltage measured on the power plug)
Vin = 11.57V

This has been measured using an external voltmeter.

The barrel jack has a diode (causing the voltage drop) for reverse voltage protection.
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Boopidoo

Ah ok, so in theory I could compensate for this voltage drop in code. But I guess it would be more exact to read the voltage from the source instead.

fungus

0.8V drop?

To me that says 'silicon diode'...
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

oric_dan

The Vin header pin is probably intended more to distribute raw power to shields
when the main board is powered from the power jack than for use to connect
input power to the main board. As noted, the difference between the 2 levels
is always 1 diode drop.

OTOH, and this comes up a number of times every week, using a high voltage
like 12V to power the board means the tiny surface-mount 5V regulator will likely
get hot if you draw more than a couple of hundred mA off of it.

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