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DOYT
I don t understand.......... why do I get in the red circle 5V when I measure with the voltmeter? it should be D4 there that means no voltage.
Look at section 13.1 and 13.2 of [www.atmel.com]
If the Rpu (Pull Up Resistor) is activated on the input pin... That pin is going to have 5 volts on it if nothing 'low impedance' is connected to the pin.
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DOYT
The 5V should be in the blue circle. I followed this tutorial but my LED from the optical sensor board is not on when I plug it into the ramps.
[www.youtube.com]
The order of the pins in this videos is the same. D4 and GND on the edges and the middle pin 5V.
The Server connector pins have +, -, and signal. But what the + is connected to is optional. It isn't connected to anything until you make a decision and connect it to something.
That is what 'servo power connector' controls. The servo connectors are on one side of the reset switch. The servo power is controlled by the 3 pins on the opposite side of the reset switch.