Question about the basic arduino circuit for a motor.

hey folks --

in basic tutorial set-up spinning motor, see breadboard layout @ following link. . .

breadboard layout.

the associated circuit diagram.

i created circuit looks attachment. in autodesk-circuits page (similar fritzing), works fine. again, works fine if connect 5v , gnd motor. know transistor , diode there reason.

i don't understand why circuit example seems have "extra" connections.

for instance, in diagram (i'm total electronics noob, might sound silly), imagine current flows 5v transistor, out of transistor, through diode, motor, , ground. diode prevents current flowing "backwards" when motor slows slow , damaging board. don't know why need else make work , work safely.

their diagram has "extra" loop in it, lack of better term. can explain why theirs has that, , problem circuit is?

thanks.

i understand 5v , gnd reversed theirs, don't think that's issue. neatest way me run wires.

well,

what did pretty opposite of shown example.  secondly, diode supposed go across motor pins.  way have it... control directional flow... not why there in original design , serves no purpose.



this drew in breadboard design , explained in second image.

you drew pnp based circuit (a source design) versus sink design , confusing 2 not noob.

look carefully.  diode goes across motor allow reverse voltage spikes escape when power removed transistor switch motor. (its "coils" do)

note: there pitfalls source design using pnp's not obvious.  in relay drawing showed (which same motor) can use 12v supply motor... cannot pnp design drew without parts added.

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