Using Vin pin safely


I want to power Arduino safely from Vin and GND using 9V battery. I cannot also use 2.1 mm power plug or 9V adapter jack since I don’t have the following parts: I don’t have time even to buy that.

My concern is that I want to feed the Arduino board(with a wifi shield on it) by using Vin pin with a 9V battery. But I have read in forums here that wiring up Vin and GND in a wrong way is risky and can kill the board even the voltage regulator. Is it possible to prevent this using a diode at the end of the GND pin?

Any ideas?

You are right, wiring Vin wrong can kill the board. But you only have 2 wires -- it's hard to get wrong! Especially if you have a 9V battery clip with a red wire and black wire. Hook the red wire up to Vin, the black wire to GND, and don't get it wrong :)

If you really want a diode, hook it up in series with the red wire (anode: red wire, cathode: Vin pin).

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I dont think that combination prevents from wrong wiring. Current always will flow from positive to negative if the diode is connected to positive.

I guess the diode should always be attached to GND from the anode side. What do you think?

Nope, don't know what you are thinking here but putting the anode of a diode at GND is not going to help with miswiring.

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if you apply 9V+ to Vin the current will flow through GND of Arduino board to 9V- of the battery. if you apply 9V+ to GND the current will not flow through GND since the diode will not let it pass through. What is wrong here do you think?

We may have a misunderstanding of terminology. Generally a battery is labelled as "+9V" and "GND" (or 0V), it doesn't have a "9V-" terminal (though you could call the red wire 0V and the black wire -9V but that's not relevant here).

+9V is the red wire, GND is the black wire. Connect +9V (red wire) to a diode anode, diode cathode to Vin, then Arduino GND directly to battery GND.

If you have something else in mind, please sketch it out so we can see what you are thinking.

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I know that -9V is not in that sense used in my sentence. It is a label on the battery. But I dont see any wrong in my way I even tried it. In your way the current will still flow in reverse connection.