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I would like to know a little more about Arduino inputs and outputs.

I'm doing a small project which is composed of 1 LED strip with 40 LED's.

Can't find any definitely information about Arduino + LED strip.

At the moment all of this doesn't work correctly and I guess the reason is bad power connection .

The main power is from USB. So all of this in a car. I have ~12v (+2 or -2 Volts ) and then Voltage regulator to 5V with USB output and then cable connecting 5V through USB Arduino . Then I took wires from VIN ( pin number 30 ) to LED strip +5V ( which is basically main fuse on the strip ) and then GND to ground of led strip and of course DIN to DIN like it should be.

Conclusion is - the led strip won't work normally and colors are not proper .

How should I do connect ?

If I will take off the voltage regulator then main fuse from the car ~12V connect to the VIN (it will be a main arduino power) . GND - GND pin obviously. - and then again from same point ~12V of car will connect to voltage regulator 12V to 5V and that 5V must be with LED strip FUSE +5V ?

Is it will be correct way ? And one more question, shall I put between "main fuse from the car ~12V connect to the VIN (it will be a main arduino power)" - Voltage regulator 12V to 5V ? is it necessary ?

Thanks for you answers guys, hope you will help me with this.

I'm going to read same questions and answer with this any way. Will wait your answers too :)

  • Does your strip need 12V or 5V? This isn't clear from the question. Also: won't work normally and colors are not proper what does this mean? What do you actually observer? – chrisl Mar 27 '19 at 12:10
  • the 5 V pin is to power 5 V devices – Juraj Mar 27 '19 at 12:14
  • 5V needs , I mean on the end of strip she is flashing and shows another colors – Souelle Mar 27 '19 at 12:15
  • hm... okay then, I have to put regulator 12V to 5V before VIN connection. Actually Arduino nano tech specs says VIN can be connected from 7~16V . Thats why Im asking about it . – Souelle Mar 27 '19 at 12:18
  • okay, so.. I should connect through voltage regulator to VIN (comes 5V ) and GND . - this is arduino power . (or I can connect same USB - only for arduino power. ) and then I must take 5V on LED strip from a car voltage regulator , not from arduino VIN pin . Is in it ? What about Ground for LED strip.? Should I take it from Arduino GND to LED strip GND or never mind I can take GND from the car ? – Souelle Mar 27 '19 at 12:48
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The main power is from USB. So all of this in a car. I have ~12v (+2 or -2 Volts ) and then Voltage regulator to 5V with USB output and then cable connecting 5V through USB Arduino .

Good. That is the best way of powering an Arduino in a car. Use a phone charger is best.

Then I took wires from VIN ( pin number 30 ) to LED strip +5V

There's no such thing as a "pin number 30" on an Arduino Uno. However, powering anything from VIN when you are supplying power into the Arduino through USB is very bad.

Basically, the current has to flow backwards through the onboard regulator to get to the VIN pin - and the regulator really doesn't like that.

Instead, you should be connecting your LED strip to the 5V pin of the Arduino so it is connected direct to the 5V USB power.

Note, however, that the USB power has a limit of 500mA. This is not a limit of the supply - it is a limit imposed by a 500mA PTC fuse on the Arduino that will shut off the current if more than 500mA is drawn. It would be far better if you could cut the USB cable and take the 5V and GND wires and directly connect them to both the Arduino's 5V and GND pins, and the LED strip's 5V and GND connections. That will then mean that the LEDs are taking their power directly from the power supply, not from the Arduino.

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  • That`s Great!! Thank you so much!! I feel better now! – Souelle Mar 27 '19 at 16:08
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40 LEDs can draw up to 60mA x 40 = 2.4A (2400mA). Make sure you have a large enough current source if you are planning on using full white on all LEDs.

Arduino regulators are not selected to support 2.4A. 600-700 mA tops, and then only if the voltage to the barrel jack is 7.5V max. With 12V, much less current is supported as the regulator gets hot dissipating (12V - 5V) x current draw as excess heat.

And 500mA for USB as noted due to PTC fuse.

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