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I have this setup,

schematic

simulate this circuit – Schematic created using CircuitLab There is also a button connected to the Arduino and every time the button is clicked the arduino cycles 3 levels of brightness on the LEDs. The problem is that when the LEDs are at full bright the Arduino no longer has enough voltage to run ~3v down from ~4v when off and so becomes locked at full brightness.

From what I have learned in physics I thought that when a circuit was in parallel the components acted as if they were independent of each other however this is not what I see here.

How do I drive both the arduino and LED strip with the same battery? Is it possible the battery is not supplying enough current?

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  • \$\begingroup\$ With a bettery battery the led strips would blow, you're lucky. \$\endgroup\$ – Marko Buršič Mar 27 '17 at 20:56
  • \$\begingroup\$ Without knowing exactly what your led strip is, we can't tell. If they are bare less with a mosfet controlled by the arduino, or if they are digital/smart less. Or if your battery is good enough for this. Your circuit as shown should work at full on but no way to control the leds. \$\endgroup\$ – Passerby Mar 27 '17 at 21:07
  • \$\begingroup\$ Inadequate schematic, & PSU current and big FET Switches \$\endgroup\$ – Sunnyskyguy EE75 Mar 27 '17 at 21:49
  • \$\begingroup\$ How did you get a 5V battery? \$\endgroup\$ – Voltage Spike Mar 27 '17 at 21:58
  • \$\begingroup\$ Your circuit does not adequately correspond to reality. You should put a resistor between the battery + terminal and the LED, with the resistor (called the battery output resistance) being determined by the battery data sheet. Notice what happens to the load voltage with increasing current drain. \$\endgroup\$ – WhatRoughBeast Mar 28 '17 at 1:06
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This idea:

From what I have learnt in physics I thought that when a circuit was in parallel the components acted as if they were independent of each other however this is not what I see here.

is based on the assumption that the power supply you are using is more than capable of driving all the items in parallel. The battery has an internal resistance, and as the current through it increases, the voltage out of the battery drops.

You are likely pulling too much current out of the battery for the LEDs, and as such the voltage from the battery drops to a level that is too low to power the Arduino.

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