Power esp8266 and led strip with a single source

Projects General Guidance
18

Wawa:
Base current for that transistor needs to be ~10% of the collector current for full saturation.

Question is, how much current is the strip channel drawing.

Example:
Strip length is 5meter, and has 60 LEDs/meter.
Strip uses 20mA per three LEDs (one colour).
That's 300/3 = 100*0.02A = 2Amp per colour channel.
That means a transistor base current of 10%, or 0.2Amp, or 200mA.
No Arduino pin can provide that.

Solution is using a darlington (mentioned in StackExchange and in post#13), or a mosfet with very low Vgs(th).
Leo..

I understand what you are saying, but it is making more confused. At the moment I want to understand how to calculate these values.

What if my strip uses a different resistance, how do I calculate the values I need?
You didn't mention a resistor to connect between the GPIO and the transistor, should I assume any will work?

on the side note: Let's say I've cut the strip to 1m, can I still use the same circuit for 5m? Will that damage the LEDs?

What I need right now is a back to basics approach. What I know:

  • I know I can't connect the strip directly to the Arduino's power source because 3.3V is not enough to power the entire LED strip
  • I know I can't power a channel on the strip with the Arduino's GPIO current because the current is too low to pass all strip resistors
  • I know the current needed on the strip is close to 2A but the original power source is only 1A (12V) and seems to work fine so I need to measure the current used
  • I know a transistor can increase the current pulled from the power source

What I want to know:

  • How do I choose a transistor that will give me all the current I need?
  • How do I calculate the best resistance that is needed from the GPIO to the transistor?
  • Assuming I'm stuck with a transistor, how do I calculate the resistance needed to pass enough current?
  • If I'm using a darlington, how do I calculate the resistance needed to pass enough current?

I've run these simulations on the EveryCircuit app:

This is the current circuit

1242×1455 209 KB

This is the darlington version suggested

1242×1477 289 KB

These simulations did not help me understand what changed. I mean, I can see the current changing, but I did not see any difference in the simulated LEDs output

I'm sorry to drag this for so long, but like I've said. I'm new to all this