I have recently put together the attached circuit to drive 5m metres of rgb led strip. The 5m led strip runs at 12V 6A, that's 2A per colour.
I'm using a circuit found on instructables:
However in the absence of the listed components I used the following: Q1-2N5088, Q2-IRF1405, R1-100Kohm, R2-4.1ohm
I ran all three colours on the circuit for about 5minutes, and it seemed fine, no excessive heat.
What I would like to know is will it be safe to run continuously for 12hrs or more, as I am working on a Christmass lights display.
I am not confident of my calculations, and would like some verification, mainly for my own peice of mind.
I do not know enough about drivers to say if the instructables will be good enough for a driver. I bought drivers to power my HPLEDs. I also put them on metal heat sinks to ensure that they would not overheat. How are you dissipating the heat? Do you have a link for the LED you are using? The LED strips usually don't need heat sinks you might be fine with out one.
You don't say what kind of RGB LED strip you have. The common ones merely have 3 LEDs in series with a current limit resistor. The length of the strip is just many 3-LED segments in parallel.
A simple driver with a Standard N-channel MOSFET, requiring 10V on the Gate to turn it on full, can be driven like this. Ardiuno outputs drive the NPNs, with 220 ohm resistor to limit the Arduino output current, and 1K on the MOSFET gate to pull the gate high to turn it on.
You may want a pullup on the NPN base to turn the NPN on and the MOSFET Gate off while the Arduino is starting up, otherwise the MOSFETs will be on when 12V power is applied and the LEDs all on until your sketch can start up and turn the NPNs on and turn the MOSFETs off.
Yeah it would be nice to know what leds you are using.
Crossroads, are you suggesting having the leds off when the arduino starts of with the transistors rather than having them fully on? Thats a cool idea, My projects always just start off fully on until the board boots up.
yeah I can see it being a problem if it gets too bright. I try to use full on to be good room lighting so it has not been a problem yet. I like your idea for how to keep them off until they are planned to turn on though. If anything it looks better not to watch the code load up.
Thanks crossroads, I have attached a datasheet for the typ of led strip's I'm using they are common anode with a 6amp draw per 5 metres as previously stated.
Thanks for your help guys, the attached circuit seems be working very well, no heat dissipation whatsoever, and the response seems very good visually when I apply music using FHT. I would still like any feedback on risks you may see here.
Thankyou.
Ok all the following attached item IS a datasheet from adafruit, and they are the same as the LED's that I have....got mine from a cheep Chinese exporter
The Instructables page is about making a constant current drive for a power LED.
This is not what you have and so that circuit is not suitable for your strips.
