So in the past I've used addressable rgbw leds for various projects, which are easy to control the colour/brightness of using something simple like a nano or a digispark.
However these strips aren't particularly cheap, and they result in a lot of hotspots rather than a more uniform glow (fine for some projects, not for others). And I don't always need individually addressable led control.
So for some projects a better use seems to be these cob strips, as they will be a much more uniform glow. Great.
However for one project in particular (and probably others) I'd much prefer a slow fade-in when the leds are turned on rather than a more stark instant-on. Which I had hoped would be possible via a nano, but it seems its not as easy as that...
(There are addressable cob options, but they are also quite expensive in comparison).
Is there a way to use a nano to control the brightness of strips like these? In a compact space (these projects need to fit inside some pretty small spaces, hence the nano/digispark).
Edit: This Strip on aliexpress even seems to come with a tiny 'touch dimmer switch' so it seems a solution exists. Wont work for me as I don't think I'd have any way to mount the switch flush with the project etc but if anyone knows how it works it might help find a solution!
They seem to be just leds.
The "dimmer" is probably a chip with a mosfet with PWM control. You can make that circuit with an Arduino board and a mosfet.
its a 1 meter strip, running from an 18650 30q cell. This already works (for addressable strips anyway, but the cob strip is within spec too. I'll be running it at 5v.
How would I set up a mosfet for it to control the brightness, and what mosfet would be small/powerful enough to do the job and fit in the space?
Change the current through the strip. There are modern switching regulators aimed specifically at LED lighting that will do this efficiently, but it's usually aa relatively complex solution.
Use PWM; at the 500 to 1000Hz PWM frequency generated by an Arduino,, the strip will look like it is continuously on, but the apparent brightness will vary with the duty cycle. This requires only a transistor or MOSFET that can handle the strip current.
PWM with a mosfet seems to be the solution required, I'm just having difficulty finding an example of a circuit that I can copy.
I plan to use a Nano, and I need a small mosfet that can handle the pwm signal from the nano to dim an LED strip up to 2meters in length (so like 14watts I believe). Tried googling but a lot of junk information is coming up.
Doesn't help that most of the semi-useful info is on reddit, and so is currently unavailable lol. And most people on this forum seem to just ... assume everyone has a bachelors in electronic engineering.
The "Wattage" of a MOSFET is the amount of power the mosfet itself can dissipate, which is only slightly related to the power of the load that the MOSFET is driving. Your 14W of LED strip (assuming a 5v strip), will need a "logic level" (so it can be driven by an Arduino) N-Channel MOSFET capable of handling at least 3A of current. (Most MOSFETs will be spec'ed to handle much more than that. That's fine.)
I'd take a look at Adafruit's Tutorial; they're pretty reliable, and hobbyist-oriented, and have actual part recommendations. (The tutorial is for an RGB strip, so it shows 3 channels; you'll only need one.)
