Project Background
I want to (UNO R4) programmatically dim 24V 2A COB LED light strip(s). Light strips like this one. I'll do 5 of them but they'll each have their own power, MOSFET(s), and PWM pin (so that they're independently dimmable). At 24V 2A, the PC817's 50mA won't cut it, and indeed optocouplers in general seem to be the wrong tool. Seems the right tool is MOSFETs. I think I understand in theory, but datasheets remain fairly opaque.
Shipping woes: LR7843 MOSFET Control Module
While trying to understand MOSFET usage, I ran across this LR7843 MOSFET Control Module. This seems perfect. I even mostly understand the circuit. Except $13 shipping means that even with 5 of them, more than half the cost is in shipping, to a total cost that seems a bit high.
Anmbest MOSFET PWM module
Amazon have anything? Only one listing seems like a potential improvement: this MOSFET PWM module, it's a bit cheaper due entirely to Prime shipping, though it has no optocoupler.
But I think that should be fine. I think the PWM won't draw much current from the arduino. I'm less certain that the 5V from the arduino will be able to switch the 24V. Can 5V PWM drive 24V (2A) through D4184 MOSFETs? Gate threshhold voltage for a similar MOSFET, AOD4184, says 1.7V to 2.6V, so it's fine, right? Or do I actually need the above optocoupler circuit where the 24V drives the MOSFET?
Which I don't quite understand given that the strip can be cut (wouldn't that change the amount of current limiting resistors?), but...
You can see the power supply here says 24V, voltage is front and center, and it makes no mention of constant current. I thought it explicitly said "up to 2A", however I cannot find that right now.
LED Supply's article on CC vs CV mentions "The most common LED strips are designed with a group of LEDs in series with a current-limiting resistor in line with them." and also "So if you see that your strip takes 12VDC, don’t worry about a constant current driver, all you will need is a 12VDC constant voltage source as the current is already being regulated by on board circuitry that the manufacturer has built in." Which is the case here, the LED strips say they are 24V 48W.
You can shop around and find a much better price. I averaged less then 1$ us for them. It took about 10 days for them to arrive, no problem. Yes they have the opto isolator which is the primary reason I purchased them.
A 2A power supply is designed to deliver a maximum current of 2A at the given voltage.
If you take more, you might melt a fuse, the voltage may drop, the thing may get very hot, the extra current may not get delivered, your thing may release magic smoke. All depending on the design... anyway, it is usually not a constant current supply but a constant voltage supply.
I don't see resistors in the image in the link you send. I have no experience with COB strips, but based on the image I'd not count on it without further research to make sure. The power supply that is shipped with the strip can very well be a dedicated LED driver, which means it's a constant current driver.
Opto isolation is not needed for 24V, it just complicated things. There are many MOSFETs that switch just fine with a 5V signal to the gate. Actually 24V to the gate is too much for many MOSFETs... so the module should include voltage limiting there (typically a 12-15V zener).
