Hello, basically I want to separately control 9-1 watt leds through 9 of the digital pins on the arduino, I planned on using logic level mosfets but I just need some
More info I'm rather new to arduino , I figured out the code side but I just need to figure out how exactly to power them
, I was curious what kind of resistors I need also and if I need 9 separate Mosfets or if I need 9 drivers if I want to run them all parallel? Powered by 12vsupply
they are 3.5 v to 3.7 v leds 350ma
Any help would be greatly appreciated!
about the resistors:
you need a 1k on every mosfet gate (especially for PWM mode) and for the load on the led you need a resistor of
(12 - 3.7) / 0.350 = 23 ohms
of power (12 - 3.7) * 0.350 = 3 watt (better more 
)
about the mosfets:
you can use ALMOST any TO220 N-channel mosfet, read the datasheet and look for a graph with some lines, one for every voltage on the gate (vgs) (it's usually the first graph), you may need an heatsink if you use PWM
about the connection:
if you connect them in groups it's better to connect them in series, probably you cannot connect more than 2 on every channel, in this case you need a smaller resistor (subtract another 3.7V on the formulas)
about the power supply:
are you sure that it can handle 4 amperes of power?
screwpilot:
about the resistors:
you need a 1k on every mosfet gate (especially for PWM mode) and for the load on the led you need a resistor of
(12 - 3.7) / 0.350 = 23 ohms
of power (12 - 3.7) * 0.350 = 3 watt (better moreYes actually I have some mosfet breakout boards that have the surface mount 1k resistors , i those will work
Here they are:I hope it's okay to post links in here
about the mosfets:
you can use ALMOST any TO220 N-channel mosfet, read the datasheet and look for a graph with some lines, one for every voltage on the gate (vgs) (it's usually the first graph), you may need an heatsink if you use PWMI don't plan on a heatsink either these will only be flashing a couple times a minute for 30 minutes or so a day
about the connection:
if you connect them in groups it's better to connect them in series, probably you cannot connect more than 2 on every channel, in this case you need a smaller resistor (subtract another 3.7V on the formulas)Okay thanks for your info, very helpful
about the power supply:
are you sure that it can handle 4 amperes of power?No I'm not sure I'm very new at this , I'm glad you bring that to my attention,
I'm not committed to 9 leds, I can do with less, how many would I be able to run on 12v? Do I need a 12v with more amperage?
But I do need to run them in at least 5 different series to have separate control form the arduino of 5 different light sets flashingI hope I used the quotes right also lol
Any help again is greatly appreciated
Nope don't think I did the quote thing right
I think I'm beginning to realize now I can only run 3-4 separate series because of the forward voltage of 3.4
I think I'm beginning to realize now I can only run 3-4 separate series because of the forward voltage of 3.4
Maybe 2 in series...
If the LEDs are all going to turn in & off together, you only need one MOSFET. But , if you use current-limiting resistors, each set of series LEDs needs a separate resistor.
Do you understand LEDs? You need to control the current, not the voltage... Of course, you do need sufficient voltage.
LEDs (like all diodes) are non-linear. At low voltages, the diode's resistance is high and very little current flows. As you approach the breakdown voltage (operating voltage), the resistance drops dramatically and current increases. If you exceed the breakdown voltage, you'll get excessive current and fry the LED (and possibly the LED driver).
For everyday low-power LEDs we use a current-limiting resistor. The supply voltage divides between the LED and series resistor. That means we subtract the LED's operating voltage from the power supply voltage to find the voltage across the resistor. We use the resistor voltage and the LED's rated current, and Ohm's Law to calculate the required resistor value. (Since the resistor and LED are in series, the same current flows through both.)
As a general rule, the voltage drop across the resistor should be about equal to, or greater than, the voltage across the LEDs. So, you don't want to put too many LEDs in series to the point where there's not much voltage drop across the resistor.
You can use a series resistor for a 1W LED, but the standard practice is to use a switching constant-current power supply. You can buy or build one, but switching supplies require an inductor and they are somewhat tricky to build.
If you can find a constant current power supply with enough voltage capability, you can put ALL of your LEDs in series. (That's assuming the LEDs don't need to be independently switched or dimmed.)
@cruzreagan
3 leds of 3.5v in series will pose a drop of 12v almost for sure
you cannot connect them this way because the voltage drop on the resistor is too small and it will surely vary courrent a lot for various reasons over time
those mosfet modules seem ok (and logic level aimed) but you allways need a series resistor calculated with that formula
i'v made a constant courrent led driver that is also switchable and... if you don't know even the Ohm's law forget about developing such a thing , you can try to find it online, maybe
Ok thanks to both of you, very good information like I said I'm very new at this and I just simply want to have control to seperatly flash 4 or 5 different 1 w leds, from the arduino, ..they are randomly flashing from each other not all the same.., so that is what I don't understand ..if I need separate drivers for each led if I want separate control from the arduino
Or is a separate mosfet and proper resistor for each flashing led enough if only flashing like lightning
For 30 minutes a day
I can buy whatever i need ,there is just so many different drivers I don't fully understand
I'm trying to find some projects online to copy but none really match or no one finishes
I just don't really get it..ya know I've got it all figured out on small prototype with breadboard and my
Small leds but can't figure out what I need to do to upgrade them to 1 watt
i'm not sure about what you are trying to ask\do
but i think you need one mosfet and one resistor per channel, you can save power if you connect 2 leds in series per channel (and they will turn on\off simulaneously), trying to economize on parts like one resistor for all the circuit is possible but you need to turn only one channel on per time and even in this case i strongly suggest you to use one resistor per channel (it's foolproof)