Hello !
I tried to use my arduino to build a PWM dimmer in order to drive 40x 3W LEDs. The PWM is set to only use 40W. The setup worked well for two weeks but stopped working.
Since the board is dead now, I suppose I messed something up.
The LEDs use 12 V so I decided to use the same power source (12V, 5A) to also power the arduino via the VIN pins (like shown in the schematics)
I use a mosfet (DC 15A - 5-36V 400W - MOSFET D4184 Module PWM Variateur de vitesse moteur DC 15A - 5-36V 400W - MOSFET D4184 | eBay) for the dimming itself, driven by the arduino.
The fuse is dimensioned to melt at 4A (since it did not melt I guess that the error is in the control circuit).
Does this theoretically sound correct? I am wondering if it is my design or my soldering skills which are to blame. Thank you very much for any thoughts on the toppic!
It is the arduino nano. I checked again and the mosfet is still working
The Nano might theoretically be able to accept up to 12V input but the onboard regulator has no heatsink and 7V is a relatively large voltage drop so heat dissipation is going to be an issue. You might want to think about providing an external regulated 5V supply.
I would probably also consider putting a current limiting resistor between D9 and SIG to protect the Arduino in the event of the switch module failing.
I don't see anything obviously wrong that would fry the Arduino. Maybe static discharge when you touched the board? (If there's a static charge on your body you can sometimes kill a board without seeing a spark or feeling a shock.)
Or it could be a random failure, or maybe your 12V supply puts-out a higher-voltage spark when it's switched-on.
There are a couple of issues here that could fry your power supply or drivers -
LEDs are "current driven". They are non-linear (like all diodes)... Their resistance changes with voltage. With a little too-much voltage, their resistance drops and you get excess current and something can burn-up. With a little too-little voltage the resistance increases, current drops and the LED will be dim.
And the "perfect" voltage varies a little from part-to-part and with temperature. The voltage on the datasheet is the "nominal" voltage.
You need a constant-current source or some kind of current limiting. With "regular little" LEDs we use a current limiting resistor, but since this is inefficient and the resistor has to dissipate power in the same ballpark as the LED, most high-power LEDs use a special constant-current power supply (or constant-current driver). With a constant current power supply the voltage "falls into place" as long as the current is correct.
You can use resistors but they have to be high-power resistors. And the power supply needs enough wattage to power the LEDs plus the resistors.
And, when you "set to 40W" that's the average power. PWM is either fully-on or fully-off so you are getting current peaks in excess of the power supply's rating. (Some power supplies are OK with that and some are not.)
Thank you a lot for your kind replies. I will try to use a separate 5V power source to keep power circuit and control circuit apart from each other.
@DVDdoug Thank you for the input concerning the 12V power sources. I will keep that in mind for the day the power circuit fails and it comes to choosing a new power source.
@BitSeeker A current limiting resistor is something that really did not come to my mind. Thank you for the idea. I have no clue how to dimension the resistance. I thought it was best for the mosfet if the voltage is hight, isn't it? So I would have taken a small resistance like 200 Ohm. Does that sound correct?
One big problem, the MOSFET module circuit remains a mystery. No schematic.
