Hi, I am trying to switch LED lights on and off via an arduino Nano. I realize I have to use a logic level mosfet for this task or a bjt. I have designed a PCB with the following schematic and cannot get it to work regardless of what I try. I have tried switching the mosfets for BJTs, using resistors in line of the arduino signal and tried many different voltages to open and close the gates separate of the arduino.
Please let me know what is wrong with my schematic if anything and if I am missing something in my testing.
Unfortunately, I didn't have my breadboard with me and the components at the time. So, in short, no.
Although not in the data sheet, I have had success using the LM1117 in parallel to double their current capacity. Regardless though, I don't seem to be getting any power to them from the FETs anyway.
The LED does not turn on when manually shorting the drain and source, the multimeter shows no power to the LED and it seems to completely short the VIN of the board. My power supply shuts down.
My VIN has varied for testing. I started at 5V in and slowly increased to a maximum of 12V to ensure my VIN wasn't the issue. I am currently using an Arduino Nano (5V I/O) the control the board but regardless if I disconnect the Arduino and feed 12V to the gate, it still does not open or close.
Finally, I would like to supply you with a data sheet for the LED lights but unfortunately I haven't found one yet as they're just cheap amazon 3W LEDs. They're pretty ubiquitous, the have a single emitter, two ears for soldering and are SMT devices. What I do know is that they're 3W and run on 3.3V but seem to be better off on 3V for almost no noticeable change in brightness but a significant change in heat output lol.
When you parallel like that, you ASSUME that both outputs are EXACTLY 3V, that is not the case, there are differences and this means one 1117 will conduct more current that the other, in fact if the output differences are wide enough, one 1117 will regulate and the other will do nothing.
3W / 3.0 = 0.9A
How many LEDs do you have on each MOSFET?
Can you please post a picture of your project please, so we can see your component layout?
Do you have your project on a protoboard, strip board or have you already made a PCB?
Each MOSFET is controlling one OR two LEDs depending on their function. I wonder if I should use BJTs instead?
You are correct in that i am assuming the regulators are even and fortunately for right now, I don't really mind if the regulators are uneven because they are useless until the FETs work lol.
Is the schematic correct? It looks like you are connecting Vout of the regulator to ground via the mosfet. Also, why would you have the regulator ground switched by the mosfet? Shouldn't that be tied to ground directly, and the mosfet be switching the ground connection to the load?
The Vout is connected to the LED and the MOSFET is connected to the GND on the regulator. I presume the MOSFET could switch the ground on and off past the regulator but I have it switch the ground on and off prior to the regulator.
Without the connection from the regulator tab to the switched ground it might work, but as drawn you are directly shorting the output of the regulator to ground.
Thank you to everyone who helped! The issue was a vast oversight on the design do to the VOut shorting with ground. I have also switched the FETs for BJTs.
I ended up switching back to FETs for the efficiency and lack of base resistors. Unfortunately I'm not out of the woods yet, the arduino seems to be running somewhat unreliably and the flashing of the beacon is sporadic. I think there must be too much power being drawn to run the MOSFETs or perhaps something may be wrong with my code. I am too new to the coding and hardware side to figure this one out.
Hi,
Your problem is your are ground switching a regulator ON and OFF.
The regulator should be ON all the time and the power to the LEDs from the regulators be switched.
At the moment you are switching ON and OFF a device that is not designed for you application where repetitive input connection/disconnection is occurring.
As you have 1117 in parallel, they might not be starting in sync either.
