MOSFET selection for driving x6 1W LEDs

I am trying to drive serial groups of x6 1W LEDs from an Arduino.

I have a 24VDC supply which is to power a constant current circuit, the current drawn by this constant current circuit is 280mA @ 24VDC

I want to be able to switch this on and off using the Arduino but I am not being very successful! I have tried using a IRF520NPBF MOSFET but it will not fully switch on using a 5V Arduino output, the power light to the constant current driver barely illuminates and none of the LEDs illuminate. If 24V is applied to the middle pin of the MOSFET it all lights up.

I have also tried a ZTX851STZ and IRLU8726PBF and TIP120TU, the data sheet for the IRF520NPBF is here:

my basic setup is:

+24V to pin 1
constant current driver to pin 3 through to ground
Arduino +5V to pin 2
Arduino GND to the 24VDC ground

I don't fully understand the use of a MOSFET and although I have read many topics about VGs values I am not able to replicate the results I am expecting, so any help is welcome so that I can expand on what I am trying to achieve!


Do you understand the difference between high side and low side switching?

Do you realise high-side switching will need a pFET and a level shifter, whereas
low-side just needs a logic-level nFET?

You need to give us your circuit.

Constant current drivers are not meant to be disconnected from their load - you should be switching the input to the constant current driver, not the output.

Yes I am trying to switch the input of the constant current driver. I have actually managed to get it to do what I want which is to switch the driver on and off basically! I don't fully understand the MOSFET and ended up switching back to a TIP120 wired as the image. Does this look correct? should I have anything else in there for protection?

The idea eventually is to connect these LEDs and use PWM too, unfortunately the CC drivers I have got in hand don't support PWM but I can always swap them out when I become more comfortable with the circuitry.

Should I have a capacitor across the constant current input given that there is a coil in that circuit? A diode across pins 2&3 on the tip120?

Should I have a capacitor across the constant current input given that there is a coil in that circuit?

There should be one in the constant current module.

A diode across pins 2&3 on the tip120?

Not if the capacitor is there.

Thanks Paul__B much appreciated