Hi,
could you suggest the best solution for switching on/off 3A @ 48V DC with Arduino?
Time on is about 10 hours avery day.
Thanks 
How is it powered?
Relay's will need coil powered the whole, drawing power.
MOSFET just needs a voltage level.
Latching relay could be another option, you can latch and then put the rest of the circuit into a low power mode.
Also helpful if you lose power during the 10 hours and you want the relay state to stay out.
Here's an example, could be driven direct from 2 Arduino pins - high/low moves contacts one direction, low/high moves contacts the othe direction
Not clear to me from the data sheet how long the current needs to be applied to switch them, you'll have experiment a little.
Hi, thank you for your reply.
My application is a LEDs fixture, I have four cables coming from 3 different switching power supply.
- one 12V cable for Arduino and fans
- two 48V cables for LEDs
- one cable for common ground
I have 9 LEDs drivers (meanwell LDD) controlled via PWM by Arduino.
Led fixture is completely switched off during dark hours (I don't want to waste even the few mW of the LCD display 
)
The problem is drivers set up much faster than Arduino, they give full light for a while before being dimmed, so I'm thinking of: turning on Arduino, which in turn turns on the drivers via some sort of switch.
I'm already turning on/off fans based on heatsink temperature using a mosfet, but that are very few mA.
Too many options, no real clear choice.
Go with what you're comfortable working with:
Relay
Latching Relay
Logic Level, Low Rds N-channel MOSFET to switch ground for the 48V.
Panta_rhei:
Hi, thank you for your reply.
My application is a LEDs fixture, I have four cables coming from 3 different switching power supply.
- one 12V cable for Arduino and fans
- two 48V cables for LEDs
- one cable for common ground
Oh, you shouldn't common the grounds at the power supply end, common them at the Arduino and associated
circuitry (otherwise you'll get switching transients from the 48V circuits imposed on the 12V supply. The best
practice is to keep high current power wiring separated from lower power circuitry. Bring each supply's output
as a pair of wires (preferably twisted pair) to the central point - this is also known as star-grounding.
@Crossroads: thanks for your reply
@MarkT: what kind of issues could I experience because of not star-grounding? As far as I understand from the web, star grounding is often used in audio equipment to avoid interference like hums etc, but I can't detect any visible problem with my LED fixture.
Its to reduce the severity of the switching transient on the ground to the Arduino -
without an oscilloscope you won't know how big the problem is till it bites you
(say the cables are lengthened or moved - it might suddenly become unreliable).
So follow best practice. High current wiring that's switched shouldn't be shared with
wiring to sensitive circuitry. Common the grounds at the switching device only...
OK, thank you!
Panta_rhei:
Hi, thank you for your reply.
My application is a LEDs fixture, I have four cables coming from 3 different switching power supply.
heatsink temperature using a mosfet, but that are very few mA.
Hello, what type of power supply do you have and how to you split it in 3 types of voltages, i have a 24vdc and i want to power less (24v) arduino (9v) and fan (12v) from the same 24VDC supply
Hi, I have three different power supplies, two that output 48V and 3A for lighting the power LEDs, and one that output 12V and 1.5A for the Arduino and 3 fans.
If you want to use only one PSU at 24V, you could you use a switching step-down dc-dc converter for the other tensions, like the ones produced by dimension engineering.
See this model Adjustable step down switching voltage regulator, it has 3-30V as input, and 1-13V as output. There is also a 3A model if 1A is not enough.