I created a project which is a heater pad for my dogs. I'm using a 48VDC power supply as I figured lower voltage DC was inherently safer should the dogs chew on things or water got in the dog house etc..
I started out using an Arduino to switch a relay based on a thermistor embedded in the heater pad. I soon found out that relays for DC loads are not the same as relays for AC and that 4 amps and ~48VDC can't be handled by your typical relay like these https://www.amazon.com/gp/product/B07M88JRFY/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 which can handle 10amps, 110VAC just fine. (Reasons are due to arc extinguishing for DC which isn't a problem for AC for those wondering).
I've since started looking into going the Mosfet route instead and ordered some of these Mosfets https://www.mouser.com/datasheet/2/408/TK3R3A06PL_datasheet_en_20170824-1634441.pdf as it looks like they have a low RDS and I shouldn't need to worry about heat sinks at 4 amp and 48V. Researching into Mosfets though I find that they (at least n-type) are typically placed at the ground side -meaning the load is typically left with a live wire, whereas with my relay setup I had the relay in the front - before the heater load. It seems like if I were to put the Mosfet at the front of the load to act as a switch then if I put a 10K ohm resistor between the gate and source - it could cause +48V to go into the gate rather than grounding out (pulling down) the gate which would not give the desired outcome? Would it be legit to put the 10kohm pull-down resistor back to the Arduino's ground instead and still leave the Mosfet at the front of the circuit?