Use of Mosfet for hotend heating with Duet2 Wifi

[hlwerschner]

Hi,
after having fried a Duet2 Wifi, I have restarted and rewired my 3d printer (originally a Tronxy X5SA Pro migrated to Duet2 Wifi) and decided to add as much as possible (and payable) to keep the controller safe when changing any components around it (heatbed, sensors, hotend, steppers). I have for example added a Mosfet between the controller and the heatbed and feed power to the heating via the Mosfet. When I swapped the original Tronxy hotend for a new Phaetus Dragon hotend for higher temperatures I considered to also add a Mosfet to this heater. The Duet2 Wifi is said to provide a max of 6 A (fused) to extruders so my question is: Is a Mosfet for hotend heating overkill even for 2 extruders apart from the gained safety of the controller against any failures? These parts are only around 10 EUR so cost is not a problem.

[dc42]

@hlwerschner what wattage are the heaters?

It's very unusual for the hot end heater outputs on the Duet WiFi to give any problem. Using an external mosfet to control the hot end heater is almost certainly overkill unless you have a high powered hot end heater and VIN is only 12V.

OTOH using an external mosfet is a good idea when using a high powered bed heater. The bed mosfet on the Duet can easily handle the 18A rated currents, however you need to use ferrules and crimp them properly to get reliable connections to the terminal blocks at high currents.

[hlwerschner]

@dc42 The hotend cartridges go for 24V 50Watt (so a bit over 2A)... which might be some load when I will got for dual hotends in the future. I simply am playing the "burned (!) child" and have seen also a lot of threads here from burned fan mosfets etc. I would like to keep the controller as safe and happy as possible!

In this sense: what could I do to have safe (electrically speaking) fan power/control over the board? Is Mosfet possible there at all regarding PWM use?

[dc42]

@hlwerschner the fan mosfets have a much lower peak current rating that the heater mosfets, so they are more easily damaged e.g. if the output is shorted or the fan is connected the wrong way round. Whereas 2A is nothing for the heater mosfets.