Replacing Relays with Arduino Controlled MOSFETs

Forum 2005-2010 (read only) Hardware Interfacing
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I have a small project I'm working on. I have a bunch of accessories in my car- lights primarily. I would like to build an interactive control system for them using an Arduino and have the ability to dim the lights if I choose. My understanding is MOSFETs are the desired high current switching device of choice for lower voltages.

My two main questions are

  1. As long as a MOSFET is switched hard on, there are essentially no losses, correct? So to drive a pair of 55W lights for instance, as long as I have a MOSFET rated for at least 10 amps, I should be ok and there will be no substantial heat problems if i'm not PWMing?

  2. What will be the ideal way to get signal from the Arduino in the cabin to the MOSFETs in my box under the hood? I thought about using CAT5 for the interconnect, simply because it's cheap and has 8 conductors. Will using logic level MOSFETs with direct connection between them and the Arduino work, going about 5 feet? Or would it be better to use standard MOSFETs with the Arduino driving gate drivers and then making the long distance run at higher voltage? Will my CAT5 idea even work or am I going to need shielded cable?

Thanks

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if you are going to be in the engine compartment, then some sheided wire is going to be needed. ignition noises and such.