Fuses - But I dont understand electronics

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My friend and mentor, the late Craig Talbot, wouldn’t hear of fitting fuses into a model boat as: 'They don’t prevent anything from being destroyed by a determined idiot'! I admit that I followed this until I witnessed a fire in a model which could so easily have been prevented had a fuse been fitted.

The purpose of a fuse is primarily safety. A fuse probably won’t stop a stalled motor from blowing the output FET's in a speed controller, but it will blow fast enough to stop cables and contacts from overheating and catching fire. Choose a value which is just a little above that at which you get nuisance blowing of the fuse, e.g. try a 5A fuse in circuit with a 10A ESC (electronic speed controller) and if it continually blows when the motor is at full load, replace it with a 7.5A one or even higher rating if required, but don’t exceed the maximum rating of the ESC with the fuse value. For those who want to know whether to fit a fuse between the battery and ESC or between the ESC and the motor, there’s no harm in doing both, but you must ALWAYS fit one in the positive line between the battery and the ESC somewhere. This is also the place for the main On/Off power switch.

For fuse values of less than about 2A you can use those clear glass cartridge fuses fitted to an in-line, spring–loaded holder. These aren’t very useful for higher currents, as the contact area at each end of the fuse is very small which can produce excess heat and melt the holder. I favour the automotive ‘blade fuses’ which go up to 30A, are widely obtainable, and are not expensive. You can even buy a fuse holder for these with an indicator diode which glows either red or green depending on which way the current is flowing, which is very useful for setting motors up, Photo 16. Finally, don’t fit fuses or fused boards inside a box or have them way down deep in the hull as you’ll need to be able to get to them easily for checking and replacing them.

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