hi there one and all
FLJ has made light of the statement of putting a fuse in the negative side of the supply. For those who have no electrical knowledge whatsoever, a little insight might help one understand.
When we look at electrical circuits, we naturally think that the voltage plus current flows from the positive to the negative - or the red to the black wire - in actual fact it is the reverse. Also, inside the majority of electrical speed controllers/switchers/sound modules etc., the electrical 'track' on the back of the circuit board in places is thinner than fuse wire.
So, if one has a direct short or one reverses the polarity of the supply, one is going to get a 'weak-spot' and that weak-spot is going to be the thinnest part of the board which is going to burn out and not the fuse.
One of the reasons for this happening, is, inside the circuits there are components such as diodes which (for the non-electrical minded) work like a 1-way gate - where it only allows electricity to go 1 way but, it doesn't allow electricity to come back.
There are also things called electrolytic capacitors which again, or the non-electrical minded, they are similar to a battery which store up electric and then discharge it at a given time and these only work in a particular way.
So....can you see where we are going here - these components are all fitted into a circuit in a certain way - so that they will all allow current to pass through in one direction. Not the opposite direction - so, if we connect our battery up the wrong way round - they are not going to function as they should, thus blocking the flow of electricity/current and therefore causing a build up and 'busting' the weakest point on your circuit board being either - the thin track of the circuit board or a very fragile other component such as a transistor or an IC (integrated circuit).
over and out - keep it simple
aye
john e
bluebird