Please 'Boom' Responsibly As most of you have noticed, the noise ordinances have become much tougher lately. Most of this is due to idiots, yes IDIOTS, who drive through residential areas with their windows down while their system is playing at full power. To make things worse, the music they listen to has all sorts of foul language that's not suitable for small children, (who may be playing outside). There are even a few people, who are even beyond idiot status, that play their systems at full power through residential areas after 10:00 PM (when many people go to bed). I don't believe that this type of behavior is good for the industry. If the fines get too stiff, people will stop buying large systems. If this happens, more people will get out of car audio (who wants a mediocre system). People get interested in things because they're exciting. A deck and four 6.5" speakers are not going to interest many of the younger car audio enthusiasts. If car audio enthusiasts keep annoying more and more people, the fines will keep getting tougher. All of this will only reduce interest in the equipment that fuels the industry. If you want to listen to your system at full volume, get out on the highway where there's little chance of bothering anyone. When you get to a red light, turn it down. If the only thing attractive about you is your 'system', you have some work to do. Bottom line... Think about what you're doing. Think about other people. It's not the end of the world if you have to turn the volume down for a little while.

Circuit Breaker:
A circuit breaker's function is, like a fuse, to break a circuit path when a predetermined amount of current is passed. In my opinion, circuit breakers should never be used to protect electronic devices such as radios, amplifiers or crossovers. Most common circuit breakers (thermal snap action) take far too long to open the circuit path. This does not mean that they are not useful. When they are properly selected they do a good job of protecting wiring and devices such as electric motors. Some breakers are self resetting. Others require manual resetting. I strongly recommend using a manual reset type. This will allow you to watch for any problems when the circuit path is restored.
Thermal Circuit Breakers:
The diagram below shows the simplified version of a self resetting circuit breaker. In this device, the current flows from the battery terminal, through the bi-metal strip and then to the other terminal. The bi-metal strip is made of two different types of metal which have different coefficients of expansion. This means that one will expand more than the other when the rise in temperature is the same for both pieces. In this case, the two metals are bonded to each other. (now keep in mind that this is a simplified diagram) When the strip heats up from the current flow through it, one type of metal expands more than the other. In this case, the black metal expands more than the red and the strip tends to bend upward and disconnect the contacts. You can see that the metal starts to bend as the current increases. When the temperature reaches a given point, the piece will snap into the open position and the current flow will stop. The bi-metal strip is stamped into a special shape which causes the 'snap' action. This will assure that there is EITHER a solid connection OR a complete disconnect. You can see a similar snap action in the top of some soda cans. If you push down on the top it starts to bend downward. After the pressure reaches a certain point, the top will snap down. If you release the pressure slowly, the top will snap into it's original position. This is what happens when the bi-metal strip cools in the breaker.


Below is one example of a self resetting thermal circuit breaker.

Magnetic Circuit Breakers:
Some circuit breakers use a magnetic actuator to trip the circuit. In this type of breaker, the current flow through the electrical device (amp, fog lights...) passes through an electromagnetic actuator. When the current flow reaches a preset level (determined by the current rating of the breaker), the magnetic field in the electromagnet is strong enough to trip the breaker and allow the contacts to open. This type of breaker generally has to be manually reset. A well designed 'magnetically' actuated circuit breaker can operate very quickly (possibly as fast as or faster than a fuse of equal current rating).
In the following diagram you can push the 'overcurrent trip' button to simulate too much current flow and trip the breaker. Then press the 'reset' button and watch the breaker reset. The 'show legend' button will show you a legend of the parts. Keep in mind that this is just a generic diagram and doesn't depict any particular breaker.

Thermal/Magnetic Breakers:
Some breakers use both thermal and magnetic trip functions. The magnetic function works the same as the previous explanation. The thermal part functions a little differently than the previous example. In the combination breaker, the bi-metal strip is more likely to be used to trip the breaker internally (by tripping the latch) instead of pulling the contacts apart when heated.
Reliability:
In my opinion and from my experience, circuit breakers are less reliable than fuses (especially when the breaker is mounted in the harsh environment under the hood). Quality fuses like ANL and Maxi fuses have a solid element (no solder connections) and will almost never have an intermittent or poor electrical connection. A circuit breaker will eventually have higher contact resistance than when it was new. This is especially true if the breaker has been tripped (by overcurrent) more than a few times. If you're going to compete and can't take a chance of having a problem like a bad connection in the power line, you should use a good quality fuse. Now I know that people have had fuses blow in competition but it was because the fuse was not properly rated, not because the fuse was defective. For those who have had trouble with glass fuses, read the fuses page of this site.

You should remember:
1.Do not use a circuit breaker in place of a fuse to protect electronic components.

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