Fuses rarely protect the electronic circuit to which they are connected as when it is a device failure then it has failed and the fuse then disconnects the power but in terms of electronic components it takes an eternity to do so. If the fuse wasn't in there though then you could have cascade failures and a very good chance of excessive heat, smoke, and possibly fire. So a 2A fuse won't protect a 1A regulator circuit any better than a 5A one will.
On the other hand, if you have a 1A regulator circuit -- a 5A fuse isn't any better than a 2A fuse.
The regulator is shut down or browned out if more than 1A is demanded. We seem to be ignoring that the regulator itself can be a quite sophisticated protection device. And I have tried to mention that fuses are only one of several choices for protection of circuitry. FUSEs tend to be more about protecting power distribution networks from overload and people from physical harm.
5 volts at 1 amp provides 5 watts of power. 746 Watts is one horsepower. 1046 watts is one BTU. Most often, fuses are neither approriate nor useful in low wattage situations. Often the circuit is just made more rugged to deal with abuses.
I did visit Digikey and found fuse products down to 2ma ratings and able to be installed on circuit boards via surface mount and wave soldering. But I am pretty much at a loss to see how these are really a good solution. Replacement requires pulling a circuit board, and the chances of accidentally blowing a 2ma fuse are problematic. So I don't see that these either protect people or equipment in a wise manner.
IOW, include fuses for a good reason and make them easy to replace.
Fuses rarely protect the electronic circuit to which they are connected as when it is a device failure then it has failed and the fuse then disconnects the power but in terms of electronic components it takes an eternity to do so. If the fuse wasn't in there though then you could have cascade failures and a very good chance of excessive heat, smoke, and possibly fire. So a 2A fuse won't protect a 1A regulator circuit any better than a 5A one will.
True, the fuse does not protect the components on the board, but having a correctly rated fuse makes it less likely that the traces and circuit board will be damaged by excessive heat or fire.
Yes, as I said "cascade failures and a very good chance of excessive heat, smoke, and possibly fire" and of course that goes for the copper too although it's a sad pcb layout that has long narrow fuse-like tracks to carry power (what were they thinking). Most of my high-current traces are short, thick, and wide.
Fuses rarely protect the electronic circuit to which they are connected as when it is a device failure then it has failed and the fuse then disconnects the power but in terms of electronic components it takes an eternity to do so. If the fuse wasn't in there though then you could have cascade failures and a very good chance of excessive heat, smoke, and possibly fire. So a 2A fuse won't protect a 1A regulator circuit any better than a 5A one will.
True, the fuse does not protect the components on the board, but having a correctly rated fuse makes it less likely that the traces and circuit board will be damaged by excessive heat or fire.
Yes, as I said "cascade failures and a very good chance of excessive heat, smoke, and possibly fire" and of course that goes for the copper too although it's a sad pcb layout that has long narrow fuse-like tracks to carry power (what were they thinking). Most of my high-current traces are short, thick, and wide.
I agree. When I lay out a PCB the power traces are substantial and there are ground/power planes on multi layer boards. I saw too many interface boards on minis with vaporized power/ground traces to skimp on the copper.
it's a sad pcb layout that has long narrow fuse-like tracks to carry power (what were they thinking). Most of my high-current traces are short, thick, and wide.
I've necked traces down on purpose many times to create a specific failure point should it ever become necessary. I put through-hole pads on either side then if there is a fault I can solder a fuse in after the fault is repaired.
I've been doing it for a lot of years now and it has saved me a ton on fuses and fuse hardware. I haven't had to solder many fuses in, but the ones I did it worked perfectly.
it's a sad pcb layout that has long narrow fuse-like tracks to carry power (what were they thinking). Most of my high-current traces are short, thick, and wide.
I've necked traces down on purpose many times to create a specific failure point should it ever become necessary. I put through-hole pads on either side then if there is a fault I can solder a fuse in after the fault is repaired.
I've been doing it for a lot of years now and it has saved me a ton on fuses and fuse hardware. I haven't had to solder many fuses in, but the ones I did it worked perfectly.
Tesla pretty much has gotten this design scheme right.
The focus is containment of a problem that otherwise might spread. And that is pretty much what fuses are all about, containment of a problem via shutting out a branch of a circuit.
In the case of the Tesla, periodic visits to their service department can identify cells that require replacement before you lack enough capacity to get around. The whole nature of lithium batteries really does require that each and every cell have a device attached that will cut out a failing cell before in overheats and extends the problem to those around it.
But, I am NOT sure this is really a fuse. It usually is a device that monitors over-voltage, under-voltage, and maybe even battery cell temperature. Personally, I consider a fuse to be a one-shot device that requires a human to check the circuit before reset, and 'fuses' that reset on their own are not really fuses....just a protection circuit.
Modern voltage regulators with current cut-off, thermal cut-off, reverse polarity protection, voltage protection, and such are a protection circuit that autonomously resets if conditions change.
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I'll post results as I get them :-)
On the other hand, if you have a 1A regulator circuit -- a 5A fuse isn't any better than a 2A fuse.
The regulator is shut down or browned out if more than 1A is demanded. We seem to be ignoring that the regulator itself can be a quite sophisticated protection device. And I have tried to mention that fuses are only one of several choices for protection of circuitry. FUSEs tend to be more about protecting power distribution networks from overload and people from physical harm.
5 volts at 1 amp provides 5 watts of power. 746 Watts is one horsepower. 1046 watts is one BTU. Most often, fuses are neither approriate nor useful in low wattage situations. Often the circuit is just made more rugged to deal with abuses.
I did visit Digikey and found fuse products down to 2ma ratings and able to be installed on circuit boards via surface mount and wave soldering. But I am pretty much at a loss to see how these are really a good solution. Replacement requires pulling a circuit board, and the chances of accidentally blowing a 2ma fuse are problematic. So I don't see that these either protect people or equipment in a wise manner.
IOW, include fuses for a good reason and make them easy to replace.
Yes, as I said "cascade failures and a very good chance of excessive heat, smoke, and possibly fire" and of course that goes for the copper too although it's a sad pcb layout that has long narrow fuse-like tracks to carry power (what were they thinking). Most of my high-current traces are short, thick, and wide.
I've necked traces down on purpose many times to create a specific failure point should it ever become necessary. I put through-hole pads on either side then if there is a fault I can solder a fuse in after the fault is repaired.
I've been doing it for a lot of years now and it has saved me a ton on fuses and fuse hardware. I haven't had to solder many fuses in, but the ones I did it worked perfectly.
It'd be nice to see a picture of that...
The focus is containment of a problem that otherwise might spread. And that is pretty much what fuses are all about, containment of a problem via shutting out a branch of a circuit.
In the case of the Tesla, periodic visits to their service department can identify cells that require replacement before you lack enough capacity to get around. The whole nature of lithium batteries really does require that each and every cell have a device attached that will cut out a failing cell before in overheats and extends the problem to those around it.
But, I am NOT sure this is really a fuse. It usually is a device that monitors over-voltage, under-voltage, and maybe even battery cell temperature. Personally, I consider a fuse to be a one-shot device that requires a human to check the circuit before reset, and 'fuses' that reset on their own are not really fuses....just a protection circuit.
Modern voltage regulators with current cut-off, thermal cut-off, reverse polarity protection, voltage protection, and such are a protection circuit that autonomously resets if conditions change.
http://batteryuniversity.com/learn/article/safety_circuits_for_modern_batteries
All it is is your normal fusing rig with a skinnier trace between the pads. For 1oz copper I figure 1A per 25 mils width.
It isn't perfect but it works very well. I wouldn't use it on anything precision, but it works great for field wiring (lights, solenoids, etc).