3D Printed Indicating Fuse Box
BEHOLD! The indicating fuse box! Gone are the days that you must ask yourself, “Did the Earth stop spinning? Or did I just blow a fuse?!?” For eons, mankind has been stuck with boring fuse connections, BUT NO MORE!!! If a fuse goes out, the light next to it does as well. Easy peasy.
Actually, indicating fuse blocks are nothing new. In my day job, I spec and use them frequently in industrial control cabinets at chemical and gas plants. The idea behind them is simple: If a fuse blows, either the LED will turn ON or turn OFF depending on how you wire them (or buy them as the case might be).
I created this simple mini-project for one of my many 3D printers. A good chunk of printer control boards (for example, RAMPS 1.4) typically use things called “polyfuses” in the place of normal fuses. These are great in certain applications because they “blow” when the current gets too high and then automatically “reset” after power is removed. The issue I had with them is that they don’t actually blow when a certain current is reached, they blow when the polyfuse itself gets too warm. When you are pulling 15-20 amps through one of these for a heated bed, they tend to get warm….
Long story short, ACTUAL fuses don’t typically have the same problems as polyfuses. A typical fuse is rated to blow within 1-hour at continuous rated current (ex. 1 Amp through a 1 Amp fuse). As long as you derate your fuses by 20% or so, you are golden.
The beauty of actual fuses is that if you pick a rating that is slightly too low, it isn’t difficult to replace it with a higher rated fuse. In other words, if you find a “10A” fuse keeps blowing repeatedly (and your wiring can handle it), you can easily just pop in a “15A” fuse in its place. No soldering, no fans to keep a polyfuse cool, just pop in a new fuse.