Electronics > Beginners

RTC = Fuse?

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ftransform:

--- Quote from: Wytnucls on January 07, 2013, 11:17:26 am ---A PTC in series on the supply side, followed by a MOV or better still a GDT (gas discharge tube) across to the output ought to do the job, protecting the circuit against overvoltage. (Both of the same voltage, 270V for instance in Europe)
The fuse (250V) is there to protect for overcurrent (usually due to a short in the circuit), anything over 3A.

--- End quote ---

I think I will bodge in a gas discharge tube I took out of something else in addition to the other repairs.  :-+
Are PTC's known to be particularly flakey components? As I mentioned on the other supply the fuse remained shorted but the PTC was damaged to a point where it completely disintegrated when I touched it with my pinky.

Neilm:
PTCs can overheat and be destroyed if they have more current than the pass current but less than the stop current. They end up over heating and breaking. This happens if the designer has either miscalculated the fault current or the circuit has endured a prolonged overload.

Neil

ftransform:

--- Quote from: Neilm on January 09, 2013, 07:34:27 pm ---PTCs can overheat and be destroyed if they have more current than the pass current but less than the stop current. They end up over heating and breaking. This happens if the designer has either miscalculated the fault current or the circuit has endured a prolonged overload.

Neil

--- End quote ---

Ugh, I'm having trouble selecting a replacement.
Do you think a 4R one will work as per the suggestion of SeanB?
There are so many choices.

Do you think I could maybe hook up the device to a logging meter, get a graph of the current vs time and make a selection based on that information?
Documentation for this device is unavailable.

Neilm:
The only way to properly specify this would be reverse engineer the circuit and figure out the expected fault currents, accounting for the ambient temperature in the unit.

If you try hunting on the web for specifying these. They also referred to a "resettable fuses".

Neil

ftransform:

--- Quote from: Neilm on January 10, 2013, 07:13:52 pm ---The only way to properly specify this would be reverse engineer the circuit and figure out the expected fault currents, accounting for the ambient temperature in the unit.

If you try hunting on the web for specifying these. They also referred to a "resettable fuses".

Neil

--- End quote ---

 |O

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