Current & Voltage Limiter

Thread Starter

mattd860

Joined Jan 9, 2016
58
Hi All - I'm looking for a fuse (preferably a PTC Resettable Fuse) to limit the max current to 150mA. I'm also looking for a fuse to clamp voltage above 5.5v dc.

I need this for a fail safe just in case my 5.0v linear regulator ever failed.

Can anyone refer me to such a device(s) and provide a link to one on Digikey or Mouser?
 

AnalogKid

Joined Aug 1, 2013
8,488
Colin, take 150 mA where?

matt - What response time do you need for your protection? Neither a standard fuse nor a PTC are particularly accurate or fast because they both depend on a small mass heating up for their protection effect. If you are trying to prevent something from being damaged in milliseconds, you will need an electronic circuit rather than a thermal device. Do you really need to shut down the output upon an overcurrent condition, or would a current limiter be sufficient? A current limiter might only reduce the output voltage a bit for a minor overcurrent, or shut it down completely for a current spike.

ak
 

mcgyvr

Joined Oct 15, 2009
5,394
What do you think is going to happen if take 150mA??
Depending on the time curve... nothing will happen more than likely.. (other that it being a good heater)
As stated above by AK fuses have time curves (and are slow/horrible for use as a current limit in an application like this)..
Most if not all can take 100% of the rating for ever without issue and may take 5-10 minutes or more to trip at 125% of the rating,etc... 1 minute at 150%... 1 second at 200%,etc...
All stated on the specific time curve chart for that fuse..
 

dl324

Joined Mar 30, 2015
10,984
Hi All - I'm looking for a fuse (preferably a PTC Resettable Fuse) to limit the max current to 150mA. I'm also looking for a fuse to clamp voltage above 5.5v dc.

I need this for a fail safe just in case my 5.0v linear regulator ever failed.
Fuses and PTC thermistors probably don't work the way you expect. Have you considered adding current limiting to your power supply? Or a power MOSFET to disconnect the supply if it exceeded a certain voltage?
 

Thread Starter

mattd860

Joined Jan 9, 2016
58
I'd like to prevent an arduino processor (ATtiny85) and associated circuity from burning out. I have 12v dc in and 5v dc out. If the regulator failed and sent +12v to the 5v circuitry it will likely burn everything up - literally. I don't care if the the processor and circuitry are permanently damaged if the VR fails but I just want to prevent a fire.
 

crutschow

Joined Mar 14, 2008
25,122
I'd like to prevent an arduino processor (ATtiny85) and associated circuity from burning out. I have 12v dc in and 5v dc out. If the regulator failed and sent +12v to the 5v circuitry it will likely burn everything up - literally. I don't care if the the processor and circuitry are permanently damaged if the VR fails but I just want to prevent a fire.
In that case, all you need is a fuse.
 

mcgyvr

Joined Oct 15, 2009
5,394
Your link doesn't go to a product..
I'd go for a fast blow 200mA fuse (and fuse holder) to prevent any nuisance tripping..
And prepare your design for the extra heat (fuses are "heaters")
 
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