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Topic: Where should I connect fuse? (Read 5019 times) previous topic - next topic

vd853

I want to connect an inline fuse to protect my circuit,  but there is a 12v and 5v source coming in. They both have a common ground so should I connect the fuse to the common ground?

el_supremo

A fuse should always be placed between the voltage source and the circuit (load).
12V -> fuse -> circuit -> Gnd

Pete
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JimboZA


A fuse should always be placed between the voltage source and the circuit (load).
12V -> fuse -> circuit -> Gnd

Pete


Testing my understanding here: I'm guessing that's to minimise dangling live wires that could still get to ground and drive the load?
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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

MAS3

What will happen when GND gets disconnected from the board (by a blown fuse) , but 12 volts and 5 volts are still connected to that circuit ?
Have a look at "blink without delay".
Did you connect the grounds ?
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CrossRoads

It's often said the fuse is more to protect the wiring to the device, than the device itself.
The fuse doesn't disconnect GND, it disconnects the source voltage. No source voltage = no 12V/5V.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

larryd

We use to say the component usually protects the fuse ;)
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Grumpy_Mike


We use to say the component usually protects the fuse ;)

Yes that is exactly right. 

A fuse in modern electronic circuit is useless.

CrossRoads

Good for motor driving, can save the power supply/drivers if the motor stalls and the electronics can't handle the resulting surge when the motor looks like a dead short.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Grumpy_Mike

Can't agree with that. Most power supplies will have current limiting either fold back or crow bar. It will be so fast that the fuse will not have time to blow, but the components in the H-bridge will.

DrAzzy

Fuses should always be put on the positive side, before the load. If you're not generating the 5V from the 12V or vise versa, yeah, that's two fuses.

Whether your circuit justifies a fuse depends on what you're doing. I typically only use them where there's potential for destruction beyond just burning out parts - like if you've got enough power behind something set stuff on fire, or you're using  lithium batteries where you don't trust the short circuit protection.  Fuses certainly aren't useless for saving parts too, though - I've trashed 4 small PCBs in the past 2 months that would have been saved by a fuse.

3 were DC-DC converters with no current limiting, and another was a custom board where there was a short through a ground trace, where the damage to the parts was caused by the absence of ground on the bottom of a voltage divider after the ground trace failed.
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MarkT


Good for motor driving, can save the power supply/drivers if the motor stalls and the electronics can't handle the resulting surge when the motor looks like a dead short.


Well when my motor driver kept blowing 60A fuses I used a 4 mm^2 piece of copper
instead - this protected the wiring because the wiring was 6 mm^2.
The MOSFETs didn't seem to care, but 200A 600W ISOTOP MOSFETs are
made of sterner stuff than a mere fuse!
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vd853

I'm asking because I want to know if the fuse will protect both the 12V and 5V components if the fuse was connected right before the common GND.

Grumpy_Mike


I'm asking because I want to know if the fuse will protect both the 12V and 5V components if the fuse was connected right before the common GND.

No putting a fuse in the ground is wrong and will not work anyway.

Paul__B


No putting a fuse in the ground is wrong and will not work anyway.

It's not just wrong, it is diabolical!

If you have other things connected to both the power supply and the circuit "protected" by the fuse, and those things have their grounds connected (such as through power cords), then very strange things happen, such as ground connections catching on fire!

Pelleplutt

I f you blow the fuse connected to common, the 5 volt to your circuit will be reversed and i some cases would your equipment will be burnt .
Not good.

Pelle

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