Circuit protection, Fuse? - M0 + Lipo battery

Please tell us which board you are using.
For CircuitPython issues, ask in the Adafruit CircuitPython forum.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
IoTAll
 
Posts: 230
Joined: Wed May 31, 2017 6:34 pm

Circuit protection, Fuse? - M0 + Lipo battery

Post by IoTAll »

Hi!

I am working on a project where I am using an M0 Feather with a Lipo battery.
The Lipo battery is connected to both the feather and a 5V boost from Abafruit, powering a DC motor, controled by the feather through MOFSET transistors.
At max, the whole project can draw 1.5A~2A from the Lipo battery.

I am trying to secure my project if something wrong happens. I could imagine that a component could burn, a short circuit would appear somewhere, a motor could be stuck and current increase a lot, some water accidentally getting to the electronics and creating shortcuts, an issue with the Lipo battery or anothing else.

I read that one solution to reduce the risk of bigger issue, or potentially fire could be to add a fuse between the Lipo battery and the rest of the project, but I dont see this very often used in schematics (Arduino type of forums).

Is it a necessity? What are the kind of fuses I should be looking for?
Is there any protection I should add to make my project safer?

Any advice would be great!

Thanks!!

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Circuit protection, Fuse? - M0 + Lipo battery

Post by adafruit_support_mike »

You want a fuse.

Most microcontroller projects don't use much power, or will be supervised so that things like overload protection aren't as necessary.

For your application, adding a fuse will be a good idea.

User avatar
IoTAll
 
Posts: 230
Joined: Wed May 31, 2017 6:34 pm

Re: Circuit protection, Fuse? - M0 + Lipo battery

Post by IoTAll »

ok thanks a lot for the confirmation!

I am looking into this eFuse TPS2596. There is a video made on this chip on Youtube channel GreatScott https://www.youtube.com/watch?v=JOhQ3ns ... atScott%21

This seems to have over current, over and under voltage.

But I am wondering: this protection is already supposed to be provided by the Lipo battery protection circuit itself.
So I guess this is a double repeated protection in case we don't trust the battery protection circuit.

Am I right?

One more drawback from this kind of chip I guess is that, if something goes wrong in the project, it will disconnect the battery from the project, but might reconnect it right after as the short circuit disappeared if I am not mistaken.
This might make that the project continuously starts and stops as the issue on the project.

So I am wondering if it is not better to have a fuse which blows if the current is too high in the project, and then stays that way.

Am I progressing in the right direction?

Thanks!

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Circuit protection, Fuse? - M0 + Lipo battery

Post by adafruit_support_mike »

IoTAll wrote:But I am wondering: this protection is already supposed to be provided by the Lipo battery protection circuit itself.
So I guess this is a double repeated protection in case we don't trust the battery protection circuit.
The fuse keeps the protection circuit from setting the LiPo on fire.

Fuses are for gross overload conditions, like shorting the positive and negative terminals together. A protection circuit can try to keep the amount of current flowing through that short circuit below a certain level, but will still have 3.7V-ish on one side and 0V on the other side. All the power in that voltage and current has to be converted to heat by the protection circuit, and can easily fry a component.

Fuses burn up first to protect everything else.

Most voltage regulators also have built-in protection to handle conditions like a short between the rails, but they're last-ditch attempts to limit the damage from an emergency condition. They keep the regulator alive long enough for a fuse to blow and remove the emergency condition.
IoTAll wrote:So I am wondering if it is not better to have a fuse which blows if the current is too high in the project, and then stays that way.
I think so, yes.

Polyfuses are mid-level protection against mistakes while you're working with a prototype at the bench. It's embarrassingly easy to make a connection that will fry a circuit, and a polyfuse will keep that kind of mistake from killing a whole bunch of hardware. They just give you a few minutes to think about the mistake before they reset and conduct again.

Polyfuses do degrade every time they trip though, so they're not suited to long-term circuit protection or serious emergencies.

IMO, the correct response to an emergency condition is to treat it like an emergency, not something that will go away if you ignore it long enough. Fusible links (their formal name) do exactly that. They force you to examine the system and fix whatever made the fuse blow before the circuit will work again.

Locked
Please be positive and constructive with your questions and comments.

Return to “Feather - Adafruit's lightweight platform”