Avoiding Power loss and prevent shorts - 12V/5V - Pi controlled Fans.

Thread Starter

pspeth

Joined Mar 23, 2020
2
I have 12V in connected to a (12 to 5 DC to DC converter -> Pi) and (supplying 12V to a Relay that will turn Fans on and off).

The issue I want to prevent is if I short the cable going to the fans, it shuts down the Pi and can possibly to other damage.
What is the best way to prevent shorts from affecting the Pi while without diminishing the power to the 12V Fans.

My system goal is keeping the overall design simple and cost effective.
- 1 12V power input for the system
 

Thread Starter

pspeth

Joined Mar 23, 2020
2
The system I am working on will be a part of a kit that kids will be building.
If it is ok, let's assume that a short would be rare but possible.
Any thoughts on how to prevent this from causing the entire system from losing power?

Thanks
 

nsaspook

Joined Aug 27, 2009
7,602
The system I am working on will be a part of a kit that kids will be building.
If it is ok, let's assume that a short would be rare but possible.
Any thoughts on how to prevent this from causing the entire system from losing power?

Thanks
12vdc hitting the RPi board even with modest current limiting is likely to cause a permanent fault on the RPi board even if it doesn't completely short the power supply . You best bet is to use shrouded interconnects that are recessed for power and potentially hazardous system signals.
Example:
https://www.molex.com/molex/products/family/sl_connectors
https://www.pololu.com/product/2717
 

Reloadron

Joined Jan 15, 2015
5,646
Fast acting fuse downstream of the DC/DC converter pick off. That plus everything mentioned. It doesn't take much of a dip to reset a Pi or similar.

Ron
 

Boardleash

Joined Mar 19, 2020
1
nsaspook already hit it, but "to piggyback", solid connections. if it is really concerning, and if only for piece of mind, a current limiter could ease concerns. but if part of the concern is overheating and you feel it necessary, an inline fuse. the first part of this answer is more cost effective; the latter incurs more cost (and maybe unnecessarily).
 

ElectricSpidey

Joined Dec 2, 2017
1,258
12vdc hitting the RPi board even with modest current limiting is likely to cause a permanent fault on the RPi board even if it doesn't completely short the power supply . You best bet is to use shrouded interconnects that are recessed for power and potentially hazardous system signals.
Example:
https://www.molex.com/molex/products/family/sl_connectors
https://www.pololu.com/product/2717
How could shorting the lines to the fan apply 12 volts to the Pi?

Me thinks that would be a separate issue.
 

nsaspook

Joined Aug 27, 2009
7,602
How could shorting the lines to the fan apply 12 volts to the Pi?

Me thinks that would be a separate issue.
I've no idea of how his fans, power lines or interconnects will actually be constructed in this kit so a general way to help prevent shorts from loose connectors to anywhere was provided.
 

Tonyr1084

Joined Sep 24, 2015
5,091
I don't see any chance of a short. (return paths not shown) (a.k.a grounds or commons)

But leave it to a child to find a way to short it. A friend (when I was a child) told me he had an unbreakable comb. So I broke it.
1585000495588.png
 

ElectricSpidey

Joined Dec 2, 2017
1,258
All you need to do is keep the 12 volt supply from dipping below 7 volts or so, and the Pi should be fine.

This is why I suggested current limiting, because using a fuse the supply could still detect a short and shutdown.
 
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