Over Voltage/Over current protection

Thread Starter

tibibs

Joined Aug 25, 2021
6
Hi,

I have developed a small system that fit in a box and I would like your advice on what should be done in order to protect my electronics a bit as I am not an expert and I feel like my system is very exposed now.

so far the architecture is like this:

---------------Custom Box-----------------24VDC Sensors

------- being the cables

In my box, I have a PCB driving the 24VDC to my sensors, and a step-down regulator to give 5V to a Single board computer (raspberry pi zero like). the step down regulator used is this one:

Should I also include some kind of over current or overvoltage protection in my box? what would be the easiest way to implement it? I can include it in my PCB if needed.

Thank's for your help,

Tibibs
 
Last edited by a moderator:

Ian0

Joined Aug 7, 2020
3,525
Meanwell make a pretty good power supply. I would think that part of it has all the protection it needs, but the link you attached is for a 48V power supply.
 

Thread Starter

tibibs

Joined Aug 25, 2021
6
sorry about that, I went too fast writing the post.
It should indeed be this PSU
Ok, so I actually don't need to add any additional details in the box itself like a fuse or similar?
would be a good news then
 

Ian0

Joined Aug 7, 2020
3,525
A mains fuse where the mains connection enters, to protect from shorts on internal mains wiring would be required.
The supply should deal with faults on the 24V side.
How are you producing your 5V supply?
 

Ian0

Joined Aug 7, 2020
3,525
It says on the datasheet
“During normal operation, this product can get hot enough to burn you.“
That’s not going to be a reliable product.
Semicoductor and capacitor life halves for every 10°C increase in temperature, and “hot enough to burn you” is >100°C, so expect a sixteenth of the life that it would give if it were not too hot to touch.
Better put some protection on that 5V rail - a big Transorb, or a crowbar, because when a buck regulator fails it puts full supply voltage on the output.
 

du00000001

Joined Nov 10, 2020
84
...
In my box, I have a PCB driving the 24VDC to my sensors, and a step-down regulator to give 5V to a Single board computer (raspberry pi zero like). the step down regulator used is this one:
...
I assume your SBC won't draw anything near to the 5 A the Pololu DC/DC is capable to supply. So I don't expect the Pololu running hot as it would be way oversized.
I'd expect one of the fancy 7805 replacement DC/DC converters (available e.g. from Recom, Traco and others) should do the trick - being simple and cheaper.
 

Thread Starter

tibibs

Joined Aug 25, 2021
6
Hi,

sorry I have been a little bit away from this post

for the pololu DC/DC step down converter, so far I haven't seen it becoming that hot in my usage. indeed, as mentioned by du00...1, I am way below the current rating.
Regarding the price, it is not much of an issue, I won't fabricate so many units. the size is a bigger factor.

why do I need an over current protection? no specific reason and was more about asking for advice as I am not an expert.
seems to be reasonnable not to get one.

it was just a general question about what safety feature I should include in my box in order to get a minimum level of protection.
 
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