MOSFET Choice for controlling ATX PSU Rails

Thread Starter

elephunk

Joined Nov 21, 2016
26
Hey guys, I'm looking for some help if someone fancies it.

I am looking at running 2 ATX Motherboards from 1x 1.2Kw ATX PSU. I would like to make a PCB to distribute and control the power rails going to each motherboard so I can turn each one on and off via an Arduino. I understand I will need PNP FETS to control the rails and that's about it up to now.

After reading as much as I can understand at the mo, I think this one maybe suitable but just wondered if anyone fancied throwing their advice in.
Also I'm a bit fuzzy on level shifting the arduino to drive the FETS and wondered if this was the way to do it??



Obviously, the choice of components in the circuit above are only for demonstration.

Thanks
Iain
 

AlbertHall

Joined Jun 4, 2014
11,598
The circuit that you show uses a bipolar junction transistor as the switch. If you do this you will need resistors at the places shown by red arrows below. It would be better (less voltage drop and less heat) to use a MOSFET instead of the TIP30.
levelshift.gif
 

Thread Starter

elephunk

Joined Nov 21, 2016
26
The circuit that you show uses a bipolar junction transistor as the switch. If you do this you will need resistors at the places shown by red arrows below. It would be better (less voltage drop and less heat) to use a MOSFET instead of the TIP30.
View attachment 125853
Cheers AlbertHall, yeah I am aware that I will need resistors in those places, I hadn't put them In yet as I haven't chosen a MOSFET yet. I am thinking of using the IRF5305 as the FET

Thanks again
Iain
 

Thread Starter

elephunk

Joined Nov 21, 2016
26
Any reason why you can't use relays?
I was looking at relays and did consider it for a while but the reasons I decided against it were, I didn't want the audible click from "normal" relays, I couldn't find a solid state relay at a price point comparable to FETs that could handle the current provided by the PSU (5v rail is 25A), and I would like to learn about FETs at the moment as they appear to be more diverse in their applications and uses.

If you have any info persuading to the other then feel free to share as I need to learn this stuff.

Thanks
Iain
 

Thread Starter

elephunk

Joined Nov 21, 2016
26
Isn't the IRF5305 suitable for that?? If I were to use either the IRF5305 or the FQP27P06 in the circuit above in place of the tip30, using a 2n2222 to drive it?? Sorry for my lack of understanding but I'm wondering why you've suggested the FQP27P06 over the IRF5305.

Thanks
Iain
 

Dodgydave

Joined Jun 22, 2012
10,088
You can omit T3, and put T1, to T6 with Base Resistors to your Arduino, also you need resistors on the Gate terminals and Collector loads.
 

R!f@@

Joined Apr 2, 2009
9,751
Relay is a safer choice.
You will here click once and you think that click is louder than the fans running ?

One leaky FET and you are in for trouble.
 

Thread Starter

elephunk

Joined Nov 21, 2016
26
What do you need, Ids or I-zener?
I'll be honest, I don't even understand this question. Is it related to the diode inside the FET???
And also the symbol of IRF5303 was wrong, please recheck the datasheet.
Yeah I know, my Eagle doesn't have much choice in FETs in TO220 Verticle, and this is the only one I could make work, I will be addressing this very soon.

Thanks all
Iain
 
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