ATX power supplies and RF stages

[KA5BBC]

Has anyone had success with using an ATX power supply not only for the RPi but in providing power to the Minitouner, the Pluto, the LimeSDR, and the likes of the REF France 433/1.2/2.4 amplifiers etc?
I'm fortunate in that my project case came with a 550 watt modular power supply as I can easily modify cables to supply bus bars, buck converters, and more. I would like to utilize this as it would be a neat and secure solution for the case.. I just don't want to cook my equipment.

[G3GJA]

Just be aware that only the 5v rail is properly regulated in an ATX power supply.

The 12v rail's voltage depends on the current loading on the 5v rail, so if you are only running an amp or so to feed the 5v kit you may find that the 12v rail is low voltage.

Another thing to be aware of is the ripple. I've used Pi filters of 2 x 22µF low ESR caps (tantalum) and 220µH 3A inductors in my Raspberry Pi controlled units powered by SMPS. Alternatively, regulate down to 6.5v with the SMPS and then use a linear low drop-out regulator to 5v.

Chinese ATX power supplies are notorious for causing noise on the AC supply because they save a few cents bypassing the chokes in the AC primary side. PFC is often missing too, but that's not much of a problem at lower power levels.

Clive G3GJA

[g0mjw]

I wonder if it is really worth it. ATX supplies are not ideal for most radio applications. You could use it, it's possible, but I wouldn't do it that way. Better take in 12V and use a switching regulator with filtering to get the 5V for the PI and Minitiouner.

[KA5BBC]

Thanks Clive.. I had not realized that the 5V rail is controlling the 12v output beyond the standby rail.. I do plan on some form of filtering and regulation so hopefully will resolve the ripple issue.

Just be aware that only the 5v rail is properly regulated in an ATX power supply.

The 12v rail's voltage depends on the current loading on the 5v rail, so if you are only running an amp or so to feed the 5v kit you may find that the 12v rail is low voltage.

Another thing to be aware of is the ripple. I've used Pi filters of 2 x 22µF low ESR caps (tantalum) and 220µH 3A inductors in my Raspberry Pi controlled units powered by SMPS. Alternatively, regulate down to 6.5v with the SMPS and then use a linear low drop-out regulator to 5v.

Chinese ATX power supplies are notorious for causing noise on the AC supply because they save a few cents bypassing the chokes in the AC primary side. PFC is often missing too, but that's not much of a problem at lower power levels.

Clive G3GJA

[KA5BBC]

I did find a fantastic breakout board on Amazon for $10 which has traces thick enough to handle all the current an ATX supply can give..

PXL_20200926_155647206~2.jpg (1.56 MiB) Viewed 3884 times

[FRANCOIS F1CHF]

hello
did you keep the item number on amazone site ?
thanks

[KA5BBC]

hello
did you keep the item number on amazone site ?
thanks

This is Amazon US but it should be easy to find..
https://www.amazon.com/dp/B01NBU2C64