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I have a bunch of 5V devices (Raspberry Pi and Arduino devices, and LED strips) that need a power supply. I'm currently using a bunch of transformers from BTF Lighting (the ones shown on the image below, not the black ones) which work well, but have one major caveat: they all consume four to five watts of power, even when not powering anything at all.

enter image description here

When the number of those devices is limited, this is not a big deal. However, as I do more and more “smart home”-type projects, 5W multiplied by the number of transformers remaining on permanently starts to be problematic.

Ordinary phone USB chargers have a consumption of less than 0.1W when not powering anything. I would be glad to use them, but they are mostly rated 2A or 3A. This is perfectly fine if I need to power a Raspberry Pi, but not OK for a LED strip (5V, 4A transformers from BTF Lighting were heating a lot when used with one strip + Raspberry Pi + Arduino, so I'm relying on 5V, 12A transformers, or on 20A transformers when needed).

So, where can I find a transformer which would match the following requirements?

  1. Be as energy efficient as the high quality USB phone chargers.
  2. Have the same format as the transformers on the image above (i.e. screw connectors).
  3. Have 5V 12A and 5V 20A variants.
  4. Include over-voltage protection and short-circuit protection.
  5. Cost less than $40.
  • Except for #2 a standard ATX power supply for a PC. If you can find a small PCB with screw adapters, you can cut off the molex/sata end solder them to the PCB. Short the 2 pins together on the ATX 20/24 pin plug and you have power. – cybernard Nov 13 '19 at 18:09
  • @cybernard: you may consider posting that as an answer, since it is one. – Arseni Mourzenko Nov 13 '19 at 18:11
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Except for #2 a standard ATX power supply for a PC. If you can find a small PCB with screw adapters, you can cut off the molex/sata end solder them to the PCB. Short the 2 pins together on the ATX 20/24 pin plug and you have power.

I know this adapter is $10 + $3 shipping and handling, but it works with any ATX PSU. enter image description here

https://www.amazon.com/20-pin-Supply-Breakout-Module-terminal/dp/B07KDX5CK8

So that plus the PSU could put you slightly over the budget, but you can re-use the adapter on any future PSU.

Newegg also has

https://www.newegg.com/p/2S7-01JK-0ECN9?Description=power%20supply%20atx&cm_re=power_supply_atx--9SIABKSACR7267--Product

enter image description here

This one has 2 12v which combined would be 29A

https://www.newegg.com/p/N82E16817159046?Description=power%20supply%20atx&cm_re=power_supply_atx--17-159-046--Product

enter image description here

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