I am designing a 3D printer. I need 12V and 5 amp for powering the printer extruder and 11 amp for powering the heated bed.

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At the moment I am using the model Model S-240-12 capable of delivering 12V at 20 amp.

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In order to reduce some weight I thought that if I replaced the switching power supply for something smaller it would be great

I was thinking in replacing it for this AC-DC Adapter that says that it can deliver 12V DC at 16 Max:

AC-DC Adapter: 100-240 VAC to 12V 16Amp, 192W

So here I have some doubts.

1) If I am correct if I use the AC-DC Adapter provided in the link, I just need to make a current divider with the ramps and it will work fine, isn't?

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2) The switching power supply has 3 terminals. Is it possible to connect the COM terminal that I want with any of the 3 +V terminal to close the circuit? Or is there an specific order that I have to follow?

3) Every closed connection of the switching power supply terminals is it capable of delivering 20 amp? But if one closed connection at the moment is delivering 20 amp. The other two closed connections are not going to be capable of delivering anything, right?

4) In my local city, it is not possible to find AC-DC adapters capable of delivering 16 amp. The maximum amount of current that I have found is 6 amp. After that if you want something that can deliver more current you need to use an switching power supply. So why is this? How is it possible that this company has an AC-DC adapter with those specifications? Is it legitimate?

  • \$\begingroup\$ i do not see any ATX supply in your pictures ... did you forget to include it? ... ATX is used in computers \$\endgroup\$
    – jsotola
    Apr 22, 2018 at 3:05
  • \$\begingroup\$ I think you are right. It would be a Switching Power Supply \$\endgroup\$
    – Nau
    Apr 22, 2018 at 3:09

2 Answers 2


I think you better keep using the 20A supply that works well. Pulse currents from extruders and stepper motors can be stressful to supplies loaded to the max.

So for reliability and performance, it is better to use a supply rated for 25% more than you need and consider , a longer heavy guage cable if you prefer to remvoe the supply from the fixture but then put an ultralow ESR 16V Cap near the boards DC input to handle the pulse edge's high current.


You are unlikely to find a 16 amp supply in that form factor. The reason you only find 6 amp ones around you is because low voltage high current results in too high a voltage drop and heat over the small cable and connector. This is the same reason your 20 amp supply has 3 V+ and common ground connections, so you can spread the load across them. To answer your questions

  1. You don't need to split them, your load will pull what it needs.

  2. Yes, all the v+ and ground are the same. But you want to divide your load across them. Don't put 20 amps on a single pair.

  3. As mentioned above, no. You get 20 amps between the 3.

  4. See above.

And as Tony mentioned, you don't want to use a supply at its 100% max. 80% is best for long life.


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