DIY 3D Printer from scratch – Power Supply

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DIY 3D Printer from scratch – Power Supply
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Welcome to, this article is part of the DIY 3D Printer from scratch, and we will learn how to choose the best 3D Printer Power Supply.



What are the available kinds of power supply?

There are two main kinds of power supply available, we will focus on the Switch-mode because of its efficiency, but is always good to know the other option.

Switch-mode power supplies:

Nowadays  practically all power supplies within the power range required by RepRap printers (250~350W) are switch-mode power supplies (as opposed to linear power supplies, which are considered technologically outdated).

Switch-mode power supplies have relatively complex circuits that convert mains AC electricity to the DC voltages required by RepRap steppers and electronic circuits. The main advantage of an Swith-mode power supply is its high-efficiency in converting energy.  for more information you might want to take a look at this full explanation

There is also this video, it talks about step-up converters, they are NOT the same, but the logic behind it is, and its easier to understand:

Linear power supplies:

This kind of power supply usually use a transformer to reduce the AC voltage, to about 16V AC, then a rectifier circuit will take care of converting the AC voltage into DC, and a stabilizer circuit will make it stable.

The disadvantage of this system is its low efficiency, high cost and taking huge amounts of space. You can read more about this here

How to choose the you switched power supply model?

There are two main models of switched power supply available, the ATX and the INDUSTRIAL (also known as CCTV or OEM). we wont talk about Xbox/Playstation power supply because they are simply the same, with less power output and worse cooling.

Industrial PSU’s

Power Supply

Industrial PSUs are switch-mode PSUs designed to supply a fixed DC 12V or 24V rail with  high current capabilities (1A to 100A or even more). In the last couple of years, due to the development of LED lighting and CCTV, they have become relatively inexpensive and are now widely available. There are many models available, some with extremely good output, some not.  you might want to check the reviews that the PSU got.

Main advantages:

  • Cheap (30A is about 20-50$)
  • Regulated output voltage between 9-16v
  • Regulated fan (less noise when not in use)
  • Easily replaceable (under 5 min)
  • widely available



ATX PSU’s also are switch-mode PSUs designed to supply some fixed voltages to be used in a computer. In our case we only use the DC 12V output.  Usually the ATX have a medium range current capabilities (from 20 to 40A), that are the required to run a computer properly. ATX power supply have the advantage of being extensively used, every computer has one, for this reason they are extremely cheap, while having great protection and output stability.

Main advantages:

  • Cheap (400w is about 20-50$)
  • Wide range of fixed voltages ( -12V; -5V, 0V or GND, +3.3V; +5V and +12V)
  • Great protections embedded (short-circuit, wrong voltage input, wrong frequency input)
  • Easily replaceable (under 5 min)
  • Power factor correction
  • widely available
  • can be turned off automatically at the end of a printing (see more)

There are two main disadvantages of using this kind of power supply:

  • it takes more space.
  • The total output is divided between all the voltages, meaning: in a 500W PSU, you might only have 300 available to the 12v rail.
  • Soldering skills needed (or at least tools and a connection board) to assemble and make it work.

Power factor correction, why this matters (or don’t) ?

Power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit. This is confusing right? Let me explain better, take a look at this two kinds of power:

  • Working Power – which is converted into useful work such as turning motors or producing light.  This power is also called “Active” or “Real” power. It is measured in watts (W).
  • Non-working Power – which doesn’t do useful work and is only used to “energise” the magnetic or electrostatic properties of the equipment. This power is also called “Reactive” power. It is measured in volt-amperes-reactive (VAr).

Now we will use the beer analogy:

The total content of the glass – beer and froth – represents the Total Power.

The froth, representing Non-working Power, does nothing to quench your thirst.

The beer, representing Working Power, does quench your thirst.

To get greatest value for money from the glass of beer it needs to be full of beer with no froth.


Now, going back to electricity terms:

Now you must be thinking:  “Right, i understood why a PSU with power factor correction is good, but if i remember well, only inductive or capacitive loads gets affected by this, right?” Yes. the steppers are inductive loads, and although they wont create a big phase dislocation, the price of an PSU with embedded active correction is almost the same as one without.

TL;DR:  It’s good to use a PSU with PFC, but not mandatory!.

PSU Efficiency and why it matters!

If my PSU is rated for 80% efficiency, where does the other 20% go?

Simple answer: Heat. Any electricity not converted from AC to DC is given off as heat (loss).

Will there ever be 100% efficient Power Supplies?

Simple answer: Everything in the universe loses energy in some way (heat, radiation, light, etc). so it’s physically impossible. However we can get close, there are systems with 98% of efficiency.  (i’ll not enter the strange world of superconductors or the quantum universe, since its simply a PSU for 3Dprinting, and not a nuclear fusion generator for an mars mining base…)

If I have a 500w PSU, does that mean it will always draw 500w of power?

No. The amount of power drawn is determined by the components of the 3D Printer and how much they require. The amount of power drawn will only be equal to what is needed, and no more. If all the components require 300w to run, then the “load” on the PSU will be 300w and hence the power draw of the PC will always be 300w+Inefficiency no matter if it is a 500w PSU or 1000w.


How to choose the most efficient PSU? What the 80 Plus ratings mean?

The basic 80 Plus rating means that the PSU is rated for at least 80% efficiency at 20% load, 50% load, and 100% load.

The 80 Plus Bronze rating means that the PSU is rated for at least 82% efficiency at 20% load, 85% at 50% load, and 82% at 100% load.

The 80 Plus Silver rating means that the PSU is rated for at least 85% efficiency at 20% load, 88% at 50% load, and 85% at 100% load.

The 80 Plus Gold rating means that the PSU is rated for at least 87% efficiency at 20% load, 90% at 50% load, and 87% at 100% load.

The 80 Plus Platinum(Extremely rare and expensive) rating means that the PSU is rated for at least 90% efficiency at 20% load, 92% at 50% load, and 89% at 100% load.


What is in it for me?

Good question! Take a look at these quick charts to show how much you save in a year over a standard 80% efficient 80 Plus PSU by going with an 80 Plus Bronze/Silver/Gold/Platinum

Some information about these charts.

This assumes a 12 Cent/KwH energy rate, if you pay more for your electricity, then the numbers will be slightly higher.

This also assumes the computer is running an average of 10 hours per day, again if your 3D Printer printing takes longer, then your savings will be greater.

Also remember, “load” in that chart is the percentage load of the capability of the PSU. So 20% load on the 500w PSU would be 100w, that is actually a pretty good area for where a printer would be idle.



Now, to finish this article i’ll say my opinion (please read the “personal opinion again”)
Which power supply you think is the best to use Italo?
answer:  ATX Power supply with 80Plus Gold
How much watts do i need?
For a printer WITHOUT Heated bed:  200W
For a printer with 20×20 Heated bed:  400W
For a printer with 30×30 Heated bed: 600W
For a printer with 40×40 Heated bed: 200W+, Bed powered by 220v AC using a SSR to control it.
since using higher power PSU will be a waste of money and power.
Which one you think is the best? comment below and share your ideas!,
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Comments 7

    • Profile photo of Italo Soares

      There is a guy here in brazil that makes high volume printers, but both the printer, and the operating costs are way too high.

      The printer itself is about R$30.000 (something around $9000 USD). and to power this monster is needed 4kWh to the heated bed. (if you print with PLA its not needed).
      Is uses a nozzle of 1mm, because printing the full volume on a 0.4mm would take about 8 months, with an 1mm nozzle is about 15 days.

      The printer itself is simple, you might want to see the hypercube project.
      you will only need to use bigger aluminium extrusions (on the length).

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