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How to calculate power requirements of 3D Printer & safeguard Controller

          Most new users to 3D Printing buy a kit due to the low cost in owning one, however
most do not have any engineering background. This in it's self is not an issue as we
want to encourage new users to this fascinating hobby,
but can cause problems when users decide to modify or upgrade, repair their printer.
The power supply that come's with you printer has some marking on it regarding to the power "WATTS", however most will not show the most important factor the
number of "AMPS" the Power Supply will actually deliver......

 

In this how to I will not go into formulars as to the untrained user would be confusing, and as there are some excellent calculators for ohms law will direct you to them.
However there are some tools and additional components you will need, and recommend you purchase.
Firstly and this is a must, obtain a good quality digital multimeter.

Multimeter
Secondly I do reccoment getting external mosfet switches for the heated bed and hot end.

One thing you will need to know is how to use a multimeter if you have nerver used one,
here is a good video tutorial that will show you how to use a multimeter.

When calculating the amps that is used on the heated bed and the hot end cartridge set the multimeter to ohms.
To read the impedance of the heatbed place the meter probes on the solder tabs relating to the volts  to  be applied and note the value of the reading given by the multimeter.

Heatbed


Do the same with the cartridge by connecting the probes to the wires pertruding from the cartridge.

Cartridge


Using the link below input the results  to find out the number of amps each component will require
 

 

 

Watt Volt Amp Calculator


 

fig2

 

Make a note of the amps shown in the results.
Many would think simple get a power supply to deliver amps a + amps b , but we are not quite ready.
We have to take in consideration all the other components that need to use the power supply, the controller, stepper motors,
sensors, lighting, and auxiliary boards.
The electronic boards, sensors, and lighting will only take a small amount of current between 1 to 3 amps, the stepper motors will draw a maximum of 2 amps.
To obtain the correct number of amps the system required is to make the calculation as if everything is working at the same time.
for example based on 24 v
Heated Bed = 13 amps
hot end cartrage = 1.5 amps
electronics = 3 amps
stepper motors x 5 = 5 amps this is based on 3v stepper motors

Total = 22.5 amps

The figures shown here determine you need a power supply as 24 volts with a minimum wattage of 540 watts to produce the amps required.

I would also add more to the total for future expansion which is down to the discretion of the builder

To protect the Main control board I recommend obtaining an external heatbed mosfet.

fig3

You can also use these on the hotend cartridge heater, but is not necessary.
These devices can withstand higher current, and removes excess load on the main controller.
To connect these devices are much the same as in the image, but differ slightly depending on brand.

fig4

You will have to attach an inline fuse between the power supply and the mosfet closest to the amp value of the heated bed.
For example heatbed at 13 amps = fuse rating of 15 amps.
Here is an example of a power distribution system for my printer where all components have their own fused line.

Fuse System

Power Supply


The images ubove show the power supply and the fused distribution box an earth strap.
You will notice that the power cables coming from the powers supply are of a heavy gauge, and there is a pair for both positive and negative.
This has been done to spread the load across the terminals of the power supply to reduce overload.

Tronxy X5S Build
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Comments 1

Guest - Jonathan Hall on Wednesday, 28 February 2018 14:20

MOSFETS are so cheap and easy to fit that its a shame they dont come with the kits. Always upgrade power supply and add MOSFETS to all my printer kit or otherwise.

MOSFETS are so cheap and easy to fit that its a shame they dont come with the kits. Always upgrade power supply and add MOSFETS to all my printer kit or otherwise.
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Saturday, 15 December 2018

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