Transformer turns question

Paul Frost · Jan 23, 2016

i am wanting to make a transformer to turn 240V into 14V, min 3A, i find many complicated formulas online, can someone give me a simple expleanation on how many turns do i need to make, how thick does the wire need to be etc etc... Thank you!!

unksol · Jan 23, 2016

You need to use the formulas. They are pretty simple. If you can't you shouldn't be messing with it as you'll probably electrocute yourself

Ralston18 · Jan 23, 2016

Just "google" something like "How to make a DIY transformer".

There will be a lot of links show up.

Here is one:

http://www.brighthubengineering.com/diy-electronics-devices/96783-designing-your-own-transformer/

The formulas are needed to design the tranformer to meet the requirements. There is no simple explanation beyond just the basics.

There are also safety considerations and you are dealing with potentially lethal voltages/currents.

The time spent learning the forumulas and planning your transformer accordingly will be time well spent.

And you and the transformer will be safer for it. Be careful!

nukemaster · Jan 23, 2016

I would like to point out that you will also have to design for your power usage requirements.

Under light loads you may have MUCH higher than 14 volts and it will drop to 14 as you get to a 3amp load.

Because of this, regulation may be required.

You have 2 options for regulation.

Linear regulators. These types of regulators will eat any extra voltage and release it as heat. They have awful efficiency(even more so when dropping more voltage). These regulators tend to have less noise than switching regulators and are used in sensitive circuits(sometimes after a switching regulator that takes the voltage down the majority of the way).

Switching regulators. In a very basic way these types of regulators rapidly(the frequency depends on the regulator.) turn power on and off so fast that the average voltage seen by the load is regulated. They use capacitors(most regulators have some kind of capacitor on the input and output) and and many times coils to smooth out these rather sharp on off cycles and makes the power less noisy. Switching regulators have VERY high efficiency and generate very little heat even under heavy load when compared to a linear regulator. This means they do not require such large heatsinks.

Switching regulators are found in all computers and used to turn 12 volts into whatever is required.

All regulators require some voltage overhead it can range from just a 1/3rd of a volt or lower to much higher. Many times 1.5-2 volts is standard(it can vary with load). For this reason your transformer also has to have some extra voltage for regulation.

monkeymanz · Jan 23, 2016

The ratio of coilsprimary:coilsecondary is equal to the ratio of voltageprimary:voltagesecondary. That being said, the easiest method is to make a step-down transformer with the primary coil having 240 turns, and the secondary having 14 turns. You can make it easier with 120:7 turns as well. Regarding the 3A, the amperage is dependant on the initial power. With 240 volts and a current of 3A it means you will need 720 watts. After stepping own to 14 volts, the amps will be much higher. Naturally there will be powerloss, so to compensate use thinner wires to reduce resistance while using laminated cores to reduce energy loss from heat.

But the question is why are you making your own transformer when you can just buy it. If you don't know the formulas, then clearly you're not qualified to do something that dangerous.

nukemaster · Jan 23, 2016

I was guessing the 3amp was on the low side

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