Friday, March 9, 2018

How to power step up step down transformer

The common application of Power Transformer is simply the power supply and you can find them in any electrical appliances and electronic devices. In daily household products you can simply get power transformers from the following items;

1. Computer power supplies and Laptop charger adapter
2. USB charger plug
3. Bug Zappers / Fly Swatter / Mosquito racket
4. Air-conditioner power supply
5. Refrigerator power supply
6. Printers power supply
7. TV power supply
8. Satellite decoder power supply
9. Audio devices power supply
10. Microwave ovens
11. Modem transformers
11. Monitor power supply
12. Game console power supply (Nintendo, Playstation, XBOX, etc)
13. Any charger plugs.

The fundamental function of transformers in the power supply unit is simply to step down or step up the voltage depending on the power usage by the electrical and electronic appliances. For example transformer in the 5 Volt USB charger is to step down the voltage from 220 volt AC power in the house hold to to 5 Volt use to charge mobile phones. On the other hands transformers in Air conditioner and Refrigerator is step up power from 220 Volt AC to higher voltage like 400 Volt to few thousands volt because they need more power.

If you are looking for a small transformers to salvage just get from any power supply part of the circuit you will find one. Some others have many power supplies ranging from big to smaller sizes - there are used to divide voltages across different sections of the circuit as some circuit require higher voltage and others smaller voltages.

Image below showing a mini transformer to step down 220 Volt AC power from the main household power to 5 volt to charge cell phones and other devices.

Transformers winding type variations:

Apart from being in different sizes transformers winding also comes in many variations depending on the applications. The simplest and most common form of transformer winding is the Step Up and Step Down where there is only primary and secondary coil. Other variation of transformers winding are as follow.

1. Center Tap Primary and Center Tap Secondary
2. Single Primary and Dual Secondary
3. Dual Primary and Center Tap Primary
4. Dual Primary with center tap and single secondary
5. Center tap primary and dual secondary
6. Center tap primary and single secondary
7. Center tap primary and dual secondary with center tap
8. Flyback transformer

Each of these variations have its own functionality and application to provide the needed power to its intended circuit. A simple one is step up transformer is used to supply higher voltage and thus it is called step up. On the other hands step down transformer is used to supply lower voltage but higher current (amp) to the circuit.

Advanced application of transformers can be use as RF mixers, noise reduction in audio amplifier circuits, etc.

How to power up transformer?

The transformers can only be powered up by AC (Alternating current). The reason being is because AC generate magnetic field from the input side of the winding coil to output side. You can open up a and investigate the transformer is not connected by wire directly but instead is wound one or more winding on the input and output side. So the only way to transfer the power from the input winding to the output is to use magnetic force generated by the AC.

Can direct current (DC) batteries powered up a transformer? This is a question that most electronic beginners would ask. The answer is yes but it cannot be powered directly without the help of a circuit. In order to do that we can use a transistor to generate AC like current to power up the transformer. A simple circuit below demonstrate how a simple circuit using a resistor and transistor to power up a step up transformer to convert DC (battery) power to AC power.

As mentioned previously the fundamental function of transformer in the power supply application is either to step up or step down the voltage depending on the intended applications. Below is a diagram of step up transformer winding where the input is from left coil and output is on the right coil. You might want to ask is it possible to power it up the other way around and make it work as step down transformer? The answer is simply YES.

In the early days before i knew anything about transformers it was so difficult to find a specific step up transformers and a step down transformers. Not knowing that either step up or step down transformers actually is almost the same thing and can be used interchangeably. I know this after some experiments of how it really works.

How to test low voltage and high voltage side of the transformer?

Now we know that step up and step down transformers can be used interchangeably - this conclude that we can power up the transformer on either side of the winding. However there is no telling which one of the winding coil side will generate the lower and higher voltage output by just looking at the physical transformer unit itself.

If you simply use the transformer without knowing the output voltage it could ruin your circuit to burnt or having not enough voltage power. Therefore we can use an LCR multimeter to measure the inductance of the winding coil. LCR means (L = Inductance, C=Capacitance, R=Resistance) - so LCR multimeter simply means a multimeter to measure Inductance, Capacitance and Resistance.

Below is a video demonstration how to measure the low voltage and high voltage of the transformer using Inductance measure of the multimeter.

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