Home Made 1.5 to 220v Inverter -TechInnovation4u

Home Made 1.5 to 220 v  Inverter

fig: Inverter

In this post we are going to construct a simplest  power inverter whose size is not more than a match box. This mini inverter circuit can operate from 1.5V to 9V DC and can be used for powering small loads like 2W to 5 watt (120/210V) LED bulb. This inverter comprises of just 3 components and even a beginner can accomplish this project with ease. It can be a good project for school science fair or as an emergency light.

Content:

• Circuit diagram of 1.5V to 220V inverter.
• Circuit description.
• Needed Material and its pin diagram.
• Working prototype images and video.
• How this circuit works?

NOTE: There are no clear explanation about its practicality and reliability in real life circumstances and there are no explanation how the circuit works. So, we are here to explain all the aspects of one such inverter, so keep reading on….

Circuit diagram: TESTED

The proposed inverter circuit is very simple and there are only 3 components to be collected to build one: a 330 ohm resistor, a medium power NPN transistor (BD139/BD137/BD135/D882) with transistor a heat sink should be used to protect it from damage and a  USB charger transformer which can be salvaged from a DC adapter. The other two components are the source and load i.e. the battery and a LED lamp (2 watt to 6 watt).

Needed Material and its pin diagram:

We can easily get this type of transfromer into old USB power circuit boards

fig: Mobile Charger

With Transistor we should definitely use a heat sink so that the inverter would least for long time. 

What LED lamp to choose for this inverter?

This inverter has very limited application because of its limited power output and rich in HF noise, the only viable application is to light-up a 120/220V LED lamp whose wattage is rated less than 6W.

A very important point to be noted is that branded LED bulbs won’t work with this inverter.

Branded LED lamps have well designed LED driver which filters out noisy power input. We purchased a well-known reliable brand for testing purpose and it failed to light-up. Later we purchased a brand which was not so well known (it was also much cheaper than the reputed brand) and it lit-up immediately.

So dear readers, if you are building this inverter get a cheap LED bulb with wattage lower than 6W; also don’t connect a LED lamp that is dimmable.  

Prototype:

Here is our prototype, we have tested this circuit using D882 which are medium power transistors and it is working fine.We can also a 470 and 1k ohm resistor at the time of testing this circuit.

The transistor is screwed with a suitable size heat sink; this is because the transistor gets hot and this inverter consumes around 500 mA when a 3 watt LED bulb is connected as load.

Testing at different voltage levels:

• 1.5V input:  At 1.5V our inverter did not light-up the bulb; this could be because our transformer didn’t suit for 1.5V operation or 3 watt load is too much for 1.5V input. But it may work for you for the transformer you salvaged.
• 2.5V input: At 2.5V we could see a dim illumination of the LED bulb.
• 3.5V to 4V input: At 3.5V to 4V input using an 18650 li-ion cell, the bulb was bright enough to light up a small area in a dark room.
• 8V / 9V input: At around 8V input (using two li-ion cells in series) the 3 watt LED bulb was bright enough to read a book in a dark room if you hang the bulb above your head.
• Above 9V: The intensity of illumination did not increase past 9V. We recommend you not to increase the input beyond 9V. We did try raising the input voltage but the transistor got damaged after 10V – 12V and this could be because the base terminal was over biased / the transistor got too hot.

Now you know how to make this inverter and make it work properly, now let’s see how this inverter works.

Pro-tip: Use rechargeable batteries to power this inverter, non-rechargeable batteries get discharged in few minutes. With two li-ion cells we were able to light up a 3 watt bulb for more than 90 minutes.   

Images and video: 

Front view of our project.

back view of our project

In view 0f our project.

Here is the video of our project.

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How this inverter works?

You may refer the circuit diagram along with the below given explanation to understand its working better.

• When you connect the battery, the +Ve supply flows through the 470 ohm resistor and through the auxiliary winding and reaches the base of the transistor. The resistor prevents over biasing of transistor.
• Now the transistor turns ON partially which will weakly energize the secondary winding and induce a small magnetic field on the auxiliary winding.
• The magnetic field induced on the auxiliary winding generates current (stronger than initial current) which will again pass through the base of the transistor, which will turn ON the transistor more and energize the secondary winding even more.
• This higher intensity magnetic field from the secondary will induce even more current on the auxiliary winding which will turn ON the transistor even further.
• While the magnetic field is getting stronger at the core, not only the auxiliary winding is receiving secondary winding’s magnetic field but also the primary winding is receiving the magnetic field.
• At some point the magnetic field gets strong enough such that the primary winding can generate enough voltage to turn on the 3 watt LED lamp.
• The strength of the magnetic field cannot rise forever, once the transistor is fully turned ON and no further changing (rising) magnetic field occurs. At this point magnetic field collapses and transistor turns OFF and the cycle repeats from the beginning of the explanation.
• The rising and collapsing of magnetic field occurs at tens of KHz frequency.

If you have any questions regarding this project, feel free to ask us in the comment section, you will get a guaranteed reply from us.