Category Archives: electronics

An easy “Joule Thief” inverter circuit to power an electric torch with two LEDs using only one 1.2 or 1.5 volt (dead) battery

These days, electric torches (flashlights) use LED bulbs. An LED bulb typically requires a minimum 1.85 volts to power on. Usually, a battery of two 1.5 volt cells (providing 3 volts) is used in torches to power them. If the … Continue reading

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Sound-activated LED lights using NPN transistor

What is wrong with the multi-colored LED light? Is it real? I have started experimenting with transistors. The amplified AC sound signal forked from the speaker (connected to the base) is enough to turn the transistor on.  The supply voltage … Continue reading

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How to create a cheap DIY backlit keyboard

Well, it is not really backlit. It is rather “overlit”. I took a clear-plastic-and-cardboard case, added a few LED bulbs and a transistor and connected them to 5 volts from a USB port. It is a cheap solution but far … Continue reading

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How to power 12v LED strip using 5v USB port – add a step-up transformer

USB ports supply 5 volts. The 12v LED strip requires at least 9 volts. I bought a step-up DC-to-DC boost transformer circuit which can step up from 1.5v and up it up 24 or 32 volts. It took 5 volts … Continue reading

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Low-cost DIY portable emergency light using LED strips & 9-volt rechargeable batteries

The white LED strips operate at 12 volts. They will light up even at at 9 volts but will be less brighter. The multi-colored LEDs are not really an emergency lighting option but are good enough to help you find … Continue reading

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LM386 amplifier in stereo & a repurposed tablet battery

LM386 is a mono amplifier IC. I couldn’t find a stereo version of it that was just as robust and simple. So, I designed a circuit with two LM386 chips. That was several months ago. In the meantime, my BlackBerry … Continue reading

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The best LM386 video tutorial ever!

Add a 1000 uF polarised capacitor between the positive and negative rails to eliminate noise that occurs when the voltage source is from an AC-DC adapter.

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