Wiring panel

There’s been a strategy in market of buying USB powered speakers for laptops. These speakers usually drives power from one available USB port and inputs audio signal from headphone port, thus consuming two ports of a notebook. Lets see how much output these kind of speakers can give.

A USB port delivers maximum 500mA current and at 5Volts, it comes to max 0.5×5=2.5Watts. So, if our circuit eats 0.5-1Watts power, only 1.5Watt is left for speakers output. Now you might ask 1.5watt wouldn’t create much sound. But believe me, under good conditions, this 1.5Watts is much more than expected. And this time we are going to use 0.5Watt-4Ohm x 2nos speakers.


These speakers are flat type having magnet inside them, and available at wholesale electronics shop in around 30rs per piece. For speaker box, use old jumbo matches box like homelite box. And for circuit, you need is an audio amplifier circuit capable of giving 0.5Watt output at each channel.

Here we will use a general purpose stereo amplifier TDA2822M IC, which comes in 8pin DIP package and usually found in mini walk-mans, etc. This IC can give up to 450 mW/channel with 4-ohm loudspeaker at 5V supply which is near our requirement.


The datasheet of TDA2822M can be downloaded in PDF format here (PDF, 362KB). The expense in making this circuit is no more than 25 rupees. Hence the total cost becomes 30+30+25=85rupees, and if we add the cost of wires, jacks etc then it well fits under 100rupees. It’s a very cheap solution when USB speakers in market costs more than 300 rupees.

Electric guitars use coils (guitarists call them pickups or elements) to convert the vibrations of the strings into an electrical signal. Usually, a guitar has more than one element builtin, so that the musician can select with a switch which element or elements are used to generate the signal. Because of the differences in construction of the elements and the varying positions of where they are mounted, each element sounds different. The elements can be roughly divided into two categories. There are the so-called ‘single-coils’ and ‘humbuckers’. Single coil elements are elements that contain one core and coil for each string. Humbuckers can be regarded as two elements that are connected in series. Many humbuckers have four connections (actually two single-coils with two connections each).

These two individual coils are usually interconnected with fixed wiring so that they are always used in series. The circuit proposed here offers the possibility of using a hum-bucker with four connections in no less than four different modes, each of which having its own sound. The only things that have to be changed on the guitar are the wiring and the addition of a four-position switch. The latter requires drilling holes in the guitar of course, but if there is a control cover plate (along the lines of a Fender Stratocaster, for example) then it makes sense to put the switch there. This avoids the need for drilling holes in the wood while keeping an (expensive) guitar reasonably unmarred. The schematic shows what the various things look like, electrically speaking, before and after the multisound modification.