Today Saiyam over at instructables gives us a great tutorial on how to build your own portable speakers. Here are some of its great features:
The first step is to prepare your enclosure and making holes for all the parts. But before that you must choose the correct enclosure for your project. Since the speakers have to be connected to your phone and have to be supported by just and audio jack, your overall project including your enclosure should be small and lightweight. Make sure that the size is just sufficient for all the parts to fit in easily and should not be too small nor too large. The best option can be to use a small plastic container used to store medicines. They can be cut easily and are cheap. The dimensions of my enclosure were- 10 x 6.5 x 2cm but it can be varied according to your needs. You can even use different materials like wood and acrylic to make your own enclosure.
For preparing your enclosure, first measure all the components and mark them on your box using a marker. Finally drill all the holes. The major things you need to add are- speakers, switch, LED, audio jack and presets. You can also use a hot knife to cut a plastic enclosure.
The amplifier circuit used here is the same as the circuit used in my previous travel speaker project. It consists of an LM386 with some external filter components such as resistors and capacitors. Since two speakers are used in the project, there are two such circuits used. The need for such an amplifier is that the audio signals given out by your phone are too low to drive a speaker loudly and are just sufficient to power an earphone. Amplifiers are present in almost every speaker you see that is in your phone, TVs, stereo systems and even DJs.
For prototyping your circuit refer to the layout above and connect everything according to it. The reason why you should prototype is to check if the circuit works or not and do any modifications. Connect the audio jack to your phone and power the circuit with a 9v battery (or any power supply between 5-15v). On playing a music on your phone, if you hear a loud sound coming from the speaker, that means you have done it alright. If it doesn’t, check the connections and try again.
After prototyping your circuit, solder the whole circuit according to the schematic given above. The best way to solder is to use a perfboard however you can etch your own circuit board or use a copper strip board.
Start by soldering the IC socket first and then all the components. Cut off the excess PCB using a pair of scissors. The need for an IC socket here is to prevent overheating and malfunctioning of the IC when soldering it.
For connecting your speakers, first glue them to the holes that were marked earlier and solder two pieces of wires to each one of them.
Finally connect them to the circuit following the schematic given above. Make sure you connect both of them with the correct polarity.
The power supply used in this project consists of two 3v coin cells connected in series to produce 6v which is enough to power the circuit. The reason that I didn’t use heavier and bigger batteries was that my enclosure was small and there was hardly any space left in it for the battery. Li-po battery was also not used here as it can give only 3.7v while LM386 requires atleast 5v to operate so there would be a need to add two of them which would eventually cost more. However if you wish to modify your project, you can use any power supply/battery between 5-15v.
I added a switch to easily switch the speaker on and off which would not require removing the batteries again and again. First solder both the holders on a piece of perfboard and connect the positive terminal of first holder to the negative terminal of the second. Then connect the positive terminal of the resulted battery pack to pin 1 of your switch. Connect the negative terminal of battery pack directly to the gnd of the circuit. Finally connect pin 2 of the switch to vcc of the circuit.
A power indicator LED is added here to prevent you from forgetting that your speaker is left on overnight which will result in draining out the entire battery. Connect a 1K resistor to the LED and then connect the positive leg of LED to vcc of the circuit and negative leg to gnd.
To check your wiring, add two batteries to the holder and switch the speaker on. You would see the LED lit up.
To add a feature of volume control within the speaker, I added two presets to control the volume of each one of the speakers. The reason why I used preset instead of a potentiometer was that the enclosure was quite small and there was a little space left. The connections were already messy which made it difficult to add them.
Connect your preset according to the following:
Finally glue the presets to the enclosure to the hole that was made earlier.
This the last step to complete your project. To connect your speaker to your phone, there has to be and audio jack to plug it in to your phone. For this project, I chose that the audio jack would be glued on to the speakers with no external wires and would be the only support of your speaker while it is connected to your phone. This would cancel the need of holding the speakers with your hand while playing music.
For connecting the jack, first connect it to the circuitry according to the following connections:
Finally glue tightly the jack to the hole that was made earlier. Make sure that it doesn’t come out even on pulling it.
Tags: DIY Mobile Speakers
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