Convert your sub-woofer to a complete FM radio + USB MP3 player

Computer + sub-woofer is a cheap but decent quality entertainment system in our daily lives. Don’t you feel lazy to turn on your computer just to list to music? Here goes the solution with a simple trick. We are going to convert our sub-woofer to a complete FM radio + USB MP3 player which makes it possible to entertain mp3s on your flash drive and listen to your favorite programs on radio from your sub-woofer alone without turning on your computer or FM radio.

Here goes the process of conversion

We need

1. Ready made USB MP3 + FM radio kit from vire silicon. Various versions are available with a remote controller. (If you are from Sri Lanka you’d find this from Pettah. But this is not yet available in E-Bay as know)

2. Circuit components

Component	Quantity
7805 Voltage regulator	1
22µF 16V Electrolytic capacitor	1
.33 µF Capacitor	1
1KΩ Resistor	1
LED	1
3.5mm Female audio connector	1

3. Small piece of a dotted copper board, connecting wires, some solder, a soldering iron and a plastic box to make the assembly looks great.

All we are going to do is to make a power supply for the USB MP3 + FM radio kit using 7805 regulator and fixing the 3.5mm Female audio connector to the kit.

Step 1: Make the power supply

Here is the circuit diagram for the 5V power supply.

Remember to solder a 2 pin wire connector so that we can connect the power supply directly to the kit.

Image assembled cct

Next question: how we are going to power the small 5V power supply? Yes we can power it from sub-woofer’s power supply itself which make the things handier. Follow the steps given below

Find out whether the power supply of the sub woofer is a AC or DC power supply,(it is mentioned on the separate power supply comes with your device). You have to open the back panel of the sub woofer to perform below steps. So don’t think twice and remove the plastic back panel fitted with screws.

Case 1: DC power supply

Just connect the power supply assembled to the pcb of your sub-woofer where external power connects to the pcb. To resolve plus and minus terminals , just use a multimeter or have a look at the capacitors connected in between + and – lines on the pcb.

If you are not sure how to resolve + and – from a capacitor , here goes how it is done.

Case 2:AC power supply

You have to examine the pcb carefully to find out where the AC power is converted into DC power and you can connect the above circuit to that point. Follow the below steps to find it

Search for the rectifier circuit given below in the figure.



It is not hard to find it and the capacitor shown in the figure will help you to determine plus and minus in terminals.

Solder the 5V power supply to the capacitor terminals.It's all about the power supply part. Please have a look at the next post to see how to complete the project.

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