Hi friends... when my daughter went to Canada to continue her studies in IT engineering, because she played Piano as a good amateur pianist, I thought I should not leave her piano intact, and I should try to play piano, while bearing my age in my mind, this undertaking is a little bit difficult but it is not impossible, so I found YouTube tutorials and downloaded a piece by Dmitri Shostakovitch (Waltz No 2) and sat down on the stool and tried to play, but I quickly realized that I needed to refer to the tutorial repeatedly while I was playing the piece and I thought if I had an amplifier to connect to my cell phone that would be fantastic, so I decided to make one but small one which could be put on the piano top with a connecting wire to my mobile, then I made that and now I am going to explain how I did that.
I had five important goals in making this amplifier which are as follows:
1- Being cheap
2- Being small
3- Easily repairable
4- Easily Chargeable
5- Being portable
This kind of amplifiers are everywhere and you can find their circuits in many sites including Instructables site and making that is not a difficult task but perhaps the most interesting part of the present amplifier is its power supply which is virtually free of charge because use has been made of laptop discarded batteries which are great batteries that makes it portable with a long charging life. Ease of repair comes when you make the housing, which I made it with two sides of that sliding and by removing these two sides everything would be accessible and repairable. Being small is the length of edges are just 13 Cm that is just enough for the loud speakers to be fit in the side, and lastly cheapness comes for the cheap parts used in it and the total price of it has become just $ 7.5 which is pretty cheap.
Step 1: The Circuits
There are two circuits in this amplifier:
1- The amplifier circuit
2- The blinking strip diodes circuit
Both of these circuits were copied from previous works of others but I did some modification in both of them, in blinking diode circuit I changed the power supply to 12 V and the R3 and R4 resistors to 100 k and I have use strip diodes for better light and smarter appearance. In amplifier circuit I have used heat sink because in my first trial the TDA2822M was burnt due to heat and because it is a small IC, I cut a bigger heat sink to 1/3 size to fit it to this IC and stick it with heat conducting glue to the top of the IC.
The specification and pin connections of the TDA2822M is included here which you can use for guidance.
Step 2: Materials and Parts
The list of materials and parts are as follows:
- One, IC TDA2822M with IC socket
- Two, speakers, 3 W and 8 Ohm each
- Two, 10 k Ohm resistors
- Two, 100 uF electrolytic capacitors
-Two, 470 uF electrolytic capacitors
-Two, 4.7 Ohm resistors
-Two, 100 nF ceramic capacitors
-One, 10 uF electrolytic capacitors
-One, 50K Ohm Linear Dual Taper Potentiometer with cap
-One, Audio jack
- One, rocker/toggle switch
-One, small perf. board
- Two, 2 -Pin Cable Wire Terminal Connectors
- Enough wires
2 - Blinking strip diodes
- Two, 10 Cm rigid strip diodes, One red, One green
-Two, 100 Ohm resistors
-Two, BC547 Transistors
-Two, 100 k Ohm resistors
- Two, 10 uF electrolytic capacitors
- One, rocker/toggle switch
- One, small perf. board
-Two, 2 -Pin Cable Wire Terminal Connectors
3 - Batteries for both of the above circuits, three 4 V batteries taken out of a discarded laptop battery and soldered in series to make them 12 V
- A power/ charging jack
- Five, 13 Cm * 13 Cm pieces of poly-carbonate sheet 6 mm thick
- Two, 13 Cm * 13 Cm PVC sheet 3 mm thickness ( i have used two of these sheets for top side)
- One handle ( I have used a spare kitchen cabinet door handle)
- Two pieces of 12 Cm* 12 Cm wire mesh screens with small mesh ( As speakers protective cover)
- 300 Cm of electrical duct with 1 Cm width ( for edges of cube sides)
- 8 screws with nuts for fixing speakers and 4 screws for fixing perf boards to bottom side of the cube.
Step 3: Tools and Related Materials
Tools needed for this project:
1- Soldering Iron and solder
4- 10 Cm Circle cutter
Step 4: How to Make It
1- Amplifier circuit should be implemented according to the circuit diagram on a bread board be tested and later should be soldered to the perf board the IC socket should be used and after the socket and other components soldered up the IC should be inserted in to the socket in right direction and then a piece of heat sink should be glued to the IC top, then after the connection to speakers and battery test the amplifier it should work other wise try to trouble shoot it before you install it in to the housing. assuming you have managed to finish the amplifier part then proceed with the second circuit i.e. blinking diode.
2- Blinking diode circuit should be implemented the same way as the amplifier part,i.e. first on a bread board and then on a perf board, there is not much difficulty here but the transistors should be soldered in a right way other wise it doesn't work properly, again test this part by in both stages i.e. bread board and perf board.
3- making the housing by first making edges by using electrical ducts as if you are making a photo frame and insert those poly carbonate sheets in to the frame and glue them together, for speakers you need to make holes with 10 Cm diameters on two of poly carbonate sheets so to be able to attach the speakers but before that you should install the wire meshes in place. be careful to glue sides in square way to make 90 degree angle between sides. Glue all sides except the front, back and top sides,make appropriate holes for switches, audio jack and charging jack on the front and insert those parts in place and glue them correctly then glue two 10 Cm rigid strip diodes in place on the front side Then screw down both perf boards on the bottom side and leave the assembly aside for next stage. Now you have a cube with two sides not built back and top.
first make a U shape frame from electrical duct and glue them in place to the existing frames and then glue a piece of electrical duct to one side of the last poly carbonate sheet and then insert the sheet in to the slots of the U frame attached in place.
The last part is the top side, first make a U frame out of electrical duct and then glue them on the top to existing frame and then insert the first PVC sheet in to the slots, then attach the door handle to the top PVC sheet and insert in in to the slot to make a tight connection.
If you have thorough look at the photos you can easily find the way to do that unless you use other methods or other materials say wood sheet etc etc
Step 5: The Testing and Enjoying Step
In this step you can test the assembly and enjoy it, try to charge it and see the result.
Hope you like this project and make it for yourself or your friend.
Thank you for your patience