Using soldering skills, here we are going to construct a simple musical bell using very basic components.

Material needed: card board/vinyl board or any other hard board

Speaker 8 ohm, IC UM 66, Transistor BC 548, Cell holder, 2 pencil cell

    1. Take a board. Paint or color it if you want. Draw the circuit diagram of musical bell on it. Label all the components. Mark three dots for UM 66 and BC 548 and two dots for cell holder.Musical Bell
    2. Have a look at the speaker. The base of the speaker is a circle. Trace the outline of the base of speaker on the speaker’s symbol in the diagram.
    3. With the help of tweezers, puncture the holes on the speaker’s outline. Remove the card board and now you can fix your speaker here.
    4. Note that UM 66 and transistor BC548 are shaped like semi circle. Both the components have curved body on one side and flat on the opposite side. Components no. is written on flat side. With the help of tweezers make three holes, where you have to insert these two components.
    5. Insert UM 66 at its place. The flat side of the component should be facing towards the flat side in the circuit diagram.
    6. Insert transistor BC 548 with its semi circle shape matching that of the circuit diagram. The Base, emitter and Collector of Transistor are marked as B, E and C respectively in the diagram.6
    7. Invert the board and label the components and pins of the components.7
    8. Mark the connections as per wiring sequence on the back of the board. We can also write the wiring sequence for our convenience. Now we can join these connections by using soldering and connecting wire. The connections to be made are joined as lines.
    9. For joining of components, first and foremost thing is preparing the connecting wire. There are three steps involved in preparing the wire before soldering.Cut; Peel; Twist
    10. Measure the length of insulating wire such that the legs of the components are connected comfortably. They should not stretch. Cut the wire slightly bigger then that length for making connections. Peel 1 cm insulation from both ends of the wire using wire stripper.
    11. Twist the uninsulated ends of the wire with the help of your fingers, so that no strand is protruding out from the tip of the wire. Your wire is ready to be soldered now.
    12. Heat up the soldering iron, clean its tip. Check the soldering iron using solder wire – if it melts, the iron is ready. Hold the iron as you hold a pen or pencil in your active hand and solder wire in the other and solder the connection. Join Base (B) of transistor to Pin 1 of UM 66.
    13. Similarly join transistor pin (E) to pin 3 of UM 66. Pin 3 has two connections, one to the emitter and other to the negative of the cell holder. So take out two wires from pin 3.
      13.1 13.2 13.3
    14. Take out two wires from Pin 2 of UM 66, one for the speaker and other for the positive of cell holder.
    15. Solder one wire from pin C of transistor (brown). One wire from pin 2 of UM 66 (blue) and wire from pin C (brown) is to be soldered to speaker. Pass brown and blue wires through the hole made for fixing the speaker and invert the board.
    16. Solder both wires to the two ends of the speaker. A speaker does not have polarity. Any wire can be soldered to any end of the speaker. 16.4
    17. Now comes the energizing part of the circuit. Connect Pin 2 of UM 66 to the positive of the cell holder and pin 3 to the negative of the cell holder. Soldering on cell holder is very sensitive and needs extra precautions.Steps to solder cell holder. A cell holder has two metallic edges at one end. Hold the cell holder in such position that metallic edges face upside. Put some solder on these metallic edges. Care should be taken that hot solder iron does not touch the plastic body of the cell holder.
      17.1 17.2
    18. Take blue wire from pin 2 and black wire from pin 3. Prepare them for soldering (cut, peel, wrap). Apply some solder wire on the uninsulated part of the connecting wire using hot iron. This process is called tinning. Now keep blue wire on positive terminal of the cell holder and using soldering iron, join the wire to the terminal. The terminal of the cell holder with the spring attached is the negative terminal. Join the black wire to that terminal.
      18.1 18.2 18.3 18.4
    19. Your circuit is complete. Insert two pencil cells in the cell holder.19

Here comes the soulful, melodious tune. Enjoy!!!