Build a simple music greeting card circuit based on UM66TXX

Musical greeting cards are very popular for special occasions all over the world and we have all gifted this thing to our dear ones before. But have you ever tried making one yourself? If not, it’s time to build one. Here is a simple musical greeting circuit that you can easily try at home and the cost required to build this thing is also very low.

Circuit Diagram:

UM66TXX series Integrated circuits :

UM66TXX is a simple CMOS IC specially designed to be used in such simple melody/tone generating circuits. It consists of an on-chip ROM which is programmed with a specific music or tune and is named according to the tune. Since it is produced using CMOS technology, it consumes only less power which proves to be a great advantage. Here is a list of ICs with programmed tones.

UM66T01 – Jingle Bells + Santa Claus is coming to town + We wish you a Merry Christmas

UM66T02 – Jingle Bells

UM66T04 – Jingle Bells + Rudolph the Red-Nosed Reindeer + Joy to the World

UM66T05 – Sweet Home

UM66T06 – Let me call you sweetheart

UM66T08 – Happy Birthday to You

UM66T09 – Wedding March

UM66T11 – Love me tenderly, love me truly

UM66T13 – Easter Heaven

UM66T19 – For Elise

UM66T32 – Waltz

UM66T33 – Mary Had a Little Lamb

UM66T34 – Trains run fastUM66T68

Use of reed switch:

You may have seen musical greeting cards that use a leaf or slider switch that activates the toner when you turn it on. The main problem with these types of switches is that the link weakens over time due to use and the circuit gradually becomes activated even when the card is in the closed position. This can be annoying most of the time.

To overcome the above disadvantages, a reed switch is used here which uses magnetic force for activation. So there won't be any unwanted activation of the tone generator part of our circuit. Place the magnet on one side of the card and the rest of the circuit on the other side. Make sure that the magnet touches the reed switch when the card is closed.

Circuit working principle:

The working of the circuit starts with the reed switch, which activates whenever it comes in contact with a magnet. Holding the magnet to one side of the card, the complete circuit is the other side of the card. When the card is in the closed state, the reed switch will be in the closed state, which makes the base of the PNP transistor to a positive potential, i.e., more than 0.7V, forcing it to the closed state.

The opening of the card will force the magnet to break its attraction and the reed switch will now be in the open state. Resistor R2 will then pull the base to ground potential. This causes the PNP transistor Q2 2N3906 to turn on, which in turn turns on the ICUM66T08.

When the IC is turned on, the output of the IC is fed into the base of the NPN transistor Q1, which provides the required current for the sounding element to work. Finally, we can get the desired tone/melody from the piezoelectric sounder. In the above circuit,

IC UM66T08 which contains the programmed "Happy Birthday to You" tone.

Notice:

You can use a raw leaf or slider switch with the above circuit instead of a reed switch, in which case, eliminate the need for R1, R2 and Q2 and connect the switch end directly to the VCC pin of the IC.

Make sure the magnet and switch are placed in such a way that they touch each other when the card is closed.

The above circuit produces “Happy Birthday Tone”, but if you need any other tone, select the corresponding UM66TXX IC from the list given above.