Test UM3481 musical circuit

The M348X series IC is a mask-ROM-programmed multi melody generator , implemented by CMOS technology.It is designed to play the melody according to the previously programmed information and is capable of generating 16 songs with 3 instrument effects : piano, organ and mandolin. The device also includes a pre-amplifier which provides a simple interface to  the driver circuit. The M3481 series is intended for applications such as toys, door bells, music box, melody clock/timers and telephones. (more…)

Dark sensor using two transistors

This works same as the other dark detector circuit. When light is falling on LDR, its low resistance drives transistor Q1-BC547 into conduction. This keeps transistor Q2 cut-off due to low base bias. The D1-LED does not get power as long as ambient light falls on LDR. When the resistance of LDR becomes high in darkness, transistor Q1 stops conducting and transistor Q2 starts conducting to turn on the D1-LED.

Datasheet of BC547: http://www.datasheetcatalog.org/datasheet/fairchild/BC547.pdf

Click the video below to see the output.


 Components for this experiment are available at buildcircuit.net.

components 2

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Light operated switch

Light operated switch works with NE555 timer and light dependent resistor. It uses relay and toggle switch idea for operation.

Remote Operated Switch

When you press an infrared transmitter or normal TV remote control near TSOP1738 infrared sensor, the 555 timer configured in monostable mode gets triggered.

Up Counter

An up counter simply counts from 0 to 9. We can use this circuit to make digital object counter. This circuit can also be used to make a digital clock.

Basic RC circuit

For the circuit to work as light operated musical bell, we need to connect the SW1- switch to N/C terminal of relay. LDR has to be kept in a dark case.

FM transmitter and Dark sensor

A dark sensor can be converted to a simple FM transmitter using the following components. This FM transmitter is very sensitive and it has transmitting range of 30 meters.

Telephone misuse indicator

When the phone line is in idle condition (on hook), the full voltage of 48V DC from the exchange appears across the line. When the phone is engaged by lifting the hand set, the voltage across the line falls down to around 12V. Thus, under idle condition (48V), VR1 is adjusted to give a positive biasing voltage to the base of Q3. As Q3 conducts Q1 gets into reverse bias and stops conduction. If the phone is engaged, Q3 stops conducting due to voltage drop across the lines, and subsequently, Q1 and Q2 starts oscillating and beeping is heard. Thus, this circuit can be used as an indicator for telephone tapping and misuse by an unauthorized person.

AM receiver from dark sensor

In this case, LDR has been replaced with capacitor C1-0.01uF and resistor R3-1K has been replaced with L1 & VC1. In place of a LED, a Piezo Diaphragm has been kept.

We just need to add inductor, capacitor and a piezo diaphragm to convert a dark detector to an AM radio.

Mode of NE555- Astable

This circuit has been configured in Astable mode. The output pulses are determined by the values of resistors R1, R2 and the timing capacitor C1. The formula for the frequency of pulses is: f= 1.44/[(R1+2R2)*C1].

Sound generator and Musical toy organ

One of the main objectives of LDR Engineering projects is to make students capable of developing their own logic for making devices. Here is an example that tells how LDR Engineering helps in developing ideas.

How to use variable resistors

There are 3 pins/terminals on a preset. The maximum resistance that a preset can provide is written on it. If 100K is written on preset, it means that we can vary its resistance from 0 Ohm to 100K. A movable metal is rotated in clockwise or anticlockwise direction that changes the resistance of preset.

OR-gate realization

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator.
As we block the light falling on LDR, the calculator starts counting.
For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys.

Object counter using LDR and calculator

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator.
As we block the light falling on LDR, the calculator starts counting.
For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys.

Water Level Indicator

We can use the logic of making an automatic light detector to make a simple water level indicator.We just need to remove LDR from the circuit and put the wires into water, then it simply works as water level indicator. There is a specific resistance between the wires that are dipped into water and conduction of electricity through water gives biasing voltage to base of transistor.

The sensitivity can be adjusted using VR1. Put 470K variable resistance in VR1.

Multivibrator

A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as light
emitting diodes, timers and flip-flops.

Remote Tester

Remote tester circuit also resembles the logic of a “dark sensor (using BC557)”. LDR has been replaced with IR sensor TSOP 1738. The circuit works as a remote tester. Pressing a remote control switch near the IR sensor, switches on the LED D2.

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