Electronic Harmonium Circuit is a simple circuit that generates 15 different notes. The modern electronics presents this Electronic Harmonium as a hobby kit for people who are interested to have hands on experience in this field. This Electronic Harmonium can generate 15 different notes of music (one at a time). It has a PCB with 15 parallel copper strips. Each strip corresponds to one note. So as the probe is put on a strip, the instrument plays a corresponding note. The circuit is build around IC1, which is used as a stable multi-vibrator. The frequency produced depends on the note selected by the probe. When we put the probe on different strips, we are effectively changing the frequency by changing the resistance between pin7 and pin2 of IC1.

About the Circuit :
IC1 as shown in the circuit diagram is wired as an astable multivibrator. When the voltage at trigger input pin2 of IC1 is below 1/3Vcc, output at pin3 changes its state from low to high. This is achieved by putting the probe on strip, which changes the voltage level of pin2 below 1/3Vcc and IC is triggered. The IC generates note according to the timing components designed using capacitor C1, resistor R1 and combination of resistors R2 to R16, which are selected using probe. At a particular instance, the combination of R1 and R2 to R16 charges capacitor C3, and voltage across the capacitor keeps on increasing. When it becomes 6V, the threshold voltage at pin6 makes output at pin3 low. Now C3 starts discharging through R2 to R16. As soon as voltage of C3 goes below 1/3Vcc, pin2 sense this voltage and switches output at pin3 from low to high. In this way, we get the square output at pin3 since C3 charges and discharges through R2 to R16. The charge and discharge times can be varied by changing values of combination of resistors from R2 to R16 through probe, which in turn change the charging and discharging periods of C3. Thus, the frequency of oscillation is changed and in turn note is changed.

For a sweet melody sound, it is required to have a symmetrical square wave. Thus, R1 should be kept small as compared to R2 to R16. For making the keyboard, PCB with copper parallel strips on it is readily available. Resistors of 5% tolerance only should be used. A resistance with 10% tolerance can change the note considerably. The circuit uses 9V DC supply, so a battery of 9V should be used for satisfactory operation.

We bring forth Electronic Lucky Number Circuit for our valued clients. Electronic Lucky Number is designed for finding out lucky number. Hobbyists may use Electronic Lucky Number to find their lucky number. When switch S1 is pressed, circuit starts counting and when it is released, it will display the random number on 7-segment display and that will be your lucky no.

About the Circuit :                
Electronic Lucky Number is very simple and easy to use. It is built around clock generator and counter IC as shown in the circuit diagram.

When switch S1 is pressed, IC1, which is a timer IC starts generating clock pulses. The frequency of which is determined by resistor/capacitor network designed around R8-P1/R9/C2. The frequency can be varied with the help of preset P1. Capacitor C1 is charged during this time.

The output clock pulses generated by IC1 at pin3 are given to IC2, which is a decade counter IC. At every clock pulse at pin14 of IC2, starts counting from 0 to 9. This BCD code is converted into 7-segment display by IC3.

Once S1 is released, the capacitor C1 discharges through R8/P1. Thus the frequency of IC1 decreases (and hence the rate of changing figures on the display) and ultimately becomes zero. Once IC1 has totally discharged, thereby, stop the display at a particular figure.

The figure displayed is enhanced by the times for which S1 is pressed. Therefore, the random effect is a natural outcome.

The circuit requires DC power supply of 5V, which is designed using IC4, diodes D1/D2 and capacitor C4.

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Electronic Toss-Up allows users start the toss by simply pushing ON the switch S2 for reset and then S1 for start. The three LED’s will flash randomly and stop at some point glowing one of them finally. Our valued clients can avail Electronic Toss-Up in different specifications at economical price.

About the Circuit :
IC 555 is used to generate clock pulse of settable frequency with the help of VR1. R1, R2, R3, and C1 are used store charge in C1 when you press S1. The charge stored in C1 depends upon the time for which the switch S1 is pressed. The circuit goes on operating till the charge on C1 goes below the trigger level of 555. Resistor R2 helps in discharging C1 when it is at the threshold level and thus avoids false glow by noise.  

The circuit is supposed to activate upon press of a push switch S1.As soon as this is pushed ON, Capacitor C2 start charging from zero level. Output pin 3 switches to HI State by virtue of pin 2 (trigger) being LO. IC4029 UP/DN counter is programmed to count down, decade mode ( by pulling down pin 10 and 9 respectively). At the first clock from pin 3 of 555, the IC 4029 clocks and outputs 2, 14, 11 & 6 go to zero state. Upon switching S2 ON, input states are loaded into outputs (2, 14, 11, 6) .The IC 4028 (one of 10 decoder) decodes and output Q0 goes Hi. On subsequent pulses from 555 the outputs Q2 to Q9 go HI one by one. The outputs are grouped in four, two, and four to glow LED Green, Yellow, and Red. The grouping is done randomly so that LEDs  Grn, Yellow and Red glow at subsequent pulses from 4028 and appear random. Diodes connected to each group (e.g. D1, D2, D3, and D4) forms an OR gate which enables LED to glow even if one of the output from each group is Hi. Resistance R8 is provided to limit LED current.