Adjustable frequency divider

1. Introduction

This circuit divides the frequency of a square wave by 10,20,30....,90. Nine switches are provided to set the frequency division factor. S1 is for 10, S2 is for 20, and so on up to S9.

2. Circuit diagram

Adjustable frequency divider

3.Circuit description

1. Square wave signal is generated by a frequency generator and is given to clk pin of  IC4017 which is a decade ring counter. The way a ring counter works is by turning on and off each of the nine pins on the beat of the clk pulse. The output is in sync with clk pulses. 
2. Switches S1 to S9 determine the division factor. If Sx is on then the signal is divided by 1x. S1=1, S2=2,...S9=9. The end node of all the switches is connected to the reset pin through a positive edge detector. The IC will reset i.e start counting from Q0 as it receives a positive pulse.
3. The divided output from Q0 of IC4017 is further used as a clk pulse for another IC4017 which divides the signal by 10. 
4. Thus the final output from Q0 is divide by 1*10=10, 2*10=20,.....9*10=90. 
5. If you are using it as a looped timmer then a microswitch is used to reset the IC to set the starting point for the timmer. 
6. The output is given to a monostable circuit made by 555 timmer IC. Transistor Q2 along with capacitor and resistor form the positive edge detector which is used to trigger the monostable multivibrator. This is how we get a pulse of fix 'on time' given by formula T=1.11RC. 

4. Circuit working demo

Thank you! hope you find this circuit useful.

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Presettable electronic timmer (crystal oscillator)

 This circuit turns on the output (LED and buzzer) for a short duration after a preset time interval of 10 to 90 seconds in steps of 10. Without the clock signal, this circuit can also be called a square wave frequency divider of divide by 10 to 90.

Circuit diagram:-

 Main components required:-

• Crystal oscillator circuit removed from wrist watch's machine or wall clock's machine.
• 1.5V battery for crystal oscillator circuit.
• Transistor BC547 - 2pcs.
• Dual timmer IC 556.
• Decade counter IC4017 - 2pcs.
• Capacitors, resistors, led, 5V piezo buzzer.
• Microswitch.

Why make this circuit?

• Precise clock pulses of 1sec because of crystal oscillator which oscillates at a frequency of 32,768 times/second. If you want to know, how to use a crystal oscillator from wrist watch then watch this video on my YT channel-  https://youtu.be/kxRkMNUYzdg
•  Set time interval from 10 to 90 seconds by input switches. No need of using RC network for time setting. Frequency is divided by cascading two 4017IC (decade counter)
• No need to buy relatively expensive microcontrollers to provide precise timing pulses.

Applications:-

• In Factories and industries where timing signals are required to drive an electrical valve, motor, relays, etc.
• Timing signals for an indication for eg- blinking tail light, workout timmer,
• Measuring pulse rate. beats per minute (bpm)
• Measuring RPM of the motor.

Working demo video:-  https://youtu.be/UKywmi5A__U

If you found this blog useful and want to support me, then you can donate me. The money you give will be used to make more advance electronics projects and setting up better lab.