Frequency generator is a circuit which generates frequency and divider circuit divides the generated frequency with various factors to get different frequency value. Various assembled frequency generator and divider circuit is available in market but that are quite expensive to buy. The group of electronics geek at dreamlover technology designs a low cost square wave signal generator and divider circuit. The frequency of 1 Hz, 10 Hz, 100 Hz, 1 KHz, 100 KHz and 1 MHz are obtained at output. The output pulse are selected by rotary switch SW1 and fed to an output jack for output.
Circuit Description of Frequency Generator and Divider Circuit
The circuit of frequency generator and divider circuit is build around decade counter ICs (7490), hex inverter IC (7404) and of course crystal oscillator XTAL1 of 10 MHz. IC3 through IC9 is a 4-bit ripple-type decade counter. A divide-by-two section and a divide-by-five section are formed by for master/slave flip-flop internally in each IC 7490. In order to change output stage of the counter on a high-to-low transition each section has a separate clock input. The internal ripple delays do not change output stage simultaneously. Therefore the decade output signals are subjected to decoding spikes and should not used for clock or strobes.
In frequency generator and divider circuit IC3 through IC9 is configured as divide by-10 counters because the output of the divide-by-two section is not internally connected to the succeeding stage.
A crystal oscillator XTAL1 with its associated circuits consist IC2 (7404) and few passive components generates 10 MHz clock pulse. The output from pin 6 of IC2 is given to pin 1 of IC3, which divides it by 10 to give a 1 MHz clock pulse at its output pin 12. The 1 MHz clock pulse is fed to pin 1 of IC4 and parallel output is connected to a pin of rotary switch as shown in circuit diagram. Similarly the output from each decade counter is given to the input of the next stage as above up to IC9.
The blinking of LED2 indicates the output frequency. However, we can identify only 1 Hz and 10 Hz frequency because above this frequency, the blinking rate is so fast that it is not possible to estimate the frequency.
Power Supply :- The input AC of 230V is step down to 9V using transformer X1 which further rectified by bridge rectifier build using diode D1 through D4. The rectified output is further filtered using capacitor C1 and is given to input of IC1 (5 volt regulator IC). The regulated 5V is obtained at output pin 3 of IC1 and is indicated by glowing LED1.
PARTS LIST OF FREQUENCY GENERATOR AND DIVIDER CIRCUIT
Resistor (all ¼-watt, ± 5% Carbon)
R1, R2 = 390 Ω
R3 = 1 KΩ
R4 = 220 Ω
C1 = 470 µF/25V
C2 – C10 = 0.1 µF
IC1 = 7805 (+5V regulator IC)
IC2 = 7404 (Hex inverter IC)
IC3 – IC9 = 7490 (4-bit, ripple-type decade counter IC)
D1 – D4 = 1N4007 (rectifier diode)
SW1 = ON/OFF Switch
SW2 = Rotary Switch
X1 = 230V AC primary to 0-9V, 250mA secondary transformer
LED1 and LED2