An IC 555 is used in a reasonably simple circuit to provide both positive and negative voltage outputs from a single 3V source, such as two AA batteries in a 3V to 9V dual power supply circuit.
The 555 IC set up as an astable multivibrator is used in the circuit.
This indicates that it oscillates a square wave continuously at its output pin 3.
The external resistors and capacitors linked to the IC control the oscillations frequency.
Circuit Working:
Parts List:
| Category | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 1k | 1 | 1/4W |
| 10k | 1 | 1/4W | |
| Capacitors | Ceramic 0.01μF | 1 | |
| Ceramic 470pF | 1 | ||
| Electrolytic 10μF 25V | 2 | ||
| Electrolytic 4.7μF 25V | 2 | ||
| Semiconductors | IC 555 | 1 | |
| Diode 1N4007 | 4 |
This circuit produces two distinct voltage outputs, a positive 9V and a negative 9V using a modest 3V power supply, such as a few batteries using a unique chip called a 555 IC.
The IC 555 can be shown as a heart, a heart beats in a regular rhythm normally.
The IC 555 in this circuit is configured to rapidly flip back and forth on a constant basis, producing a signal that resembles a square wave.
A capacitor, two resistors and a control unit regulate how quickly this switching happens.
There are positive and negative components to the IC 555 square wave signal.
The circuit employs two distinct parts that function as filters: one for each diode and capacitor.
The +9V output is produced by a single filter that only lets the positive portion of the signal pass through.
The -9V output is produced by the other filter, which only lets the negative portion pass through.
For a more stable voltage, the capacitors aid in smoothing out these filtered signals.
This dual in line package DIP based, eight pin device is well known for its stability in producing accurate oscillations or time delays.
Operating on a power source range of 3V to 12V it is very adaptable.
The 555 IC is set up in astable mode in this circuit.
Pins 2 and 6 are coupled internally within the semiconductor to do this.
Because of its special setup the IC may operate constantly functioning much like a free running multivibrator.
A significant factor in influencing the oscillation frequency is an external capacitor C1.
This capacitor charges via resistors R1 and R2 but only R2 allows it to discharge.
The duty cycle or the proportion of the whole cycle time when the output is high is determined by the ratio of these two resistors.
Capacitor C1 charges and discharges between predetermined voltage levels in astable multivibrator mode.
It discharges to ⅓ Vcc after charging to ⅔ of the supply voltage Vcc.
The IC uses these voltage thresholds as control points to transition between high and low output states.
Calculation of IC 555:
period = tH + tL = 0.693(RA+ 2RB) C
frequency = 1.44 / (RA + 2RB) C
Formulas:
To create an astable multivibrator circuit that runs on a dual power supply (3V to 9V) using the IC 555 timer, adhere to the following general formulas:
Frequency (f):
The settings of R1, R2 and C1 define the oscillation frequency in the astable mode:
f = 1.44 / (R1 + 2 * R2) * C1
where,
- F is the frequency in hertz (Hz),
- The resistances in ohms Ω are represented by R1 and R2,
- The capacitance in farads F by C1.
You may use the IC 555 to create an astable multivibrator circuit that runs on two power supplies ranging from 3V to 9V by utilizing the frequency calculation algorithm that is given.
In order to get the required oscillation frequency and performance, adjust component values as needed.
How to Build:
To build a 3V to 9V Dual Power Supply Circuit follow the below mentioned steps for connections:
- Assemble all the components as shown in above diagram.
- Connect pin 1 of IC1 555 to ground.
- Connect pin 2 to pin 6 of IC1 555.
- Connect capacitor C3, C4 and diode D1, D2 between pin 3 of IC 555 and ground to form a voltage doubler circuit to generate the +9V output
- Connect capacitor C5, C6 and diode D3, D4 between pin 3 of IC 555 and ground to form a voltage doubler circuit to generate the -9V output
- Connect pin 4 of IC 555 to positive supply of +3V.
- Connect pin 5 of IC 555 to ground through capacitor C2.
- Connect pin 6 of IC 555 to pin 2 of IC 555.
- Connect pin 7 to positive supply through resistor R1.
- Connect resistor R2 between pin 7 and pin 6 of IC 555.
- Connect a capacitor C1 to ground from pin 2 and pin 6 of IC 555.
- Connect pin 8 of IC 555 to positive supply.
Safety Notes:
- Make sure there is enough light for you to view the wiring and components properly.
- Use wire cutters and soldering irons in a safe and proper manner.
- If at all feasible, have a backup person nearby who can help in case something goes wrong.
- Before powering on the circuit, meticulously check all connections to ensure they match the circuit diagram
Conclusion:
In conclude, a 555 IC based circuit for a dual power supply that ranges from 3V to 9V provides a rather easy method of producing positive and negative voltage outputs from a single low voltage source.
Small electrical projects that need both positive and negative voltage rails may find this helpful.
References:
How can I power a 3.3v circuit with a 9V power supply and two AA batteries?