This article shows you how to build a special power supply that can give out different amounts of power voltage from 0 to 15V.
It can also provide up to 5 amps of current, which is enough to power many electronic devices.
This power supply is also stabilized, which means the voltage stays steady even if the input power changes a little.
Circuit Working:
Parts List:
| Component | Value | Quantity | Notes |
|---|---|---|---|
| Resistors (1/4 watt) | All resistors are 1/4 watt unless specified | ||
| 1k | 3 | ||
| 10k | 2 | ||
| R6 | 1 | Maximum output current < 5A; value not specified | |
| Potentiometer | 10k | 1 | |
| Preset | 22k | 1 | |
| Capacitors | |||
| Electrolytic | |||
| 4700μF 35V | 2 | ||
| 100μF 25V | 2 | ||
| Semiconductors | |||
| IC | 741 | 1 | |
| Transistors | |||
| 2N2222 | 3 | ||
| 2N3055 | 3 | ||
| BC547 | 3 | ||
| Zener Diodes | |||
| 10V | 2 | ||
| 5.6V | 2 | ||
| Bridge Rectifier | 6A4 | 4 | |
| Transformer | 18V 5A | 1 |
This regulated power supply allows for adjustment within the range of a few volts to 15V using P1, while P2 sets the upper limit to 15V to 0V.
The value of R6 is calculated as 0.7V divided by Imax where Imax represents the maximum current.
For instance, at Imax = 5A R6 is determined to be 0.14Ω.
It is advisable to equip T1 and T2 with heatsinks as power losses can be significant at a low output voltage and Imax equal current.
Formula:
Typically, we employ a linear voltage regulator circuit to construct a Stabilized Adjustable Power Supply utilizing the IC 2N3055, which can offer an output of 0-15V at up to 5A.
When combined with other parts, the 2N3055 transistor functions as a power amplifier or pass element to control the output voltage.
To set the output voltage Vout:
Vout = Vref (1 + R2 / R1)
where,
- Vref: is the reference voltage, which is usually established using a steady voltage reference or a Zener diode.
- R1 and R2: are resistors in the voltage divider network.
To regulate the base current of the 2N3055 transistor and hence restrict the output current, you may use a current sensing resistor in series with the load and utilize the voltage drop across it.
How to Build:
Building the adjustable power supply described requires careful attention to the components and steps involved.
Circuit Connection:
- Connect the input voltage source to the LM317 input pin, and ground it.
- Connect R1 between the LM317 output and adjustment pins.
- Connect R2 between the adjustment pin and ground.
- Connect P1 between the adjustment pin and ground.
- Connect C1 between the adjustment pin and ground.
- Connect C2 between the output pin and ground.
- Connect R3 between the LM317 output and the base of T1.
- Connect R4 between the base of T1 and ground.
- Connect T1collector to the output pin of the LM317 and connect T1 emitter to ground.
- Connect R5 between T1 collector and the base of T2.
- Connect T2 collector to the output pin of the LM317 and connect T2 emitter to ground.
- Connect C3 between the output pin of the LM317 and ground.
- Connect D1 between the output pin of the LM317 and the adjustment pin.
- Connect P2 in parallel with R5 to set the upper voltage limit.
- Calculate and install R6 based on the formula R6 = 0.7V / Imax.
- If using a lamp L connect it in parallel with the output to reduce power losses.
Testing and Adjustment:
- Power up the circuit and measure the output voltage with a multimeter.
- Adjust P1 to set the desired voltage within the specified range.
- Use P2 to set the upper voltage limit e.g.15 to 0V.
- Ensure proper heat dissipation for T1 and T2 by attaching suitable heat sinks.
Precautions:
- Double check connections and component values before powering up.
- Monitor the circuit during initial testing to identify any issues.
- Use appropriate safety measures, such as avoiding short circuits and ensuring correct polarity.
Conclusion:
This is a simplified guide, and it is crucial to refer to the datasheets of specific components and follow safety guidelines when working with electronics.
If you are not experienced with electronics, consider seeking assistance from someone with more expertise.
Users often use such power supplies in electronics labs, workshops or testing environments where a stable and adjustable power source is required for various experiments, prototyping or powering electronic circuits during development.