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please give me a schematic to build a power supply for 12 v
coste916

coste916

@copilot please give me a schematic to build a power supply for 12 v
1y

copilot

Sure, I can guide you through building a basic power supply circuit using the LM317T to output a stable 12V. The LM317T is a highly versatile regulator that allows for an output voltage to be precisely adjusted to your desired value using just two resistors.
Given that your project incorporates an LM317T and we're aiming for a 12V output, here's a basic schematic setup:
Components Needed:
  • LM317T Voltage Regulator (U1)
  • Input capacitor (Cin): 0.1uF (C1)
  • Output capacitor (Cout): 1uF (C2)
  • Adjust capacitor (Cadj): 10uF (Optional, improves ripple rejection) (C3)
  • Resistor for setting output voltage (R1): 240 Ohm
  • Resistor for setting output voltage (R2): Adjust as per formula to get 12V output
Connections:
  1. Input Capacitor (Cin) Connection:
    • Connect C1:1 to U1:VI (Pin 3)
    • C1:2 to Ground
  2. Adjust Capacitor (Cadj) Connection (Optional):
    • Connect C3:1 to U1:ADJ (Pin 1)
    • C3:2 to Ground
  3. Output Capacitor (Cout) Connection:
    • Connect C2:1 to U1:VO (Pin 2)
    • C2:2 to Ground
  4. Adjusting Resistor (R1) Connection:
    • Connect one end of R1 to U1:VO (Pin 2)
    • Connect the other end of R1 to U1:ADJ (Pin 1)
  5. Output Resistor (R2) Connection:
    • Connect one end of R2 to U1:ADJ (Pin 1)
    • Connect the other end of R2 to Ground
Voltage Calculation:
To set the LM317 for a 12V output, you'll use the formula for the output voltage of an LM317:
Vout=1.25V×(1+R2R1)+IADJR2V_{\text{out}} = 1.25V \times \left(1 + \frac{R2}{R1}\right) + I_{\text{ADJ}}R2
Assume:
  • Vref=1.25VV_{\text{ref}} = 1.25V
  • IADJ≈0I_{\text{ADJ}} \approx 0 for simplicity, as its contribution is minimal
For a 12V output and given that R1=240ΩR1 = 240\Omega, we rearrange the formula to solve for R2R2:
12V=1.25V×(1+R2240Ω)12V = 1.25V \times \left(1 + \frac{R2}{240\Omega}\right)
R2=(12V/1.25V)−1240ΩR2 = \frac{(12V / 1.25V) - 1}{240\Omega}
Calculating R2 gives us a value of about ( 1.82k\Omega ). A standard value of ( 1.8k\Omega ) for R2 will closely achieve the 12V desired output.
Remember, the input voltage (VI) should be at least 2-3V higher than the desired output voltage due to the dropout voltage of the LM317T, making a minimum input voltage of around 15V advisable for a 12V output.
Please adjust the capacitor values as needed based on your specific applications, especially regarding the input ripple and load requirements. Capacitors with higher values can be used to improve the smoothness of the output voltage if your circuit is sensitive to voltage fluctuations.
1y
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ADJ
VO
VI
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LM317T

LM317T
Description

Created
Last updated by adrian95
2 Contributor(s)
adrian95
javiier

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Properties

Part Type
Integrated Circuit
Manufacturer Name
https://www.st.com/
Manufacturer Part Number
LM317T
Designator Prefix
U

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50–1.2M$0.2174–$1.61
110–185K$0.00
100–14K$0.00–$2.2193
30–38K$0.56–$4.85
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218–1.4M$0.1616–$2.236

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