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LM317 Adjustable DC Power Supply DIY Kit — 1.25–37V 1.5A, Electronics Teaching & Training
LM317 Adjustable DC Power Supply DIY Kit 1.25–37V 1.5A, Electronics Teaching & Training
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LM317 Adjustable DC Power Supply DIY Kit — 1.25–37V, 1.5A, Electronics Teaching & Training
This LM317-based adjustable DC power supply DIY kit teaches the fundamentals of linear voltage regulation through hands-on PCB assembly. Using the LM317T adjustable positive voltage regulator, the completed circuit provides 1.25V to 37V output at up to 1.5A, adjustable via an onboard potentiometer. The kit includes all components, a pre-drilled PCB, and is ideal for electronics students, hobbyists, and anyone learning about voltage regulation, resistor dividers, and PCB soldering.
Key Specifications (Completed Circuit)
| Parameter | Value |
|---|---|
| Regulator IC | LM317T (TO-220) |
| Output Voltage Range | 1.25V – 37V (adjustable) |
| Max Output Current | 1.5A |
| Input Voltage | Vin = Vout + 3V minimum (max 40V) |
| Regulation Type | Linear (low noise, no switching) |
| Adjustment | Onboard potentiometer |
| Protection | Internal current limiting, thermal shutdown (LM317T) |
| Output Ripple | <1mV (linear regulator, very low noise) |
LM317 Voltage Setting Formula
| R1 (fixed) | R2 (adjust) | Output Voltage |
|---|---|---|
| 240Ω | 0Ω | 1.25V (minimum) |
| 240Ω | 1kΩ | ~6.5V |
| 240Ω | 2.4kΩ | ~13.75V |
| 240Ω | 5kΩ | ~27V |
| 240Ω | Max pot | Up to 37V |
Formula: Vout = 1.25 × (1 + R2/R1) + IADJ × R2, where IADJ ≈ 50μA (negligible)
LM317 Linear Regulator vs LM2596 Buck Converter
| Feature | LM317 (linear) | LM2596 (switching) |
|---|---|---|
| Output noise | Very low (<1mV) | Higher (switching ripple) |
| Efficiency | Low (Vin−Vout × Iout = heat) | High (75–90%) |
| Heat generation | High at large Vin−Vout | Low |
| Best for | Audio, RF, ADC, noise-sensitive circuits | Battery-powered, high-current, efficient |
| Learning value | High (teaches regulation fundamentals) | Lower (IC handles everything) |
Why Choose This LM317 DIY Kit?
- Hands-on learning — teaches voltage regulation, resistor dividers, capacitor filtering, and PCB soldering
- LM317T regulator — industry-standard IC with comprehensive datasheet and application notes
- 1.25–37V adjustable — covers most low-voltage DC supply needs
- Very low output noise — linear regulation ideal for audio, RF, and ADC power supply applications
- All components included — no additional parts needed, solder and use
Frequently Asked Questions
Q: What input voltage do I need for this LM317 kit?
A: LM317T requires a minimum 3V dropout (Vin − Vout ≥ 3V). For a 5V output, use at least 8V input. For a 12V output, use at least 15V input. Maximum input is 40V. Use a DC adapter or transformer + bridge rectifier as the input source. The kit does not include a transformer or AC-DC rectifier.
Q: Why does the LM317 get hot during operation?
A: LM317 is a linear regulator — it dissipates the voltage difference as heat: P = (Vin − Vout) × Iout. At 12V input, 5V output, 1A: P = (12−5) × 1 = 7W. This requires a heatsink on the LM317T TO-220 package. Always attach a heatsink when operating above 500mA or with large input-output voltage differences.
Q: Can I use this kit as a bench power supply?
A: Yes — the completed kit functions as a simple adjustable bench supply. For a complete bench supply, add a voltmeter (0.28" LED panel meter) to monitor output voltage, a current meter for load current, and an input from a 24–40V DC adapter. The LM317 kit provides the regulation stage; add input filtering and output protection as needed.
Package Contents
- 1× LM317 Adjustable Power Supply DIY Kit (all components + PCB, unassembled)
