In the event, we need to build a variable DC power supply that output of 1A and can adjust up to about 30V.

Most people will use LM317 because of high-efficiency, easy to apply and cheaper

**Description**

It has an adjustable 3-terminal positive voltage regulator designed to supply more than 1.5 A of load current with an output voltage adjustable over a 1.2V to 37V range.

It has an internal current limiting, temperature detects shutdown and safe area compensation.

### LM317 pinout

**Figure 1: LM317 pinout on TO-220**

Look:

**Connection Diagram various LM317 Pinout**

LM317T on TO-220: output 1.5A

LM317L on TO-92: output 100mA

LM317K on TO-3: output 1.5A

LM317 on DPARK: output 1.5A

### Basic Features

- Output current in excess of 1.5A
- Output-Adjustable between 1.2V and 37V
- Internal Short-Circuit Current Limiting or Output is short-circuit protected
- Internal Thermal Overload Protection or Current limit constant with temperature
- Output-Transistor Safe Operating Area Compensation
- TO-220 Package like 2SC1061 transistors.
- There are 1% output voltage Durability
- There are max. 0.01%/V line regulation(LM317), and 0.3% load regulation (LM117)
- There are 80 dB ripple rejection

**Figure 2 the basic circuit diagram**

**Basic circuit diagram**

If the power supply filter has distance from IC-regulator too much. Tt should insert Ci to lower noise before IC-input.

Next in the figure circuit. The Co is not needs if you do not high-efficiency, but we put it better. It will keep lower an output ripple.

As Iadj is controlled to less than 100uA, the little error Unimportant in most applications.

The input voltage to the LM317 must be at least 1.5v greater than the output voltage.

## LM317 calculator

This **calculator** will work for most DC Voltage Regulators with a reference voltage (VREF) of 1.25. Typically, the program resistor (R1) is 240 ohms for the LM117, LM317, LM138, and LM150.

Some said Iadj is very low current.

So, we may reduce it down. To be shorter and easy.

Vout = 1.25V x {1+R2/R1}

Which is better?

For example:

You use R1 = 270 ohms and R2= 390 ohms. It causes output is 3.06V

Is it easy? If you have voltages choice with most resistors. In local stores near you.

look at the list:

### Output Voltage with R1 and R2 List

1.43V : R1 = 470Ω, R2 = 68Ω

1.47V : R1 = 470Ω, R2 = 82Ω

1.47V : R1 = 390Ω, R2 = 68Ω

1.51V : R1 = 330Ω, R2 = 68Ω

1.51V : R1 = 390Ω, R2 = 82Ω

1.52V : R1 = 470Ω, R2 = 100Ω

1.53V : R1 = 390Ω, R2 = 82Ω

1.56V : R1 = 330Ω, R2 = 82Ω

1.57V : R1 = 270Ω, R2 = 68Ω

1.57V : R1 = 470Ω, R2 = 120Ω

1.57V : R1 = 390Ω, R2 = 100Ω

1.59V : R1 = 390Ω, R2 = 100Ω

1.60V : R1 = 240Ω, R2 = 68Ω

1.63V : R1 = 330Ω, R2 = 100Ω

1.63V : R1 = 270Ω, R2 = 82Ω

1.64V : R1 = 390Ω, R2 = 120Ω

1.64V : R1 = 220Ω, R2 = 68Ω

1.65V : R1 = 470Ω, R2 = 150Ω

1.66V : R1 = 390Ω, R2 = 120Ω

1.68V : R1 = 240Ω, R2 = 82Ω

1.71V : R1 = 330Ω, R2 = 120Ω

1.71V : R1 = 270Ω, R2 = 100Ω

1.72V : R1 = 220Ω, R2 = 82Ω

1.72V : R1 = 180Ω, R2 = 68Ω

1.73V : R1 = 470Ω, R2 = 180Ω

1.73V : R1 = 390Ω, R2 = 150Ω

1.76V : R1 = 390Ω, R2 = 150Ω

1.77V : R1 = 240Ω, R2 = 100Ω

1.81V : R1 = 270Ω, R2 = 120Ω

1.82V : R1 = 150Ω, R2 = 68Ω

1.82V : R1 = 330Ω, R2 = 150Ω

1.82V : R1 = 180Ω, R2 = 82Ω

1.83V : R1 = 390Ω, R2 = 180Ω

1.84V : R1 = 470Ω, R2 = 220Ω

1.86V : R1 = 390Ω, R2 = 180Ω

1.88V : R1 = 240Ω, R2 = 120Ω

1.89V : R1 = 470Ω, R2 = 240Ω

1.93V : R1 = 330Ω, R2 = 180Ω

1.93V : R1 = 150Ω, R2 = 82Ω

1.94V : R1 = 270Ω, R2 = 150Ω

1.96V : R1 = 390Ω, R2 = 220Ω

1.97V : R1 = 470Ω, R2 = 270Ω

1.99V : R1 = 390Ω, R2 = 220Ω

2.02V : R1 = 390Ω, R2 = 240Ω

2.03V : R1 = 240Ω, R2 = 150Ω

2.06V : R1 = 390Ω, R2 = 240Ω

2.08V : R1 = 330Ω, R2 = 220Ω

2.10V : R1 = 220Ω, R2 = 150Ω

2.12V : R1 = 390Ω, R2 = 270Ω

2.13V : R1 = 470Ω, R2 = 330Ω

2.16V : R1 = 330Ω, R2 = 240Ω

2.16V : R1 = 390Ω, R2 = 270Ω

2.19V : R1 = 240Ω, R2 = 180Ω

2.23V : R1 = 470Ω, R2 = 390Ω

2.25V : R1 = 150Ω, R2 = 120Ω

2.27V : R1 = 270Ω, R2 = 220Ω

2.27V : R1 = 330Ω, R2 = 270Ω

2.29V : R1 = 470Ω, R2 = 390Ω

2.29V : R1 = 180Ω, R2 = 150Ω

2.31V : R1 = 390Ω, R2 = 330Ω

2.36V : R1 = 270Ω, R2 = 240Ω

2.37V : R1 = 390Ω, R2 = 330Ω

2.40V : R1 = 240Ω, R2 = 220Ω

2.44V : R1 = 390Ω, R2 = 390Ω

2.50V : R1 = 470Ω, R2 = 470Ω

2.57V : R1 = 390Ω, R2 = 390Ω

2.61V : R1 = 220Ω, R2 = 240Ω

2.65V : R1 = 330Ω, R2 = 390Ω

2.66V : R1 = 240Ω, R2 = 270Ω

2.73V : R1 = 330Ω, R2 = 390Ω

2.74V : R1 = 470Ω, R2 = 560Ω

2.75V : R1 = 150Ω, R2 = 180Ω

2.76V : R1 = 390Ω, R2 = 470Ω

2.78V : R1 = 270Ω, R2 = 330Ω

2.78V : R1 = 220Ω, R2 = 270Ω

2.84V : R1 = 390Ω, R2 = 470Ω

2.92V : R1 = 180Ω, R2 = 240Ω

2.96V : R1 = 270Ω, R2 = 390Ω

2.97V : R1 = 240Ω, R2 = 330Ω

3.03V : R1 = 330Ω, R2 = 470Ω

3.05V : R1 = 390Ω, R2 = 560Ω

3.06V : R1 = 270Ω, R2 = 390Ω

3.06V : R1 = 470Ω, R2 = 680Ω

3.08V : R1 = 150Ω, R2 = 220Ω

3.13V : R1 = 220Ω, R2 = 330Ω

3.14V : R1 = 390Ω, R2 = 560Ω

3.18V : R1 = 240Ω, R2 = 390Ω

3.25V : R1 = 150Ω, R2 = 240Ω

3.28V : R1 = 240Ω, R2 = 390Ω

3.35V : R1 = 220Ω, R2 = 390Ω

3.37V : R1 = 330Ω, R2 = 560Ω

3.43V : R1 = 270Ω, R2 = 470Ω

3.43V : R1 = 390Ω, R2 = 680Ω

3.43V : R1 = 470Ω, R2 = 820Ω

3.47V : R1 = 220Ω, R2 = 390Ω

3.50V : R1 = 150Ω, R2 = 270Ω

3.54V : R1 = 180Ω, R2 = 330Ω

3.55V : R1 = 390Ω, R2 = 680Ω

3.70V : R1 = 240Ω, R2 = 470Ω

3.82V : R1 = 180Ω, R2 = 390Ω

3.83V : R1 = 330Ω, R2 = 680Ω

3.84V : R1 = 270Ω, R2 = 560Ω

3.88V : R1 = 390Ω, R2 = 820Ω

3.91V : R1 = 470Ω, R2 = 1K

3.92V : R1 = 220Ω, R2 = 470Ω

3.96V : R1 = 180Ω, R2 = 390Ω

4.00V : R1 = 150Ω, R2 = 330Ω

4.02V : R1 = 390Ω, R2 = 820Ω

4.17V : R1 = 240Ω, R2 = 560Ω

4.33V : R1 = 150Ω, R2 = 390Ω

4.36V : R1 = 330Ω, R2 = 820Ω

4.40V : R1 = 270Ω, R2 = 680Ω

4.43V : R1 = 220Ω, R2 = 560Ω

4.44V : R1 = 470Ω, R2 = 1.2K

4.46V : R1 = 390Ω, R2 = 1K

4.50V : R1 = 150Ω, R2 = 390Ω

4.51V : R1 = 180Ω, R2 = 470Ω

4.63V : R1 = 390Ω, R2 = 1K

4.79V : R1 = 240Ω, R2 = 680Ω

5.04V : R1 = 330Ω, R2 = 1K

5.05V : R1 = 270Ω, R2 = 820Ω

5.10V : R1 = 390Ω, R2 = 1.2K

5.11V : R1 = 220Ω, R2 = 680Ω

5.14V : R1 = 180Ω, R2 = 560Ω

5.17V : R1 = 150Ω, R2 = 470Ω

5.24V : R1 = 470Ω, R2 = 1.5K

5.30V : R1 = 390Ω, R2 = 1.2K

5.52V : R1 = 240Ω, R2 = 820Ω

5.80V : R1 = 330Ω, R2 = 1.2K

5.88V : R1 = 270Ω, R2 = 1K

5.91V : R1 = 220Ω, R2 = 820Ω

5.92V : R1 = 150Ω, R2 = 560Ω

5.97V : R1 = 180Ω, R2 = 680Ω

6.04V : R1 = 470Ω, R2 = 1.8K

6.06V : R1 = 390Ω, R2 = 1.5K

6.32V : R1 = 390Ω, R2 = 1.5K

6.46V : R1 = 240Ω, R2 = 1K

6.81V : R1 = 270Ω, R2 = 1.2K

6.92V : R1 = 150Ω, R2 = 680Ω

6.93V : R1 = 330Ω, R2 = 1.5K

6.94V : R1 = 180Ω, R2 = 820Ω

7.02V : R1 = 390Ω, R2 = 1.8K

7.10V : R1 = 470Ω, R2 = 2.2K

7.33V : R1 = 390Ω, R2 = 1.8K

7.50V : R1 = 240Ω, R2 = 1.2K

8.07V : R1 = 330Ω, R2 = 1.8K

8.08V : R1 = 150Ω, R2 = 820Ω

8.19V : R1 = 270Ω, R2 = 1.5K

8.30V : R1 = 390Ω, R2 = 2.2K

8.43V : R1 = 470Ω, R2 = 2.7K

8.68V : R1 = 390Ω, R2 = 2.2K

9.06V : R1 = 240Ω, R2 = 1.5K

9.58V : R1 = 330Ω, R2 = 2.2K

9.77V : R1 = 220Ω, R2 = 1.5K

9.90V : R1 = 390Ω, R2 = 2.7K

10.03V : R1 = 470Ω, R2 = 3.3K

10.37V : R1 = 390Ω, R2 = 2.7K

10.63V : R1 = 240Ω, R2 = 1.8K

11.25V : R1 = 150Ω, R2 = 1.2K

11.44V : R1 = 270Ω, R2 = 2.2K

11.48V : R1 = 330Ω, R2 = 2.7K

11.67V : R1 = 180Ω, R2 = 1.5K

11.83V : R1 = 390Ω, R2 = 3.3K

12.40V : R1 = 390Ω, R2 = 3.3K

12.71V : R1 = 240Ω, R2 = 2.2K

13.75V : R1 = 330Ω, R2 = 3.3K

15.31V : R1 = 240Ω, R2 = 2.7K

16.25V : R1 = 150Ω, R2 = 1.8K

16.53V : R1 = 270Ω, R2 = 3.3K

16.59V : R1 = 220Ω, R2 = 2.7K

18.44V : R1 = 240Ω, R2 = 3.3K

19.58V : R1 = 150Ω, R2 = 2.2K

20.00V : R1 = 220Ω, R2 = 3.3K

23.75V : R1 = 150Ω, R2 = 2.7K

24.17V : R1 = 180Ω, R2 = 3.3K

28.75V : R1 = 150Ω, R2 = 3.3K

For example, you need 4.5V from AA 1.5Vx3 in a series. But you do not have them. How to do? You have only LM317 and a lot of resistors. Yes, It can use it instead.

Look at the list above in 4.5V voltage we can use R1 = 150Ω, R2 = 390Ω.

It is easy, right?

### LM317 heat sink calculator

What is the size of the heat sink enough?

While The LM317 is running. It is so hot. Though it has over-temperature cut-out. But we do not need it hot. We always install the heat sink.

Someone ask me. How much should you use the smallest heat sink? LM317 has a maximum temperature of 50 °C/W without a heat sink.

I found this site good with the LM317 heat sink calculator.

## For example LM317 circuit

**Variable DC Power Supply 1.2V to 30V 1A**First projects**Linear power supply Regulator selector 1.5V,3V,4.5V,5V,6V,9V at 1.5A**It’s easy to the selects voltage output.**0-60 volt 30V Dual DC variable power supply using LM317 LM337**It’s high volt and starts voltage at zero! good job.**Best DC power supply 3Amp to adjust 1.2V-20V & 3V-6V-9V-12V**High quality, 3A adjustable voltage regulator. Using LM317 and 2N3055 so easy and cheap. Adjust voltage in steps 3V, 6V, 9V, 12V. And In fine, 1.25V to 20V.**4 Lead Acid Battery charger circuits**

See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431. Easy to build.**Dual power supply 3V,5V,6V,9V,12,15V**

Dual power supply circuit,can select voltage levels 3V,5V,6V,9V,12,15V at 1A and -3V,-5V,-6V,-9V,-12V,-15V at 1A, use LM317 (positive) LM337(negative) […]**LM338 / LM350 / LM317 VOLTAGE REGULATOR CALCULATOR****USB Battery Replacement**

This is a USB 5V to 1.5V Step-Down Converter Circuit. When we use a Cheap MP3 Player which uses only one 1.5V AA battery as its power supply.**Low dropout 5v regulator**

This is 5V low dropout regulator circuit using a transistor and LED only so easy,lowest voltage input is 6V so across it is 1V only, make output is 5V 0.5A**Gel cell battery charger circuit**

It can charge any size of the Gel cell batteries and extend the life of the Gel Cell battery. While the circuit is running, the LED indicates charging.**Nicad Battery Charger using LM317T**

Here are Universal NiCd and NiMH battery charger circuit. It uses IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V. Low-cost circuit

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pleasr can this idea be used to build solar charge controller?

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I/p supply is +24V DC .

IAM LEANING A LOT I THANK VERY MUCH OUT OF THE MANY THINGS U ARE REVIEWING.

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