Using a LM317 Adjustable Regulator

A good regulator, to have in the parts bin, is the LM317 Adjustable Voltage Regulator. It is capable of producing 1.25 – 37 V. The voltage is set by 2 external resistors. I like to use a 220 ohm resistor and a 5k potentiometer. This gives you the capability to adjust exactly to the desired voltage.

The LM317 is rated at 1.5 amps; and, if more amperage is needed, several can be used together. It also includes current limiting and thermal overload protection. When conditions return to normal, the regulator will resume operation.

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This is the typical setup I use. A 1N4002 diode can be used in place of the 1N4004 used in the schematic. The manufacture example also shows a 240 ohm resistor instead of a 220 ohm resistor. I usually have the 1N4004 and 220 ohm resistor on hand. A link to the Data Sheet is provided at the bottom of the page.

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When mounting the components, remember to leave room for a heat sink. Some applications do not require them; but, I usually use one anyway. Before connecting to a device, make sure to set the voltage. Use a multi-meter and adjust the potentiometer until you have the proper voltage.

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D1 Mini Pro Power with the LM317

This regulator will be powering a D1 Mini Pro; so, the voltage is adjusted to 5 volts. The output is connected to the 5 volt pin on the D1 Mini. A second regulator will be installed and adjusted to 3.3 volts to power accessories. The LM317 is capable of providing a lot more amperage than the built on regulator.

Links

http://www.ti.com/lit/ds/slvs044x/slvs044x.pdf

https://km4nmp.com/2019/05/11/lm7805-regulated-5-volts/

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