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How to set voltage on LM317 adjustable voltage regulator? Answered

How do you set the voltage regulation on an LM317 to 5 volts?

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AndyGadgetBest Answer (author)2013-02-05


You can work it out yourself from the formulas in the datasheet but the easy way is to use an online LM317calculator
Alternatively, you could use an LM323 fixed 5V regulator.

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Xixfas (author)AndyGadget2013-02-05

How do i actually do it.(sorry if i sound mean)

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Xixfas (author)Xixfas2013-02-05

i guess you could say mechanically.

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AndyGadget (author)Xixfas2013-02-05

 
You make up the circuit I've linked in the answer above with an LM317, a 0.1uF and a 1uF capacitor and 2 resistors. If you make R1 = 270R and R2 = 820R, that will give you an output of 5.05V which is close enough.
The input voltage must be at least 7.5V for this circuit to work - A 12VDC wall-wart would be fine.
You could make up this circuit on stripboard quite easily. Look HERE for some LM317 project ideas.

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Xixfas (author)AndyGadget2013-02-06
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framistan (author)2013-02-05

when mounting the heatsink tab on the LM317, be sure to keep the metal tab "isolated" from touching chassis ground (metal). this is because on most other regulators such as the 7805 or the 7812 regulators, the metal tab is OK to touch chassis ground. but the LM317 metal tab is NOT like other regulators. You must put insulators on the regulator tab to ALLOW heat dissipation.... and also simultaneously.... to not electrically touch metal ground. (chassis negative). if you neglect this precaution, then your regulator will short to ground and not work.

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