Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [lm317]

3-terminal adjustable linear regulator

258 questions
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This LM317 diagram doesn't make any sense to me

So this is the basic wiring for an LM317 as a voltage regulator, and very little of it makes sense to me. First off, if one pin is for my adjustment, why do I need \$R_1\$? \$R_2\$ will give me just about any value I need to send. Is \$R_1\$ really…
Jared Cravens
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Problems controlling an LM317 with an op-amp

I have the following circuit, part of my LM317 digitally adjustable power supply. The problem that I have is correctly controlling the LM317 at U2: if I pull it's adjust pin to the ground, the output will go to 1.25 V. So far so good. The problem…
Nicu Surdu
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Smartest way to use current limit using LM317?

As i understand, using this circuit: Will cause the current to go right through the POT and resistor, which will generate a lot of heat. Is there a better way to use current limiting with LM317 without all of the current passing through the…
Xane
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2 answers

LM317 Heat sink, how big?

Thanks to the help of a few of the other guys I have my AC to DC rectifier working, and the rest of the power supply working. Now while testing the power supply, my 18V AC transformer gets rectified and put into my circuit below And I end up with…
Ashley Hughes
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5 answers

Resistors values to use with LM317

I know that ratio R1 to R2 determine the output voltage of LM317. E.g. R1 = 200, R2=330 ohms will produce about 3.3V. My question is, what if I use 2K and 3.3K for R1 and R2? What is the impact of increasing the resistors values but keeping the…
lyassa
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How should I select the resistors for this constant-current application for a 317?

Over at OnSemi, they have a little doc about using a 317 voltage-reg as a current source: http://www.onsemi.com/pub_link/Collateral/AND8109-D.PDF Their final example, providing constant current to an indeterminate number of strings of LED's is…
Jemenake
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LM317-based adj power supply output takes a while to stablize

I recently built-up a quick little LM317-based adjustable power supply schematic: However I've noticed the output can take several seconds (on the order of 10 or so) to "settle down" after turning the trimmer to desired output voltage. What happens…
Craig
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LM317 µA Constant Current source possibility?

I want to create an adjustable µA Constant Current source using a LM317. It is typically stated to have a 5mA to 10mA minimum current for proper regulation. The On-Semi version linked above shows a graph where this actually depends on the Vin-Vout…
Passerby
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LM317 getting hot

Should an LM317 (specifically a TI LM317MQDCYR) rated for 500ma output current really be getting hot to touch when only pulling 170ma at 5V? Package is SOT-223, input is 9V. Is this normal?
Craig
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2 answers

LM317 Train Power Supply

I am attempting to build a circuit to run my HO trains with a common rail. When I use this circuit LM317 works for a period of time then gets stuck at the input voltage (At that point the LM317 fails and needs to be replaced). The train draws 300…
user32804
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Potentiometer with LM317

I am trying to make an adjustable power supply with an LM317 and a potentiometer. The only problem was that there were some conflicting schematics online about how to connect everything. Can some please verify that it is correct or identify what I…
ben
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LM337 Unstable regulation

For an audio project, I need a low noise +/- 12V supply. I have a linear power supply of +/- 15V and I decided to use the LM317 and LM337 to decrease the voltage to 12V. The circuit that I use is the following, I followed the recomendation on the…
Kostr
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Building a Battery Charger with an LM317

I was told that i could make a simple battery charger from a LM317 and a resistor to charge some Ni-MH Batteries. Can someone just expand on this a little such as how it works as I don't really understand it. Some more information is that there are…
Dean
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LM317 running digital pulses. Results are Noisy

The set up of my experiment so far: A. I use a simple LM317 linear voltage regulator to supply constant voltage of +5V to Vdd of my Laser driver circuit. B. Also I use another LM317 linear voltage regulator to supply voltage Vlda ( Up-to 12 volts…
Rene Duchamp
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Controlling MOSFET's resistance using negative feedback

I wanted to use LM317 in a power supply project but wanted to control voltage digitally or with voltage. One possible way was to change one of the voltage divider resistors on the schematic below, with some device used as voltage controlled…
Anthropomorphous Dodecahedron
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