Questions tagged [lm317]

3-terminal adjustable linear regulator

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2answers
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Keeping the output of a heated LM317 constant

I have built a power supply using an LM317: simulate this circuit – Schematic created using CircuitLab When the supply is on for a rather long time (several hours) with a respectable load, the ...
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1answer
3k views

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 ...
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2answers
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Power Supply Diode Keeps Burning Out

I am trying to replicate the circuit I found here: (source: cogeco.ca) This is a photograph of what I have built: In my photo I have labeled one diode in the bridge rectifier which has burn out ...
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2answers
5k views

Using a 12VAC Transformer For a LM317T Power Supply

I have found a circuit diagram for a regulated power supply using a LM317T regulator which I wish to build as my first electronics project. The only problem is that instead of a 24 VAC transformer I ...
4
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2answers
1k views

List of LM Integrated Circuits?

Does anyone have / know of a list of all the LM integrated circuit packages available? The EE stockroom at my university recently reorganized and they cataloged several pages of part numbers without ...
7
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2answers
2k views

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 ...
13
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1answer
5k views

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 ...
4
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1answer
7k views

What use are the transistors in this (LM317 based) power supply circuit?

I am looking to do a small bench power supply project and am studying various designs based around a LM317. Basic I know but I still seem to manage to have have some questions. Fig 22 on page 8 of ...
2
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1answer
2k views

Why are the output voltages way too high on this stacked LM317 circuit?

I'm making a circuit that is intended to "simulate" a stack of 6 Li-Ion cells, for testing a BMS. Here's the schematic: Schematic of cell simulator circuit The ICs in red boxes are LM317 voltage ...
0
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2answers
5k views

12V voltage regulator with the least drop out voltage

I have a DC adapter rating 12 V 750 mA. I broke open its case and saw that its rectified but not regulated. I need 12 V for my design and do not want to buy a transformer. Do you know ...
5
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2answers
36k views

Add on/off indicator LED to circuit

I'm working on my first small electronics project; building a small LM317 based power supply. I've built the circuit as shown in the data sheet (black part of the circuit diagram below) on a perfboard....
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3answers
2k views

LM317 Ground Problems

I have a LM317 setup as a 3.3V regulator. I am getting 12V input from an Agilent Technologies E3631A Variable DC Power Supply. On this same board I also have a LM7805 regulating to 5V. All of my ...
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2answers
5k views

Typical LM317 resistor values

Is there a place that I can get a hold of a table with common voltages by using standard resistors? (Sorry that this is poorly worded but I cant figure out how to say it better, so I will give an ...
6
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1answer
3k views

LM317 Resistor Values Performance

What is the performance tradeoff of using different resistors with the LM317. For example using a 300 Ohm and 400 Ohm resistor vs. using a 3k and a 4k resistor. Specifically I am interested in knowing ...
3
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1answer
3k views

LM317 current limiter, driving with uC

I am somewhat confused on how the current limiter configuration works with the LM317. It's configuration looks as so: Datasheet: http://www.ti.com/lit/ds/snvs774l/snvs774l.pdf The formula given is \$...
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2answers
9k views

LM317 - bringing down to 0 volts (with a uC)

I am wanting to build a custom power supply for myself, and am having trouble understanding how to drive the adjust pin with a microcontroller. The datasheet for it is here: http://www.ti.com/lit/ds/...
4
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1answer
22k views

Simple LM317 variable voltage supply, does it limit current too?

I had wanted to build a power supply for so long, and had never really understood the calculations involving the LM317. I had found a kit (pcb+parts) online and it had renewed my interests in using it ...
5
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5answers
17k views

LM317 to create constant current of 2mA?

I have a circuit where I want to have a constant current of 2mA through a variable resistor. I've been told that I could probably use a LM317 as a current regulator, with one resistor on the ouput. ...
2
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1answer
7k views

Dual polarity vs dual rail power supply

My previous post turned out to contain too many questions, so I'll focus on the main one first, and figure the rest out as needed. I'm looking at building a DC lab power supply, roughly 1.2-14 volts ...
7
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4answers
5k views

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 ...
4
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2answers
9k views

Is this 7805-based design correct?

I found this design on internet: It is said to be a regulated power supply with variable DC output 5-15 V, 400 mA. My first question: Is this design around 7805 correct? I am asking because it doesn'...
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2answers
2k views

Noise when powering headphones amplifier through USB port

This question is actually connected with this one: Getting 1.2V from USB I've successfully connected my FIIO E3 headphones amplifier to USB (so that I don't have to use batteries). But I've notices ...
2
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2answers
4k views

LM317 voltage regulator circuit drops Vout on load

I'm attempting to build a voltage regulator circuit for a DIY stir plate using a CPU fan supplied to an LM317 voltage regulator circuit. I have everything wired up on a board just like the diagram, ...
9
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2answers
18k views

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 ...
8
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4answers
20k views

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 ...
2
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7answers
6k views

Controlling high output LED's with a microcontroller

I'd like to build a circuit to precisely control the current through a couple of (LED and laser) diodes. I would like to minimize the number of components if possible. Power consumption is not a ...
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3answers
3k views

Is it normal for LM317 to give a higher voltage without a load?

I just built a small 5.1V regulator with LM317, using 220 and 680 ohm resistors. However, I measure 8.6V at the output without a load connected. Is this normal, i.e. under a load (about 120 ohm) it ...
7
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2answers
4k views

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?
6
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4answers
21k views

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 ...
4
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6answers
3k views

What's causing this high frequency ripple on the output of my LM317?

I'm using an LM317T to regulate 5 V to 3.38 V for a microcontroller. R1 is 330 ohms and R2 is 560 ohms. There isn't any input capacitor and the output capacitor is 470 µF 25V, because I ...

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