Questions tagged [lm317]
3-terminal adjustable linear regulator
255
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LM317 voltage regulator varying voltage output depending on the load
I have designed a circuit using a LM317 to provide a 13 V voltage rail. The Vin is 24 V. I have voltage voltage divider networks which supply different voltages to a logic comparator which is ...
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2
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High-current transients with LM317 LD driver in Falstad
I have been building a laser diode driver in Falstad, but for the first 200 μs there is a current spike of over 70 A! This would mean instant death for my laser diode.
If you are curious the laser ...
4
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2
answers
808
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How can I make this regulator output 2.8 V or 1.5 V?
I looked at an LM317AG-TN3-R which functions as a regulator. I'm trying to make sense of this part of the datasheet:
I don't quite understand how I can now get 2.8 V and 1.5 V respectively. How do I ...
2
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2
answers
90
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LM317's based "0-V to 30-V regulator circuit" - what is the purpose of diode on the schematic from TI's LM317 datasheet section 9.3.1?
What is the purpose of the diode in the schematic of the LM317-based "0-V to 30-V voltage regulator circuit" from section 9.3.1 of TI's LM317 documentation?
Schematic:
I simulated the above ...
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2
votes
2
answers
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Why is the LM386 so noisy when powered from wall?
I am using an LM386 to amplify an electret signal. Configuration for a gain of 200x is shown below. When powered from my bench power supply in quiet conditions, the output is around 4 mV (RMS). ...
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3
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917
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Does the LM317 voltage regulator have a minimum current output of 1.5 A?
The LM317 voltage regulator is supposed to have a minimum current output of 1.5 A. What does that mean? I am only familiar with the idea of a maximum current output. With this minimum current, will ...
2
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3
answers
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Increasing only current using LM317
For the LM317 there is a precision current regulator circuit. This circuit uses an LM317 and only one resistor between the out and adjust pins. The operation of this circuit completely satisfies me, ...
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1
answer
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LM317 adjustable current regulator for LED
I am driving a 10 W LED from a LM317 regulator. With a variable resistor in between the OUT and ADJ pins of the LM317, I can easily get an adjustable current source (20-350 mA). However, I need to ...
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1
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Shorting LM317 in/outputs to skip over it and get full input voltage
I am new to the electronics world. I wanted to make a variable voltage source for various uses. I decided to use the LM317. I will be using a slide switch instead of the dip switch to select between ...
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1
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1
answer
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LM317 at low temperatures
The LM317 chip has an operating temperature range of 0 to 125 degrees Celsius. What happens if I use it at low (negative) temperatures? Will it work? What parameters will be affected by the ...
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Is there a way to match multiple load impedances with one circuit
My goal is to create a test fixture that can provide multiple voltages such as +-24 volts DC to multiple devices with different input impedances for each device. The ranges of input impedances are ...
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LM317 output overvoltage protection
I am new to electronic design and have two questions about my circuit.
I know that an LM317 has stable output, but when I tested on a breadboard I found out that when I disconnected RV1, the LM317 ...
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1
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1
answer
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LM317 Voltage Regulator With Inversely Selected Output
I am dealing with an old circuit that used a curious form of voltage regulator control. It relied on seven resistors that it would control individually, and the parallel combination of this resistance ...
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2
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LM317... Do we need resistors?
In the circuit below, I replaced LM1117 with LM317. Do I need to add resistors at the output terminal? and how can I calculate the output voltage in this case?
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4
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Why is this LM317 giving an unexpected output?
Just for fun, I used an LM317 IC with two resistors (1.5k and 470 ohm) to get an output voltage of around 1.8 volts and used this circuit with a wall clock.
It worked amazingly well when I connected ...
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2
votes
1
answer
147
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LM317 current limiting/set via differential amplifier works in simulator but glitchy when built
I am trying to build a single LM317 power supply, with current limiting using a differential opamp and potentiometers.
I've came up with this (see schematic) and have built it on a breadboard but the ...
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3
votes
3
answers
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Adding overload indicator to LM317
I am working at a LM317 power supply (tracking pre regulator) and I found on the internet a schematic for overload indicator, which I added into my simulation and into my test circuit.
After ...
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LM317 vs Rheostat
I am trying to limit the voltage to a 12 volt , 25 watt silicone heating pad. I am trying to decide between a rheostat and an LM317 voltage regulator which I would control using an external ...
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1
answer
303
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LM317 Vout instability under load
I hooked up a 9 V power supply to a LM317 (the power supply provides enough current, 2 A, and its heatsink is present) since I need to get 5.1 V in order to power a Raspberry Pi.
The Raspberry boots ...
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1
answer
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LM317t doesn't output as low as expected [closed]
I have an LM317t based variable power supply that I designed. According to the math on the regulator's datasheet my output range should be between 1.25v and 13.7v but after testing today my voltmeter ...
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1
answer
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Is it safe to charge Lithium Ion battery directly with a 4.2 volt supply?
I have been working with Lithium ion 3.7 volts batteries and have been charging them using TP4056 module. However, the module doesn't last longer and gets damaged within a couple of weeks or a month. ...
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3
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Linear (LM317 based?) high current / voltage regulator ( 30 amps at 0 - ~35 volts)
I'm looking to make a linear (LM317 based?) high current / voltage regulator (30 amps at 0 - ~35 volts).
I looked at some desings online but still have some problems with it.
Maybe you can guide me ...
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0
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1
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Voltage drop with 2 LM317 in parallel/different output voltages
I believe it might be a silly question but I'm not 100% sure about this, so I would like your opinion:
There are 2 LM317, both connected in parallel from the same source and they output respectively 5....
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2
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234
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LM317 is dissipating too much power
I used an LM317 in my circuit to get a regulated 1.5 volts output from a 3.7 volt battery using two resistors (220 and 60 ohm.)
It worked fine, but the circuit dissipated too much power even when not ...
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0
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189
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LM317 low output current
I need to make a 1.5 V voltage source for a motor with maximum current drain 1 A.
I made this circuit:
The output voltage without load is 1.46 V, which is fine. When I connect a load resistor which ...
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2
votes
1
answer
517
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LM317 regulator with PNP pass transistor voltage drops when adding load
I'm trying to make a ~4V 2A regulator with the LM317. It works with minimal load but when I increase the load the voltage drops instantly to 3.4V. I'm not sure what's happening.
I'm trying to build ...
0
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1
answer
278
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Resistor and potentiometer values to obtain 1.25-12V variable with an LM317
I want to make a variable power supply up to 12V. For that I want to select resistor and adjust potentiometer values. I have calculated below values from this website.https://circuitdigest.com/...
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0
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268
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LM317 digitally-controlled constant current power supply
I'm designing and simulating (with the intention of building) a lab power supply. I like a challenge so I'm trying to make it digitally controlled (also because I'm a programmer). I'm doing this for ...
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Design Questions for Dual Tracking Power Supply Using 15 Volt 800mA Secondary Transformer, LM317, LM337, and Op Amp
I am experimenting with the design for a dual tracking power supply using LM317/LM337. I recall circuit analysis but my design skills have not been used for a while so I have novice level questions. I ...
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X9C103 10k digital potentiometer with LM317 0 - 20 V DC voltage source
I need some help about my current project. I am trying to do a voltage source which can be controlled remotely (0 - 20 V). I am using LM317T for this project. I examined the LM317T datasheet and ...
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4
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849
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LM317 potentiometer
I'm designing a voltage regulator using the LM317, and I've seen people using 2 different configurations when it comes to the potentiometer. I tested both on a simulator and on a breadboard, and both ...
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vote
2
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Pre-regulator sizing
I want to make a voltage regulator for a symmetric power rail +30/-30V. The idea is to use an LM317 and an LM337.
I want to be able to regulate with a Vin that can go up to +60V (and -60 and negative ...
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2
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Does the lm317TG require a load resistor in the final design or just for testing?
I'm building variable voltage regulator, the regulator has levels of 9, 12, 15 and 18 volts and a potentiometer that allows for incremental adjustment between the levels, so at level 18v you can drop ...
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1
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Does the LM317 take ANY voltage and convert it into the adjusted one?
I am pretty much a beginner in these parts, so can you help me?
Does the LM317 take ANY voltage and convert it into the adjusted one?
By "ANY" I mean that is in its voltage range, etc.
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1
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Can I use 2 LM317s cascaded?
I have a 20 - 0 - 20 transformer which is giving about +/-27 V after rectification. I need +20 VDC, +16 VDC, 5 VDC and -20 VDC. I thought of regulating from 27 to 20 then 20 to 16, and finally 16 to 5....
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Is my heat sink calculation for the LM317 correct?
Using the formula PowerDissipated = (Vin - Vout) * Iout where:
Vin = 12 V
Vout = 2 V
Iout = 450 mA
Power dissipated = (12 - 2) x 0.45 = 4.5 W
And heat sink value = (...
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1
answer
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Driving strings of high power LEDs - different ways with fault protection
I'm trying to find the best method for driving around 30 x white LEDs plus 10 x RGB. The power supply can be 24V. The LEDs will be dimmable, 3W or 1W, 0.350A or 0.7A (I'd need to limit the current a ...
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3
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LM317 Voltage Regulator
I want to regulate a voltage suppose 60 V, but I only have an LM317 (or any similar voltage regulator IC) with voltage regulation range of 30 V max.
Is there any way I can use a combination of two or ...
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3
votes
2
answers
226
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LM317 - Why could I not get more than 200 mA from the output?
My task is to heat a coil, with a resistance of approximately 0.8 ohm. I need to make a constant current source to make it work correctly. I want to use LM317T as a constant current source, but I ...
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4
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644
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Can you connect two LM317s either in series or parallel to help spread out heat?
I am designing an adjustable voltage regulator.
The regulator will have be able to switch between maximum Vout of 9V, 12V, 15V and 18V and will have a variable resistor that can adjust the voltage ...
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0
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2
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181
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LM388 (or LM317) Torque (current) limiting motor driver
I am designing a small handheld electronic screwdriver for a university project. The motor in this screwdriver requires a torque limiter to stop it stripping screws out of plastic parts and i am ...
0
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1
answer
167
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Variable Current Lead Acide Battery Charger
Digitally controlling charge voltage with some regulator like Lm317 is a matter of using some resistor and transistor as stated in lm317 datasheet to select from multiple pre defined voltage.
But what ...
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What is the voltage drop across a TIP41c when it passes 2.9A for long durations?
simulate this circuit – Schematic created using CircuitLab
I'm having trouble understanding from the datasheets what exactly happens when I put a circuit as follows:
The two 20W LED don't have a ...
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2
answers
126
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Driving an electromagnet for 10 seconds without overheating the coil
I have the following issue that I would like to discuss.
I have an electromagnetic lock based on an electromagnet rated at 24V/44 ohms and a PSU at 24V. Basically, you apply a voltage at the coil and ...
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0
votes
5
answers
202
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LM317 / linear regulator, estimate of heat capacity
Quick question - what do you think the heat capacity of a LM317 might be? The use case is that I want to ignite e-matches, which requires are short duration high current and would prefer to just use ...
0
votes
2
answers
314
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LM317 not regulating higher voltages
I wanted to make a power supply providing roughly 8V (+-2V) for small currents, given a whole range of different DC voltages (...
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216
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LM317/338 constant current open circuit
Suddenly I am baffled, as a hobbyist I made a variable constant current power supply based on LM338. But I never thought what could happen if I accidentally turn it on without load, will the voltage ...
2
votes
1
answer
62
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5 Volt Regulator 120 mA no Heat Sink
What is a better DC-DC Voltage Regulator than LM317, I am making a 5V Regulator to Drive an IC that takes 5V at 110 mA, but the LM317 draws 2 W power and gets HOT and the box I use does not have Room ...
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Are low ESR caps away from the LM317 liable to cause instability?
I'm building a standard LM317 supply for testing/general use:
Image source: ElecCircuit - Variable power supply using LM317
The datasheet states the output cap (C3) is not needed for stability, so I ...
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vote
2
answers
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LM317 regulator with NPN pass transistor alternatives and ripple consideration
I have built a simple LM317 regulator power supply and would like to add a pass transistor to provide more current and lower output impedance of the circuit.
Here are two alternatives, one I copied ...
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