Questions tagged [lm317]

3-terminal adjustable linear regulator

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1 answer
103 views

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 vote
1 answer
70 views

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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0 votes
2 answers
106 views

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?
4 votes
4 answers
686 views

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
93 views

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 ...
3 votes
3 answers
268 views

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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0 answers
59 views

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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0 votes
1 answer
196 views

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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-2 votes
1 answer
90 views

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 ...
-1 votes
1 answer
98 views

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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0 votes
3 answers
339 views

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 ...
0 votes
1 answer
130 views

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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0 votes
2 answers
155 views

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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1 vote
0 answers
126 views

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 ...
3 votes
1 answer
351 views

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 votes
1 answer
186 views

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/...
0 votes
0 answers
177 views

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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1 vote
1 answer
443 views

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 ...
1 vote
2 answers
637 views

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 ...
3 votes
4 answers
704 views

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 ...
1 vote
2 answers
113 views

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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0 votes
2 answers
52 views

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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0 votes
1 answer
135 views

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.
1 vote
1 answer
230 views

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....
2 votes
2 answers
142 views

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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0 votes
1 answer
79 views

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 ...
0 votes
3 answers
200 views

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 ...
3 votes
2 answers
185 views

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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1 vote
4 answers
472 views

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 votes
2 answers
156 views

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 votes
1 answer
131 views

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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0 votes
1 answer
251 views

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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1 vote
2 answers
93 views

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
193 views

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
218 views

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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0 votes
2 answers
183 views

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
59 views

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 ...
2 votes
1 answer
410 views

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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1 vote
2 answers
1k views

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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0 votes
2 answers
252 views

Constant current source with bypass option

I need a current limiter for a project that I am working on. I understand that I can use a device like the LM317 in constant current mode, but how would I add a bypass circuit so that my ...
0 votes
3 answers
103 views

I need help with determining voltage wave form of LM317

Now I calculated Vout as being 5V, so is the Vout wave form the same as Vin?
1 vote
1 answer
134 views

Current limiting required for float charge?

I'm trying to make a simple float charge circuit for battery backup of an alarm. The battery specifications state that a voltage of 13.8 is required for float charging and there is no limit on the ...
0 votes
1 answer
68 views

LM317LM as a current source

I have been using LM317L as a current source for generating 2-50mA current for a load, by following the datasheet, P14: So far so good, but now I have come across LM31L-n, particularly LM317LM/NOPB, ...
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0 votes
1 answer
105 views

LM317 Ripple/Power dissipation

I'm "building" a regulated linear power supply using LM317, Min(1.25V) Max(24V) Max 1.5A, and I have like +/- 30.88V (10% of ripple(3.25v), 32.5V Maximum and 29.25V minimum, medium 30.88V) in input of ...
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0 votes
1 answer
130 views

LM317 burns adj resistor [closed]

simulate this circuit – Schematic created using CircuitLab I'm building an LM317 power supply circuit along with some capacitors. It works great until I turn the potentiometer down. When I do ...
0 votes
1 answer
100 views

LM317 adjustable constant current source - Why is the voltage between Output and Adj pins is not always 1.25V?

I am trying to create an adjustable constant current circuit using LM317 to drive LEDs of different colors. More specifically, I want the brightness of the LEDs to be the same, therefore, the ...
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0 votes
3 answers
153 views

LM317 - Voltage regulator

I want to drive a board with 5V and 3.3V but my input voltage is around 40VDC. The board will draw around 750mA. If I check the voltage on NODE1 without the 7805, I've got 28V. With the 7805 connected,...
0 votes
1 answer
58 views

Ni-MH battery charging issue - custom built transformers, LM317 gets warm

I had one variable voltage power supply built and I have been using it frequently. Although I had no issue until charging Ni-MH and Ni-Cad batteries with this power supply. Lead acid battery, ...
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1 vote
1 answer
102 views

Will this LM317 Circuit work for my application?

I am attempting to design a circuit to charge lithium 18650 batteries is a 3S configuration. I understand that a BMS is recommended, but I am not concerned with that. I have built this LM317 circuit (...
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1 vote
2 answers
548 views

Changing speed on DC motor with LM317?

I'm working on an old portable cassette recorder I had lying around and was wondering if it's possible to slow down the motor with an LM317 and a potentiometer. I've read about PWM, but I'm not sure ...

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