Questions tagged [lm317]

3-terminal adjustable linear regulator

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1answer
53 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 ...
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2answers
78 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 ...
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4answers
458 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 ...
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2answers
81 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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2answers
47 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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1answer
127 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.
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1answer
89 views

Can I use 2 LM317 cascaded?

I have a 20 - 0 - 20 transformer which is giving about +-27V after rectification. I need +20VDC, +16VDC, 5VDC and -20VDC. I thought of regulating from 27 to 20 then 20 to 16, and finally 16 to 5. Will ...
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2answers
60 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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1answer
54 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 ...
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3answers
109 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 ...
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1answer
77 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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3answers
132 views

Can you connect two lm317's either in series or parallel to help spread out heat?

I am designing an adjustable voltage regulator. The regulator will have be able to swith between max Vout of 9V, 12V, 15V and 18V and will have a variable resistor that can adjust the voltage from 1....
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2answers
76 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 ...
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0answers
56 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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1answer
82 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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2answers
58 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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5answers
105 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 ...
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2answers
87 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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2answers
103 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 ...
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1answer
58 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 ...
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1answer
166 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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2answers
520 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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2answers
129 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 ...
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3answers
74 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?
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1answer
75 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 ...
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1answer
59 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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1answer
74 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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1answer
98 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 ...
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1answer
70 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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3answers
83 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,...
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1answer
39 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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44 views

Higher input current than output current in LM317

I am doing a power supply to a TFT Display that works with 3.3V, my main supply is 12V and TFT current draw is approximately 150mA (A simple schematic of my circuit is below). I put two LM317 because ...
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1answer
74 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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2answers
239 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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2answers
430 views

What is the input - output voltage relationship of an LM317 voltage regulator circuit?

I'm looking to create the simple adjustable voltage regulator below However, I am confused by the input-output voltage relationship. Looking at the LM317 data sheet (https://www.onsemi.com/pub/...
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1answer
85 views

LM317 - voltage limits

I have a couple of active PA monitors with only unbalanced inputs. I want to be able to use the balanced monitor outputs from my mixer, so I am planning to build in a balanced to unbalanced converter ...
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0answers
156 views

LM317 using 2N2222 as current limit

I am trying to build a current limiting circuit using LM317. The goal is to limit output current to ~150mA with 25V input and output at >20V. I built the circuit according to ST datasheet, using the ...
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1answer
213 views

How to calculate current sink

Below schematic is what I have on the breadboard: simulate this circuit – Schematic created using CircuitLab R1 is there to sink 10mA of current to bias LM317, but 470 ohm is a value that I ...
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1answer
643 views

CV/CC with a single LM317?

In all designs that I could find they used two LM317, one for CC and another for CV. Is there a reason why no one used a circuit like this with only one LM317? simulate this circuit – Schematic ...
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1answer
676 views

Why does my 12V SLA Battery behave strangely when charged by simple LM317 circuit?

I'm currently working on a DIY alarm circuit and I have need of a charge controller for a 12V SLA battery. I picked up a XH-M603 charge controller (https://www.banggood.com/XH-M603-DC-12-24V-Charging-...
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2answers
276 views

LM317 to step voltage up

I am sorry for questioning the "law of conservation of energy" first of all. The expression for the output voltage of the LM317: Vout=1.25*(1+R2/R1) contains no any relation to the input voltage. ...
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4answers
1k views

12V lead acid charger with LM317 not charging

I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V. The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0....
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2answers
210 views

How do you drive a 1 watt LED?

I want to build a 1 watt led driver, the led requires 350mA@3.2V approximately. I bought a LM317( 0.5A and 1.5A versions) for this purpose but I can't figure out the schematics of the LM317 and ...
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2answers
1k views

LM317 Voltage Regulator multiple output where one is 12v constant and adjustable

Is it possible to output LM317 in a parallel circuit where there are 2 voltage and has a different output voltage where one is 12V constant and the other is adjustable using potentiometer?
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8answers
9k views

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 ...
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4answers
368 views

Adjustable Power Supply with LM317

I want to create an adjustable power supply for my electronics projects, and the cheapest/fastest option seems to be using an LM317. However, I do not want to blow things up by doing something wrong (...
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1answer
231 views

LM317 Constant Current vs Transistor Current Limiter

LM317 with Current Limiter configuration: Current limiter circuit with transistors: I am used to drive LEDs in my PCBs with LM317. However I recently came across this circuit which will cost less. ...
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3answers
245 views

LM317 temperature [duplicate]

I recently bought this LM317, and I connect it with resistances in order to get 4.2 V: LCSC LM317 clone product page The problem is when I connect it with a 12 V 500 mA power supply it gets extremely ...
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0answers
624 views

Op Amp-based CV LM317 power supply

As many others before, I'm aiming to build my own simple CC CV lab bench PSU based on the LM317 regulator. Now, I've defined most of the circuitry, but I'm stuck with a particular design choice ...
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2answers
1k views

LM317 - Input Voltage

I want to calculate the resistors required with: Input voltage = 9.0 volts Output voltage = 3.0 volts All the datasheets omit to give the input voltage in the formula: Vout=1.25*(1+R2/R1)+(near ...

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