Questions tagged [lm317]

3-terminal adjustable linear regulator

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1answer
59 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
72 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
48 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
40 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
52 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
63 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
87 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
53 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
63 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
35 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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0answers
38 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
65 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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59 views

Do I need a laser diode driver for this? (noobegginner)

I have a blue laser diode, with max specs of: 2.4w 2.2A 5.2V Currently, im using a ion power bank with a skinned usb wire to power it. The maximum current I measured from it is only 1.4A, and voltage ...
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2answers
108 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
175 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
59 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
103 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
54 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
235 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
394 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
170 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
885 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
145 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
762 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
8k 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
269 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
134 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
151 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
404 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
743 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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2answers
398 views

LM317 maximum current output as a voltage regulator

I built the following circuit in LTSpice using LM317. With a current load at the output, stepping from 0.1A to 1A, I noticed the output voltage collapsed at around 800mA. This is a surprise, since I ...
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2answers
916 views

Solar charger in commercial application based on an LM317 IC [closed]

I have been working on a project of a commercial LoRaWan node. I want it to be powered by 3.7 battery and I consider to add a solar charger. For now, I have implemented a circuit based on an LTC3652 ...
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1answer
213 views

Why Current draw in DC variable power supply is not sizable?

I have done a DC variable power supply, and checked it using multimeter the output voltage ranges from 1.3v to 19v, but the problem is when I added a DC load(small DC motor) it was not working, why? ...
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2answers
74 views

voltage stabilizer current

I want to make voltage stabilizer using ic lm317, to power off five white LEDs in series. I need to regulate the current through the diodes in the range of 700mA-1500mA. Have anybody idea how to ...
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1answer
74 views

Dual channel linear power supply

As a learning project, I'm trying to create a simple linear power supply using LM317. The basic circuit is well documented on internet, but I want to create a variant that allows me to have multiple ...
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1answer
232 views

LM317HV power supply

I have a few questions regarding the following schematics: ![/imga] ![/imgb] Initially I was testing the first schematic to see if it works good. The result of the tests were good, the power supply ...
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1answer
401 views

DC signal output 0-5V with constant 10mA

I am designing a Digital Logic Board and need to add a DC signal output from 0 to 5V (with potentiometer) with a constant 10mA. I have checked designs with LM317 and LM334 for adjustable current upto ...
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0answers
36 views

how to choose/design a capacitor value for surge current(for protection) for DC brush motor?

I am driving a DC BRUSH Motor at 30.V.D.C and the current is 300 Millie ampere, it is powered by L.M.317 I.C .My sir is suggesting to provide a capacitor as a protection form surge/peak current ...
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2answers
1k views

Eliminating negative output voltage in a LM317-based power supply adjustable down to 0V

I've been looking to build a linear power supply with current limiting and output adjustable down to 0V and I found this circuit in a LM317 datasheet.: So I've built it on a breadboard with minor ...
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2answers
274 views

LM317 output voltage is rising unexpectedly

I am using LM317 to get 5.5V out of 12V input In my circuit R1 is 220R, R2 is 741R Expected current is ~700mA. link to the data sheet This of course will produce a lot of heat, so I choose quite a ...
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1answer
957 views

Dual power supply by chaining two lm317 voltage regulators in series: will it work?

I am short an adjustable negative voltage regulator, so I am trying to link two lm317 regulated power supplies to form a dual power supply. Is this possible? They are both connected to a center tap ...
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2answers
161 views

LM317 Vout drops on load

I built a very basic circuit to get around 5.5V from a +15V source I have a 220 Ohm between Adj and Vout and one 470 Ohm, one 220 Ohm and two 100 Ohm in parallel between Gnd and Adj summing up to ...
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2answers
788 views

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, ...
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0answers
96 views

What do you think about my PSU design?

I have designed a symetrical PSU using LM317, LM337 plus power BJTs. The desired output range is at least 24V-2V @ 6A max. Altough not shown in the schematic, i plan to add power resistors and a ...
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1answer
134 views

Old laptop power brick > DIY current regulator > 20w COB LED - will it do what I think it will? [closed]

I have a salvaged 20W battery-powered work light: the housing and LED inside. Before the electronics and the original 7.4v dead battery got tossed, I hooked up a somewhat discharged 7.4v battery to it ...
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2answers
355 views

Current regulation before or after voltage regulation?

I'm making a +12V/-12V power supply (2.5A max. output current each) with voltage regulation and current limiter (+ option to go lower on voltage than 1.25V). In the datasheets, I've came across, that ...
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1answer
577 views

Explain adjustable 4A regulator

I cannot understand how this circuit works. https://imgur.com/a/OAQSF4Y I have found a basic explanation online but is not enought to make calculations. "Using three LM317-N devices in parallel ...
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1answer
290 views

LM317 intermittent current source

I need a 50 mA current source despite the load value (resistor LOAD), and I need the current flowing just when the microcontroller says so. It works fine with LOAD = 0 ohm and IL = 50 mA, but when I ...
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3answers
144 views

How to wire up a mini potentiometer?

Sorry for the crappy schematic, but how do I wire up a potentiometer to have variabile resistance (like the symbol an the bottom). I'm using it in a 317T voltage regulator circut.
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3answers
308 views

Lm317 input connected to output?

I am figuring out the schematic of an existing e-bike controller. Specifically I am trying to replace an lm317t with a custom made switch regulator that outputs the same voltage. But first I want to ...

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