Questions tagged [lm317]

3-terminal adjustable linear regulator

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54 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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69 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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85 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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52 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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75 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
44 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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71 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
206 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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119 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
769 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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137 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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485 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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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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194 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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95 views

BQ2002, LM317 NiMH charging circuit. How to control the current output?

I have designed a charging circuit utilising the BQ2002 and LM317 for 2x 1.2V NiMH batteries, and it is to be charged using a 5V USB input, I need the output current to be between 550 mA and 1A. I ...
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1answer
79 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
123 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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261 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
536 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
323 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
814 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
156 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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71 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
68 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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158 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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234 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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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
969 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
240 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
679 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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147 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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685 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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93 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
116 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
293 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
493 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
277 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
124 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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281 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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1answer
82 views

LM317 equation help

So I have this voltage regulator circuit. Applying the voltage divider, Vadj=R2/(R1+R2) * Vout then Vout = Vadj * (R1+R2)/R2 = Vadj * (1 + R1/R2). Why every site shows Vout = Vadj * (1 + R2/R1)?...
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1k views

Alternative to LM317 [closed]

I am working on a battery charging circuit based on a solar panel and require a constant voltage supply of, let's say, 5.0 V to the battery. However that's not what one gets from the solar panel. This ...
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1answer
1k views

LM317HV + NPN pass transistor

I am currently designing a new power supply schematic using LM317AHVT and NPN transistors. The base schematic is from this website: https://sound-au.com/articles/power-supplies2.htm#s10 I wanted to ...
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1answer
251 views

Why there is transistor on LM317 ADJ pin? [closed]

I would like to understand the meaning / function of the transistor on LM317 ADJ pin on the following circuit. Image source
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2answers
5k views

LM317 voltage regulator with high current boost by 3 npn transistors

I am building a rectifier (~230V+-10%/50Hz) with voltage regulator from scratch. My output needs to be 3.3V with a maximum current(before short-circuit protection trigger) of 16A. I have chosen three ...
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1answer
2k views

LM317T with weird pinout?

So, some time ago I bought some LM317T voltage regulators. Today, I made a 50mA constant current circuit like this: Now, before you tell me that my circuit is wrong and that it should be wired in ...
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378 views

LM338T Output to 5V issue with LM1085-IT 3.3V

I am using 12V , 2A DC power supply as an input to LM338T and LM1085-IT 3.3 , for 5V and 3.3V output respectively. The issue i am facing here is when these both voltage regulators are connected in ...
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2answers
1k views

Simple constant current regulator for a 1.6A laser LED

My intent is to build a simple driver for a laser LED with an operating voltage of 4.6 volts and forward current 1.6 amps. I have some spare LM317s that I would like to use, however they can supply 1....
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1answer
243 views

Need help with LM317 (500 mA) out of 3 volts supply Calculations [closed]

Does LM317 regulate a constant current of 500 mA out of 3 volts supply (Vin) ? Need help with its associated calculations please. !
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1answer
244 views

EPROM programmer voltage/signal switch

I am trying to make a basic EPROM programmer for M27C322/160/800 chips, mainly as an learning exercise since I know I can buy adaptors for programmers I already own. I found a very useful resource in ...
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3answers
160 views

How to measure positive, negative and inbetween currents

I am making a variable +12V / -12V bench power supply, where I will have 3 output pins: 0- -12VDC | GND | 0- +12VDC, where I want to measure all possible voltages and currents. I will use voltmeters ...