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Questions tagged [lm317]

3-terminal adjustable linear regulator

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22 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
48 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
99 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
80 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
185 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
133 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 ...
2
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2answers
635 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 ...
1
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1answer
118 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
65 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 ...
1
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1answer
59 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
82 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
109 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
32 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
476 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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1answer
157 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
321 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
121 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
565 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
77 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 ...
1
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1answer
102 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 ...
1
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2answers
200 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
338 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 ...
3
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1answer
242 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
108 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
221 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
56 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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1answer
758 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 ...
1
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1answer
924 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: http://sound.whsites.net/articles/power-supplies2.htm#s10 I ...
1
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1answer
213 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
3k 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
1k 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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2answers
292 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
841 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
191 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
173 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 ...
3
votes
3answers
124 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 ...
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2answers
369 views

Transient Power Supply with LM317 and LM2576

I have a power supply to power up a 8W LED board and a raspberry pi. I have used a 24VAC (12-0-12V) 2A transformer to feed the bridge. I have also used a LM317 to provide a voltage of approx. 15.8V ...
2
votes
1answer
212 views

LM317T outputs current on Adjust pin with nothing connected between adjust and Vout?

I have a LM317T-based simple circuit and I'm using a 12V battery to power it. I connected the Vin to + 12V and made a constant current circuit as shown here. Now, I'm using a variable resistor of 100k ...
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2answers
574 views

Li-ion charger circuit with LM339N

I recently found a dead laptop battery and disassembled it, found 6 batteries of CGR18650. So when I checked with them my multimeter, they had quite bit of voltage. So I decided to charge them, since ...
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1answer
464 views

100 mA current sink with LM317 does not work above 25V

I needed a current sink for something and I arranged one with LM317T: simulate this circuit – Schematic created using CircuitLab It has a switch to select whether I want to sink 100mA or 500mA ...
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2answers
275 views

LM317 power regulator ajust is affected by MAX485 chip

Ok, I'm completely puzzled by what is happening to my LM317 power regulator adjust pin voltage. Here is the schematic of the power supply section of my PCB that distribute the 3.3v (VDD) to the ...
4
votes
3answers
3k views

LTspice model for LM317 and the calculators gives different output voltages for the same resistors values

I found LTspice model for LM317 in a very trustable recommended source, downloaded and simulated the following circuit: As you see above in LTspice for R1=240 and R2=1.5k the output voltage is around ...
2
votes
1answer
97 views

3-terminal adjustable voltage regulator: elegant way for Vout=0 when Vin<(setpoint + dropout)?

As I just discovered, when a 3-terminal adjustable voltage regulator (LM317, LD1086) is operating with Vin less than setpoint + dropout, its output is unregulated Vin - dropout. I want it to output ...
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2answers
323 views

LM317 Get Stable Output voltage at 1,25 V

I am currently trying to use the LM317 with a stable output voltage of 1,25 V. The general formula is $$ Vo = Vref\cdot\left(1+\frac{R2}{R1}\right) + Iadj\cdot R2 $$ I used this circuit to create ...
2
votes
2answers
775 views

Current booster with LM317 not working properly in LTspice simulation?

I was playing around in LTSpice with this "current booster" circuit I found on this paper but it doesn't seem to work as I expected. I set up R2 and R3 in order to get a Vout of about 14.82V. If we ...
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2answers
1k views

Driving a laser diode with an LM317

I want to make a a line of sight sensor. I want to drive a laser diode with constant current and aim it at a photodiode, then using a transimpedence amplifier I will monitor any changes in light ...
5
votes
2answers
1k views

LM317 Sealed lead acid charger

I have a couple of Yuasa NPW36-12 12V 7.2Ah batteries from a phased out UPS unit. The batteries are barely one year old and have less than 100 charge cycles on them. I don't have a lead acid battery ...
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3answers
309 views

Step up voltage previous to LM317

Three "simple" questions here: 1-I know the diferencies between linear and switching DC-DC converters/regulators. Are there any applications where the disadvantages (specially noise and ripple) of ...
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2answers
321 views

LM350 variable voltage regulator SNAFU

My LM350 regulator with smoothing caps (C1:0.33uF, C2:1uF polarized, R1:150 R2:10ohms+trimpot) does not work. It works without capacitors. I am an idiot. What have I done wrong? I tested all the ...
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2answers
641 views

LM317 output voltage to 0 V with transformerless negative voltage created through a buck converter

I try to construct a shut down pin or a feature which can set the output of LM317 or LM78XX with negative voltage that is created through a transformerless buck converter. A buck converter having ...