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Questions tagged [lm317]

3-terminal adjustable linear regulator

0
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1answer
109 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 ...
0
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1answer
64 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
98 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 ...
5
votes
2answers
484 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
65 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
vote
1answer
69 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
vote
2answers
46 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 ...
0
votes
1answer
242 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
votes
1answer
201 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 ...
1
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3answers
77 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
122 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
40 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
353 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 ...
0
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1answer
377 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
147 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
1k 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
372 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
164 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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0answers
52 views

Surface Mount Heatsink Pad

This is regarding, specifically, the TI LM317 surface mount package. http://www.ti.com/lit/ds/symlink/lm317.pdf For this component, and packages like it, how does one go about managing thermal ...
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2answers
408 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....
0
votes
1answer
105 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
116 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
107 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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1answer
207 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
107 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
342 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 ...
1
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1answer
282 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 ...
1
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2answers
158 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
2answers
1k 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
84 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 ...
0
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2answers
206 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
389 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 ...
1
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2answers
766 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
837 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
231 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
208 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
479 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 ...
0
votes
1answer
366 views

LM317 maximum resistor/pot - Current regulator - Reference voltage

Here is my circuit design. Are there any problems here? Here are my questions: 1, I notice that R1 is either 120 or 240 ohm in the datasheet. Is that because of the 1.25v reference voltage, and the ...
1
vote
4answers
2k views

LM317 based Voltage Regulated High Current Power Supply Problem

I am new to electronics and have been exploring easy to make DIY things for a while now. I am using the following circuit to make a voltage regulated high current DC power supply. The problem is, I ...
0
votes
1answer
221 views

Why Lm317 burnout and the potentiometer sparks?

so I tried to make a power supply using Lm317 and it works fine when i used a 12 v transformer but when I used a 9-0-9 transformer like in the picture,when i turn potentiometer, it sparks and then ...
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0answers
199 views

DC 30v Adjustable PSU using Lm317

This is the adapter i got in My hand I need a cheap diy stable circuit for making an Adjustable PSU using LM317 Voltage Regulator. I got a adapter with output power supply of DC 30v 400mA. I need a ...
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2answers
513 views

Can i use 47uf instead of 10uf in LM317 Adjustable voltage regulated circuit?

Please refer the images above for the circuit, my question is can i use 2x47uf cap instead of 2x10uf cap in the circuit, since i dont have any 10uf cap in my hand, Thanks.
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2answers
119 views

Power Supply for xl6001 12V Switching LED Driver

I have 2 nos 7W LED Modules, each of which are fed from a separate XL6001 based LED Driver. The DC power input to the drivers is from a 12V, 7.5AH SLA Battery. The LED driver takes 12V DC from the ...
5
votes
4answers
3k views

Purpose and explanation of resistor near output of LM317, high-current, adjustable-regulator circuit

I'm trying to make a high-current, adjustable-voltage regulator using LM317 data sheets. Specifically, I am using the schematic below. So, what is the point of the resistor related to Note A? Is it ...
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votes
1answer
85 views

Can you vet this simple design? It is a slight modification of a LM317 Adjustable Voltage Regulator circuit

Hey, guys! I am making a voltage regulator adjuster circuit. Simple, but I want to not only be able to adjust the power of the output but with the flip of a single-pole-double-throw switch, be able to ...
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0answers
509 views

Voltage drop when loaded LM317T regulated power supply

I put together a power supply like this one: The difference is that I fixed the output voltage to 12V, and has a single output. The transformer I'm using is rated 15V 1A. With no load the output ...
1
vote
2answers
160 views

Seeking means of maximizing energy use from LiIon battery supplying a 3.3V load

I have a device that operates with 3.2 V MAX, and I wish to power it from a standard 3.7 Li-Ion battery. A fully charged battery=4.2V. I used a simple LM317 circuit to drop voltage to 3.2V and it ...
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votes
0answers
31 views

Have modulating output, not enough current

So what I have is a 0-10Vdc (or 0-20mA) output on a commercial grade PLC. the output is only rated for 40mA @ 10Vdc. I want to drive a computer fan that varies it's speed based on 0-12Vdc but could ...
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0answers
68 views

LM317 thermal cutoff for voltages more than 37V above ground

I'm using the LM317 and LM337 for regulation of positive and negative high voltage rails. I noticed in the datasheets (LM317, LM337) that they have a thermal cutoff, but I wonder if this could ...
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2answers
279 views

Connecting 12V fan to LM317 DIY PSU circuit

I am working on a simple adjustable DIY power supply using an LM317 voltage regulator. J1 in the image below represents the transformer rated at 18VA, which rectified produces about 25V DC. The output ...