# Questions tagged [lm317]

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### Building a linear Power supply

Being a poor student and a hobbyist, I've decided to build a power supply. For simplicity's sake, I've chosen a linear supply, build around 2 variable independent channels with 3 commonly used taps - ...
246 views

### LM317 equivalent backfeeding

I have a simple circuit using an LM317-type voltage regulator (ZLDO1117GTA) as a constant-current source. The input is connected to a 15v source, and the output is charging a lead-acid battery. In ...
422 views

### Help Me to Identify what is the Cause for Heating with this Circuit

I built below voltage Regulator Circuit and noticed that after sometime 1K resistor is getting a lot of heat and also I connected the multi meter to Output of this circuit and adjusted preset to ...
337 views

### Help me to Identify whats wrong with this Circuit

I built this circuit which I found below Link Source Link I used the Parts as shown in circuit Diagram. When I connect only a battery which is voltage lower than 12V without input power source no ...
4k views

### How long to charge a super-capacitor with LM317

I am trying to charge a super-capacitor to 2.5V with LM317. According to datasheet the maximum output current of LM317 is 1.5A and there is internal current regulator in side it. So what is the ...
2k views

### Puzzled with the result of LM317 constant current

So, LM317 can be used as a constant current regulator by adjusting the voltage in the Adj pin. The internal voltage reference is 1.25V, and so using a 1.25/0.900 ~= ...
3k views

Would this work as a constant current load since I don't have a high power pot? Is there a better way to do it? simulate this circuit – Schematic created using CircuitLab
8k views

### Floating LM317 (used at high voltage) protected by two Zener diodes

In Marty Brown's Power Supply Cookbook, I found the following variation of the floating linear regulator. I'm aware this topic has been discussed in at least one other question; the two-Zener wasn't ...
2k views

### lm317 current source

I want to use LM317 to make a current source circuit for driving high power LEDs (500-700mA). The schematic in it's datasheet has no capacitor, but in some schematics there are one or two capacitors ...
2k views

### need advice with LM317T current limiting circuit ,new alternative

i am using an LM317 as a Current Regulator for series LED similar to protecting LEDs From over current ( in time of short circuiting) for my LEDs and Mosfets, similar to this picture: the problem ...
641 views

### LM317 - Caps necessary on 9v Battery?

I am designing a circuit which uses the LM317 variable voltage regulator to power a device from 1.25v-3.7v. The device powered by the LM317 will accept +-0.2V from the output of the LM317 and takes ...
818 views

### Function of the FET in LM350/LM317 programmable current limiter

My question pertains this circuit which is from this question, which in turn is a circuit straight from the data sheet. I don't understand the function of the FET in this circuit. Surely, with the ...
3k views

### Why a diode to GND in 0-30V LM317 circuit?

I'm looking at reference design 9.3.1 from http://www.ti.com/lit/ds/symlink/lm317.pdf where a LM317 is used between 35V and -10V to obtain a 0-30V regulation. What is the purpose of the diode? would ...
162 views

### 24 VAC source unable to drive servo motor

Here's my power supply (schematic except without the transformer since my source is already at 24 V AC and using a 100 uF electrolytic as my smoothing capacitor): 24 VAC rectifier -> 100 uF smoothing ...
606 views

### 19.5V to 15V - what's the best way to lower the voltage?

The problem is: I've got a power supply capable of outputting 19.5V 4A. I need to lower the voltage to power up a laptop that requires 15V and 2A. Which way is the best to do it? Construct a voltage ...
715 views

### LM317 and PWM grounds

I have a question regarding the LM317 and PWM. My circuit receives +12v and has three grounds (R,G,B) that are PWM. I need to drop the voltage down to 3.2 volts from the 12 volt source. NOTE: I know ...
6k views

### Cheap switch-mode regulator “comparable” to LM317 [closed]

I've always appreciated the LM317 linear power supply regulator for being a sturdy workhorse. In particular, it's easy to build a simple regulator circuit which "just works" using an handful of ...
3k views

### Practicality of this LM317T PWM Voltage and Current control circuit

Ive been trying to design a LM317T power supply with a PWM (Arduino MCU etc) adjustable voltage and current limit. After various circuits, videos and tutorials i have designed the following circuit in ...
528 views

I'm trying to change the voltage regulation circuit in order to obtain a different range of voltage. My feeder uses a diode bridge and a transformer, that are not displayed in the scheme(it works). My ...
9k views

### Providing a linear adjustable DC voltage from PWM ( 1.5V to 3.3V)

I'm not an electrical engineer, so a simple task has me baffled for the last week or so. I am working on project where I am required to feed a blackbox device with a stable adjustable voltage. The ...
11k views

### LM317 voltage regulator short circuit

I made this standard LM317 voltage regulator circuit: It worked as expected, but then I tried connecting a TDA2005 audio amplifier. I connected the LM317 to my audio amplifier as a power supply and ...
2k views

### 3.1 volt 400 mA laser driver

I've done quite a bit of searching here and on Google, but I think I still need help. Using either of these power supplies: 12V 1A or 5V 2A How can I build a circuit to drive a laser diode with ...
691 views

### Power adapter versus Power supply

I have a mini water-pump/motor hooked up to an LM338 (similar to LM317, but capable of higher current output). I set up the LM338 to create a 6.1-V output, from an 18-V input; this was done by ...
10k views

### How to protect LM317 from output short?

In the below circuit, the diodes protect the LM317 against both of the caps discharging into the IC when input or output is shorted. LM317 is itself capable of having it's output shorted without ...
302 views

I've attained most of the material I need to build my first power supply. The specs are mostly dictated by the parts I have. My intention is a dual isolated variable output power supply that I can ...
2k views

I am new here to StackExchange and new to electronics in general. As my second electronics project (the first being a blinker circuit for a bandolier of LEDs) I am building a regulated linear power ...
2k views

### LM317 3.7 v battery charger

I have build simple LM317 power supply.Input is 12v (I am using computer power supply), and the output is around 4v .I was ...
136 views

### How does the LM317 bypass adjustment terminal reduce ripple amplification?

According to the LM317 datasheet it says that the adjustment terminal must be bypassed to ground to improve ripple rejection, so that the ripples aren't amplified. Could anyone explain how this is ...
156 views

### lm317t charger with a load?

I have a plan to make a solar charger for battery and at the same time power a load.I want to use lm317t to keep constant current.I can not find any reference on how a lm317t effects a solar panel ...
482 views

### Could LM317 in basic regulator configuration (see description) fail to regulate?

So I have a regulator using a 317 in a basic configuration. One minor change is the introduction of a 10uF electrolytic capacitor between $R_{ref}$, and ground. $$R_{ref} = 240 \Omega$$ R_{adj} = ...
311 views

### Current Regulator placement

I want to start building a tube headphone amp from the details on DIY Audio Projects, but I'd like to understand what I'm doing there too. Source: DIY audio projects. While I get most of it, I can'...
2k views

### LM317, basic voltage regulator, why does it get hot when not connected?

I have built this little voltage regulator circuit: circuit diagram I am a hobbyist, so these may well be screamingly obvious questions. I ask because I haven't found the answer to my first question. ...
770 views

### Output voltage of unity-gain buffer varying with current?

I'm working on a VLC+IR transmitter that runs from batteries. I decided to use an LM317 so that the discharging battery wouldn't really affect the current through the LEDs. (Disclaimer: I've never ...
1k views

### LM317, supply connected to output

I am designing a prototype 5VDC fan speed control unit. I am using an LM317 as a voltage regulator. This will step the voltage from a LiPo battery or arbitrary wall adapter down to 5V. Pulse width ...
897 views

### LM317T not working properly?

I am using an LM317T, trying to use it to create a constant 5v output. I've wired it from the diagram shown here. I am using a pot trimmer to control R2. As far as I can tell, it's wired properly (...
991 views

### Triple output power supply

I need to power my device with three different voltages: 3.3V, 5V and 12V. I already have a 12V 1A power supply. So my questions are: Can I use the circuit below to get these three voltages? Is it ...
705 views

### Choosing right trimmer and capacitor in LM317 circuit

I am working on stable, low ripple +22V power supply for TLC5940 IC. I am working a circuit based on the model of Texas Instrument's LM371 circuit . Now, what kind of R2 and CADJ should I use for this ...
194 views

### ICSwitching between solar panel and batteries

I would like to charge the NiMH batteries, when there is excess power from the solar power and use the power stored in the batteries, when I need it (to drive a motor and at night). I have the ...
385 views

### Differences between a LM317AHVT and a LM317T

Is there any practical difference between the LM317AHVT and LM317T vis-a-vis regulating a 900mA, 9-12V LED?
3k views

### What's the most efficient way to derive negative voltage for a bench power supply?

I’m building a bench power supply based on two LM317 with the following specs: Input: 127VAC (from mains) Output: adjustable from 1.25VDC to 15VDC Current: limit adjustable from 100mA to 1.5A In the ...
17k views

### LM317 based power supply with current limiting

I'm trying to build my own Bench Power Supply but I'm having a hard time to find a good design (circuit/project) for it. Here are my requirements: Input: main using a 18V 2A transformer Output: 0-...
3k views

### LM317 Voltage Regulator + ammeter = firecracker?

simulate this circuit – Schematic created using CircuitLab I don't know what I'm doing wrong. Perhaps someone can explain this. Is there any reason an ammeter would cause a voltage regulator to ...
1k views

### LM317 TO-220 heat sinking: Junction to case or junction to pad?

I have some LM317 ICs (TO-220) that I'm using on a power supply. I'm trying to figure out the heat sink values necessary to keep the IC under safe operation. All of my requirements are with 700 mA ...
30k views

### What are the maximum input current and voltage for an LM317?

What should be the maximum current and voltage for an LM317? I have a transformer, which has the rating, primary: 220V Secondary:42V, 7A. Can I use this to make a variable power supply using an LM317 ...
1k views

### Variable power source from an ATX power supply?

I have an ATX power supply (400W) and I want to use make a variable power source for 3-20V using a LM317. I know that the 4 pins connectors (like the ones for the IDE devices) are +12V|GND|GND|+5V, ...
2k views

### LM317 Train Power Supply

I am attempting to build a circuit to run my HO trains with a common rail. When I use this circuit LM317 works for a period of time then gets stuck at the input voltage (At that point the LM317 fails ...
548 views

### Issue with multichannel LM317 circuit

I'm building a 4-channel 0-10v power supply for controlling a set of dimmable Meanwell LED drivers. I'm basing my design off this circuit: I simply repeated the same circuit four times on the same ...
13k views

### Potentiometer with LM317

I am trying to make an adjustable power supply with an LM317 and a potentiometer. The only problem was that there were some conflicting schematics online about how to connect everything. Can some ...