hybridfree/eevblog-posts huggingface dataset:
LM224 - Page 1
Forum section: electronics / beginners

author: tresguey
author_rank: Newbie
timestamp: February 08, 2016, 10:01:27 pm
content: I have a question about temperature ranges on data sheets. I asked a question to an engineer friend of mine about a PWM circuit I am working on. I chose the LM224 by TI without noticing the operating range was on that chip. It will be in about a 200F environment and it is rated at 185F. My engineer friend says it ok because it will not be running nowhere near max capacity. That did not make sense to me. But then again I'm very green to electronics.

author: Audioguru
author_rank: Super Contributor
timestamp: February 09, 2016, 12:00:45 am
content: If you want every circuit you make to work properly and last for a long time then use an LM124 that is rated for a max temperature of 257 degrees F. Your customers will like you.If you want to gamble and replace some of your products under warranty then use an LM224. Your customers will hate you.

author: uncle_bob
author_rank: Unknown
timestamp: February 09, 2016, 12:34:22 am
content: HiWhat will likely happen:Things like leakage and offset voltage may be out of spec. Output current may not quite be as good as you would like.All of that is a maybe. You are talking about VERY old chip designs. I would not be surprised at all to find identical performance between the various temperature range chips.That leaves the package it's self. Back when these parts came out, plastic was not a wide temperature range material. High temperature parts came in metal or ceramic packages. All of that has changed a lot in 40 years.So in this one case, these specific parts, doing what you are doing ... likely not a problem. It's mighty easy to stretch this logic WAY further than you should. High speed digital circuits do not do well at 125C when they are the 70C rated parts. Package is the same ... parts selection is different ....Bob

author: Seekonk
author_rank: Super Contributor
timestamp: February 09, 2016, 08:09:12 am
content: A long long time ago i worked in a repair shop while in college. Fixed a lot of car radios that used TO-220 transistors. I ordered the lowest voltage of the series type. With a voltage breakdown tester I sorted them by voltage. Actually there were only two types, a few low voltage ones and well over 90% were more than the maximum rated voltage for the series. The tested higher voltage ones were used for higher powered amplifiers. Every once in a while there was one with a squirrelly curve that went right into the bin. Point is manufacturers don't make a good, better, best type of a die. These qualities are sorted out when needed. To fill orders of the common stuff everything is shipped out. In less than a second they can sort out parameters that statistically indicate performance under certain operating conditions. As said before, actual cases do matter. If your circuit out performs typical published specs it will likely work well at extended temperatures. Chances are with you even if you don't test. They don't try to make bad parts.
LM2577 High Current with mosfet - Page 1
Forum section: electronics / beginners

author: tomshirvo
author_rank: Regular Contributor
timestamp: July 22, 2015, 03:47:23 am
content: So I am just wondering if with this LM2577 if I can use the "Switch" pin to connect to a mosfet or transistor to allow more than 3A of output current capacity. I know I would also require the other passive components to be rated for the current but I am looking at a 10A output. I want to be able to get 6V to 12V with 10A output!Is this possible?http://www.ti.com/lit/ds/symlink/lm2577.pdfThanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 22, 2015, 08:42:15 am
content: Not without a much larger pile of logic. Those things are ancient, slow and inefficient, anyways -- there are better around!Go with a modern controller, e.g.http://www.digikey.com/product-detail/en/TPS53014DGSR/296-30492-1-ND/3431366for buck, which is also synchronous (better efficiency at low output voltages, if you need it), orhttp://www.ti.com/product/lm3478for boost (which is peak current mode, so also mind your inductor selection).Tim
LM2577 stepping up question - Page 1
Forum section: electronics / beginners

author: Jay112
author_rank: Regular Contributor
timestamp: May 03, 2016, 12:59:49 am
content: I need 2 voltages for my project: 5v for an Arduino Nano, and 34v to power a MingHe B3603 that will be used as a current limiter, feeding 30v 20mA (to an ionic silver generator).I've never stepped up voltage before, so forgive my ignorance.The Arduino needs 5v at the Vin pin, and will be using less than 100mA. I'm not exactly sure how much current the B3603 draws when outputting 30v limited at 20mA, but I'm guessing it's not a large load.Could I use a 5v wall wart, use that for the Arduino's Vin pin, and also use that for stepping up to 34v to feed the B3603? I've made a project like this before by combining 2 wall warts and then stepping them down for the Arduino, but I'm trying to avoid the mess of having 2 wall warts.Thanks!

author: michaeliv
author_rank: Frequent Contributor
timestamp: May 03, 2016, 02:05:13 am
content: If I'm understanding you correctly you want to put 2 boost converters in series ? Why is that ?Why not use the 5v from adapter + a single converter from 5v directly to 30v ?However MingHe B3603 will theoretically not work since it has minimum 5v input.Why do you need 34v input for the MingHe B3603?

author: Jay112
author_rank: Regular Contributor
timestamp: May 03, 2016, 05:02:52 am
content: Quote from: michaeliv on May 03, 2016, 02:05:13 amThanks for replying.Not really 2 boost converters in series. I need the B3603 to give me 30 volts, limiting it to only 20mA. For the B3603 to be able to output 30 volts, it needs 34v as the input.The reason why I need the B3603 there is because the user might need to be able to modify the voltage/current settings. So if the user decides that they prefer 28v and 80mA, then they can easily do the change on their own without affecting the rest of the circuit.Would there be anything wrong with using a 5v wall wart to feed the Arduino and the LM2577, with the LM2577 stepping the 5v up to 34v for the B3603? Since I've never done any stepping-up before, I just want to make sure I'm not overlooking anything.Also, as a sidenote for anyone who's reading: I recently read that the XL6009 is an upgrade to the LM2577. Do you generally agree that it's a better component?

author: michaeliv
author_rank: Frequent Contributor
timestamp: May 03, 2016, 05:20:36 am
content: Oulps I thought that the B3603 is a boost converter. It's actually a buck converter.What you're trying to do would work. There is nothing wrong using 1 5v adapter to power both. If the LM2577 fails you might get 30V on the Arduino and fry it.The obvious solution would be to get a step-up converter that also has constant current feature but I can't find any easily on eBay.The ones that I see have a minimum input voltage of 7v to use the CC feature.The XL6009 is probably better due to the 400khz frequency vs 52khz for the LM2577 .

author: Jay112
author_rank: Regular Contributor
timestamp: May 03, 2016, 05:33:02 am
content: Quote from: michaeliv on May 03, 2016, 05:20:36 amAwesome! Thanks for the help!
LM2596 card with buttons I dont understand the meaning of... - Page 1
Forum section: electronics / beginners

author: Teljemo
author_rank: Contributor
timestamp: November 30, 2014, 11:29:44 pm
content: Look at this video:http://youtu.be/LgHvbeBRNbk?list=UU3gzJ5q340VA1yf9Icxp4EAI have this voltage regulator card.. works just fine.. with an input and output and a potentiometer in between..but the there is a display added and 2 buttons.. when I hold the right button as you see in the clip I can change.. ehh.. something.. but I don't get what it is.. and it doesn't seem to acctually change anything in the output..what is it I am missing here..(you people that use Youtube, leave a comment there too.. it would warm up my small new started channel)

author: sleemanj
author_rank: Super Contributor
timestamp: December 01, 2014, 07:36:12 am
content: Go here with Chromehttp://item.taobao.com/item.htm?spm=a230r.1.14.185.XXfVrW&id=39432149790&ns=1&abbucket=9#detailchoose to translate the page and read it. You'll get the gist. I only skipped thorugh your video but I notice you entered the calibration mode at one point (long press on button 2).(In summary, left button = on/off, right button = input/output voltage display, long press right button = calibration mode (left/right is up/dn then), long press again to exit calibration mode).

author: Teljemo
author_rank: Contributor
timestamp: December 01, 2014, 05:50:03 pm
content: Thank you.. I will try this later
LM2596 in constant current mode keeps oscillating (LM358) - Page 1
Forum section: electronics / beginners

author: igor78
author_rank: Contributor
timestamp: January 03, 2022, 09:04:12 am
content: I'm trying to use an LM2596 module off Amazon in constant current mode. This is a NiMH charger project. Need between 35mA and 1A stable current for NiMH charger.I can't get rid of LM358 opamp oscillations. The multisim-based model works OK, but the real thing oscillates. I read all I could tips I could find online, but apparently I'm missing something obvious.I put opamp and sense resistor on a separate board with soldered connectionssense-resistor ground and voltage divider ground are physically closeLM358 has 100nF decouplingI tried reducing R1 to 10k to slow down the opAmp but it made no apparent differenceI tried a capacitor across R1 to slow down the opAmp, but it made it worseI read that low-pass filter on the signal from the sense-resistor is a bad idea, as it delays op-amp reaction, so I did not do itWhat else should I try? Should I make the control signal better? What is the source of my problem? Is it an imperfect control signal or is it wrong handling of the opamp?Is there a way to fix it?Schematic is straightforward:Here is a smoothed out control signal from Arduino. 63mV pp significantly worse than simulation. I think that some portion of these 63mV p-p coming from oscilloscope probe wires coupling with something + jumper-wires also probably coupling with some noise.Here are oscillations after the voltage divider, on inverting inputHere are oscillations measured on the sense resistor. They are huge.Board layout

author: xavier60
author_rank: Super Contributor
timestamp: January 03, 2022, 11:54:16 am
content: Put a 1uF capacitor across R1.
Cheap DC-DC LM2596 Module for negative rail - Page 1
Forum section: electronics / beginners

author: jadew
author_rank: Frequent Contributor
timestamp: February 14, 2014, 02:55:57 am
content: Hello,So I got these LM2596 modules from ebay and by the look of the datasheet it appears that they can be used as inverting buck-boost.The only difference I noticed in the datasheet (between normal and inverted) is the fact that the ground and the output become reversed.I tried it, but it doesn't work, it just draws all the current it can draw from the supply.Any thoughts?Datasheet:http://www.onsemi.com/pub_link/Collateral/LM2596-D.PDF
LM2596 Power Supply - Page 1
Forum section: electronics / beginners

author: znroot
author_rank: Contributor
timestamp: March 23, 2014, 06:56:11 am
content: Hello,I have made a bench power supply with the LM2596-ADJ IC.All seem to be ok (capacitors, inductor and feedback voltage) but the IC don't want to step down: regardless of the feedback voltage provided by resistors, the output voltage is about 35V with an input of 37V (the maximum allowed I think)There is no short circuit and my microcontroller circuit (powered by an LM2574-5V fixed regulator) works well.The PCB isn't home made and electrically checked.I attach the schematic of the circuit.Thanks a lotPS: the jumper is close, I put it to future changes

author: Vancata
author_rank: Contributor
timestamp: March 23, 2014, 08:43:31 am
content: I'm just curious can you get the ~1.23v on the output with this LM2596 and 37v in the input and what current you can draw on the output with 1.23v? Guess the TJ will be mad too, cant open any datesheet here lol... my adobe crashed or something.

author: znroot
author_rank: Contributor
timestamp: March 23, 2014, 09:48:08 am
content: Yes! Now it works!!! Pin 1 and 2 were swapped.Thanks a lotThe minimum output is about 1.99V. I haven't made test yet about current at output but I will put an heatsink on the ic...
LM2596T - Double the Regulators Double the Supply Right!?!? - Page 1
Forum section: electronics / beginners

author: velvia
author_rank: Newbie
timestamp: October 30, 2024, 11:14:45 pm
content: EHLO eevblog.com/forum,Full Disclosure: I know enough to be dangerous but not enough to leave it aloneI'm in the middle of "solving" a dumb "problem" in a dumb way and wanted to check with the smarts (Y'all) to make sure I'm not going down the wrong path (the path of wasted money and insurance claims). I was looking at the LM2596T Datasheet (https://www.ti.com/lit/ds/symlink/lm2596.pdf) and, best I can tell, I can duct-tape two of them together to get a +/-12V Dual supply from a 20V input.The github is a mess because of who I am as a person but all the related KiCad files are here:https://github.com/velvia-fifty/AudioThings/tree/main/PSUPlease, excuse the inner workings of my brain while taking notes, I have no idea what she's on about either...I've also attached incorrectly created PDFs so you don't even have to leave the site for a laughShort story shorter:I'm trying to spin USB PD into ±12V how "directionally correct" am I?221 Bye,fifty

author: ArdWar
author_rank: Frequent Contributor
timestamp: October 31, 2024, 12:42:04 am
content: Yes, you generally can use buck converter as inverting buck-boost. TI have several whitepapers and appnotes on that if you're interested in the finer details of it.As for your implementation, I guess you're still yet to put the switching diode and inductor for the negative supply?

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 31, 2024, 12:47:25 am
content: I think you've confused 8-3 and the 8-5 examples in the datasheet.

author: velvia
author_rank: Newbie
timestamp: October 31, 2024, 01:35:23 am
content: Quote from: ArdWar on October 31, 2024, 12:42:04 amThanks for the validation.This was throw together in a fit of insomnia this morning (still going!) so I didn't want to chase rabbits.This is the rough order of magnitude for overall size right? (if that makes any sense...)Like, for DC to DC rolling my own*, I can't shrink this down appreciably right? I'm targeting USB PD (so 20V up to 5A) and all I could think was two inputs, but then having to rely on them being different PD adapters.(I know that's an incredibly loaded question full of more questions but I appreciate y'all humoring me)*As in hand solderableQuote from: Kim Christensen on October 31, 2024, 12:47:25 amThanks for the nudge, I assumed that's what I'd want but I'll be honest I don't grok Inductance, like at all so that required a few too many cycles for an "are we sure we can do this"I went with 8-3 because I was hoping to avoid having COM and GND and potentially having to care about audio grounding later (it's all in my head). Having it all run off PD is worth so much more for what I'm aiming for.Maybe I'll learn me an inductance or two while I'm banging my head against this for "fun"
Switching Regulator Li-Ion voltages to 5V 3A - Page 1
Forum section: electronics / beginners

author: ben11235
author_rank: Newbie
timestamp: February 02, 2013, 10:16:25 pm
content: I'm looking for an IC that can step up typical lithium ion voltages of about 3.2 to 5V and source ~2-3A of current. It also needs to be a through hole package. Thanks!EDIT: Would a MSC34063 IC work with an external npn or pnp switch? 3A is a little bit high for the rated power though.

author: CarlG
author_rank: Regular Contributor
timestamp: February 03, 2013, 06:27:55 pm
content: Try Linear Tech'sselector guide
LM2903 unexpected behaviour - Page 1
Forum section: electronics / beginners

author: RichC
author_rank: Contributor
timestamp: April 30, 2021, 09:02:04 am
content: Hi all, first post here.I have an LM2903 I'm trying to use to detect a threshold on a rising voltage (from an RC circuit). I have a basic comparator circuit with a voltage divider on the inverting input. Vcc is 5V, input ranges from 0 to Vcc over a few seconds.This works fine if the divider is set below about 3.5V, however if I set the divider higher (ideally I'd like 4.4V) the output stays low even with the non-inverting input at Vcc.Any ideas why this isn't working? The data sheet suggests it can handle full range inputs.

author: toeeks
author_rank: Newbie
timestamp: April 30, 2021, 09:29:31 am
content: I've only had a quick glance at the datasheet, but I don't think the LM2903 supports rail-to-rail input.Have a look at the datasheet's section on the "Input voltage range". It's given as the range from 0 to (V+) - 2 volts.So when you run your comparator on a 5V supply, it's operation is only guaranteed up to 3V on any of the inputs.

author: RichC
author_rank: Contributor
timestamp: April 30, 2021, 09:42:01 am
content: Ah you are right, I missed it because the table was split across pages. Vcc - 1.5V is specified.

author: Warhawk
author_rank: Frequent Contributor
timestamp: April 30, 2021, 09:51:11 am
content: Quote from: toeeks on April 30, 2021, 09:29:31 amThis is correct.

author: Ian.M
author_rank: Super Contributor
timestamp: April 30, 2021, 10:00:30 am
content: Quote from: RichC on April 30, 2021, 09:42:01 am.... at 25 deg C. Over the full temperature range, its Vcc-2V as Toeeks said. Ignoring worst case limits can catch you out quite easily: build a working prototype on a breadboard on your bench in an air-conditioned lab, then go to production and find some or all fail at significantly colder or hotter ambient temperatures.

author: RichC
author_rank: Contributor
timestamp: April 30, 2021, 11:20:17 am
content: A valid point.So now I can either source some rail-to-rail comparators, or add a voltage divider, decisions.
LM294012CT linear LDO regulator. - Page 1
Forum section: electronics / beginners

author: sureshot
author_rank: Regular Contributor
timestamp: August 14, 2018, 11:33:43 am
content: Just a quick question on the LM294012CT. I've used this regulaor with a rewound transformer of 14.70 Volts AC it worked out ok after filtering. But i was wandering if its viable for use with a 12 Volt transformer, after filtering it would be about 16.92 Volts DC. It would probably be a bit higher than that, as the transformers put out 13 Volts some even close to 14 Volts. I know I've got 1.4 Volts drop across the bridge rectifier. And would be using a series pass transistor, so probably another 0.7 volts drop. The regulator has a 0.5 drop out voltage. So do you think a 12 Volt transformer would be viable ?Thanks for reading, any help appreciated.

author: CJay
author_rank: Super Contributor
timestamp: August 14, 2018, 12:06:56 pm
content: Your transformer is rated to provide 12VAC at it's rated load, measuring it off load is likely to give a higher voltage which will drop when it's loaded.I'd answer no, it's probably not going to be good enough.

author: sureshot
author_rank: Regular Contributor
timestamp: August 14, 2018, 12:23:23 pm
content: Thank you for your reply, i did think it might be border line area . But wasn't 100% sure. Thanks again.

author: CJay
author_rank: Super Contributor
timestamp: August 14, 2018, 12:40:09 pm
content: Check your PMs

author: Zero999
author_rank: Super Contributor
timestamp: August 14, 2018, 01:06:03 pm
content: It might work, if Schottky diodes were used for the bridge rectifier and a massive filter capacitor.

author: sureshot
author_rank: Regular Contributor
timestamp: August 14, 2018, 06:31:10 pm
content: Yes I did think it might be possible with those diodes for a bridge, and a high capacitance, capacitors with a high ripple voltage rating. I think it's really all on the transformer, if it's got more than 12 Volts, and can hold an AC load.
LM2941 low drop out regulator adjustment question - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 23, 2018, 11:22:15 am
content: I am building a 12V DC in to 5 to 12V DC out adjustable voltage regulator. I used the circuit in this link at the bottom:http://www.reuk.co.uk/wordpress/electric-circuit/lm2941-1a-low-dropout-adjustable-regulator/and I made, as a starting point, R1 1k (1%) and R2 2.7k (1%) in series with a 10k multi turn linear pot. I find there is only any adjustment below full input voltage in the last 1.75 turns where the pot goes from 1.8k down to zero Ohms. What values for R1 and for the series resistor for R2 given I only have 1k and 10k multi turn pots and wish to maximize useful range of the pot?Thanks!

author: StillTrying
author_rank: Super Contributor
timestamp: April 23, 2018, 12:10:45 pm
content: Are you sure R1 is not accidentally 100 or 120R.10K + 2.7k for R2shouldgo from 4.7V to 17.9V.

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 23, 2018, 12:16:24 pm
content: I measured R1 just to be sure and it's definitely 1k. I am only inputting 12V though, from a fixed supply, so ideally want the range 5v or below to 12V less voltage drop out. thanks for the thought, easily done with multi band resistors!EDIT, I assumed, (yeah, I know, I know.....) that the multi turn pot had its centre terminal connected to the wiper, it appears that's not the case, so I will check this out later and re-test!

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 24, 2018, 12:54:21 pm
content: Mea culpa, had the pot wired up wrong, works fine now, sorry for the bandwidth!!!
LM2950 from ebay - Page 1
Forum section: electronics / beginners

author: alhenriq
author_rank: Newbie
timestamp: March 03, 2021, 04:58:14 am
content: I have a quick question I purchased an LM2950 from eBay the TO-92 pkg version. I applied 9 V at Vin And I do see 5 V at Vout, however under no load, I see a reading of 2 milliamps at Vin and the specs were kind of stating that I should be seeing quiescent current around a few microamps, unless I’m reading it incorrectly. Is this amount of current draw expected on a LM2950?

author: magic
author_rank: Super Contributor
timestamp: March 03, 2021, 07:23:14 am
content: Be sure to place the required capacitor at the output (preferably electrolytic, I suppose) because it could be oscillating.Or it may be fake. Check if your "LM2950" meets the dropout voltage specification, for starters.

author: alhenriq
author_rank: Newbie
timestamp: March 03, 2021, 04:38:20 pm
content: I had placed the required capacitors for Vin and Vout, I guess I am avoiding the obvious that this is a fakeThank you for your response

author: wraper
author_rank: Unknown
timestamp: March 03, 2021, 05:21:45 pm
content: IMHO you got cheapest 78L05 they could find or something similar.

author: StillTrying
author_rank: Super Contributor
timestamp: March 03, 2021, 05:57:20 pm
content: Is it a bare LM2950-5.Are the caps polarity the correct way around.Arrange a small 0.1mA to 1mA load on the output.

author: magic
author_rank: Super Contributor
timestamp: March 03, 2021, 06:05:28 pm
content: Yeah, it seems pin-compatible with 78Lxx. As I said, test the dropout voltage: connect Vin to 5V and load Vout with 1kΩ to ground, see the difference between Vout and Vin.

author: MikeK
author_rank: Super Contributor
timestamp: March 03, 2021, 09:04:06 pm
content: Buy components from a legitimate vendor, like Digi-Key. Why do you think there are components on eBay? What do you think happens to components that are manufactured but don't pass quality control? For a small order, Digi-Key is like $5 USPS to my door arriving in a couple days. It's just not worth buying from sub-par vendors.
LM301A replacement for this particular circuit? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: May 13, 2025, 06:06:02 am
content: Hello, in appnote #19 for MIC29152, there's a linear adjustable power supply circuit. It is simple and reliable, and as I guess, by reducing value of Rs and using more powerful chip, like MIC29752, output current can be significantly increased (yes, I'm aware of heat dissipation).http://notes-application.abcelectronique.com/026/26-20182.pdfHowever, question is, which modern opamp can replace LM301A in this particular circuit?Also, according to data in table #1, constant current capability is very bad, can it be improved somehow?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 13, 2025, 06:49:56 am
content: I am afraid, the problem is not the LM301, but the way the constant current part is implemented. It is done a a kind of afterthough to a normal voltage regulator. The shunt also sees the supply current (including the base current) from the regulator. There is the capacitor at the regulator input that is needed to get a stable voltage there, but this means getting a slowed down response at the shunt. This makes the regulation tricky and likely needs it to be slow.For better performance I would do a complete redesign / starting point with the power transistor and regulator part separate.

author: Zero999
author_rank: Super Contributor
timestamp: May 13, 2025, 07:27:14 am
content: Use the LM201A instead. Farnell and DigiKey sell them.https://uk.farnell.com/on-semiconductor/lm201adr2g/op-amp-1mhz-0-5v-us-soic-8/dp/2844915https://www.digikey.co.uk/en/products/detail/onsemi/LM201AVDR2G/1476656

author: David Hess
author_rank: Super Contributor
timestamp: May 13, 2025, 12:10:18 pm
content: Quote from: LinuxHata on May 13, 2025, 06:06:02 amThe LM301A is used because its common mode input range includes its positive supply. Many slower JFET parts like the TL061, TL031, or TLE2061 could be used. A rail-to-rail input part like the OPA990 or OPA196 could also be used. Because of C2, faster parts like the TL071, TL051, or TLE2071 might work just fine, but performance will be the same.QuoteA redesign would be required to improve the current limit.
LM311 Doubt - Page 1
Forum section: electronics / beginners

author: Sarvesaa
author_rank: Contributor
timestamp: October 24, 2022, 10:19:16 am
content: Hey friends,I am designing a circuit using LM311. There is a voltageinputfrom a another circuit.I want the comparator to go high if theinputvoltage is greater than the reference voltage and to go low if theinputvoltage is lower than the reference voltage.I want you help for this thank you.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 24, 2022, 10:35:29 am
content: Take a look herehttps://components101.com/ics/lm311-differential-comparator-icReference on the minus input and the signal to check on the positive input will do what you want.
LM317 adjust pin current + general questions - Page 1
Forum section: electronics / beginners

author: bitshift
author_rank: Regular Contributor
timestamp: March 16, 2015, 06:05:54 pm
content: Hey everyone,I've been building an adjustable power supply with the LM317T. The datasheethttp://www.st.com/web/en/resource/technical/document/datasheet/CD00000455.pdfstates the adjust pin current is typically 50uA but maximally 100uA.When I measure the current using my multimeter, I measure 4.17mA. This is a lot more than I was expecting.I've attached a picture of my circuit.If I understand multimeter burden voltage correctly, then this could not be the cause because the burden voltage could only lower the current and not increase it.This leads me to believe my understanding of the LM317 is incorrect.From what I understand, in the basic configuration, the output is 1.25V higher than the voltage of the adjust pin both referenced to ground.R1 is placed from the output to the adjust pin in order to satisfy the minimum load requirement. This is because there is always a 1.25V differential across R1 giving you a reliable current. If you're driving the adjust pin with an op amp, you can take R1 out but then you need to guarantee the minimum load current in another way.R2 is for.... well I don't actually know. I think this is where the problem lies.What is the purpose of R2?Now back to the current measurement on the adjust pin. Since the LM317 is a linear regulator I am going to assume ohms law applies. As a result the current on the adjust pin should change depending on the voltage applied to it. This seems to compute since I'm applying 5V to the adjust pin with a resistance of 1.2K which gives me the measured 4.17mA. So why does the datasheet state 50uA - 100uA on the adjust pin?

author: MLXXXp
author_rank: Frequent Contributor
timestamp: March 16, 2015, 06:19:09 pm
content: You're measuring the total adjust circuit current, including that flowing through R1. For the adjust pin current you need to measure between the adjust pin and the junction of the two resistors. Move the resistor leads from column 6 to column 5, then place your ammeter between column 6 and column 5.Since there will be a constant 1.25V across R1, there will be a constant current through it. Almost no current flows out of the adjust pin (50uA - 100uA), so the current through R2 will equal the constant current through R1. Therefore, there will be a constant voltage across R2. The voltage across R2 plus 1.25V will be the output voltage.

author: bitshift
author_rank: Regular Contributor
timestamp: March 16, 2015, 06:37:45 pm
content: Quote from: MLXXXp on March 16, 2015, 06:19:09 pmPerfect explanation thanks MLXXXp!When I measure the the current from the adjust pin to the junction of the two resistors I get a nice and typical 48uA
LM317 Constant current resistor Switch - Page 1
Forum section: electronics / beginners

author: kozlojak
author_rank: Contributor
timestamp: March 19, 2013, 12:59:15 am
content: I am trying to run a LM317 in constant current mode but I need to be able to switch the current level using 3 resistors controlled from a microchip to change the current. I just cant seem to find a way to switch between R1, R2, and R3 using a microchip.See the attached quick mock up

author: Thor-Arne
author_rank: Unknown
timestamp: March 19, 2013, 07:58:01 am
content: You could use some relays driven by transistors. Just google it.

author: Alana
author_rank: Frequent Contributor
timestamp: March 19, 2013, 12:45:49 pm
content: Or if possible move constant current source to ground level and use NPN or MOSFETS.

author: ptricks
author_rank: Frequent Contributor
timestamp: March 19, 2013, 01:48:15 pm
content: As mentioned easiest way is with a relay. Other methods would require quite a few more parts.

author: David_AVD
author_rank: Super Contributor
timestamp: March 19, 2013, 09:36:10 pm
content: The problem with the LM317 based CC circuit is that the load current passes through the resistors you want to switch.This means the switching mechanism is in that current path too. Using relays would be the easiest way to do this.By the way, what current levels are you talking about?
lm317 heatsink - Page 1
Forum section: electronics / beginners

author: ascot
author_rank: Contributor
timestamp: July 30, 2020, 11:11:27 am
content: anybody got a link for heatsinks for 317

author: mikerj
author_rank: Super Contributor
timestamp: July 30, 2020, 11:15:58 am
content: No one can specify a heatsink without details of the power dissipation and acceptable temperature rise, or whether its convection cooled or forced airflow etc.The LM317T is is a standard TO220 package, so you should be looking for "TO220 heatsink" rather than "LM317 heatsink".

author: newbrain
author_rank: Super Contributor
timestamp: July 30, 2020, 01:03:04 pm
content: What mikerj said.To break you in on the topic, look at this video from our host:

author: MarkF
author_rank: Super Contributor
timestamp: July 30, 2020, 01:33:05 pm
content: Here are three different models that will work for a TO-220 package that I've used.But, you need to calculate the model and height you need.

author: MasterT
author_rank: Frequent Contributor
timestamp: July 31, 2020, 03:23:19 am
content: The bigger the better:https://www.arrow.com/en/products/529902b02500g/aavid-thermalloy
LM317 - how it works ? strange REF feedback. - Page 1
Forum section: electronics / beginners

author: boo9
author_rank: Contributor
timestamp: February 02, 2015, 04:44:59 pm
content: I have a broken PWM control board for inductive loads, 24A, input 10-40V DC (not stabilized)There is a LM317 to supply DC to IC (IC markings are erased but I suspect SG2524) about which I have a question.I dont understand LM317 configuration here, if someone please explain that to me.How does the feedback voltage from OUT gets to REF pin of the LM317, there is a resistor divider, OK I follow that, but then there is C2 cap that follows, separating the resistor divider from the rest of the cirucit, Can feedback loop work correctly with C2 placed there ? There is no current flowing from OUT throu resistor deviders, only during charge/discharge. Assuming C2 is charged to some V, can LM317 operate correctly and stabilize the V to the board ?From what I manged to probe, the bottom connector of C2 goes to 12-13 pin of the IC (right row, two middle pins), the SG2524 has collector of two output transistors there.cheers

author: Zero999
author_rank: Super Contributor
timestamp: February 02, 2015, 08:59:02 pm
content: A capacitor is often connected between Vref and 0V to improve the ripple rejection. There's an example on the datasheet.

author: boo9
author_rank: Contributor
timestamp: February 02, 2015, 09:05:04 pm
content: The C2 cap is positively not on REF/Ground pins on this board.

author: Circlotron
author_rank: Super Contributor
timestamp: February 03, 2015, 01:40:11 am
content: Maybe it is a design mistake that nobody picked up because the board sort of worked - until now - and this is the cause of the failure?

author: boo9
author_rank: Contributor
timestamp: February 05, 2015, 10:23:21 pm
content: @Circlotron - you are correct, I just saw same design different board and there is a ground path from C2/R47k point.
Lm317 input current VS output current - Page 1
Forum section: electronics / beginners

author: Asim
author_rank: Regular Contributor
timestamp: September 03, 2014, 07:24:48 am
content: Hello allMy question is if i supply the regulator with 500 mA ( as an example) what is the maximum output current I can get? Or there is no current losses? And of there are ,how much losses ?Thanks

author: Simon
author_rank: Unknown
timestamp: September 03, 2014, 07:26:44 am
content: linear regulators use around 5mA for themselves (quiescent current on the datasheet) the rest is yours, linear regulators are like an automatic variable resistor and can't ever give out more current than comes in.

author: Asim
author_rank: Regular Contributor
timestamp: September 03, 2014, 07:31:41 am
content: Quote from: Simon on September 03, 2014, 07:26:44 amAlright , thanks

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 10:49:41 am
content: A floating regulator like the LM317 only uses about 5 microamps for itself which is lost through the adjustment pin. Most of its quiescent current flows to the output so it is available to the load which explains why it has a minimum load requirement of somewhere between about 1 and 10 milliamps.The quiescent current for a 7805/LM340 flows out the common pin and is unavailable to the load.

author: Dave
author_rank: Super Contributor
timestamp: September 03, 2014, 10:00:19 pm
content: Datasheets, people.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 10:58:56 pm
content: I was going by memory.Check out the common pin current on a 7805.

author: Simon
author_rank: Unknown
timestamp: September 04, 2014, 05:39:17 am
content: does it matter ? we are talking no more than 5mA and if that it going to make a difference when your drawing 100's of mA then something is wrong.
LM317-lm337 0 volts and current limit is it possible this way  - Page 1
Forum section: electronics / beginners

author: DarkZero
author_rank: Regular Contributor
timestamp: January 22, 2017, 06:53:49 pm
content: so i needed +-15v 1A so i tought how hard can it be lm317 and lm337 works fine now since i have both +-v why not go to 0 and while at it why not current limit so i came up with the circuit in attachment now spice says it somewhat works i dont know if it will work for real i want to hear opinions

author: ZeTeX
author_rank: Frequent Contributor
timestamp: January 22, 2017, 07:08:18 pm
content: .. where is the current limiting part?I don't see any sense resistor.. the circuit looks weird..

author: DarkZero
author_rank: Regular Contributor
timestamp: January 22, 2017, 07:38:21 pm
content: there will be sense resistor with differential opamp going into this comparator which will connect adj to -1.25v which will give 0 output or w/e is needed to maintain current i should also mention that r2 and r3 are supposed to be pots

author: Benta
author_rank: Super Contributor
timestamp: January 22, 2017, 08:06:26 pm
content: I don't understand what you are trying to do and what your goal is. Sorry.Perhaps a bit more information?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 22, 2017, 08:17:08 pm
content: There is no point of fixing the individual voltages. So the difference from positive to negative supply might kind of work, but it could end up with +8 and 2 V instead of a +-5 V. The adjustment currents and internal ref voltage for different chips will be different too - so one regulator will not work properly.The mosfet can only bring down the voltage to a +- 1.2 V - so current limit can not work with a short.So short: it just does not work that way. Adding an extra lower current limit to the LM317 is not easy - it is rather difficult.

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2017, 10:57:44 pm
content: What are you trying to do?What does V3 & V4 represent?

author: DarkZero
author_rank: Regular Contributor
timestamp: January 23, 2017, 07:28:18 am
content: V3 will be a fixed voltage V4 will be output of differential amplifierwhat im trying to do is dual supply that goes 0-15 volts and 10mA-1A this is positive part of the supply, lm337 will provide -1.25v for the lm317 to go to 0 volts, transistor is supposed to short adj pin to -1.25 resulting in 0 volts at the output i used mosfet because with bjt i didnt get 0 volts at the output only 0.6 when i did simulation , opamp is used as comparator which will turn on and off transistor, comparator will have ref voltage and the voltage coming out from the differential amplifier which is not in schematic its what v3 and v4 are for.

author: Zero999
author_rank: Super Contributor
timestamp: January 23, 2017, 09:20:57 am
content: So U3 is acting as a comparator. You could get rid of the MOSFET, swap the inverting and non-inverting inputs and use a comparator IC such as the LM311 or LM393.A more simpler option is the LT3081, which can go down to 0V and has adjustable current limiting.http://cds.linear.com/docs/en/datasheet/3081fc.pdf
lm317 or opamps for linear psu? - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: January 04, 2016, 12:41:44 am
content: Hey! i currently have 2 linear psu that goes from 1.25V to 24V 1 amp each, ive made them using a lm 317 that controls 2 2n3055, they work pretty well and i had them for around 3 years, im going to make another one with the same voltage specs but this time 5 amps, since i had this transformer laying around.Now, the question is, is it better this way with the lm317, or would i get better performance using opamps? i found a circuit with a lm358 thats capable of voltage and current control, ive tested it and works well toowhich method should i choose?

author: dom0
author_rank: Super Contributor
timestamp: January 04, 2016, 12:46:49 am
content: 'Discrete' op amp circuits can easily outperform old regulators like the LM317, but need more parts, proper design and more board space to do so.Tip: Most "DIY lab supply" schematics on the net are poor, don't work well or don't work at all. It is also common practice to overload transformers and dimension heat sinks way to small, forget protection circuits etc.A good way to get a feeling how a good design looks is to look up any old pure analog lab supply from a reputable manufacturer (HP-Harrisson, Statron, W&G, R&S, Delta Elektronika, Power Designs Inc., and many many more) and take a peek at the service manual circuit description and schematic.

author: poorchava
author_rank: Super Contributor
timestamp: January 04, 2016, 01:12:07 pm
content: In general it depends on what you expect from your power supply. For example I've found myself not needing high precision and high power at the same time.I guess if I was in your boots I'd build a big one using LM317 not caring too much about output power and then another one based on opamps (but not necessarily LM358, it's really low end) which will have better precision.Sent from my HTC One M8s using Tapatalk.

author: XFDDesign
author_rank: Frequent Contributor
timestamp: January 04, 2016, 02:30:03 pm
content: "Now, the question is, is it better this way with the lm317, or would i get better performance using opamps?"The problem here is that you have not qualified "better performance."What kind of performance do you want? What is the #1 most important thing you're attempting to achieve?

author: Audioguru
author_rank: Super Contributor
timestamp: January 04, 2016, 04:26:17 pm
content: An LM317 has very good voltage regulation. If you simply "hang" a NPN emitter follower on its output then the voltage regulation is ruined due to the Vbe changing when the load current changes.Adding a PNP transistor across the LM317 and fed by its input saves the very good voltage regulation and another transistor can provide current limiting.
LM317 Power Supply Design. (SOLVED) - Page 1
Forum section: electronics / beginners

author: Mint.
author_rank: Frequent Contributor
timestamp: January 13, 2012, 11:57:44 pm
content: Well I am designing an Lm317 voltage regulator, however I am a bit stuck. I have no idea how much current the lm317 needs to operate, and I cannot find it on the data sheet. I need this to understand what wattage to pick for resistors. I am planning to power this from 12v dc charger that supplies 3A, will I need to place some kind of resistor before the Vin? Or is the 50ohm resistance enough inside the 317?See attached picture for circuit.

author: vk6hdx
author_rank: Regular Contributor
timestamp: January 14, 2012, 12:20:35 am
content: Quote from: Mint. on January 13, 2012, 11:57:44 pmHi Mint, are you referring to the quiescent current? If so this is available on the datasheet. Otherwise the current required by the 317 @ vin will be proportional to the current drawn @ vout.No need to use a currently limiting resistor on vin as the 317 has all the internal protection it needs.

author: Mint.
author_rank: Frequent Contributor
timestamp: January 14, 2012, 12:25:45 am
content: Quote from: vk6hdx on January 14, 2012, 12:20:35 amPerfect! Thanks!

author: metalphreak
author_rank: Frequent Contributor
timestamp: January 14, 2012, 09:51:31 pm
content: That is also where you get the value for power dissipated by the regulator. Current in is the same as current out, combined with the voltage drop across the regulator (Vin - Vout), gives you the power dissipated.P = (Vin - Vout) x IThe greater the different between input and output voltages, the lower the efficiency as the regulator consumes more power.
LM317 Simple Lead acid battery charger - Page 1
Forum section: electronics / beginners

author: corrado33
author_rank: Frequent Contributor
timestamp: November 18, 2014, 06:51:17 pm
content: Quick question.Could I use a simple LM317 set to 14.X volts with a series resistor to charge lead acid batteries? Many of the circuits online are (relatively) complicated, using comparators and other things. I mean, when the battery gets up to whatever voltage you have set plus the voltage drop across the resistor, the current will stop flowing... correct? I'm most likely looking at that wrong, but it seems like you can easily have an essentially auto cut off charger without the use of any comparators or similar.

author: macboy
author_rank: Super Contributor
timestamp: November 18, 2014, 08:24:44 pm
content: If you want it to just stop charging by itself, then set the voltage output to 13.8 V. This is the "nominal" float charge for lead-acid batteries. To fast charge at 14.4 V, you need to detect the drop in charge current and reduce the voltage to the float voltage to finish the charging. If you keep the voltage at 14.4 V after the fast charge phase is done (after the current drops) then the battery may off-gas (convert its water to hydrogen and oxygen), and the plates will erode over time. Float charging alone won't give you optimum capacity, but it is perfectly safe for set-and-forget charging.You also generally need to limit the current at the beginning of the charge (when the battery voltage is below the charger voltage of 13.8-14.4 V) to generally no more than 1/10 of C (capacity). The internal current limiting of the LM317 should limit current to around 2 A (it is guaranteed to deliver 1.5 A but will do more before limiting) so it should be safe with 20 AH batteries without additional limiting. Otherwise, you can use a resistor; there will only be a maximum of ~2 VDC across the resistor even when the battery is very empty, so it will need to be a smallish value.
LM317 SOURCE - Page 1
Forum section: electronics / beginners

author: nico2984
author_rank: Newbie
timestamp: August 17, 2015, 09:25:15 pm
content: Hi, I need to build a 0 to 5V regulator (1A max) with a overcurrent protection (foldback)I usually implement a protection when I have an additional output series transistor to increase the current rating of the power supply (external pass element), but in this circuit I don't need it.How can I implement the protection?

author: tron9000
author_rank: Frequent Contributor
timestamp: August 17, 2015, 09:28:16 pm
content: have a look at daves videos on designing power supplies

author: rsjsouza
author_rank: Super Contributor
timestamp: August 17, 2015, 09:36:50 pm
content: I am not sure if I understood it correctly, but theLM317has built-in current limiting circuitry. Do you mean something else?

author: nico2984
author_rank: Newbie
timestamp: August 17, 2015, 09:40:47 pm
content: Quote from: rsjsouza on August 17, 2015, 09:36:50 pmYes, I have to implement another overcurrent protection additionally to the LM317 built-in

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 09:53:18 pm
content: I see PolySwitch Resettable Fuse mentioned a lot

author: nico2984
author_rank: Newbie
timestamp: August 17, 2015, 10:10:22 pm
content: Thanks ez24, but I forgot to mention that this is an exercise from school.I updated my design.I have to design a voltage regulator (1A, 0 to 5v). The input can variate between 40 to 45v. Also I have to implement and overcurrent protection (foldback current protection).

author: nico2984
author_rank: Newbie
timestamp: August 17, 2015, 11:39:03 pm
content: Yes, the standard 317 only rated to 40v, that's why I put the Q1. It's reduce the Vin to 30v.It's winter here

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 02:38:16 am
content: To OPIf you want more responses, change the title of your post. Your title means nothing, you need to ask for ideas in your title and use up all the space (it is free).Something like: "Suggestions for current feedback in a LM317 circuit needed"Does you circuit have a -10v input ?