Building a power supply using LM317  - Page 1
Forum section: electronics / projects

author: Mint.
author_rank: Frequent Contributor
timestamp: January 05, 2012, 05:43:56 am
content: All the ones on the net are different. I got no idea what to choose from. So I'm just asking somebody here to show me the right one. I would like to have 1.2v-30v and 1.5A (which is default if I am correct). I would also like to power the whole project using an AC Adapter however I am unsure of what voltage and current I need.ALSO adding a voltmeter would be handyeither one of these:eBay auction: #http://www.ebay.com.au/itm/DC-0-30V-Analog-Volt-Voltage-Voltmeter-Meter-Panel-/180782649228?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2a177c4f8ceBay auction: #[url=http://www.ebay.com.au/itm/Slim-DC-Digital-Voltmeter-Panel-DC-0V-99V-Red-LED-Panel-Meter-Ear-/130624868235?pt=LH_DefaultDomain_0&hash=item1e69d94f8b]http://www.ebay.com.au/itm/Slim-DC-Digital-Voltmeter-Panel-DC-0V-99V-Red-LED-Panel-Meter-Ear-/130624868235?pt=LH_DefaultDomain_0&hash=item1e69d94f8b

author: don.r
author_rank: Frequent Contributor
timestamp: January 05, 2012, 06:03:02 am
content: If you can live with 18v max many of the tattoo power supplies on eBay use 317s and have a display built in all for about $15.http://www.ebay.com/itm/Cast-Iron-LCD-Tattoo-Power-Machine-Gun-Supply-White-Black-Color-Choice-/280742868687?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%252BC%26itu%3DUA%26otn%3D5%26pmod%3D130625905801%26ps%3D63%26clkid%3D5388409084021487111#ht_2189wt_922

author: Mint.
author_rank: Frequent Contributor
timestamp: January 05, 2012, 06:05:02 am
content: Yes, but you see, I would like to build one myself.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 05, 2012, 06:45:57 am
content: I have one here:http://www.axtsystems.com/index.php?option=com_content&view=article&id=84:psu8&catid=35:psu&Itemid=64I use it for audio work mostly, from the 1176 (+30V/-10V rails) to more conventional +/-16V rails.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: January 05, 2012, 07:22:22 am
content: Here's a version I made using an LM317 and a wall wart.Ten Buck Lab-Grade Variable Power Supply

author: slateraptor
author_rank: Frequent Contributor
timestamp: January 05, 2012, 08:26:29 am
content: Quote from: MintyCondition on January 05, 2012, 06:05:02 amYes, but you see, if you can't differentiate between LM317 variants on your own volition, what makes you so confident that you can successfully complete a custom-spec design? Surely you don't expect to do all the parts shopping while your generous "support network" does all the actual engineering?Keep it real. Start with one of the readily available LM317 kits on market, build it up, understand everything there is to know about it. Contrary to popular belief, the road ahead of you will require lots of reading and study.

author: Mint.
author_rank: Frequent Contributor
timestamp: January 05, 2012, 09:21:26 am
content: Mate if you ain't gonna help don't post.Quote from: slateraptor on January 05, 2012, 08:26:29 am

author: slateraptor
author_rank: Frequent Contributor
timestamp: January 05, 2012, 09:50:08 am
content: Pareto inefficiency abounds.Here's your sign.

author: vtl
author_rank: Regular Contributor
timestamp: January 05, 2012, 10:01:14 am
content: Quote from: MintyCondition on January 05, 2012, 09:21:26 amHe wasn't being a dick, seemed like sound advice to me. Have you even looked at the LM317 datasheet yet? It is one of the most comprehensive datasheets out there in terms of possible application circuits. The National Semiconductor datasheet seems to be the best one with a whole heap of example circuits.

author: PStevenson
author_rank: Regular Contributor
timestamp: January 05, 2012, 10:14:34 am
content: Quote from: MintyCondition on January 05, 2012, 09:21:26 amhe was helping! I remember when I asked for help on here a while back someone just basically called me a dick and left it at that, he's suggesting that you do a kit which is where most of us started except me cause my dad was too much of a tight arse to pay for one, he threw a radio and a datasheet at me and said "make one out of this if you need one that bad" kits are the best way to start because not only do you get the knowledge you also get the confidence when it works!

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 05, 2012, 12:47:08 pm
content: Quote from: MintyCondition on January 05, 2012, 06:05:02 amusing LM317 as PSU is so easy. you just need the datasheet and start build from there (real circuit example provided inside, many variation from the simplest to complete protection with reverse diode). i suggest get several LM317 as parts in case you blow some while in learning. in case you found some bug in your circuit, post it here, problem and picture so to avoid to be called as a dickmy 2 cnts.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 05, 2012, 12:59:51 pm
content: Quote from: PStevenson on January 05, 2012, 10:14:34 ami believe he's not that tight arse as you think. he have the money but would like to teach you how to become "independent" and "excellent".

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 05, 2012, 01:03:42 pm
content: Quote from: Jon Chandler on January 05, 2012, 07:22:22 amany reason why i have to register/login to see the content?

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 05, 2012, 01:14:43 pm
content: Quote from: don.r on January 05, 2012, 06:03:02 amNice! This is a great place to start. I might get one and if its a total piece of rubbish at least you get a cheap housing with a screen on it to built your own design.

author: PStevenson
author_rank: Regular Contributor
timestamp: January 05, 2012, 02:06:20 pm
content: Quote from: Mechatrommer on January 05, 2012, 12:59:51 pmthat was just a side effect, trust me, he was a tight arse hahaalso I was 9 and I don't think I should have been playing with the mains at that age !I remember his sage advice to this day- "don't touch the thick wires before the transformer"

author: don.r
author_rank: Frequent Contributor
timestamp: January 05, 2012, 02:50:32 pm
content: Quote from: SimRacer on January 05, 2012, 01:14:43 pmIts not too bad. I built a PSU out of one by simply swapping the two 1/4 plug inputs to banana jacks and adding a few of wires. Its basically a switching supply leading to an LM317 controlled by a pot. The case is thick sheet metal.

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 05, 2012, 02:53:11 pm
content: Quote from: don.r on January 05, 2012, 02:50:32 pmGreat to hear you say that because I had the same idea with the banana plugs. I might also add a load switch.

author: don.r
author_rank: Frequent Contributor
timestamp: January 05, 2012, 03:06:25 pm
content: The only problem with it, and this applies to nearly all 317 based PSUs, is that the switch on voltage spikes even if the pot is turned down so a load switch may not be a bad idea along with perhaps a replaceable fuse in the output since the input fuse is soldered to the switching PSU.

author: IanB
author_rank: Super Contributor
timestamp: January 05, 2012, 03:07:41 pm
content: Quote from: Mechatrommer on January 05, 2012, 01:03:42 pmNot sure, that didn't happen to me.

author: eternal_noob
author_rank: Regular Contributor
timestamp: January 05, 2012, 10:07:53 pm
content: I'd say: While you're at it, build a dual 15v supply!I think you will discover rather quickly that you rarely need more than 12V for most projects. If you build a dual 15 Volts, you can run it as a dual rail supply, two independent adjustable channels, or in series. Much more versatile! The drawbacks are of course more transformer iron and twice as many components, but you will not regret.A couple of suggestions:Use transformers that can deliver at least twice the current needed, for a stable output at higher voltages and load.Use big heat sinks for durability and quality components. There's nothing more irritating than crappy ten-turn potentiometers made in China. Believe me, I have tried and I'm now using TRW pots.

author: ciccio
author_rank: Frequent Contributor
timestamp: January 05, 2012, 10:27:17 pm
content: Quote from: don.r on January 05, 2012, 03:06:25 pmTo avoid voltage spikes follow the suggestion in National handbook, and put one electrolytic cap (100 uF) from REG terminal to Ground and another one (100 uF) from output to ground.I designed a commercial product, sold in hundreds of pieces, that uses a LM317, and it does not have voltage spikes.Another suggestion: LM350 is a pin to pin replacement for LM317, but with higher current (3 A).Best regards

author: don.r
author_rank: Frequent Contributor
timestamp: January 06, 2012, 12:22:43 am
content: Quote from: ciccio on January 05, 2012, 10:27:17 pmInteresting. The PSU in question has 1000uF caps between both input and ground and output and ground and a 10uF cap from REG to ground. It might be worth raising the capacitance from 10uF to 100uF on the last one.

author: Mint.
author_rank: Frequent Contributor
timestamp: January 06, 2012, 09:31:42 am
content: Interestingly enough everybody has different views on what value of capacitors to use

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 22, 2012, 12:46:25 am
content: I ordered one of those tattoo supplies on ebay. Turned up DOA. Going through the process of getting another sent to me. The $15 spent though is worth the price as I planned to rip out the insides and replace with my own LT3083 circuit. here are a few pics of the internals. Not very nice.

author: Bored@Work
author_rank: Super Contributor
timestamp: January 22, 2012, 10:09:31 am
content: A SMPS followed by a linear power supply. At least they made an attempt to ground the metal chassis, although I wouldn't trust the soldering.

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 22, 2012, 11:08:39 am
content: Quote from: BoredAtWork on January 22, 2012, 10:09:31 amThe ground soldering is really bad. Also the mains wire is too thin for my liking. Just poor construction all round.

author: metalphreak
author_rank: Frequent Contributor
timestamp: January 22, 2012, 11:14:40 am
content: The black coloured version looks a bit more professional in terms of the case. Probably just as bad inside though.

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 22, 2012, 11:44:58 am
content: Quote from: wilfred on January 22, 2012, 11:18:46 amIt's so close that at first I thought it was shorting, but there is a bee's dick clearance.

author: caroper
author_rank: Regular Contributor
timestamp: January 22, 2012, 12:19:21 pm
content: Here is a link to a Nuts and Volts Magazine article that gives an excellent introduction to Liner Supply's and the LM317.Analog Power Supply Design

author: Bored@Work
author_rank: Super Contributor
timestamp: January 22, 2012, 12:35:00 pm
content: Quote from: Teknotronix on January 22, 2012, 11:08:39 amBut they at least tried. I recently had a look inside an Atten AT1501D USB bench power supply. A rather strange thing (analog ammeter, USB pass through). They didn't even make an attempt to ground the metal enclosure. It had a fixed two wire power cord but nothing inside would have counted as double insulation for me.

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 22, 2012, 12:38:06 pm
content: Quote from: BoredAtWork on January 22, 2012, 12:35:00 pmYeah there are some dodgy products out there. At least they tried like you say. If they are not already, its only a matter of time before these cheaply made items are responsible for serious injury or death.

author: Teknotronix
author_rank: Regular Contributor
timestamp: January 22, 2012, 12:38:55 pm
content: Quote from: caroper on January 22, 2012, 12:19:21 pmNice one!

author: don.r
author_rank: Frequent Contributor
timestamp: January 22, 2012, 05:04:44 pm
content: Quote from: Teknotronix on January 22, 2012, 11:44:58 amI added some electrical tape under the pot and replaced the wires with heavier gauge. You get $15 in parts and its an OK second (or third...) variable supply but its not "lab" grade unless by lab you mean the dog...

author: SeanB
author_rank: Super Contributor
timestamp: January 22, 2012, 05:25:38 pm
content: Did you connect the case to the unused earth pin in the power socket?

author: Chet T16
author_rank: Frequent Contributor
timestamp: January 23, 2012, 06:06:29 pm
content: Quote from: Teknotronix on January 22, 2012, 12:46:25 amI just got one of these today, the boards seem identical but I look to have more space inside.Can't complain for the money even with having to replace the mains wiring.

author: MikeK
author_rank: Super Contributor
timestamp: February 05, 2012, 05:31:09 pm
content: I have one of these:http://www.tequipment.net/ElencoXP-720K.htmlI'll never use the AC output, and I still need to add a display for the variable outputs.