Noobie Question About Power Supply. - Page 1
Forum section: electronics / beginners

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 04, 2013, 03:17:36 pm
content: I need to build a power supply for my small projects with ajsutable outputI need it to work from the socket (AC) 220-240 ~ at a frequency of 50-60 Hz and spit out a perfect DC voltage of 0-25 (or a bit more of 15 volts but 25 volts would be optimal).As for the amps it would be ideal for have up to 3 amps (4.5.6 will do as well but i need mostly 3 amps or less for my small projects) if possible above 1 amp.Thank you i would please like a schematic and the components list.If the schematic or the components are not available at least tell me where to look for this kind of project.Usefull links i found searching for a project.http://leoricksimon.blogspot.gr/2006/04/lab-power-supply.htmlhttp://tuxgraphics.org/electronics/200707/bench-power-supply-unit.shtmlhttp://www.microsyl.com/index.php/2010/03/31/bench-power-supply-0-25v-0-5amp/http://makeprojects.com/Project/0-24-Volt-2-Amp-Bench-Top-Power-Supply/1428/1#.UObyIuTckluAgain thank you.

author: firewalker
author_rank: Super Contributor
timestamp: January 04, 2013, 03:38:07 pm
content: Have a look at Dave's on PSU project.http://www.eevblog.com/2011/11/28/eevblog-221-lab-power-supply-design-part-1/http://www.eevblog.com/2011/11/29/eevblog-222-lab-power-supply-design-part-2/http://www.eevblog.com/2011/12/03/eevblog-224-lab-power-supply-design-part-3/http://www.eevblog.com/2011/12/07/eevblog-225-lab-power-supply-design-part-4-pwm-control/http://www.eevblog.com/2012/01/06/eevblog-232-lab-power-supply-design-part-5/http://www.eevblog.com/2012/01/11/eevblog-233-lab-power-supply-design-part-6-lt3080-testing/http://www.eevblog.com/2012/01/20/eevblog-238-power-supply-design-part-7/http://www.eevblog.com/2012/01/31/eevblog-240-power-supply-design-part-8/Alexander.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 05, 2013, 08:24:33 am
content: And i though i had seen all videos of Dave thank you man you saved me a lot of trouble

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 05, 2013, 02:21:20 pm
content: I watched the videos and i have to say : first thank you and second i would like to ask you if you have anything more simple because this is a bit complicated for me ....and i do not have a problem using a power supply that outputs 1.25 to 25 volts...... great design but i can not find the parts and i am a bit too noobie to understand the schematic.

author: Unknown
author_rank: Unknown
timestamp: January 05, 2013, 02:35:27 pm
content: Too bad Dave didn't finish either of the designs yet.I would discard the Tuxgraphics (its poor use of a MCU with a slow ADC in the feedback loop has been discussed several times on this forum) and the makeprojects.com (no current limit, only goes down to 1.25 V) designs. The other two appear to be reasonable at first glance, the microsyl looks better than the leorich one (hard to read schematic, don't like the huge cap at the output, think what that will do to your poor component if you short it). I noticed one obvious mistake, though (4 Vac should be 40 Vac).

author: Thor-Arne
author_rank: Unknown
timestamp: January 05, 2013, 03:04:03 pm
content: Hereis another lab-psu project.I'm basing my design on this one.Have you considered using the78XXseries or theLM317regulators ?Designs with these are really simple, and might be a good starting point.These normally give you 1 or 1.5 amps, although there are more powerful version available to a higher price.Are you sure you really need a "proper" lab-psu, and that much power?I'm asking because you find these schematics to be complicated.Also, the price of a DIY "proper" lab-psu can easily be more than the price of a commercial one.If you only need various fixed voltages you could easily do this with a few 78XX regulators,and if you need current limiting a LM317 would do.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 05, 2013, 10:40:08 pm
content: Thank you so much. Truth be told i am a noobie in schematics !!! (i only understand basic schematics like 555 timer chip projects and stuff.) I think that with a bit help (form my father (he is an electrician but he can understand basic schematics and he also has a friend who is a electronic enginiere) i will figure this out and build it)Also when i said proper i did not mean a milivolt acurracy but a nice decent power supply that when i set it to 5 volts it will not give me 4.5 or 6 !!! Sorry for the missunderstanding about the decensy of the power supply.

author: Thor-Arne
author_rank: Unknown
timestamp: January 05, 2013, 11:13:37 pm
content: No problemA friend of mine just started and had some trouble understanding schematics and parts, I sent him the attached schematic and he went on making several like that for different voltages versions of that.Only thing that needs changing is U1, C4 and R1This is actually what I use when i play with the arduino and need some extra juice.Very simple and reliable. short circuit and thermal protection.It has a V_Unreg out for the VIN pin (or power jack) on the arduino (must have common ground with the arduino).

author: Spawn
author_rank: Frequent Contributor
timestamp: January 06, 2013, 12:02:31 am
content: I have no idea where I got it from but here a 1.25V…25V and 3A power supply, really simple to build and you can modify it to your needs. If I brake some copyright with this and get warned I will remove it.It is really close to your requirements with it's 3A:

author: FenderBender
author_rank: Super Contributor
timestamp: January 06, 2013, 03:18:23 am
content: I haven't built this yet, but it seems well designed.http://www.extremecircuits.net/2010/06/fully-adjustable-power-supply_17.html

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: January 06, 2013, 04:24:36 am
content: Quote from: FenderBender on January 06, 2013, 03:18:23 amI like this one.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 11:21:39 am
content: FenderBender,Spawn,Thor-Arne Thank you so much i now have all the designs i need.Now i only have to check all the designs and choose the best for me and i think that all of your schematics are good for me i am going to choose the most suitable for me. Also thank you for your responce and your willing to help me.Ill come back with my desicion of what to make.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 07:14:31 pm
content: After putting a lot of thought in your suggestions (thanks to all of you again btw) I decided to go with Thor's idea or FenderBender's idea because these have1: what i am looking2:are easily constructed3:have detailed schematics and components4: i can find the components i need easilyThor's Ideahttp://www.electronics-lab.com/projects/power/001/index.htmlFenderBender's Ideahttp://www.extremecircuits.net/2010/06/fully-adjustable-power-supply_17.html

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 08:24:29 pm
content: I was looking a the schematic of one of the power supplies and i was a bit concfused by the diodes ...Go herehttp://www.electronics-lab.com/projects/power/001/index.html(the link)And search for that D1, D2, D3, D4 = 1N5402,3,4 diode 2A - RAX GI837U (at the part list)Or press CTRL + F and copy paste it )Do i need to buy all 3 kinds of diodes or one will do just fine ? and i could not find the RAX Go837U can i use something else instead?Thank you

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 09:15:32 pm
content: Quote from: ChrisGreece52 on January 06, 2013, 08:24:29 pmThere's just several alternatives, just buy 4 identical diodes.Preferably rated with a higher amperage than your transformer.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 09:42:29 pm
content: Thank you for you quick responce but i can not afford the components they cost $51.58!!!(from ebay i got to buy 50 resistors to use 1 and the 50 cost about 0.99 usd i will try to buy them from another site from which i can get each individual component cheaper! and it offers cheap shipping to Greece)Note: remember that i am a highschool student in one of the most poor countries.As for the other schematic i could make it for 15 usd but i dont know how to find a -5 volt output transformerThank you

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 09:51:55 pm
content: NegativeSparkfun Did not have all the components or even a majority of them...

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 09:56:18 pm
content: You can get your parts fromTayda, I haven't checked that they stock everything though.As for the -5V, you can use the charge-pump (is that the correct term for it) circuit from the example I posted a link to. The negative rail is the lowest line in the schematic that connects to pin 4 on the IC's. (R2, C2, D5, D6, C3, R3 and D7)

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 10:07:28 pm
content: ONLY ONE WORD I LOVEEE YOUUUUU IT HAS EVERYTHING AND FOR A LOW SHIPPING PRICE THANK YOU I LOVE YOU LOVE YOU LOVE YOU!!!!!Dave MUST refer this in one of his videos!!!

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 10:09:34 pm
content: LOL, you're welcome.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 10:17:28 pm
content: One question though and sorry for that i may need some info.Is the polyester capacitor the same with the polyester film box type?Thank you again

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 10:25:35 pm
content: Yes, use the box type polys.I recommend to buy a little more than you need of the cheap parts, nice to have a little in stock if possible.Just add the parts you need first, and change quantity in the cart before checking out.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 10:28:27 pm
content: I am now putting in cart the ammount that i will need from every product then i will increase their quantityAlso question 2 will a TL082 Be the same as the TL081and question 3 will the 2N2219 be the same as 2N2222 or the 2N222A

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 06, 2013, 10:31:51 pm
content: I did not find some of the components for the original design .those i will buy from ebay.(components i did not find1: 2.2Kohm 1Watt resistor2:0.47 Ohm 5Watt resistor3:3300 uf 50 V electrolytic capacitor4:2n2219 (i found the 2N2222 )5:TL081 ( i found the TL082)Another Issue is the transformer i need one from 220-240 Volt Ac 50-60 Hz to 24 Volt Ac and 3 AmpsCan i use a dc input instead of an ac?Thank you

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 10:55:38 pm
content: TL082 is a dual op-amp, you can use TL071 (and several other pin compatible op-amps).You can parallel up several electrolytic caps to achieve the capacitance you need, this is not a critical value.I would just use 4700 uF instead.For the resistors I'd use some with higher wattage than specified 2,2k 3W and 0,47 10W or 15W.For the transistor you can use the 2N2222 it's just another housing.CheckAllTransistorsto find equivalent transistors.And no,you must use a proper transformer. Copper wire wound round a core.This is probably the most expensive part so be careful choosing it.

author: Thor-Arne
author_rank: Unknown
timestamp: January 06, 2013, 11:10:49 pm
content: In my project I use a toroidal transformer from RS, you might have to look in similar places.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:09:42 am
content: Could not find a decent one .... searched in radioshack and i have found nothing....Also i found this one on ebayhttp://www.ebay.com/itm/NEW-24V-3A-AC-POWER-SUPPLY-ADAPTER-FOR-LCD-monitor-TV-/270597957696?pt=US_Monitor_Power_Supplies&hash=item3f00e52840but it outputs a dc voltageIf you see the Technical Specificationshttp://www.electronics-lab.com/projects/power/001/index.htmlit says it runs on a 24volt ac and it says 3 amp input max .. shall i get lower amp transformer and if i do it is bad if it is a dc one?

author: Unknown
author_rank: Unknown
timestamp: January 07, 2013, 12:27:49 am
content: This circuit won't work with DC input: it needs an AC input to generate the negative voltage. A transformer with a lower current rating should be fine, but you will have to adjust some resistors (eg. R7) to lower the maximum current limit.The article is wrong about the transformer, by the way. A 24V/3A transformer will not be able to supply 3A DC, you'd need a 24V/5A transformer for that. The DC voltage after rectification is higher than the AC voltage (hence the 30 V output from a 24 Vac input), so the current must be lower, otherwise you would be creating free energy.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:43:40 am
content: Thank you but i am a bit confused.Can i use something to generate negative voltages?Also can you suggest me a decent transformer (please suggest one that i can order)

author: mariush
author_rank: Super Contributor
timestamp: January 07, 2013, 12:55:49 am
content: Transformers are in general expensive because copper is expensive and because they're heavy.This circuit you chose needs a transformer because its output is AC current and the way it's used in the circuit, the bridge rectifier (made from those 4 diodes) separates the AC wave into positive DC voltage and negative DC voltage. With a switching power supply like the one you mention, you only get positive DC voltage.I would suggest checking RS-Online.com and Farnell.com for transformers.You must pick a 24VAC one or higher, but you can choose one rated for lower current to save money. But you obviously won't get 3A of DC current at the output.And like above poster says, if you pick a 24VAC transformer, you may not get 30V DC out of it, you should pick a 32 VAC transformer if you really need 30V and more.The cheapest you could probably get from Farnell would be this one:http://uk.farnell.com/pro-power/ctfc20-12/transformer-20va-2-x-12v/dp/1780849which does 24 V AC at 0.8 A, so you could do this circuit to output up to 0.6-0.7A or soA bit more expensive but also more powerful, is this onehttp://uk.farnell.com/multicomp/vtx-146-080-118/transformer-80va-2-x-18v/dp/1675067does 36 V AC at 1.11A or 18V at 2.2A, depending how you wire it.If you can live with up to about 20V DC, this will give you that and up to about 1.5-1.8A current.http://uk.farnell.com/pro-power/ctfc50-15/transformer-50va-2x-15v/dp/1780858<- 2x15VAC or 1 x 30VAC 1.67AThis would probably be the cheapest you can get from Farnell that would be suitable to get 3A and 24V :http://uk.farnell.com/pro-power/ctfcs100-12u/transformer-100va-2-x-12v/dp/1780896I don't know how much shipping is, but maybe if you order everything from Farnell it would be cheaper and more convenient than waiting 3-4 weeks for stuff to come from Hong Kong (that's where Tayda is)PS. The circuit you chose is a bit difficult to understand a the schematic is kinda badly drawn, be careful how you make the wires, lots of wires cross over on the drawing but they're only connected where it's a round filled circle.You'd be better off doing the power supply FenderBender mentioned:http://www.extremecircuits.net/2010/06/fully-adjustable-power-supply_17.htmlThis circuit accepts DC input, so you could use a 19v laptop adapter with no problem, or a transformer that output AC provided you convert the AC to DC using a bridge rectifier.The -5v is also not a big of a deal, you can generate that -5v from the 18-19v using a cheap chip like MC34063 (but you'd need to do some math to pick the components it needs, the datasheet has everything including example circuit to get negative voltage out of it :http://uk.farnell.com/stmicroelectronics/mc34063abn/ic-dc-dc-controller-34063-dip8/dp/1077180)

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:08:24 am
content: I think thathttp://uk.farnell.com/multicomp/vtx-146-080-118/transformer-80va-2-x-18v/dp/1675067this one is the best for me !!! i do not think that i will need more than 20 volts or 1.8 amp bit will that change the components (any of them) or the wiring please take a look at the schematic to see why i am a bit confussed

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:11:25 am
content: But it does not offer shipping to Greece its UK only.

author: Thor-Arne
author_rank: Unknown
timestamp: January 07, 2013, 01:16:11 am
content: Quote from: ChrisGreece52 on January 07, 2013, 01:11:25 amBummer, what about RS?It's this one by the way RS # 671-8978Or something similar.

author: FenderBender
author_rank: Super Contributor
timestamp: January 07, 2013, 02:04:10 am
content: I buy most of my transformers from a company called Antek. Their website isn't working right now but they also have an eBay store. Good transformers and they are very good value.http://stores.ebay.com/Antek-incHowever, shipping to Greece is around $20 so that's probably not going to work for you.

author: Unknown
author_rank: Unknown
timestamp: January 07, 2013, 02:22:06 am
content: Quote from: mariush on January 07, 2013, 12:55:49 am0.6 A from a 0.8 A transformer sounds optimistic to me. If you have enough capacitance, then DCV will be sqrt(2) (=1.4) * 24 V, or 34 V (minus rectifier loss). This means that the current must be reduced to 1/sqrt(2) times the AC current if we assume conservation of energy. Since a circuit with a rectifier and capacitor only charges capacitors at the peaks of the input voltage, there will be short bursts of a much higher current draw, so some fudge factor is used. I believe there's a Hammond document describing a factor 0.62, I usually use 0.6.Transformers are usually one of the most expensive parts of a linear power supply (together with heat sink, input caps, case and power transistors). Ideally you would want to reuse a transformer or acquire them from a surplus dealer. Shipping is expensive because of their weight, though.

author: mariush
author_rank: Super Contributor
timestamp: January 07, 2013, 02:28:20 am
content: Quote from: ChrisGreece52 on January 07, 2013, 01:11:25 amIf you checkhttp://export.farnell.com, you'll find out they work with a local distributor in Greece :http://www.farnell.com/distributors/greece_dar.htmDarlas Electronic Applications SA5, Kimonos Str122 44, EgaleoAthensGreeceTel: +30-210-59.86.179Fax: +30-210-59.11.161Email: darlas@darlas.grWeb:www.darlas.grCheck the website or give them a call and see if they work with regular people and not just companies, how much they'd charge you extra, all that.Yeah, they seem to have an online order, but their pages are really hard to browse, they don't let you exclude out of stock transformers so you have to go from page to page as far as I can see:http://www.darlas.gr/comersus/store/comersus_listCategoriesAndProducts.asp?idCategory=17521983PS.Turns out you can copy the product name and paste it in the search box on top right on that darlas website and it finds the Farnell item, for example enter "VTX-146-080-118" and you get this page:http://www.darlas.gr/comersus/store/comersus_viewItem.asp?idProduct=1838768Looks like they're making everything more expensive, 19.7 euro versus 12.7 euro on Farnell (10.2 uk pounds is about 12.7 euro). But I'm not sure if they do free shipping or not, i'd be worth it then. Check everything out.

author: SeanB
author_rank: Super Contributor
timestamp: January 07, 2013, 05:11:28 am
content: Just buy the 1N5404's and get 10. 3A 400V diodes for general purpose use are fine at lower voltage and lower current. They are useful as spares, just not suitable for use in high speed switching like as rectifiers for the output of a switching supply, there you will be better off using a UF5404, same ratings but a much faster switching ability. Can still be used at low frequency, but they are not as robust. I have seen the iN5404 used in supplied delivering 5A, where they run for years at a very high temperature.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:04:28 pm
content: Quote from: FenderBender on January 07, 2013, 02:04:10 amSr that was an answer to Thor Arne who asked if Radio Shack is offering shipping to Greece.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:06:41 pm
content: Quote from: FenderBender on January 07, 2013, 02:04:10 amYou are right .... its a bit expensibe but ill see what can i findThanks

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:12:11 pm
content: Quote from: mariush on January 07, 2013, 02:28:20 amThank you very much you saved me a lot of frustration but unfortunately 1st the shop is in Athens (no problem but i had to pay shipping cost it would be cheap but i needed money)2nd The same transformer costs 5 euros more than if ordered it from UK.And 3rd THIS ITEM IS OUT OF STOCK!!! I CAN NOT BELIEVE IT im so unfortunate ....

author: LEECH666
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:06:36 pm
content: If you're going to build this supplyhttp://www.electronics-lab.com/projects/power/001/index.html,please note that the original design isn't very good and has some issues (only one 2N3055 for example). There is a revised version available on the Electronics-Lab forums that fixes these issues.I attached the updated revision 2 circuit diagram and the parts list (revised by audioguru), however there are still some minor errors in there, for example D12 is the 10V (1W) Zener Diode and not the LED (which is LED1 in the parts list). The potentiometers RV2 and RV3 are unmarked in the circuit diagram, and R11 seems to be missing on the parts list.Cheers,Florian

author: Thor-Arne
author_rank: Unknown
timestamp: January 07, 2013, 01:17:20 pm
content: @LEECH666Thanks a bunch.This saves me from having to discover these issues myself.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:26:25 pm
content: Thank you very much for this man with this thing that u have done you saved me 1st a lot of time and 2nd a lot of money maybe.

author: ptricks
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:51:37 pm
content: I wouldn't recommend the opamp based supplies for someone starting out, while the circuits are fairly simple there is a lot that can go wrong in the laying out of the circuit on a board, like oscillations and noise.For a first supply and one that can built just about anywhere in the world, the LM1084 is the way to go. Add a pass transistor if you want more current . It is the simplest variable supply you can build .http://www.electronics-lab.com/projects/power/010/index.html

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 02:01:52 pm
content: That seems pretty neat thank you but the only dc power supplies i got are phone chargers from 4.9-5.7 volts a 9volt transformer and a Hp power brick i got from an old printer that outputs +16 volts (500 miliampere) and +32 volts (375 miliampere)I could use some resistors to get the 32 volt it needs down to 18 or i can use the 16 volt 500 miliampere output to have a good solid output but will less maximun voltage...what you say(thanks btw)

author: ptricks
author_rank: Frequent Contributor
timestamp: January 07, 2013, 02:18:43 pm
content: Quote from: ChrisGreece52 on January 07, 2013, 02:01:52 pmIf you have a DC adapter then you can just connect it where to C1 and forget about the bridge.The LM1084 will work up to 27 volts so I would use the 16VDC supply for now . The great thing about this circuit is if you find a better source supply later you just swap the transformers and the circuit will still operate the same but with the higher voltage and currents.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 02:21:27 pm
content: Quote from: ptricks on January 07, 2013, 02:18:43 pmOK so i will power this thing up with my +16 volt Dc power supply and i will be finethank you

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 02:35:23 pm
content: Seems pretty ok but what is the 2pin pbtand can i use diodes instead of the rectifier ? and if i can which diodes will work the best?

author: mariush
author_rank: Super Contributor
timestamp: January 07, 2013, 04:18:31 pm
content: This circuit is much simpler but it also won't give you current limit like a regular linear power supply would give you.If you power it with DC from that adapter, you don't need the BR1 bridge rectifier. When you'll use an AC transformer, you'll use one, or you use 4 diodes which just have to be rated for the maximum current you'll use. For example, 1N4007 diodes are rated for 1A , 1n5401, 1n5402 and possibly 03,04 etc can do 3A and so on.That PBT is just regular connectors, like these:You don't need them, use whatever you like.Now keep in mind this LM1084 is a plain linear regulator, there's loads of linear regulators :http://uk.farnell.com/linear-voltage-regulatorsorhttp://uk.farnell.com/ldo-voltage-regulatorsLM1084 is used there simply because it can do 3A, but it's kind of expensive. There's plenty of other chips that work the same and have the same pins with same behavior.But all plain linear regulators need about 1.5-2v above what you want to output to work properly, so if you feed this LM1084 with 16V you'll only be able to get 1.25-14v in stable conditions.For example these can do from about 2.2A to 5-7A depending on model , check the details for eachhttp://uk.farnell.com/fairchild-semiconductor/lm317t/reg-linear-1-2v-to-37v-adj-3to220/dp/2102581http://uk.farnell.com/national-semiconductor/lm338t/v-reg-adj-1-2-32v-to-220-3-338/dp/9489428http://uk.farnell.com/national-semiconductor/lm350at-nopb/ic-v-reg-linear-adj/dp/1469103If you want a regulator that works with less voltage difference, check the ones in the second link, the LDO regulators .. these only need 0.3v or more, depending on the model.for examplehttp://uk.farnell.com/stmicroelectronics/ld1084v/v-reg-adj-1-25-28v-1084-to-220/dp/1087148http://uk.farnell.com/stmicroelectronics/ld1085v/v-reg-adj-1-25-28v-1085-to-220/dp/1087152http://uk.farnell.com/national-semiconductor/lm1085it-adj/v-reg-ldo-3a-adj-1085-to-220-3/dp/8207364http://uk.farnell.com/linear-technology/lt1585ct-pbf/ic-v-reg-ldo-adj-to-220-3-1585/dp/1273603Last, these chips generate the exact voltages you want by throwing out the difference as heat. Ex if you give it 16v and you want 3.3v at 0.1 A, then the regulator will generate (16v-3.3v) x 0.1A = 1.27 watts as heat.The chip alone without any heatsink on it will only handle about 1.5 watts continuously, and then it will turn itself off and on all the time to keep itself cool. So you need a heatsink on to keep it cool.For example something like this would be the minimum you'd have to usehttp://uk.farnell.com/multicomp/mc33278/heatsink-to220-x-2-7-6-c-w/dp/1710623http://uk.farnell.com/multicomp/mc33278/heatsink-to220-x-2-7-6-c-w/dp/1710623http://uk.farnell.com/aavid-thermalloy/507302b00000g/heatsink-to-220/dp/1611415http://uk.farnell.com/aavid-thermalloy/577202b00000g/heatsink-to-220/dp/1611441http://uk.farnell.com/wakefield-solutions/274-1ab/heatsink/dp/1611445Other than the first two (and even those are iffy) you may need a fan to blow some air over the chip if you're going to use it for a long time at about 5v or less (10v difference or more from the input)

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 07, 2013, 09:05:46 pm
content: This one seems to be finehttp://uk.farnell.com/stmicroelectronics/lm338k/ic-v-reg-adj-1-2-32v-to-3-2-338/dp/1094254What do you say? I was a bit confused about the adjust (because it is a 2 pin regulator but i now know from the datasheet that the pins are input and adjust and the case is the front thing is the output DATASHEET :http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000548.pdfThank you

author: lamaseed
author_rank: Newbie
timestamp: August 28, 2015, 02:34:31 pm
content: Greetings!I am a newbie with electronics and so i decided to create a power supply for my electronics bench (under construction). I have looked around and this power supply has everything i want. I have bought the materials and all, although i couldn't get the TLE2141.There is a thing in the schematic i do not get though. It has been said that the LED is actually a 10V 1 W Zener. In the schematic there is another Zener like this connecting the positive rail and Q3 which is not mentioned on the BOM list. So the system has 2 of these diodes or it is some sort of mistake?Thank you in advance!P.S First post

author: Cliff Matthews
author_rank: Unknown
timestamp: August 28, 2015, 03:23:30 pm
content: Quote from: FenderBender on January 06, 2013, 03:18:23 amLooks like a white smoker. I see max Vcc on TL071 is 18v.In that schematic it sits scarily across the +18 and -5v rails.Oops, my bad(looking at the wrong pdf) spec says 36vBut still, those who 'd want to modify the input past ~26v (to take advantage of the 317/mj3055's range) would be asking for trouble.