design of circuit for 0-24v 5amp regulated power supply - Page 1
Forum section: electronics / beginners

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 17, 2017, 06:26:14 pm
content: I am noobie so plz help and co-operateI was thinking to use 12-0-12V 5A center tap transformerI know by connecting 2 12v wires I'll be getting required 24v ac but i am stucked at which components shall be used and how, for making regulated power supplyMy ultimate aim is to make an 48v 5amp power supply to run an electric motorSo just thought I'll make 2 , 24v 5amp power supplies which could then be connected in series for getting the required 48v 5Amp as an outputIf you could help me with designing a circuit for making an 24v 5amp regulated power supply that will be really helpfulI have found a circuit for 24V 1ampBut my requirement is for 5amp and i am not sure which components should be replacedLink to circuithttps://drive.google.com/file/d/0B0H4hwbNhR-GTkRHQ0ZjY2dDTWM/viewImage is also attachedAny suggestion and help will be appreciatedThnks

author: Ian.M
author_rank: Super Contributor
timestamp: September 17, 2017, 06:40:17 pm
content: Comes from:https://www.eevblog.com/forum/beginners/how-to-make-regulated-power-supply-of-0-48v-5amp-using-24-0-24-v-5amp-center-t/Basic Technical Forum Etiquette: Please don't start multiple new topics for the *SAME* project unless your new question is totally unrelated to your previous questions or the previous topic has jumped the rails and the discussion has gone way off into the long grass of stuff you don't understand and have no interest in. Otherwise your readers have to research your previous posts in other topics to get the broader picture of what you already know, have and can do, which wastes our time and yours. If a previous topic jumped the rails, link to it , but mention that after post #n you no longer found it helpful and why.(N.B. I am not an administrator here and these are just strong recommendations, not official rules)The quick answer to "But my requirement is for 5amp and i am not sure which components should be replaced" is *ALL* of them except the power LED. Yes there are circuits that boost the output of a LM317 regulator, but unless you design is good, you loose the thermal overload protection, and they invariably require more headroom than the original unboosted circuit. If you want an easy intro to higher current linear PSU circuits, consider using the LM723 with external pass transistors.

author: IanB
author_rank: Super Contributor
timestamp: September 17, 2017, 07:16:41 pm
content: Quote from: VickySalunkhe on September 17, 2017, 06:26:14 pmAs Ian.M said, please do not ask the same question twice in two different topics.However, you do not normally need a regulated power supply to run an electric motor, unless it is a special motor. Normally just a rectified output from a transformer will be sufficient.

author: Zero999
author_rank: Super Contributor
timestamp: September 17, 2017, 07:59:39 pm
content: As Ian said, a regulated power supply is not required for a motor.One thing which might be an issue is the motor start up current, which with a load with a lot of inertia, can easily last longer than that taken by a smoothing capacitor. Make sure the rectifier diodes are overrated and use slow blow fuses, so they don't blow when the motor starts.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 04:31:13 am
content: hello hero999thnks for your helpcan you plz tell me where should i keep the fuse in the circuitand what should be its specificationas i am going to work with 5Amp current.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 04:35:48 am
content: thanks IanB for your helpi asked the question once again as i found out taking out 48V 5Amp from transformer as DC its tough and i was not able to search for the components which will support the requirementslm338 is there but voltage range is 2.5 to 32 Vthats why i thought to change it to making 2 24V 5Amp power supply and will connect it in seriescan you suggest me which capacitor, resistor,transistor and fuse should be used?your help will be really appreciated

author: IanB
author_rank: Super Contributor
timestamp: September 18, 2017, 04:43:16 am
content: I think you are asking the wrong questions. You think you need a regulated DC power supply, but you may be wrong. If you tell us what you want to do with the power supply you may get better answers. For example, if you want to run a motor maybe you don't need any capacitors or voltage regulators at all.So instead of asking how to make something, tell us instead what problem you are trying to solve and ask for help solving that problem.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 04:52:16 am
content: okay may be because i am completely new to this concepti need to run motor rated at 48V 500W dc motorat first instead of buying batteries which will cost too much at such an early stage i thought to build a power supplyand give it to the motorpreviously i have started the motor using 2 regulated power supply unit in series of 30v 500mA by setting the voltage 24v on each psubut now i don't have access to those psu so thought to make of my ownwhat do you suggest?thanks

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 06:15:16 am
content: Quote from: VickySalunkhe on September 17, 2017, 06:26:14 pmNow there are more elegant ways to do it but the easiest way would be to get two over rated transformers that can put out 24VAC, in your example of 12-0-12 transformer aim for 12 amps total rating from each transformer.Wire up each transformer to a separate bridge rectifier and smoothing capacitor, the smoothing capacitors should be rather large about 20,000 uf if absence of ripple matters at all.At this point check that the DC output is in fact between 37-39V out of the capacitors, if it is a little high you can use a 10A rated diode to drop it though this may cause issues at higher currents.If it is a little below 37 don't worry too much as it would only mean a slight decrease in total output voltage, if the voltage is correct you can use two LM338 regulators linking one's output to the ground of the second.Feel free to ask for more details. Also for this to work without blowing up you would need a rather large slab of metal to serve as a heat sink, if you would like to avoid using a heat sink there are adjustable switch mode supplies available that could be used without a heat sink and in place of the LM338.http://www.ebay.com/itm/XL4016-DC-DC-Buck-Step-Down-Power-Module-4V-40V-to-1-25V-36V-8A-200W/192211314397?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649All of this arguably irrelevant for a motor driver but it is what you asked for in the title.

author: IanB
author_rank: Super Contributor
timestamp: September 18, 2017, 06:30:12 am
content: Quote from: VickySalunkhe on September 18, 2017, 04:52:16 amOK, but still more information would be helpful. You say the motor is 48 V 500 W, which means it will draw over 10 A at full load. And yet you say you have run the motor with a 500 mA power supply, which is much less than 10 A.Therefore, what do you want to do with the motor? Will it be powering some machine, or do you just want to see it run? The amount of power drawn by a motor depends on how much you load it. If you just want to see it spin, you don't need that much power. You probably don't even need 48 V. It will run on 24 V or even 12 V.So you see, the answer all depends on what you will use the motor for.If you want to power the motor and just make it run, then you can get a suitable transformer, put a bridge rectifier on the output (a big one, suitable for the required current), and connect that directly to the motor. There is no need for any electronics at all.Next, if you want to vary the speed of the motor, a voltage regulator is not the way to do it. You will want some kind of motor speed controller that switches the power on and off very fast, like a thyristor controller or a PWM controller.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 02:13:00 pm
content: Thanks IanB for your replyActually i have a throttle and control unit which supplies power to the motor accordinglyMotor , its actually an dc hub motorI am working on e bikeI am from Computer engg field so my knowledge about electronic and electrical field is not goodMotor specificationthrottle voltage 30VAt the later stage i am going to use li ion batteries but for now i am thinking to make regulated power supply.For now i am thinking to build 2 24v 5A regulated power supply and will connect it in seriesUsing center tap transformer ill get more than 29 v from one power supplySo thought to make an regulated psu so i can test the motor under various voltage levelsVarying between 32-53VFrom some source i found out 12-0-12v 5amp will not produce 5amp supply and now i was curious why not?So plz guide me how can i achieve this?I have found this circuit but its for 24v 1Amp and my power requirement is 5ampLink to circuithttps://drive.google.com/file/d/0B0H4hwbNhR-GTkRHQ0ZjY2dDTWM/viewThanks a lot

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 02:16:34 pm
content: Quote from: VickySalunkhe on September 18, 2017, 02:13:00 pmThe LM317 is the little cousin to the LM338 i mentioned earlier, all you would really have to do is change regulators. Perhaps read my earlier post?Also a 5 amp rated supply won't deliver 5 amps because, simply put, it is only rated for 5 and in reality there is always loss in linear circuits. So in simple terms if you want 5 amps usable at peak voltage aim for 12 amps or so rated transformer.More complex terms as to why a 5 amp supply won't deliver 5 amps. OK if you have 24VAC out of a transformer that is 5 amp rated that is at 24V RMS whereupon converting to DC you get the peak to peak voltage smoothed, so 24V would become near 40V which would in effect half the current at its upper voltage limit. Besides that any circuitry will impose some resistance, especially linear no matter how good, so then there is some loss already however the problem is further compounded by the efficiency which in linear supplies and regulators is typically 50% or below. Nothing is perfect, even switching supplies top out at 98% at the cost of imposing high frequency noise but i digress. Hope this helps.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 02:26:56 pm
content: Quote from: neo on September 18, 2017, 06:15:16 amThanks neo for your rplyBut i didn't get why did you mention voltage range 37-39VDoes single 12-0-12V transformer going to output that much voltage?And you mentioned if voltage are okay use two lm338 sry but i didn't get why to use two?What i am thinking is build 2 separate 24V 5amp regulated psuAnd then I'll connect it in series to get 48V 5amp dcAm i correct?Or if there is some other method which will be good plz suggest meYour help is really appreciatedThanks a lot

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 02:33:38 pm
content: Quote from: neo on September 18, 2017, 02:16:34 pmThanks neo for your replySo what do you suggest for which transformer (or how many) should i opt for so that i can fulfill my requirement of giving as supply voltage between 32V to 53V to the dc motorThanks

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 02:41:46 pm
content: Quote from: VickySalunkhe on September 18, 2017, 02:26:56 pmI have built a few 5 amp supplies and every time i have built one i find 24VAC puts out up to 40VDC once rectified and smoothed, as said this is because it is the peak to peak voltage.You don't have to use two LM338s, the only problem with one is that it only outputs about 1.2 to 35VDC regulated, you need about 37VDC in to get that because of the aforementioned efficiency and a small voltage drop. I said two because you said your ultimate aim was a 48VDC 5 amp supply which can be achieved if you have two separate LM338 power supplies linked in series.As for a transformer, all you need is two 24VAC windings, so this could either mean two 24VAC 12A transformers with their primaries linked in parallel or one big transformer with two separate 24VAC windings, very important for functionality separateNOT24-0-24VAC, with a 12 amp rating on each winding.Also an important mention if you are going to build an LM338 supply then i would recommend two things.First to keep in mind you will need a large heat sink about 5 pounds with forced air cooling, bigger is better though.Second, buying spares because you will blow at least one up learning, i did, and i have found some difference between regulators with their power handling.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 02:50:26 pm
content: Thanks neoI just had a thoughtWhat will happen if I'll use 24-0-24V 5Amp center tap transformerIf ill use wire 1and 3 with a bridge rectifier I'll get 48VBut what will happen if I'll use wire 1 and 2 with a bridge rectifierAnd wire 3 and 2 with another bridge rectifierAs far as i see wire 1 and 2 will generate positive 24V dcAnd wire 3 and 2 will generate negative 24dcSo is there a way i can convert that second way to positive and somehow connect those two power supply wires in series to get 48VAm i thinking rightOr all this stuff is actually wrong?Sry for too much confusion but i am trying to know what and how they are going to work..Thanks a lot...

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 02:57:04 pm
content: Quote from: VickySalunkhe on September 18, 2017, 02:50:26 pm24-0-24VAC would work to build a power supply, each half going to a separate bridge rectifier with the center tap being ground. The problem with this is that it, once smoothed, it would be two 37-40VDC supplies with common ground, perfect for a dual channel supply but incapable of being linked in series.Also worth mentioning is that the only difference between 24-0-24VAC and two separate 24VAC windings is that the center tap has the windings in series.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 03:06:27 pm
content: So shall i use 2 12-0-12V 5Amp center tap transformerAnd make 2 separate regulated psu using those transformerAnd then connect them in series?As you said I'll get 37v from 1 psu so i can adjust both psu to 24v then connect it in series i can easily staisfy my motoAm i Right?Amd if i am rightCan you plz suggest me changes required inLink to circuithttps://drive.google.com/file/d/0B0H4hwbNhR-GTkRHQ0ZjY2dDTWM/viewOther thanLm338 ,10Amp diodes and capacitor of 20000ufAs u suggestedThere are other components left like 2 more capAnd 3 resistors what about them?Thanks a lot neo really appreciate your help

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 03:15:02 pm
content: Quote from: VickySalunkhe on September 18, 2017, 03:06:27 pmThe pleasure is mine, i like linear supplies.12-0-12V will work but it will need to be more than 5 amp rated, as i said 12A at 24VDC is only 7A at 40VDC and as i have also said overrate. For example 10A at 24V would in theory work but may not be able to provide the full 5 amps at the desired voltage.Also it makes for a better supply, better adjustability, if for the 5K potentiometer you were to use a ten turn potentiometer. Of course that is strictly optional.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 18, 2017, 03:25:10 pm
content: So do i need to change the rest of the components or not ?other than the transformer rating, diodes, lm338 and cap u statedThanks neo you really have helped to clear out some concepts

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 03:29:16 pm
content: Quote from: VickySalunkhe on September 18, 2017, 03:25:10 pmHigher current rated diodes and an LM388 are all that are really needed, i recommend changing the capacitor to a larger value for reduced ripple though that is strictly optional.

author: neo
author_rank: Super Contributor
timestamp: September 18, 2017, 04:07:13 pm
content: Also, with the LM338 you will need a large heat sink, about 5 pounds with forced air cooling for both. Bigger is of course better when it comes to cooling.

author: Zero999
author_rank: Super Contributor
timestamp: September 18, 2017, 06:10:04 pm
content: All right, it sounds like you do need a regulated power supply after all, but do you really have to make one? Perhaps you should look at buying a 500W 48V power supply first? I doubt it would be cheaper to build one.http://www.mouser.co.uk/ProductDetail/Mean-Well/RSP-500-48/?qs=8uyp%2fy7yFW51E4MJhz7yTA==I'm still confused as to whether 5A or 10A, 24V or 48V is required?One thing to bear in mind, with TO-220 regulators, such as the LM338, is the maximum practical power dissipation, for that package type, is around 50W, so you'll only be able to get 5A out, when the difference between the input and output voltage is under 10V.The maximum differential voltage for the LM338/317 is 40V, which can also be problem because with 24V or more out, it's likely you'll need a transformer which will give over 40V, after the rectifier, which will destroy the regulator, if it ever goes into current limiting mode.The output current and power dissipation of the LM317 can be increased by adding by pass transistors.A cascode and zener diode, can be used to overcome the maximum 40V differential rating.

author: Avacee
author_rank: Unknown
timestamp: September 18, 2017, 06:24:29 pm
content: You could buy one and reverse engineer it for around £25.http://www.ebay.co.uk/itm/DC-48V-10A-Universal-Regulated-Switching-Power-Supply-for-Computer-Project-OL-/282556976292http://www.ebay.co.uk/itm/DC-3V-5V-12V-24V-36V-48V-Universal-Regulated-Switching-Power-Supply-LED-CCTV-PSU-/151886747221http://www.ebay.co.uk/itm/Universal-DC48V-8-3A-Regulated-Switching-Power-Supply-Transformer-Switch-SU-/282535948603Though at those prices you're probably more likely to learn how to make something with zero to few safety features.

author: neo
author_rank: Super Contributor
timestamp: September 19, 2017, 03:19:44 am
content: Quote from: Hero999 on September 18, 2017, 06:10:04 pmTo the underlined bit, this problem can be solved with a variac, at least i have done that.It may be cheaper to buy one but it is educational to build one.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 20, 2017, 01:34:05 pm
content: Hi neoI starter making the power supplyI tried it total 3 times at 3 different placesFirst two time it was working fineBut at the 3rd location the something happend in the pot and so now i cannoy regulate the power supplyWas willing to know what could have happend?Can i use 47k pot instead of 5k pot and what will happen if i do this?Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: September 20, 2017, 01:52:03 pm
content: No.Pots are rated fror dissipation by the power the whole track can handle. Convert that to a current by I=sqrt(P/R), and that gives you the macxmum current for any part of the track.A 47K pot would need to be rated for 5W dissipation, and only a small fraction of its rotation would be usable. You probably burnt out the pot, as a 5K pot needs a minimum 1/2W rating to handle the 10mA minimum load current of the LM317 regulator (via the 120R resistor), and most small pots are rated for less than that.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: September 20, 2017, 01:56:36 pm
content: Thanks Ian.MSo what do you suggest for which should i go forI need to regulated around 38V 5AmpThanks

author: Ian.M
author_rank: Super Contributor
timestamp: September 20, 2017, 02:58:16 pm
content: If you want a linear PSU, use aLM723.I posted a LTspice sim of the regulator section of a Philips PE 1535-00 0V - 40V, 0A - 0.5A. single output PSU,. Given a big enough heatsink, it would be fairly easy to extend to 5A:* To beef up the pass transistor to handle 5A, add three 2N3055 transistors B and C paralleled with 0.1R individual emitter resistors for current sharing, to V26, the BDY20 to make a Darlington pair, with an extra 47R resistor from the 2N3055 bases to the lower end of the emitter resistors.*Replace V111, V112 with fast >100V, >7A diodes.*Decrease R137 to 0.22R to increase the current limit to 5A.Caution: if the peak input voltage is >45V, increase the Zener voltage of V109. It needs to be Vin_peak-16V, or a few volts more. If you use a 50Hz or 60Hz transformer and a bridge rectifier to feed it, you will probably need a preregulator as the PSU cant tolerate more than about a 12V swing between the peak unloaded input voltage and the troughs of the ripple at full load. Another pair of paralleled 2N3055 transistors should do the job in a Darlington capacitance multiplier circuit with a >1A driver transistor, with the voltage across the capacitor clamped to 45V by a chain of 15V zeners.The heatsink needs to be *MASSIVE* and probably fan cooled, as worst case, with the output shorted it will be dissipating 225W + whatever the preregulator dissipation is. e.g. with a 44V 8.33A secondary feeding it, at 10% high mains voltage that could be another 115W.A better option would be to find a used 48V, 300W or greater telecoms SMPSU, and either hack it to drop the output voltage to a fixed 38V, or trim it down to 45V and use it to feed the modded Philips ciruit I have just described if you need a fully variable output.