Power Supply Guidance - Page 1
Forum section: electronics / beginners

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 29, 2023, 11:41:37 pm
content: I am posting this thread as guidance for my decision-making process as well as absorbing knowledge that I currently don’t possess from individuals that are kind enough to share their knowledge and experience.I have a little bit of understanding on the subject matter of power supplies but would like to expand my knowledge.I have a few decent multimeters at my disposal. I have a decent soldering station with an assortment of tips. (FX-951).I have a HP 6236B triple output power supply. It’s old. I was given the power supply from a client where I did some work. It works. It’s a little rough. The analog gauges need replacing. Some of the knobs are slightly cracked. But these are all things that I could fix up. As far as operationally it puts out voltage. I am not sure how clean the power supply is as I do not have an oscilloscope at the current time.I can program an Arduino. I can do a little bit in C++ as well as Java.I understand CAD software to a high level and can pretty much manufacture any kind of enclosure and or part that I may need as far as an enclosure or mounting tabs or knobs etc. I have access to all sorts of CNC and fabrication equipment.The power supply that I would like to either acquire or build would have a budget of around $500.This power supply would be used for voltage injection for fixing boards. For development that I do when it comes to some of the lower voltage CNC controls (no need to go over 60V), and just basic learning electronics. Some basic battery charging needs as well.I would like it to have the ability to set voltage as well as limit the amount of current.I am not particularly concerned with efficiency.It does not have to be portable.So, the people that have a lot of experience in this field.Is it better to buy a linear power supply? I am fairly familiar with the offerings from Siglent, Rigol and GW and I also looked at the RD RD6012PW.Is it better to buy a cheaper switch mode power supply and do some modifications to get rid of the noise and ripple?Is it better to build a linear from scratch using a toroidal transformer.Or some other option that I am completely unaware of.I am basically looking for guidance and education. Any response is appreciated.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 30, 2023, 01:58:58 am
content: look for a big old transformer at say a radio rally.thats the heart of a linear psu,once you have that look for schematics for your voltage+ current needs.

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 30, 2023, 04:32:24 am
content: I have been designing power and power supplies since about 1978. There are no easy answers to your question.1) Dealing with mains voltage is potentially dangerous and is for the knowledgeable only. So I strongly advise against you designing your own AC/DC switching power supply for example. If I wanted to build something for myself I would start with a laptop power supply which typically produces 18V or so at 50 Watts or more. These give you a great value in $/watt, size, and safety. A mains frequency transformer will be big and expensive for the money, and will probably need more cost and size downstream than the 18V switcher would. The mains frequency transformer is big old technology and does not have mass production behind it. But....if you were going to do that, I do not know why a toroid would be better. In fact if you were to use a mains frequency toroid transformer, you might have more issues with inrush current as I have encountered some years ago.2) Downstream of the big transformer or laptop power supply you would still need to do some switching power conversion to get voltage up or down. If you decide to reduce voltage with a linear regulator, that can produce a lot of heat. Even around 1980 when switching power conversion was much less mature than it is today, I think that a half-decent switcher may be less failure prone than a powerful linear, due to the problems with power transistors getting too hot for some reason.3) The above does not make light of the knowledge and skill needed to build a good switching power converter. All of the details, particularly pcb layout are very important. Proper pcb layout requires understanding the design fully, or else copying a good existing design.What I have is a (is it 300W?) cheap Chinese made bench power supply. The biggest problem with it is that the output has a lot of switching noise, so I placed a large toroidal common mode choke between the output terminals and anything I power with it. That works well.

author: alligatorblues
author_rank: Regular Contributor
timestamp: October 30, 2023, 05:23:02 am
content: If you go on eBay, you can find a 900W DC PSU with VC limiting, 15A 60V, linear and drifts <1.0mV no matter how long you run it. It can use sense wires, so it can monitor the output right at the load. It's air cooled without a fan. It's made by Lambda. I had it connected to a bus, and I was fooling around with TEC cooling. That can suck a lot of current. So, I turned the current up all the way, and just let the voltage regulate it.I was using a thermocoupe with braided metal covering the wire, to monitor temp. of the TEC cooler. That metal braid accidentally got draped over 2 of the bolts on the bus I was using, and shorted the DC output. That means it was drawing as much current as possible. I didn't notice the VA meter on the bus until 12 hours later.I lifted the metal braid off the bolts, and put a powerful fan on the transformers. It has 2, so you can wire it for 240VAC, or 120.It took a bit to cool down. But no damage was done to the supply. That is the toughest dc supply I've come across. And I put a triple 300W (900W) resistor at about 3 Ohms on it, and monitored the drift for a whole day. Its 1.0mV spec is correct. I also put a thermocouple inside the supply when it was loaded with 3 Ohms, and it ran at about 90 F.That cost me $200 with shipping. If you tried to build that, the cost would be $3-5,000. And it wouldn't be safe. You can learn about DC supplies, but most people want something better than they can build. And, switching supplies are noisy as hell. You don't need a scope. Just measure the AC in the output signal.Switching supplies work in PC and Mac computers, because all the parts in a computer are made to tolerate +-10%, and all kinds of noise. But, SMPS is cheaper, lighter, smaller, and most loads don't care about the noise.

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2023, 06:08:10 am
content: Quote from: JJ_023 on October 29, 2023, 11:41:37 pmAny reasonable DMM in ACV mode will display 100 Hz ripple from a linear PSU.QuoteWith a healthy budget like that you can buy far better than you can ever hope to make with limited experience.QuoteFor all these uses including charging reverse voltages are the risk.You can carefully manage this but inserting a adequately rated series diode offers the best protection.QuoteThis is not so easy for the novice PSU builder and something I skipped when building my own in favor of a purchased unit that had this feature.QuoteIMO if you want/need the features they offer, yes.$399 SPD3303X-E we sell lots of which came at some surprise however study of their specs and features and particularly their impressively low 300uV ripple and noise reveals why customers select them.*Series mode offers 60V @ 3A and *Parallel mode 30V @ 6A. (*no external connections)Latest HW versions have resolved the pesky 2A diode bridge failure and added OSD of Serial and Parallel modes.QuoteThere's 2 things you need deal with here, RFI and output ripple and each can be significant to be troublesome.You certainly can reduce output ripple but reducing RFI is another matter for the inexperienced.QuoteToroidal has the advantage of a useful space saving formfactor but otherwise it's no better than any other power transformer.Anyways, you have choices, tart up your old HP and keep using it.Go in balls deep and build your own.Buy a SMPS and see if you can live with their noise, RFI and ripple.Buy a new linear PSU with all the fruits you seek and if it's for you sell what you already have to reduce your total outlay.Good luck.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 30, 2023, 03:38:57 pm
content: Quote from: p.larner on October 30, 2023, 01:58:58 amI have read all of the data sheets for a lot of the popular LDO's such as the Texas Instruments - LM338 LDO (I actually have a bunch of LM338 from Texas Instruments on hand.) They have schematics for voltage and current regulation.If you are going to be researching schematics for this particular need what would be the best way to approach that? Going to Google could be hit or miss. Is there a place to look for tried-and-true tested schematics for these types of applications?

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 30, 2023, 03:54:36 pm
content: Quote from: Konkedout on October 30, 2023, 04:32:24 amRegarding your points.1. I feel fairly comfortable working with mains voltages up to 400V. (I do so fairly often). I understand the risks and liability associated with that. I don’t think I would attempt to design a switch mode power supply if I went down the design path I would pursue a linear power supply design. Just to clarify I would not attempt to design something like that on my own, this is the reason I am posting on this forum. I would ask for people such as yourself with considerably greater expertise and experience for step-by-step guidance. So if I did decide to go down this path I would be following someone’s detailed instructions versus my own design.I am not set on a toroidal transformer and I am open to modifying that consideration. My train of thought there was that it takes up a lot less space and should produce less interference. I do not have a space consideration for this particular design of power supply so if I needed to step up to bulkier components I can do it.2. I understand what you are saying. My question is if you utilized more robust power transistors could the design still have longevity? I understand the heat dissipation and the efficiency cons and pros of both designs. I am not overly concerned with efficiency, so if the components were chosen properly can a reliable power supply with longevity be made in a linear fashion versus switch mode?3. Like I said I think I would pursue a linear design over a switch mode power supply design for the reasons that you mentioned about proper PCB design.When you say you placed a “toroidal common mode choke” between the outputs what size is that choke? What was your output like without that modification and then what was the final result under load?

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 30, 2023, 04:03:03 pm
content: Quote from: alligatorblues on October 30, 2023, 05:23:02 amI was wondering if you have the actual model of the power supply you are referring to. I did look on eBay and they had Several different models under that particular brand. I am curious to see if the model is analog or digital in terms of control, and just in general curious as a reference point.I appreciate the suggestion for measuring AC at the output signal.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 30, 2023, 04:18:08 pm
content: Quote from: tautech on October 30, 2023, 06:08:10 am

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2023, 08:11:17 pm
content: Quote from: JJ_023 on October 30, 2023, 04:18:08 pmMost DMM would struggle with 1 MHz AC which is where I would use a scope instead.Quote from: JJ_023 on October 30, 2023, 04:18:08 pmUnderstood however getting 500W from a linear PSU with the features you seek is a considerable challenge.You're getting into SMPS and fan cooled territory here.Quote from: JJ_023 on October 30, 2023, 04:18:08 pmLimited, consult datasheets. Typically reverse voltage protection as good as an adequately rated diode is not inbuilt.Quote from: JJ_023 on October 30, 2023, 04:18:08 pmSee closing comments.Quote from: JJ_023 on October 30, 2023, 04:18:08 pmIt's a considerable challenge to build a good and well behaved PSU.There are many things to consider and solve.Low output ripple.Low output capacitance.Good power ON/OFF behavior.Good load and supply step response.Adjustment and readout resolution.You could also look deeper at what you have already, say how you could series the outputs of your HP to provide voltages you might need and direct attention to cost effective solutions to provide high currents for LV work.Eg. SPD1168X 16V @ 8A

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 12:34:08 am
content: Quote from: tautech on October 30, 2023, 08:11:17 pm

author: watchmaker
author_rank: Unknown
timestamp: October 31, 2023, 01:26:59 am
content: Quote from: JJ_023 on October 30, 2023, 04:03:03 pmOK. Why not just buy a used Instek or Tenma PSU off eBay. I am kind of compulsive, but I am also starting out and bought THREE! (Watchmakers always have a backup plan to the backup plan when making a part for a unique watch that may result in the ultimate loss of the original part, like repivoting a pinion that may split).So, for less than $120 USD each, I purchased an Instek 4 channel GPS 4303 with CC and CV, a Tenam badged Thurlby single channel TSX3510P programmable (but no time programming) and an Instek PSM 6003 w/ Time/step programming as well as CC and CV.Your $500 could buy all three off ebay if you look. The GPS-4303s are easy, the other two you have to be patient.The constant current feature is almost required.If you want a nice elephant (that weighs as much), I have a Lambda LK-351 FMOV that has constant current and the FMOV is a user settable overload trip point. 35 vDC 30 A. Be forewarned, it weighs 135 pounds! W/ manual and schematics.But you can have it if you come get it in New Hampshire.Regards,Dewey

author: xavier60
author_rank: Super Contributor
timestamp: October 31, 2023, 02:03:46 am
content: A diode permanently placed in series with a PSU output won't protect against a reverse connected battery.Linear PSUs with current sourcing topology like Harrison will tolerate momentary applied reverse polarity from a battery assuming no parallel output diode is present.My PSU has survived having a 12V SLA battery reverse connected for a few seconds.https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg3582664/#msg3582664This does place large dissipation stress on the pass transistors as well as eventually being fatal for the output capacitor.A small mod could be added to turn off the pass transistors when reverse polarity is sensed.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 03:03:26 am
content: Quote from: watchmaker on October 31, 2023, 01:26:59 am

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 03:07:23 am
content: Quote from: xavier60 on October 31, 2023, 02:03:46 amSo could you elaborate on what the previous poster suggested. Maybe I misinterpreted something.Quote

author: DonKu
author_rank: Regular Contributor
timestamp: October 31, 2023, 03:20:18 am
content: Quote from: JJ_023 on October 30, 2023, 03:38:57 pmBad Caps provides popular Power Supply schematics:https://www.badcaps.net/forum/forumdisplay.php?f=32

author: xavier60
author_rank: Super Contributor
timestamp: October 31, 2023, 03:22:00 am
content: Quote from: JJ_023 on October 31, 2023, 03:07:23 amIm not really sure. For a series diode to offer any protection, it needs to be a permanent part of the battery pack's charging port.The alternative is a parallel output diode, which most PSUs have fitted as standard and have at hand a charging lead which has a conventional fuse or a Polyswitch.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 03:32:46 am
content: Quote from: DonKu on October 31, 2023, 03:20:18 amI will check it out. Thank you.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 03:34:23 am
content: Quote from: xavier60 on October 31, 2023, 03:22:00 amI wasn't really sure that's why I asked for clarification from the original poster as well as yourself.

author: watchmaker
author_rank: Unknown
timestamp: October 31, 2023, 10:37:34 am
content: Quote from: JJ_023 on October 31, 2023, 03:03:26 am

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 07:57:34 pm
content: Quote from: watchmaker on October 31, 2023, 10:37:34 am

author: dobsonr741
author_rank: Frequent Contributor
timestamp: October 31, 2023, 08:51:05 pm
content: I suggest try working with the 6236B first. Or try to answer why the 6236B is not suitable as-is, and why fixing it not an option. Be honest to yourself and listen to your own concerns. Will teach a better lesson than going to build a brand new DIY supply, on the long run.

author: JJ_023
author_rank: Frequent Contributor
timestamp: October 31, 2023, 11:08:43 pm
content: Quote from: dobsonr741 on October 31, 2023, 08:51:05 pmI think yours is a good suggestion. I am familiar with the unit. I might keep it. I might sell it. I might give it away to some kid that needs it. What I am not going to do is have it as my primary power supply. For that I need something a little bit more robust. I've given this a lot of thought. I am reaching out for different opinions on this forum because whatever I do know about the subject or don't know about the subject there is just no substitute to listening to other people's points of view, especially people with a lot more experience as well as the variety of experience.Some of the suggestions that I've gotten so far have been helpful. Buying versus Building. Old versus New.I am familiar with the benefits of a manufactured unit. It will be more polished. The interface and design will be worked out, etc.Building a linear power supply would give you more bang for your buck in terms of the capabilities in sheer power. It would also probably enable you to select more robust and better quality components. I can definitely build a better quality and looking unit as far as the enclosure and mounting goes, by leaps and bounds.The downside would be that some of the desired characteristics without a lot of assistance and input from more knowledgeable people would be difficult to accomplish.All I am trying to do is take in a bunch of different opinions, learn something along the way, and hopefully make the right decision for myself and my needs.So thank you for your opinion.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 01, 2023, 12:02:24 am
content: I just rebuilt a Small Lambda Lab power supply.. What a job. I slightly redesigned the components and used a new self designed control board. I think it took over 40 hrs. I also have many different PS up to a big HP that weighs 40 Kilos.So, I have some comments.Some SMPS PS are very good at what they do but the harmonics of various components can interfere with the device you are testing. They are made usually for specific things they power and the harmonics (or spurs) are outside of anything that should affect their intended power user. A 28 V SMPS PS for cell tower stuff did not work for me at all since I power HAM radios. There was all sorts of interference. I now use an old huge HP PS for the 28 Volt radios and a Yaesu 12 V for the regular stuff. I do not know if spurs are important in the work that you would be doing, for my radio work they were horrendous.I think you said you need volts up to 60 Volts.. To get a linear PS that would go to 60 V and still go down to 5 V would require lots of attenuation. Lots of heat generated. Some PS have two or three secondary windings (or taps) on the transformer and a relay which switches to higher or lower voltages to circumvent this problem. More complexity and try to find the appropriate transformer.Most regulated Linear PS are built for a specific small range of volts and are adjustable in that range.Sounds to me like you could benefit by buying PS of different voltages. The HP Lab type unit is very nice for powering small stuff like 12 V boards. Perhaps putting some digital meters in place of the analog ones might be feasible and give you a good reading, the analog meters are not extremely accurate, even when new. But I do not know if this is necessary for your purposes. Maybe just calibrate the HP with a good voltmeter and draw a line on the plastic meter cover. Lab supplies are very nice for powering boards with little power requirements. You can sometimes even tell that some components are not working by knowing how much power the board requires. Replacement knobs can be found if desired or perhaps new 3D fabricated ones.I think you said you work with CNC controls. Perhaps you have access to some scrap units and can rescue the PS that you would need to power your device under repair? Especially for the higher voltages. If the controls are powered by SMPS or Linear would not seem to matter.The SMPS would be optimized for the control unit being tested.Your budget would be quite adequate. I purchased my 12 V (actually 13.6 V) Yaesu PS broken for $20 and it was a very easy repair.Your HP was an even better deal since it was free.It is usually pretty easy to fix Linear Supplies with fixed voltage outputs (as long as the transformer is good), SMPS are not easy.Lab PS like your HP can also be quite complicated to fix.However the fixed volt units do not offer variable power (amp) control although they do have over power protection and the good ones have volt and amp meters..

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 01:13:42 am
content: Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amWhat are the specifications of the power supply you built? (Voltage Current Ripple)Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amI have read a few books on power supply design. I do understand the tremendous benefits that they offer especially when it comes to efficiency. But if I was going to build one it would be a linear power supply. Or as stated in the beginning maybe modify a commercially available option to get a cleaner output.Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amI don’t think it would be difficult to get a suitable transformer as I would not be trying to hunt one down. I would just simply order a new one from Digi or similar.My thought process would be similar to what it seems some of the commercial offerings do. That would be to get a transformer like you said primarily with 2 taps. Then technically you would have 2 outputs 0-30V that you could then put in series. I don’t know if that would present major issues for me maybe some knowledgeable members could chime in.Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amThe HP really doesn’t come close to the current requirements or voltage requirements that I occasionally have. It also doesn’t have any type of current control which to me is important.Having said that I can easily make all of the knobs out of aluminum on a CNC designing them in CAD. The analog gauges I never really cared for on any devices. I think I would just figure out a way to put banana jacks in their place and use some of my multimeters that would plug into those banana jacks to set up the voltage and current as well as monitor the voltage and current.The busted output terminals I would just replace with some offering from Pomona.Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amI come across some of that stuff fairly often. Especially when I end up at the scrap yard on an industrial site in the back. I know that you can find some gems, but honestly I would just buy what I wanted brand-new from a place like Digi-Key and not worry about the transformer working or not down the line.Quote from: Wallace Gasiewicz on November 01, 2023, 12:02:24 amThis HP does have an amp meter. Like I said I would probably figure out a way to plug-in multimeters quickly to set the current. The problem is the unit only goes up to .5 Amp on the 20V side.

author: Jwillis
author_rank: Super Contributor
timestamp: November 01, 2023, 03:15:25 am
content: Digikey is pretty limited when it comes to power transformers. Have a look at Antekhttps://www.antekinc.com/.They're in the US so shipping might be reasonable.I bought several of these from 100Va to 1000Va and they are outstanding. You can even request extra taps . Had two custom transformers made for tap switching on power supplies.The transformer for a linear supply is probably going to be the most expensive part of the project so you may as well get it right the first time.A little extra current overhead is better than not enough. Also I would suggest that if you want 30V X 2 get at least 35V x 2, at least, to offset any voltage sag. Voltage sag is an unavoidable product of transformer regulation.No transformer has 100% regulation. Toroids will give better regulation than E cores.For high amps I would suggest multi tap switching. This will keep your regulators and power transistors operating much cooler than single tap. By this I mean that as you increase voltage output the taps switch to higher voltages at the transformer by adding the secondary taps together.Basically the difference between the voltage Input and the voltage Output multiplied by the load current gives you Watts of energy that needs to be dissipated as heat at the regulator and/or power transistors. So by tap switching the heat dissipation can be kept manageable.And a word of advice on the filter part. Don't get carried away with adding more filter capacitors to lower the ripple. Just to half the output ripple you need to double the capacitance at the filter. This will just introduce extra inrush current that can damage transformers and components. Don't be afraid to use chokes in the filter. With the right value you can have a clean output with fewer capacitors. Contrary to what some people believe they do not need to be enormous and would take up far less room that an equivalent number of capacitors to get the same result.Hope this helps some . Good luck and have fun.

author: tautech
author_rank: Super Contributor
timestamp: November 01, 2023, 07:45:43 am
content: Quote from: JJ_023 on November 01, 2023, 01:13:42 amThere's other ways to skin that cat too.Use 2 identical transformers and switch their outputs together prior to the bridge with a DPDT switch.One must get their phasing right otherwise you switch them to short.I did this with manual switching for my first proper PSU build with old 12V lighting transformers (NOT SMPS) giving 2 output ranges of ~15 and 30V primarily to reduce excessive heat losses at low output settings.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 01, 2023, 01:18:10 pm
content: To try to answer your question the Lambda is an old LP 5222FM I have schematics for later units that are very similar0 to 40 volts 0 to 1.3 (maybe) amps. It was a gift, rebuild was an experiment. It does work.I also rebuilt an HP 6268 PS 0 to 40 V 0 to 30 Amp supply. It is a monster. This is a very interesting power supply. Two huge transformers. Cooling for the output transistors thru a "tunnel" heat sink, the fan blows thru a hollow heat sink and the regulator transistors are mounted on the sink. If you wanted to build a sophisticated High Power linear PS you may wish to read about it. The control boards are very complex and do not resemble "normal" 12 volt regulated supplies.About ripple. I cannot see anything over the noise on my scope probes. There is noise that is plus minus 10 millivolts on the probes. I have not tried to use any other tricks to get a better reading. This is true of both these supplies.This is ambient noise in my shack and I know I need better grounding etc... Anything I touch with the probe gives this noise. It is 60 Hz and a lot of other freq.So I really cannot answer you question about ripple..... the Lambda specs say 150 micro volts. Old Linear Lambda are really good PS.Wally

author: tautech
author_rank: Super Contributor
timestamp: November 01, 2023, 09:09:02 pm
content: Quote from: Wallace Gasiewicz on November 01, 2023, 01:18:10 pmLinear PSU ripple should be 2x mains frequency.....unless one has built an unexpected oscillator into it.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 10:53:11 pm
content: Quote from: Jwillis on November 01, 2023, 03:15:25 amI don’t really find that to be so. I think they actually offer more of a selection than the website that you recommended. At least that’s the impression I get.QuoteI had an extensive look at their website. I really do appreciate the introduction. They have some really neat offerings and I will definitely be ordering something off of there at some point for some of my needs.I have a question about their transformers. Are they 100% copper wound?QuoteI was leaning in the direction of multi tap to begin with. But since you said this particular company could do multi tap would it make more sense to have 3 separate voltages versus 2 if the output is 60 V?Is there a better option than several Texas Instrument LM338 in parallel for controlling voltage and current output?QuoteHow many taps would you recommend?How would you recommend this switching be accomplished? I would love to be able to incorporate something solid-state that should I want to develop a digital control down the road and write some code it would make switching seamless. I know every time you introduce something you’re going to have inductance, capacitance to contend with. Would a solid-state solution for a switch introduce or hurt the quality of the output?QuoteI have read a few pretty technical books on power supply design (by no means am I implying that everything made sense to me ) and the route that I was going to go down was smaller capacitors in parallel, along with some inductors. I am not sure if this is the best solution. I would love to hear your input on that.Realistically right now I am ascertaining as much knowledge and information as I can on a macro level. Once I decide to go down the path of building this I will finalize the transformer and appropriate rectifier, figure out the heat sinking solution and the case. If I get that far without any hiccups I would start a new thread asking for help on a properly designed filter for the circuit that I already built.QuoteThis has definitely been helpful thank you.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 10:58:14 pm
content: Quote from: tautech on November 01, 2023, 07:45:43 amWhat would be the benefit of using 2 identical smaller transformers?What would be the drawback of using 2 identical smaller transformers?How would one get their phasing right with only a multimeter (access to several multimeters)?Is there a way to incorporate the switching through a solid-state switch without affecting the output of the linear supply? I would love to be able to have the option of possibly having digital control and writing code for this power supply.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 11:06:09 pm
content: I was wondering if you could elaborate on something you said earlier in regards to charging batteries with the power supply.Quote from: tautech on November 01, 2023, 09:09:02 pmWhere and how would you incorporate this particular diode(S)?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 11:09:21 pm
content: I would like to add something to this post.Helping guide somebody, or just in general helping somebody takes time.Time is a precious commodity.Thank you to everybody who has participated and/or is going to participate in the future. It is greatly appreciated.Thanks for bearing with me, it is a process.

author: xavier60
author_rank: Super Contributor
timestamp: November 01, 2023, 11:10:14 pm
content: I should add, with increasing voltages, the Safe Operation Area limitations of BJT pass transistors becomes difficult to deal with.It's one of the main reasons for power transistors being put in series in high power audio amplifiers.SOA would be easier to deal with if a 60V PSU was to be designed as two 30V PSUs in series.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 01, 2023, 11:32:43 pm
content: Quote from: xavier60 on November 01, 2023, 11:10:14 pmSo I understand the whole concept and reasoning behind doing it in series.My idea was to use LM338 in parallel for each of the 30V supplies. My thought process would be that it would distribute the power therefore each particular component would be easier to manage in terms of thermal properties. Any thoughts on that?So when I see some of these commercial linear power supplies at 150V I assume they are adding in series up to the desired voltage? It makes sense to me for a 60V supply, but would seem cumbersome at much higher voltages.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 02, 2023, 12:04:00 am
content: Th Linear PS with the relay feature that I have has a noticeable change in voltage when the relay kicks in.. It is not seamless. There is a small bump in the adjustment at this point. This is "automatic" and a circuit engages the relay.I assume you are going to use the LM 337 to drive big final regulator transistors (BJT or mosFET)In the goodvariablePS much more complicated mechanisms are used. There are more advanced chips for this and it is possible to use op amps to control the final regulators.Usually there are multiple output transistors in parallel with at least one or two stages of amplification for their control.Here is a Lambda Schematic with both voltage and current control.

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 12:04:28 am
content: Quote from: JJ_023 on November 01, 2023, 11:32:43 pmIm not familiar with the LM338, I generally work with discrete power transistors. But yes, parallelling devices increases current handling and reduces the effect of the device to heatsink thermal resistance, assuming that they are made to share the load current.It's possible that high voltage PSUs use multiple series pass transistors amongst other techniques such as pre-reregulation or auto tap changing where multiple unregulated voltage are available for multiple power transistors to choose from.Edit: I see that the LM338 is a higher powered version of theLM337LM317. It would be dificult to add real Constant Current control to it.

author: alligatorblues
author_rank: Regular Contributor
timestamp: November 02, 2023, 12:39:06 am
content: Quote from: JJ_023 on October 30, 2023, 04:03:03 pmIt's a Lambda LK352 FMOV. There's one on eBay right now:https://www.ebay.com/itm/292267187150You probably don't want that one, because the seller is only offering pick up, and he doesn't know if it works. But those are on eBay regularly. For me, there are 2 brands of DC PSU, Lambda and Sorensen. Both of those make thousands of different supplies. They are professional, industrial, laboratory, commercial, military designs so they will virtually never fail unless the user is inept.For battery charging, I just fuse the line.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 12:53:30 am
content: Quote from: Wallace Gasiewicz on November 02, 2023, 12:04:00 amThat makes total sense to me. I assume that the relay is introducing inductance as well as capacitance which in turn translates to a change. Would that be correct thinking?If so can a solid-state solution be used instead?QuoteMy current idea is to use the LM338 and not use BJT or FET (again I am open to changing all of this if convinced that a better option exists).Here is a link to the datasheet and another document which will help you get familiar with the LM338 and see if my thinking is on track.https://www.ti.com/lit/ds/symlink/lm338.pdf?ts=1698801363519&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM338https://www.ti.com/lit/an/sbva026f/sbva026f.pdf?ts=1698854705877&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS7A45Thank you for the Schematic. 😊

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 01:01:36 am
content: Quote from: xavier60 on November 02, 2023, 12:04:28 amThere are some really good examples of using current control with LM338 in the Texas Instruments datasheet.https://www.ti.com/lit/ds/symlink/lm338.pdf?ts=1698801363519&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM338I have built CC power supplies using the LM338 for certain applications like simple LED drivers.What do you think would be the problem controlling the current in a linear power supply using the LM338?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 01:24:45 am
content: Quote from: alligatorblues on November 02, 2023, 12:39:06 amThanks for the model number and the suggestions.I was wondering if you or any other members know of any high-quality less known power supply manufacturers. I know there are a couple out of Japan, and there are probably some coming out of Korea.My thought process is because they are less known you could probably get a better deal for what you get.When you talk about fusing the line I assume you are referring to a fast blow in series with 1 of the binding post on the power supply?

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 01:25:30 am
content: Quote from: JJ_023 on November 02, 2023, 01:01:36 amThe addons for CC I have seen, usually involve needing a negative control rail of another LM317 in series, increasing drop-out voltage.Which particular design did you choose?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 02:18:12 am
content: Quote from: xavier60 on November 02, 2023, 01:25:30 amI haven’t really chosen any design that is why I am asking all these questions. However I have used on page 20 figure 35 , which includes LM317 and a modified version of figure 37 in the past for some of the needs that I had.Again if I was sure I would not be asking all these questions. 😊

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 02:50:01 am
content: Quote from: JJ_023 on November 02, 2023, 02:18:12 amThey mostly appear to be current regulators. Adding CC to an LM317 voltage regulator gets messy.The design I linked earlier has been designed as a CV/CC PSU from the ground up. It has been working on my bench for near 3 years but as a 30V supply.The Onsemi data PDF for the TIP35C indicates that maximum allowable dissipation starts to degrade at over 30V. Even with tap switching, the dynamic aspect of SOA is difficult to account for. So I can't say how many parallel TIP35C's would be safe for a 60V design.https://www.onsemi.com/pdf/datasheet/tip35a-d.pdf

author: Jwillis
author_rank: Super Contributor
timestamp: November 02, 2023, 03:12:02 am
content: QuoteYes they are with larger gauge than you would normally see for an equivalent power ratingQuoteOff the shelf adjustable regulators or designs around op amps each have their merits and disadvantages. It really depends on how in depth you want to get in your designQuoteDepends on the power dissipation of the regulators and/or transistors. Personally I wouldn't go less than one tap for every 10V to 15V of output voltage. The narrower the tap range the cooler the regulators and power transformers remain across the range of output voltage and current. Example: For 30V output tap configuration would loo something like 0-15-22-30V. By keeping the tap voltage higher than the most common voltage s used. You don't need to specifically use those tap ranges but it worked for me on one supply. On a 40V supply I used 0-10-20-30-40V for a 20amp supply, but in hindsight found that to not work as well as I would like. Still on the bench with that one.To many taps can lead to problems as well. You don't want to have it constantly switching taps while your working.QuoteI just used a lm339 quad comparator with lm431 voltage references to switch 12v 30A relays.QuoteBy using an LC Pi filter you can significantly reduce ripple without the need for a large amount of capacitance. Some math and some experimentation.QuoteI won't kid you and say this is an easy task. Design and prototyping a complex system takes time, patience, a lot of learning and a lot of mistakes. This 0-40V 20A supply is on nearly its 4th year of development and I'm just starting to put it to PCB design. I'm not a professional electrical designer and can't give it my full attention but I still have fun tinkering and improving the design.I'm sure the many good people here would be happy to help you out. My knowledge and experience is limited but I don't mind helping where I can. It's OK to get things wrong. That's half the learning experience.What did was bought a bunch of different cheap Chinese power supply kits and studied the crap out of them. After a while things started to become clear of how they function. Now I apply what i learned to what I designed.

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 04:27:53 am
content: The worst case scenario would be, maximum transformer voltage tap selected, output transistors already hot, then the output is short circuited. Some time will pass for the tap switching to react and the filter caps to discharge to the lower tap voltage.TIP35C BJTs will be at highest risk of second breakdown while there is more than 30V across them.A simple mod could be added to temporarily set the CC to some safe current while the unsafe condition exists, some tens of milliseconds."File test" comes to mind.

author: tautech
author_rank: Super Contributor
timestamp: November 02, 2023, 07:30:50 am
content: Quote from: JJ_023 on November 01, 2023, 10:58:14 pmForm factor. Series connection for higher voltages or parallel for higher current.Quote from: JJ_023 on November 01, 2023, 10:58:14 pmHigher magnetising (idle) currents.Quote from: JJ_023 on November 01, 2023, 10:58:14 pmConnect one output pair, test for voltage between the other pair. 0V = correct phasing for a parallel connection.Quote from: JJ_023 on November 01, 2023, 10:58:14 pmOnly if a DPDT SS switch is available.Quote from: JJ_023 on November 01, 2023, 10:58:14 pmUse a DPDT relay and supporting circuitry.

author: tautech
author_rank: Super Contributor
timestamp: November 02, 2023, 07:44:16 am
content: Quote from: JJ_023 on November 01, 2023, 11:06:09 pmWith typical LM*** regulators the norm is to fit a reverse polarity diode (consult datasheets) but this is to protect said regulator from capacitor discharge NOT a battery that might be connected to the output.An output series diode OTOH will protect from reverse currents from a battery however not from a reverse polarity connection.You could incorporate a output crowbar and fuse or just be darn careful to double/triple check connections or face this

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 02, 2023, 01:25:16 pm
content: More, hopefully not entirely useless. comments:Regulators like the LMxxx are not used in parallel because they are not exactly the same in their performance. One regulator will take more current than the other and this is a factor which can lead to failure.Usually big BJT or mosFETS are used in parallel for the final output and a high watt low value resistor ( like 3 ohms) is put in after the output of each parallel transistor in an effort to equalize them,My redesign of my Lambda was done in a matter of weeks. I blatantly stole parts of the design from various schematics and the output consists of a pre driver, a bigger driver and three big TO3 BJT. This is the original design of the Lambda. All this for only one amp at 40 volts. And you need a nice big heatsink for the final transistors.A lot of the designs I saw have two power sources, one for the very constant housekeeping power used for op amps and regulators and one that is the source of variable output power. Notice there are two rectifier bridges in the schematic I sent. There are also two separate windings on the transformer I started with.Things like op amps and more involved regulators need a constant voltage to maintain any consistency. Also the 40 or 60 volts or more you start with in your variable output chain is way too much for most of these op amp like components.One neg is linked to the other positive in an effort to keep voltages "separate" .This is a design problem that is to be dealt with in the entire project. I had a lot of trouble with this concept. My shrink was of no help.Also ALL voltages both the positive and negative MUST be kept away from the chassis ground.I had a few accidents and blew a few output transistors but fortunately I had purchased a bag of big TO3 transistors very cheaply at a Hamfest.My design ended up with a volt regulator (18 V) three op amps and I used a mosFET for the current limiter. The current limiter takes a voltage from across a current sense resistor (very small value maybe 1/10 ohm) at the output of the entire PS and uses the voltage across the resistor to control an op amp which controls the mosFET. The mosFET is just before the chain of BJTs (pre driver, driver and 3 output) in the "final stage".You can use big mosfets as the output stage. I have a little PS that uses them. Probably cheaper in the long run.I now have an appreciation of the complexity of variable lab grade supplies and no longer wonder why they cost so much.Please note that I am just a hobbyist and not an engineer so I maybe using the wrong terms (pre driver etc)I dropped out of engineering school when my advisor told me my degree would not allow me to drive a train.

author: tautech
author_rank: Super Contributor
timestamp: November 02, 2023, 06:48:32 pm
content: Quote from: Wallace Gasiewicz on November 02, 2023, 01:25:16 pmThis, ^^^ and this again ^^^

author: themadhippy
author_rank: Super Contributor
timestamp: November 02, 2023, 08:12:04 pm
content: Quoteuse 2 and that annoying minimum 1.25v output voltage almost disappears

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 02, 2023, 10:30:16 pm
content: I did incorporate two big series diodes in the output of my design, since they were already there in the original Lambda design.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 10:31:11 pm
content: Quote from: xavier60 on November 02, 2023, 02:50:01 amCould you elaborate on the comment “gets messy”.QuoteWhy are you mentioning the TIP35C? To increase the current capacity of the power supply?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 10:46:49 pm
content: Quote from: Jwillis on November 02, 2023, 03:12:02 am

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 10:49:50 pm
content: Quote from: JJ_023 on November 02, 2023, 10:31:11 pmIt gets messy dealing with the residual 1.25V so the output can go to 0V during current limiting. Find an LM317 design with current limiting and you will see.I mention the TIP35C because it's one of the parts I have used in a successful design. Also, the data PDF shows a good example of SOA limitations at high voltages.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 02, 2023, 10:54:43 pm
content: Quote from: tautech on November 02, 2023, 07:30:50 amI am not sure I follow. Could you elaborate a little bit more please?

author: xavier60
author_rank: Super Contributor
timestamp: November 02, 2023, 11:17:12 pm
content: TIP35C's can be used to boost the current capability of an LM317.This is an idea I have experimented with. Current limiting is very fast acting but will not be as precise as opamp based designs.Some components values could need optimizing.https://www.eevblog.com/forum/projects/lm317t-stability-under-bypassed-load/msg4980517/#msg4980517

author: tautech
author_rank: Super Contributor
timestamp: November 03, 2023, 12:44:51 am
content: Quote from: JJ_023 on November 02, 2023, 10:54:43 pmThink about it.A transformer schematic shows a dot for the windings start however in reality they are rarely identified on a physical transformer and for something like a lighting transformer who really cares as paralleling such would never be done.There's only 2 secondary side leads on each, connect one from each together and measure the potential between the other pair.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 03, 2023, 02:13:33 am
content: Quote from: tautech on November 03, 2023, 12:44:51 amI appreciate the explanation.

author: Jwillis
author_rank: Super Contributor
timestamp: November 03, 2023, 03:25:25 am
content: Quote from: JJ_023 on November 02, 2023, 10:46:49 pmI use both, but for bench power supply design I prefer opamps because of flexibility in the design. Also by keeping the current pass elements separate from the voltage control, theirs less chance of voltage drift due to excessive heat.To much heat in electronics leads to stability issues and reduced component life. If large heat sinks and noisy fans are not a problem for you then you can get away with a tap less or single tap transformer.But consider this. A lm338 with a 35V input adjusted to 1V output with 4A current. Vin - Vout X A= Watts of dissipation. 35V - 1 X 4 is 136W of heat you need to sink. ψJT Junction-to-top characterization parameter 2.1 °C/W gives you around 285oC of heat that needs to be dissipated into the heat sink. If you tap switch so the the Vin in relation to the Vout is reduced to 10V , that's 40W or around 84oC. This would require a smaller heat sink.You can spread the heat out using multiple elements, but that can become just as complex as tap switching.Using simple switches would work as long as you don't forget to change taps at the wrong time.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 03, 2023, 02:03:58 pm
content: If you are adding voltages as in switching the taps on a transformer, there will be a change in the total voltage that is not exactly the same each time you change a tap. These things are not exact. Say you have ten taps at ten Volts each. each tap is not exactly 10 Volts and not the same as its neighbors.Then the regulating circuit must be able to deal with the different voltages and especially the higher voltage.There are double or triple PS like my Sencore 402 that add tworegulatedoutputs. Each output is max 30 V so you can get 60 volts by pushing a button and adding them in series. You can also add them in parallel to get more amps.I have very little idea on how they do this since I think it would bring up the neg rail of one supply to pos 30 volts. I do not know the implications of this.Perhaps someone else knows how to do this.Another thought:If you wish to have a very predictable constant output voltage, you need a good reference voltage to compare it to. These days the reference voltage is included in PS control chips so that the reference diode is at the same temp as other components and more stable.If you do not care about being a few millivolts off an external good zener controlling an op amp will suffice but temp changes will affect the reference volts and consequently the output by a few millivolts. The output will wander a bit.In my experimental rebuild of my Lambda I used an external Zener and op amp for a reference voltage. The voltage does wander a bit.Also I cannot find any info on the Sencore 402

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 03, 2023, 11:50:01 pm
content: Quote from: Jwillis on November 03, 2023, 03:25:25 amI am familiar with opamps and some of what they do. But to be honest I don’t have a lot of exposure to them and therefore not fully aware of all of their uses. I’ll have to explore and educate myself on the topic. If you have any technical literature on op amps that relate specifically to a linear power supply it would be greatly appreciated, if not I’ll try to ascertain them.QuoteI am fairly aware of what heat does to electronics. As well as managing airflow in enclosed environments. So I totally understand everything you are saying in that regard. I am not bothered by noisy fans and I have almost unlimited access to chunks of aluminum for heat sinking. As funny as it sounds fan noise actually helps me work and focus.QuoteIs that a typo? Don’t you mean “At the right time”?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 04, 2023, 12:05:40 am
content: Quote from: Wallace Gasiewicz on November 03, 2023, 02:03:58 pmThis is a valid point and is 1 of the reasons why I thought basically 2 taps would be easier to design and manage. Both separate circuits having 0-30V that could be added in series to get 60V. Besides the thermal considerations is there anything else to contend with it going down this path?QuoteIt seems creating series and parallel connections is something that is prevalent in commercial power supplies to either increase the voltage capability of the power supply or the current capability at the lower voltage. If you connect the 2 outputs together in series shouldn’t it be 60 V? Or if you need extra current capabilities at the lower voltage, putting them in parallel?QuoteI know they sell voltage references. Can’t that be incorporated?https://www.ti.com/lit/ds/symlink/tl431.pdf?HQS=dis-dk-null-digikeymode-dsf-pf-null-wwe&ts=1699056194193

author: xavier60
author_rank: Super Contributor
timestamp: November 04, 2023, 12:13:47 am
content: For voltage reference, there is no need to look any further than the ubiquitous TL431, used in ~99% of PSUs.Edit: I see it has already been linked.

author: artag
author_rank: Super Contributor
timestamp: November 04, 2023, 12:24:17 am
content: I agree with dobsonr741. You'll have to spend a lot of money to get something of that quality new.It may not meet all your needs, but you can look out for others of similar quality to cover other ranges.If you get a modern chinese switch-mode it will likely die (I've seen plenty do that) in a year or so and will be hard to fix. The old HP will be fixable, and worth fixing. At least a couple of generations newer will still be linears - I have 6632, E3632, E3630 and they're all linear. There's likely a reason for that.The only reason I'd consider a switcher as a bench supply is if I have particular needs of space, weight or very high power. Those often apply for a piece of portable equipment but not for something that stays on the bench.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 04, 2023, 12:31:35 am
content: So here is one thing that I’ve been pondering.Based on a recommendation from 1 of the posts for a toroidal transformer, a website was suggested. After spending some time on the website, a thought came to mind.According to the recommendation they seem to make a fine toroidal transformer as well as offering other products.While consider buying their toroidal transformer an option popped into my head.They have a 68V power supply which is 1 of their toroidal transformers with some filtering caps and I assume a rectifier. Here is the link.https://www.antekinc.com/ps-10n68-1000w-68v-power-supply/According to the recommendation they can create additional taps.This particular supply comes on I aluminum mounting bracket. I can then incorporate that into my own aluminum housing.They also have a soft start option.https://www.antekinc.com/ss-12-soft-start-module/They also have a fuse module.https://www.antekinc.com/fm-3-fuse-module/While I explore linear power supply design further I can purchase a RD6012PW which would give me a user interface far beyond what I am willing to develop. This unit I personally have never played with but I have done a little bit of research. This is there better unit supposedly with the claim of Output ripple typical: 20mV VPP.https://www.aliexpress.us/item/3256805750975781.html?My thought processes are that I could have a working power supply while I develop and learn.At the same time have a good quality 68 V power supply I can use in my future designs or even sell it to a client in some control system.The RD6012PW is not that big of a financial waste if it turns out to be garbage.What do you guys think of this thought process?

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 04, 2023, 12:53:04 am
content: Quote from: artag on November 04, 2023, 12:24:17 amI agree with both of you. But that particular HP unit just does not meet my needs.I would not mind looking at similar quality units but I am just not well versed in all of the options of brands.I am familiar with some of the stuff that already has been mentioned the others were a new discovery for me. I even asked for some Japanese power supply recommendations as I know some of those are high-quality, are less known about, and not as desirable.I have looked on eBay and a lot of these recommendations for used quality power supplies are about as much as a $400 offering from Rigol or GW or comparable. At that price point I rather buy a new linear supply versus a used one. Maybe somebody could explain to me what I am missing in some of those older offerings.Even though in the post above I referenced a switch mode (RD6012PW) I agree with what you are saying and ultimately will end up with a linear supply.Having said that what do you think of some of the Chinese offerings in terms of linear supplies?Rigol and comparable?

author: tautech
author_rank: Super Contributor
timestamp: November 04, 2023, 01:48:20 am
content: Some points to ponder:Any linear PSU that can't beat a 20mV ripple is shit. Period !To get to 60V output a 2ch PSUparalleledin series is a better configuration because most regulators are not designed to operate with such voltages unless you build your own design.2 outputs also offer the advantage of parallel and series configurations (sometimes at just the punch of a button) and in series mode permit a tracking +/- supply when configured to be center tapped.Add that both outputs need be isolated from one another and mains GND where in some models several units can operate in series mode up to a limit of 500V above mains GND.The more you look at what's available in the marketplace under $500 the harder it is to justify building your own.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 04, 2023, 02:15:10 am
content: Quote from: tautech on November 04, 2023, 01:48:20 amCould you give me several examples where I would need less ripple?QuoteDo you mean 2 channels in series?QuoteNoted thank you.QuoteI agree with you 100%. And an hour of my time is worth way more than a $500 power supply, the amount of time I have already spent on this forum asking questions I could have purchased several supplies.But sometimes it’s not about dollars and cents. Sometimes it’s about the journey, the educational process, the sharing of ideas, and picking up some knowledge along the way. I can honestly say I’ve learned a few new things just by starting this thread so to me that’s worth it. And I thank you and everyone else who have been generous enough with their time, knowledge and experiences.So in the end I may end up just buying 1 of your supplies but if I did that without posting this thread first I would not have learned anything.

author: tautech
author_rank: Super Contributor
timestamp: November 04, 2023, 02:36:31 am
content: Quote from: JJ_023 on November 04, 2023, 02:15:10 amAudio stages, especially first and preamp stages.Quote from: JJ_023 on November 04, 2023, 02:15:10 amYes, corrected in an edit.Quote from: JJ_023 on November 04, 2023, 02:15:10 amTBH I never initially thought alotof SPD3303X/X-E but in the last while we have sold more of these than scopes.Latest HW is somewhat improved from earlier versions, the pesky diode bridge failures already mentioned but the latest Series/Parallel mode indications on the display and how ch1 acts as the master for all adjustments in these modes.When we get more (now sold out) I'll put a couple of pics up of the display indications as the websites don't show the updates.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 04, 2023, 01:33:34 pm
content: Quote from: tautech on November 04, 2023, 02:36:31 amI had an inkling that is where you would go. At the moment I really don’t mess around with any of that.That’s 1 of the reasons why my current HP supply is lacking. I just need more current and voltage than it can provide. So to me current and voltage with reasonable ripple is more important than ultrapure.I think in the next couple of days if I have the time I’m going to look more into op amps as it seems relevant and is where I lack knowledge and where it will help me in the future when it comes to controlling things better. I have built some pretty heavy duty single voltage power supplies in the past, and deployed them in an industrial environment. That’s why earlier I stated I feel pretty comfortable with mains voltages. I just want to dig deeper and gain a little bit more knowledge in the subject of linear power supplies when it comes to op amps.QuoteThat would be great to see some of that.Here is a follow-up question. I assume if you bought 2 units you could expand up to 120V and up to 12A with a combination of series and parallel between both units and switching both units between series and parallel?As a side note I know that as the voltage goes up the amperage would remain at 3A at 120V and 12A at 30V.So I guess the question is, is it possible?What are the downsides to doing this? Besides taking up more room on your desk and a much more cumbersome interface and interaction experience.I am assuming you would struggle with CC or CV features between the 2 units.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 04, 2023, 03:18:14 pm
content: I agree entirely with Tautech about building vs buying. There are good units out there that may meet your needs.You end up with a nice looking unit that works, but you miss out on the soldering, swearing and loose the "Experimental Look" that comes from using mismatched switches and parts from the junk pile.I may have missed it, but I do not know what power you need for your testing. I am somewhat familiar with production equipment and a lot of it requires a good deal of power to manage servos and small motors. On the other hand the control boards do not use a lot of power and usually use smaller volt values. That is just the control units, not necessarily the actual big motors doing the job.Also production equipment does not use the low ripple laboratory grade supplies we have been talking about. These things are used in environments where the ambient electrical noise can be quite high. Even if the PS of a particular unit would be perfect the neighboring units can overwhelm the circuits with their EMF. Especially if you are somewhere where they are using high voltage, high Horse Power three phase AC motors and then using 3 phase transformers and rectification to power variable speed DC motors.

author: tautech
author_rank: Super Contributor
timestamp: November 04, 2023, 08:57:43 pm
content: Quote from: JJ_023 on November 04, 2023, 01:33:34 pmUp to yes.120V @ 3A or 60V @ 12A theoretically however never attempted 2 units in parallel. This capability I would need to check with HQ.QuoteWell you can set them to go into CV or CC modes by limiting current capability.QuoteThey can be stacked.QuoteThey should sort it between themselves but one unit might go into a CV/CC mode and the other not.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 05, 2023, 12:50:46 am
content: Quote from: Wallace Gasiewicz on November 04, 2023, 03:18:14 pmI agree with the both of you as well as the other poster if you’re talking about it being based on economics only.QuoteI have no clue how that ties into the above statement.QuoteYou are absolutely correct with your assessment. Some of the stepper motors can be driven with 50 V and a few amps while the really large motors get into more serious numbers.My idea of building this power supply has nothing really to do with finding solutions for clients and such. It’s more about having access for a variety of needs on my desk which realistically can be anywhere between 0 and 60 V and a few amps as well as expanding and learning more on the topic for myself.QuoteThis I am all aware of that’s why something like 20mv of ripple would probably work as stated before. Should I ever get into preamplifier circuits as well as ham radio stuff then I would have different needs.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 05, 2023, 12:53:59 am
content: Quote from: tautech on November 04, 2023, 08:57:43 pmI would be curious to see what they say. I have a feeling it could be done but you would lose some of the capabilities in the process like CC/CV/OVP/OCP