Good cheap way to get rock solid 12V DC output? - Page 1
Forum section: electronics / projects

author: SpannersToSparks
author_rank: Regular Contributor
timestamp: November 26, 2018, 10:16:49 pm
content: HiLong story short, I have a piece of kit (lets just call it an SoC) that absolutely requires stable DC voltage. It can operate anywhere between 5-19.5V, but it has to berock solid. This is gets from its wall-plugged power brick, but I need to run it off battery. So dc/dc voltage regulators cropped up, and I found this beast on amazon:https://www.amazon.co.uk/Cocar-Stabilizer-Protector-Regulator-DC10-36V-12V-4A/dp/B06Y52C65W/ref=sr_1_9?ie=UTF8&qid=1543269878&sr=8-9&keywords=dc+dc+regulatorI want to power it with a 3s lipo (11.1V). The blurb says it will take anything from 10v to 32V and give back a steady 12V, so would this do the job, or are there more things to be looked at first? Is there anything else I would need or can I just string together my lipo and then on to the regulator and a dc barrel jack?Cheers!

author: langwadt
author_rank: Super Contributor
timestamp: November 26, 2018, 10:23:10 pm
content: if it can run on 5-19.5V why do you you need a "rock solid" 12V? why not the ~11V battery directly ?

author: SpannersToSparks
author_rank: Regular Contributor
timestamp: November 26, 2018, 11:11:33 pm
content: Because it is highly sensitive to fluctuation, even though it has a wide operating range. It has a lot of expensive sensitive components I guess.You are not alone in asking that question, but the manufacturer assures me stability is paramount, even if they seem to be singularly unwilling to advise me how to achieve that (liability I guess) : (

author: Marco
author_rank: Super Contributor
timestamp: November 26, 2018, 11:26:22 pm
content: It almost certainly still has quite a large ripple, they just mean they protect against some of the wild surges you'll see in automotive.Just use a linear regulator and drop voltage to 10V.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 26, 2018, 11:33:03 pm
content: I must agree that the phrases "anywhere between 5-19.5V," and "but it has to be rock solid." seem completely contradictory and antithetical.I have very strong questions about "has to be rock solid" For one thing "rock solid" seems like a pretty flaky subjective term. Does "rock solid" mean that it has poor noise rejection". If so, WHY? OTOH, a battery source slowly drooping from 11.5 to 9.5V should not be of any significant concern to something that claims to be able to operate with "5~19.5V"And if this mystery gadget really needs such "rock solid" power, I would be searching for an alternative that was better suited for the Real World. Of course if we knew what the mystery gadget was, we might be able to better understand what they may have MEANT (vs. what they actually SAID).

author: tggzzz
author_rank: Super Contributor
timestamp: November 27, 2018, 12:21:32 am
content: Quote from: SpannersToSparks on November 26, 2018, 10:16:49 pmA rock solid power brick!?5-19.5V?Use a 12V gel-cell SLA and be done with it.If your manufacturer won't define "rock solid" and "stability" in a useful way, then either they are bullshitting you or their device is poorly designed.Alternatively if you want to get useful answersfromus, you will have to provide useful informationtous. For examples, seehttps://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 27, 2018, 12:32:09 am
content: Or perhaps "rock solid" means adequate current capability? (Actual current/power not revealed.)Or perhaps "rock solid" means some amount of reserve power/current capability for intermittent/startup surges?(Again no useful information about these aspects are revealed, either.)Unless they can properly define "rock solid", I would rather not do business with them. Sounds really flaky to me.

author: SpannersToSparks
author_rank: Regular Contributor
timestamp: November 27, 2018, 02:10:52 am
content: @MarcoThank you that is useful information.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 27, 2018, 04:33:39 am
content: as this is originally from wall wart application, i guess its smps wall wart where ripple is not an issue (you wont commonly find linear or 50-60Hz transformer wall wart nowadays that can supply hefty current at decent weight) . your linked converter unit is probably boost buck convertor (11V -> 12V) another smps type, should be ok since it was working with smps wall wart (if it is). some ee people here may have different semantic of "rock solid", as in "ripple" rock solid, so they suggest linear regulator, you may mess with heatsink and design with those otherwise money. i guess what you meant by rock solid is "current" rock solid and smps is the rock solid for that. another type of rock solid is...i can tell you that it is rock solid in term of both ripple and current and as a backbone therapy.

author: Chriss
author_rank: Frequent Contributor
timestamp: November 27, 2018, 06:13:01 am
content: Between 5-19.5v and what is the meaning for rock solid in this case?Shuld that mean does the voltage should be "rock solid" between 5-19.5v?Just use a car battery as mentioned earlier and you will be fine.Sent from my GT-I8260 using Tapatalk

author: mariush
author_rank: Super Contributor
timestamp: November 27, 2018, 07:27:54 am
content: Like everyone says, the guy probably means the motherboard doesn't have built in protections against reverse voltage or over-voltage events or "dirty power" which could happen in automobiles.So, you're not supposed to power the board from the cigarette lighter for example, if you still have one.It will work just fine from its own separate power supply, or let's say from a 18v laptop adapter powered from an inverter connected to your car - the inverter has the protections and converts power to AC and then the laptop adapter converts back to DC along with filtering and smoothing and everything.... would not be the most efficient process but it would be safe.The board will run just fine from a lead-acid battery, which will have voltage between 10v and around 13.8v when fully charged.The VRM on the motherboard will probably be more efficient if your voltages are closer to the upper end, as the input current is lower this way... but it really depends on the implementation.If you want more lightweight, less space... then i would aim for a 4S (4 in series, or multiple sets of 4 in parallell) lithium battery, along with a proper charger, like this one for example:https://hobbyking.com/en_us/imax-b6-50w-5a-charger-discharger-1-6-cells-genuine.html?___store=en_usSame website has batteries compatible with the charger, for example this one:https://hobbyking.com/en_us/zippy-compact-3700mah-4s-25c-lipo-pack.htmlorhttps://hobbyking.com/en_us/zippy-compact-2700mah-4s-40c-lipo-pack.html(higher discharge current if your board uses lots of power)(they have bigger capacities but this has good price per mAh)

author: Zero999
author_rank: Super Contributor
timestamp: November 27, 2018, 08:47:50 am
content: Quote from: SpannersToSparks on November 26, 2018, 11:11:33 pmIt won't be sensitive to fluctuation, because of its wide operating range.Has the manufacturer actually given a definite specification for the power supply, other than 5 to 19.5V?It will have its own voltage regulator built-in.The only thing you need to run it off a large battery is a fuse, fitted in a suitable holder, as close to the battery as possible. If you don't know what fuse to use, look at the output current rating of the wall-plug power supply and use a slightly higher current fuse than that.

author: KL27x
author_rank: Super Contributor
timestamp: November 27, 2018, 10:21:26 am
content: Perhaps they will be more willing define what is not rock steady slightly better after each time he files for a warranty repair/replacement.

author: perieanuo
author_rank: Frequent Contributor
timestamp: November 27, 2018, 10:32:02 am
content: Hi,Well without defining 'rock solid' this discussion is going nowhere.Didn't mean to be a asshole but technical correct answer needs knowing the specs.Regards,pierreEnvoyé de mon iPad en utilisant Tapatalk

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 04:55:42 pm
content: Hi SpannersToSparks,You are not to specific about the current demand of your equipment, so I will read between the lines and assume that the supply requirements are any voltage from 5V to 19.5V DC, and a current demand of 0A to 3A.The module that you describe is a switching power supply which would introduce noise and anyway seems unnecessary.If you go for a fairly benign discharge regime for your three LiPo batteries the minimum discharge voltage could be 3V each, giving a total of 9V minimum. The maximum voltage for three fully charged LiPo batteries would be 12.6V.With this raw supply voltage range you could use a linear regulator to provide a fixed 5V.If this approach appeals just say, and we can discuss the measures necessary to make a standard regulator circuit really solid.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 27, 2018, 05:08:01 pm
content: The manufacturer helpdesk just cannot help you because they don't understand the matter, and don't have resources to get the engineer to talk to you. "Rock solid" is meaningless. If they won't give you an actual figure or graph, it's all just random babble.The product is, of course, just fine even with varying input voltage from the li-ion battery directly. The battery is much better because it won't have that much ripple voltage than their AC adaptor probably has. The fact it changes slooooowwly doesn't mean a thing, if any of the voltages is acceptable on their own.(This is a guess, of course, based on experience, but it holds 99.9% surely; we can'tguaranteethere isn't some super weird trap. For example, they may have implemented a voltage watchdogon purpose, which detects your "non-rock-solid" supply and refuses to work, calls NSA, or makes demons fly out of your grandma's nose. But, this is the unlikely scenario.)In any case, the answer to your original question is, yes, any DC/DC converter is fine as long as it meets the ripple specifications by the manufacturer. If the specs do not exist, then... I guess the power isn't very important. It will be locally regulated on the product anyway, unless it's complete shit.

author: Wolfgang
author_rank: Super Contributor
timestamp: November 27, 2018, 05:12:29 pm
content: Yeah, get a low drift reference (e.g., REF02), some quality op amp (e.g., LT1028), a pass transistor (2N3055) on a proper cooler, low-tolerance resistors (0.1%) and a proper compensation - here we are.

author: IanB
author_rank: Super Contributor
timestamp: November 27, 2018, 05:19:55 pm
content: One way to define "rock solid" is that the supply should be "stiff", meaning that the voltage remains stable in the event of load fluctuations. One of the stiffest supplies is a battery with low internal impedance. A lead acid accumulator meets this definition, but a high capacity lithium ion battery can also be have a very low impedance. Adding a regulator after the battery may ironically make the situation worse, since a voltage regulator may have poorer regulation in the event of sudden load changes than a battery by itself may have.

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 05:34:48 pm
content: Quote from: IanB on November 27, 2018, 05:19:55 pmYes, of course, that is why I said to make a standard regulator 'solid'.By the way, batteries can supply big gulps of current, but their voltage is not stable and they are noisy.

author: IanB
author_rank: Super Contributor
timestamp: November 27, 2018, 05:40:08 pm
content: Quote from: spec on November 27, 2018, 05:34:48 pmCan you elaborate what you mean here? In what sense does the output from a battery contain noise? I think if I put a battery on an oscilloscope I would see the flattest line I could imagine.

author: langwadt
author_rank: Super Contributor
timestamp: November 27, 2018, 05:49:56 pm
content: Quote from: spec on November 27, 2018, 05:34:48 pmnoisy and not stable? I'd think a lipo with a reasonable charge will beat most wall warts

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 06:12:29 pm
content: Quote from: langwadt on November 27, 2018, 05:49:56 pm

author: Kalvin
author_rank: Super Contributor
timestamp: November 27, 2018, 06:15:45 pm
content: Maybe the solution calls for a solid state power supply.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 27, 2018, 06:23:55 pm
content: We are all just wasting our time shooting in the dark.@SpannersToSparks has not (can not?, will not?) reveal what his mystery load is.So we can posit guesses forever and never get anywhere.If that cryptic (and useless) "requirement" is all that the vendor will issue, then I don't see how we can help?

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 06:32:48 pm
content: Quote from: Kalvin on November 27, 2018, 06:15:45 pmThat is correct and what the OP suggested in his opening post. Except he was considering using a switch mode PSU which would require extensive filtering to subdue the switching transients.I am therefore hinting at a linear power supply, say of 10A peak capacity feeding high value electrolytic capacitors to supply the large gulps of current, like a car battery. But also to bypass the electrolytic capacitors with high frequency low ESR capacitors to provide a low impedance and high current capacity across the frequency spectrum.That way you would have better current capacity than a battery, in the sense of this application, with the absolute voltage stabilization of a solid state regulated supply.The techniques for doing this are not difficult. One essential requirement is to use hefty conductors and star point wiring- all pretty standard stuff.

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 06:45:02 pm
content: Quote from: Richard Crowley on November 27, 2018, 06:23:55 pmYes, we could use more information, but I suggest that there is sufficient information to propose an approach.The only thing I can see that is missing is the current consumption. Specifically, what do you see is missing?

author: Zero999
author_rank: Super Contributor
timestamp: November 27, 2018, 07:02:06 pm
content: Quote from: spec on November 27, 2018, 06:32:48 pmI agree that capacitors are good for reducing the AC impedance of a battery, but don't think a regulator is required, as the voltage range of the equipment is so wide.If noise is the problem, then you can't beat batteries. Even adding a linear regulator to the battery could increase the noise, so there's no reason to have one.

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 27, 2018, 07:15:36 pm
content: Rock Solid is actually a darned good name for, what else? A Classic-Rock cover group.

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: November 27, 2018, 07:24:28 pm
content: Quote from: schmitt trigger on November 27, 2018, 07:15:36 pmI think you meanhttps://en.wikipedia.org/wiki/Rocksteady

author: langwadt
author_rank: Super Contributor
timestamp: November 27, 2018, 07:30:12 pm
content: Quote from: spec on November 27, 2018, 06:32:48 pmThe op says it is an SoC current running from a power brick and with the wide voltage specit almost certainly has switching regulators. Building something to power it that would make anaudiophoole think it might be too much is taking overkill to the extreme

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 27, 2018, 07:31:43 pm
content: Quote from: spec on November 27, 2018, 06:45:02 pmYes. Both steady-state and startup-surge (depending on what the mystery load is?)QuoteBesides current requirement, if we knew what the mystery load is, we could at least make some educated second-guesses about the likely requirements in the absence of anything useful from the vendor.We could even suggest some tests that @SpannersToSparks could conduct to characterize how the mystery load behaves.With a good photo, we might even make a cursory determination of how power is handled (internally regulated?) etc.

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 07:41:47 pm
content: Quote from: Richard Crowley on November 27, 2018, 07:31:43 pmI agree, but have you thought of one thing- the OP might not want to publish details of the equipment. I could think of many situations where this might apply. I suggest that we should try to help as much as possible.I still say that there is sufficient information to formulate a design, even if it is just an outline.

author: tggzzz
author_rank: Super Contributor
timestamp: November 27, 2018, 07:47:43 pm
content: Quote from: spec on November 27, 2018, 07:41:47 pmThere is indeed "sufficient information to formulate a design" - but not with any confidence that it would be suitable for the OP. In fact there is sufficient information to formulate a very wide range of designs!Ifthe OP doesn't want to give us sufficient information to help him, there's a good argument he shouldn't waste our time in the first place

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 07:50:44 pm
content: Quote from: SpannersToSparks on November 26, 2018, 11:11:33 pmHas anybody read this?

author: spec
author_rank: Frequent Contributor
timestamp: November 27, 2018, 07:53:36 pm
content: Quote from: tggzzz on November 27, 2018, 07:47:43 pmIn that case why are you wasting your time on this thread

author: tggzzz
author_rank: Super Contributor
timestamp: November 27, 2018, 08:53:18 pm
content: Quote from: spec on November 27, 2018, 07:50:44 pmYes - and other people have correctly indicated it contains nousableinformation.

author: tggzzz
author_rank: Super Contributor
timestamp: November 27, 2018, 09:00:51 pm
content: Quote from: spec on November 27, 2018, 07:53:36 pmTrying to coax the OP into giving sufficient information that we might be able to help him.What are you doing with that question?

author: spec
author_rank: Frequent Contributor
timestamp: November 28, 2018, 07:09:16 am
content: Thanks for pointing all that out- my bad.