hybridfree/eevblog-posts huggingface dataset:
mid-1970s NiCd pack - Page 1
Forum section: electronics / general

author: Enginerding
author_rank: Contributor
timestamp: September 25, 2020, 12:01:49 am
content: Reviving a Keithley 147 and 148.(here:https://www.eevblog.com/forum/metrology/keithley-148-nanovoltmeter-(a-brief-teardown)/msg3235722/#msg3235722)Got sidetracked playing with the ancient batteries, made by Gould. 6v, 5-cell.Made in the 6th week of 1978.[ Specified attachment is not available ]These were causing a thermal overload in the charging circuit. (described in thread)So I decided to play with them with tools I had on-hand (a few power supplies, an smu, a load, an Imax hobby charger). I am no NiCd battery expert, so should be fun.Putting it on the Imax and looking under the thermal camera, the #1 cell on the positive side was taking all the heat.After a (very short) Imax charge and discharge cycle, these delivered a whopping 100mah at 0.1a constant current load.So I cut the hot cell out, and tested hooked it up to 1.6 volts. Not good.[ Specified attachment is not available ][ Specified attachment is not available ]I can keep dialing up the voltage, and up, and up. Crap.[ Specified attachment is not available ]When hooked up to an smu and shorted, a mind-blowing 25 microamps flowed.So it seems like this cell #1 has failed high resistance? I don't know much about NCd failure, but that is interesting. Ohming out the battery directly, I get 14R.I would try hitting this would a pulse of high current. But the voltage is climbing with current.Anyways, it's an interesting failure.
Dual Power supply +-30V 2A design question - Page 1
Forum section: electronics / general

author: onky
author_rank: Newbie
timestamp: September 24, 2020, 09:58:06 pm
content: Hi,For my master thesis, I designed a constant current source & sink using OPA548. I need to power OPA548 with dual +30V 2A to source and -30V 2A for sink current from load.Since pandemic universities are closed and no access to lab bench power supply.I am thinking to use AC-DC converter from MeanWell LRS-100-36 gives output 36V 2.8A. This can be reduced down to 30V using buck converter.ON Semiconductor made my work fast, using its web application i got a circuit designed using FAN65004B (minimal design).My problemis for -30V supply. Its not easy to find any simple solution (simple because power supply design is not main part of my thesis, want to spend less time)I need advice from you guys on following:If I design two +30V circuits and short negative of first circuit to positive of second circuit to make a reference (ground), will it work as dual power supply ?Please refer image below.or any other solutions are welcome.Thanks in advance.

author: Technomaniac
author_rank: Contributor
timestamp: September 24, 2020, 10:37:47 pm
content: The inputs would have to be separate power supplies as you will need the isolation between them.

author: David Hess
author_rank: Super Contributor
timestamp: September 24, 2020, 11:05:26 pm
content: Quote from: onky on September 24, 2020, 09:58:06 pmAssuming that the outputs are floating with respect to Earth ground which should be the case, that should work fine. So buy two identical power supplies and stack their outputs. Be sure to include an anti-parallel diode across the output of each one so that a short across both in series will not drive one of the outputs with reverse polarity; anti-parallel diodes are almost always found on dual supplies for exactly this reason.
Nikola Trucks - Complete scam?  Or does hydrogen/battery vehicles have a chance? - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: September 22, 2020, 12:35:26 pm
content: Just over a week ago I posted a promo video about Nikola hydrogen powered trucks. While hydrogen powered passenger vehicles with current technology make no sense, Nikola Trucks presents a business model that is plausible.A lot has happened with Nikola this past week. The college dropout pres for Nikola just stepped down after it was revealed Nikola’s president was BSing as much as Elizebeth Holmes if not more.Sure looks like Nikola is as much of a scam as Theranos. Wondering if there is anyway Nikola will produce hydrogen powered vehicles in a year or two as promised? Or will they be another Theranos by the end of the year?
Full Bridge SMPS with UCC28C43 controller - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 21, 2020, 08:50:50 pm
content: Dear Engineers,We wish to use UCC28C43 to drive a Full Bridge.The attached shows it in LTspice.Can you think of a more lower-component-count way of doing this?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: September 22, 2020, 04:18:58 am
content: That chip is not designed for a full bridge?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 22, 2020, 04:41:18 am
content: UCC3808
Getting a power supply out of constant voltage mode - Page 1
Forum section: electronics / general

author: electrotwelve
author_rank: Contributor
timestamp: September 20, 2020, 04:10:12 pm
content: I bought aTenma 72-2690single-output power supply recently. I'm trying to manually charge an SLA battery using this supply. When I switched it on and started adjusting the voltage, it went into constant voltage mode, and even though I can set the current, the moment I exit the current setting mode, I can only see 0.000 on the current meter. How do I get this PS to exit the CV mode? Themanualis really unhelpful.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: September 20, 2020, 07:01:45 pm
content: Do you have the voltage set at the maximum voltage you want on the battery. If it's below the battery voltage then it will not charge.

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 20, 2020, 09:31:38 pm
content: you need a current source to charge a battery, and the charger voltage must be capable to rise above the battery voltage, yes, otherwise you wont be able to charge it.

author: electrotwelve
author_rank: Contributor
timestamp: September 21, 2020, 05:06:58 am
content: I set the voltage to 14.4V (12V SLA) but I'm not able to set in CC mode to set the current for the charging. How do I do that?

author: james_s
author_rank: Super Contributor
timestamp: September 21, 2020, 06:31:32 am
content: Many power supplies automatically switch to CC mode when the load on the output exceeds the current setting. Have you tried turning up the voltage with the PSU connected to the battery? The current meter should read 0.00 until there is actually current being drawn.

author: electrotwelve
author_rank: Contributor
timestamp: September 21, 2020, 08:25:26 am
content: Quote from: james_s on September 21, 2020, 06:31:32 amAh so you are saying that the battery itself is not drawing any current and hence there is no reading on the meter. I set the voltage to 14.4V (12V SLA).

author: ahbushnell
author_rank: Frequent Contributor
timestamp: September 21, 2020, 11:32:25 am
content: Quote from: electrotwelve on September 21, 2020, 05:06:58 amBefore you connect to the battery. Set the output voltage with the PS open circuit. Then short the power supply output and set the short circuit current.Then connect to the battery.
Choose diff mode, or common mode inductor? (to most  reduce interference) - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 20, 2020, 09:28:19 am
content: Hi,We are building a 48V battery operated robot of size some 50cm x 30cm x 20cm. We have an isolated DCDC module on it, producing an isolated 12V at 11A.DCDC module:https://www.mouser.co.uk/datasheet/2/281/murata_uee150w-1186537.pdfWe have put an external 33uF capacitor right at the DCDC module’s input terminals.As regards inductive filtering, we are allowed either a diff mode inductor , or a well coupled common mode inductor, at the DCDC module input, just upstream of the 33uF. We are not allowed both.There is a radio transceiver of frequency ~800MHz operating on the robot. Also some microcontrollers and small signal circuitry.So in order to reduce interference with the radios and other electronics signal circuitry on the robot, which do you pick?…either the diff mode or the common mode inductor? There is a cable of some 20cm running from the battery to the DCDC module PCB.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2020, 10:12:54 am
content: Those tend to have a lot of CM noise, but who knows, you'd have to measure one.Whether that, in turn, has any relevance for the application, depends on everything else connected to it.Tim

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 20, 2020, 09:29:31 pm
content: Thanks, i beleive that in equipments like battery powered robots, where the power bus is obviously shared by nothing else, its purely for use by the robot alone....then diff mode inductance needs only to be very small...just enough to filter off those high frequency switching harmonics which could otherwise radiate out of their supply cables. Would you agree, that the best filtration in robot applications, is a common mode choke upstream of every DCDC SMPS module?.....because common mode noise pertains to the RF emissions which could interfere with the signal circuitry on the robot.So on a robot, for input filters to the SMPS's on the robot.....common mode inductors are order of the day....diff mode inductors are needed , but only tiny ones, just enough to filter out those highest harmonics....would you agree?
External input and output capcitors not used with DCDC SMPS module? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 16, 2020, 09:05:17 pm
content: Dear Engineers,We are using the UWE-12/10-Q48NB-C DCDC module for our application.UWE-12/10-Q48NB-C Datasheet:https://www.murata.com/products/productdata/8807040483358/uwe-100-120.pdf?1583754815000Spec:Vin=42-59VDCVout=12vdcIout = 10AIsolated (500V)No fansEnclosure 50x30x10cm (totally enclosed carbon fibre 1mm thick)This module has an internal PI input filter and internal output capacitors. However, it says nothing of the values. Our contractor reasons that we can use it with no external input or output capacitors.However, I believe this is unwise. Specially since we don’t know our exact wiring input impedance in all cases of use. All the datasheet specs (transient response, output ripple, etc etc) were recorded whilst using an external Cin of 33uF and external Cout of 11uF. Therefore, I suggest that we use those values in our application. Would you agree?As you know, the input filter should have an output impedance (as “seen” from the SMPS ) of value ten times less than the SMPS input impedance at the crossover frequency. The SMPS input impedance at the crossover frequency is approx equal to ^2/Pin. In out worst case that’s 42^2/134 = 13.2 Ohms.Its anyone’s guess what the internal PI filter is. So I suggest that we should use an external input filter with impedance of <1.32 Ohms at the crossover frequency. However, the crossover frequency is not stated in the datasheet. The transient response graph suggests that when Cout = 11uF , the crossover frequency is approx. 86kHz. This value was arrived at by A(step) / {2 x pi x [delta V] x Cout}. Where “delta V” is the undershoot after the load transient step of 5A.However, since the F(sw) is only 200kHz, an 86kHz crossover sounds unrealistic. As such, I believe we should assume crossover frequency of f(sw)/10.Would you agree with this?Another quicker way would be to just use the datasheet suggested values for cin and cout of 33uF and 11uF respectively…though the datasheet says that these were simply what they used for the datasheet spec’ing, and that it was not necessary to use these.
Serch for a fifficult to find CV-CC industrial PSU - Page 1
Forum section: electronics / general

author: f4eru
author_rank: Super Contributor
timestamp: September 07, 2020, 09:38:15 pm
content: Hello,I'm looking for a 24V 150-400W PSU from a reliable brand with both CV and CC modes, with the CC mode down to 0V (like a lab supply)Form factor could be DIN rail or metal box, eventually open frame could be acceptable.It seems difficult to find, any suggestions ?

author: f4eru
author_rank: Super Contributor
timestamp: September 16, 2020, 02:26:44 pm
content: Hello,Nobody has any reference of CV-CC PSU ?

author: MasterBuilder
author_rank: Regular Contributor
timestamp: September 16, 2020, 02:49:12 pm
content: A 24V 150-400W PSU is by its nature CV (constant Voltage), i.e. it is a fixed output 24V PSU and therefore not CC (constant current).Mean Well make some nice poer supplies, is it something like this youy need:https://www.meanwell-web.com/en-gb/ac-dc-single-output-industrial-din-rail-power-ndr--240--24

author: Jeroen3
author_rank: Super Contributor
timestamp: September 16, 2020, 02:55:29 pm
content: Traco Power TSP series has constant current instead of hickup. You can use them with their battery control module (BCM) to charge batteries and create a DC UPS.

author: f4eru
author_rank: Super Contributor
timestamp: September 18, 2020, 05:27:40 pm
content: Thanks, I'll try those !The purpose is to charge up supercaps...

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 20, 2020, 09:35:35 pm
content: Also try Murata power supplies.
Fan-less DCDC modular power supply needs a Vicor Module?....thermal properties. - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 15, 2020, 07:56:57 pm
content: Dear Engineers,We wish to design a modular power supply of the following spec:Vin = 42-59VDC (14S LiPO)Vout = 12VIout = 11AIsolated (500V)Not allowed to use fans to cool it….just heatsink.Enclosure is a totally sealed carbon fibre box of dimension 50cm x 20cm x 10cm (high).Max ambient outside of box = 45degC.Given the non-use of fans, I believe you would agree with me that this more or less confines us to a Vicor module type solution? Due to the greater thermal conductivity of the material of the vicor modules.For example, A Vicor PRM48AT480T400A00 cascaded with a Vicor VTM48ET120T025A00 would cover our spec. Their datasheets give the thermal resistance of their hottest component to the case as 1 degC/W. You simply can't get that low with "open PCB" type DCDC modules, because they use gap-pad to thermally couple to their little metal base-plate.“Open PCB” type DCDC modules such as eg the Murata UEE-12/12.5-D48NB-C just can’t compete for such a fan-less application. Do you agree?The power components of the UEE-12/12.5-D48NB-C are gap-padded to the metal base-plate. Clearly, gap pad isn’t as good a thermal conductor as the Vicor module material. The UEE-12/12.5-D48NB-C module’s datasheet doesn’t even provide any thermal resistance figures.Clearly , the “open PCB” type DCDC modules must have a fan blowing over them in order for them to operate at anywhere near maximum power. Do you agree?Vicor PRM48AT480T400A00 datasheethttp://cdn.vicorpower.com/documents/datasheets/PRM48AF480T400A00_ds.pdfVicor VTM48ET120T025A00 datasheethttp://www.vicorpower.com/documents/datasheets/VTM48E_120_025A00.pdfMurata UEE-12/12.5-D48NB-C datasheethttps://www.murata.com/products/productdata/8807039893534/uee150w.pdf?1583754815000Here is a picture of an “open-PCB” type , “non-Vicor” DCDC module…..https://www.digikey.co.uk/product-detail/en/murata-power-solutions-inc/UEE-12-12-5-D48NM-C/UEE-12-12-5-D48NM-C-ND/4747528……You can clearly see that its meant to only be used with blown air. There is no high-thermal-conductance potting like you get in the Vicor modules.Surely you agree, that our Fan-less spec predicates a Vicor DCDC module approach?
Boost PFC with absolute minimum amout of output capacitance...but still works OK - Page 1
Forum section: electronics / general

author: opampsmoker
author_rank: Regular Contributor
timestamp: September 27, 2020, 06:23:28 pm
content: Please help with 250W Boost PFC followed by 2 Tran Forward?VAC input = 180-265VAC; 2TFC Vout = 58VWe wish to use only film caps at the booster output. Also, use the bare minimum amount of capacitance there, as films are expensive. Can you confirm that this will not mean the Booster and 2TFC dropping out when the 2TFC suffers a no_load to full_load transient?…..because after all, even though we only use low capacitance at the booster output, we can set our feedback loop to be fast enough so that it will avoid drop-out and yet also be slow enough to give PFC. Do you concur?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 27, 2020, 07:08:24 pm
content: Hi,The answer is probably no.Assuming the 2 transistor forward converter has a constant load, over the line cycle it will want to draw constant power. The PFC will want to draw sinusoidal current from the mains, so the power from the PFC is sine2. You need energy storage to fill in the gaps.Jay_Diddy_B

author: tom66
author_rank: Super Contributor
timestamp: September 28, 2020, 09:46:41 am
content: I used to repair LCD TVs, and one TV manufacturer had gone for a design where the primary side PFC had very low capacitance (2-3uF) and the secondary side had over 22,000uF at 24V (for an 8A output); I can only presume that they were attempting to shift the PFC stabilisation to the output side of the transformer.

author: Yansi
author_rank: Super Contributor
timestamp: September 28, 2020, 10:48:21 am
content: Yup, you can for example merge a PFC stage with the main converter. It is typical for audio applications, where the 100/120Hz output ripple douesn't matter.The simplest is to make a flyback act like a PFC. eg.:https://www.infineon.com/dgdl/Infineon-100W_Single_Stage_Critical_Conduction_Mode_PFC_Flyback_Using_IRS2982-ApplicationNotes-v02_00-EN.pdf?fileId=5546d4626eab8fbf016ed36da4f44a61orwww.st.com/resource/en/application_note/cd00004041-flyback-converters-with-the-l6561-pfc-controller-stmicroelectronics.pdf
Strange Output from Max4081 - Page 1
Forum section: electronics / general

author: majdgh
author_rank: Contributor
timestamp: September 12, 2020, 09:22:49 am
content: Hello everyone,at first thanks for the top support Forum.I have a project that i measure the current with MAX4081 in Bidirectional mode for the motor in H bridge.I have simulated the exact circuit with NI Multisim and it works correctly, so i am able to measure the current in both directions.The Ref1a is on a reference voltage of 3V and the Refb on the ground so the output is 1.5V when the current is zero. Now when i run the motor in the first direction the output of the MAX chip is about 1.6V which is correct, and all of this for now tested and works correctly. The problem is when i change the direction the output stays at 1.5 and never drops below 1.5 now matters how much current is flowing.I have checked each connection on pcb and there is no error.I measured the voltage drop across the shunt resistor and it is correct for the first direction and negative for the second direction which is also correct.I can't understand waht is rong! any idea, Thanks.
Holly shit!  NDB has a Universal life-long SELF CHARGING green battery - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: September 10, 2020, 02:34:41 am
content: Dave - I hope you take a look at NDB's web site now.NDB's Diamond Nuclear Voltaic (DNV) battery (web site as of 9/9/2020,http://ndb.technology) claims:A SMARTPHONE THAT DOESN’T REQUIRE CHARGING.EV Cars - NO RECHARGING OR REFUELING STATIONS REQUIRED.ELECTRICITY FOR EVERYONE & EVERYWHEREA MINIATURE POWER GENERATOR FOR EVERY DEVICE!And to think Tesla and the other battery manufactures just spent billions to make batteries for EV cars when they could be making nano diamond batteries which won't need to be replaced for 1,000 years. Imagine in 3020 driving around in a 2020 Tesla with the original batteries.I'm going to build a NANO Diamond Self Charging Battery factory in my backyard. Please support me with a cash contribution on Fundable so I can make millions.

author: Brumby
author_rank: Unknown
timestamp: September 10, 2020, 04:06:37 am
content: Quote from: DougSpindler on September 10, 2020, 02:34:41 amThat sounds about right for a single charging cycle.
Cheap LiFePO4 batteries - too cheap? - Page 1
Forum section: electronics / general

author: tomkcook
author_rank: Newbie
timestamp: September 05, 2020, 01:59:48 pm
content: I know there are a lot of 18650 cells out there with improbably capacity ratings. I'm wondering if anyone has any experience or knowledge on these bigger cells:https://www.alibaba.com/product-detail/3-2V-100AH-Lithium-ion-phosphate_1600071018066.html?spm=a2700.galleryofferlist.0.0.f7bf629aM16hgm&s=pAt the prices they're quoting, they work out around £70/kWh (albeit without paying import duties, charger/BMS etc - or shipping, for that matter). Is that just a bit too good to be true?It's possible that they're making up for the low cost in the shipping fees - express shipping to either USA or UK seems to be roughly the cost as the cells themselves (considerably more if you're only ordering a few) and you have to discuss shipping with them before you order.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 05, 2020, 02:58:38 pm
content: Just too good to be true.The prices of Chinese prismatic LFP cells are almost fixed. No way somebody just starts selling at third the price. Either they add a hidden cost like "shipping", or the cell is actually some 40Ah or even smaller, or just a full-fledged scam such as constructed from sand.The weight quoted is 2.15kg. That works out 150Wh/kg, which is beyond believable. Other Chinese prismatic LFPs are in range between 90-120 Wh/kg. Higher end pouch LFPs can get near 140 Wh/kg.
Switching between isolated and non-isolated supplies? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 31, 2020, 11:08:16 am
content: Hi,We have a battery powered circuit as attached. Usually the isolated DCDC SMPS module supplies the load. But every so often one battery is removed for charging etc, and we still need power to the circuit….so we then have the relay (as shown) which switches between the isolated and non-isolated 5V and Gnds. It “changeover switches” them together.What worries me is that charge pumping through the isolated SMPS may mean that even with the 1MEG resistor, there may end up being significant potential between the battery ground and the isolated ground?…especially since there are actually four isolated converters in the real circuit (not just the one as shown).Do you think there is any chance of this “charge pumping” causing a significant difference in the potentials of isolated and battery grounds?

author: Nusa
author_rank: Super Contributor
timestamp: August 31, 2020, 01:22:43 pm
content: Or, instead of a SMPS, you could plug a spare battery into an external jack and switch over to it with a manual switch. Swap the regular battery with a charged one, then switch it back. Put the old battery on the charger. You never lose isolation.

author: Marco
author_rank: Super Contributor
timestamp: August 31, 2020, 01:44:05 pm
content: Just put a multimeter across the 1 Meg resistor and measure it.
Contactor sparking with multi kW equipment is just normal accepted practice? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 31, 2020, 04:42:03 pm
content: Dear Engineers,I was being shown round a battery driven equipment of several kW power by a member of staff.The equipment has multiple electric drive inverters and BLDCs.Battery voltage is 14S LiPO , but sometimes 24S LiPO. The guy seemed worried. Then he said something which really concerned me. He said that when a newly charged battery is connected to the equipment, then if the battery is not very quickly and firmly slammed into the connector, then there is much sparking and the connector is so badly damaged that the connector has to be replaced, and that this takes much time, and is an awkward job. He told me that usually only special people are allowed to connect the battery, because it takes a “special touch” that most don’t have…….and otherwise, serious connector damage results.So I take it that there is no inrush limitation on this circuit.The inrush is obviousy into the bus capacitor banks.To me this sounds very bad, as the connector could become high resistance and the equipment could possibly fail.Can you describe…..i mean….maybe, just maybe, it is standard procedure, with high power items like this, to just save money and not use an inrush limiter?..... and just agree to replace the connector after every say five mating cycles?……I mean…is this the kind of thing which goes on with these kind of equipments?

author: tggzzz
author_rank: Super Contributor
timestamp: August 31, 2020, 04:58:40 pm
content: You and treez have at least two things in common.First you both work with PSUs and have significant problems with them.Second you start a thread, !et it run, then (arguably when the first thread contains awkward truths) start a different but closely related thread.

author: Gyro
author_rank: Super Contributor
timestamp: August 31, 2020, 05:37:27 pm
content: ^https://www.eevblog.com/forum/projects/connector-sparking-and-damage-due-to-inrush-at-mating-time/new/#new
Input/output filter of DCDC module needs replacing? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 30, 2020, 09:57:27 pm
content: Dear Engineers,I have been shown a schematic and PCB for a DCDC module power supply which has a vin of a 48V battery (14S LiPO) . Vout is 5V and 5.5W.I believe the input and output filter is very sub-optimal, and will cause problems with EMC and connector sparking and subsequent degradation.I attach schematics of the current setup, and the proposed setup. Would you agree that the proposed setup is better from an EMC point of view? (and connector lifetime point of view?)--------------------------------------------------------------------------------------------------------------------------------------------The nearest output cap to the DCDC module is some 3.5cm from the module and is a 47uF, 16v, X6S, 1210. You can see switching spikes on the Vout at the output terminals of the DCDC module which comprise 50MHz ringing, up to 5.5V. This appears to be due to the ESL of the 47u and the PCB trace inductance, ringing with the 47uF cap. I believe it needs a 100n,0603 right at the DCDC module output terminals to mitigate this.Also, there is an 82uF input capacitor, which will mean high inrush from the battery when connected, and high sparking at the connector (it will get connected/disconnected once per day). Thus I proposed an inrush limiter and smaller input capacitor value.Also, the capacitor at the input to the DCDC module is a alum poly A759KK225M2EAAE685 (2u2, 250V) with 0.685R of ESR. This to me , is more like an RC damper at the DCDC module’s input. From Middleman’s theorem, we know that at the input to a DCDC converter we need a very low impedance, (looking back from the DCDC’s input, to the input filter), so we need some ceramic capacitance there. As such, I am proposing a 100n ceramic and a 1u ceramic in parallel at the DCDC module’s input, as well as a 10uF film capacitor.I appreciate that the DCDC module works OK as it is now…and successfully supplies the load which is some 5.5W (might go up to 10W in future). However, I believe for EMC reasons, when this product finally goes for approvals testing, I believe the proposed input/output filter is preferable…would you agree?The DCDC module used is Traco “THN 20-4811WI”.https://www.tracopower.com/int/model/thn-20-4811wi-a1(the DCDC module footprint is “doubled up” as sometimes the Battery will be 24S, and a higher voltage DCDC module will then be placed)
Nano Diamond self-charging nuclear based battery to last thousands of years??? - Page 1
Forum section: electronics / general

author: dybuk
author_rank: Newbie
timestamp: August 26, 2020, 11:03:52 am
content: Hey guys,this is a new article about a startup that supposedly made a "proof of concept" nano diamond battery in UK that uses radioactive carbon to produce charge (as far as I understand).https://techcrunch.com/2020/08/25/self-charging-thousand-year-battery-startup-ndb-aces-key-tests-and-lands-first-beta-customers/?guccounter=1And here is a link to their site:https://ndb.technology/It really sounds too good to be true. What do you think about it?

author: greenpossum
author_rank: Frequent Contributor
timestamp: August 26, 2020, 11:20:10 am
content: It sounds like the result of this research:http://www.bristol.ac.uk/news/2016/november/diamond-power.htmlwhich is also mentioned here:https://en.wikipedia.org/wiki/Diamond_batteryAs I understand it the radioisotope encapsulated in a diamond shield provides the energy which is turned into current. Note that the generated energy is very low but then the battery is very long-lived.

author: Mr Evil
author_rank: Regular Contributor
timestamp: August 26, 2020, 06:54:49 pm
content: There are existing batteries using the same principle, but based on other radiaoactive substance liketritium. They last a long time, but at very low power. Despite the marketing of this new one, I get the impression that it will be similar, and so have limited use.

author: dybuk
author_rank: Newbie
timestamp: August 26, 2020, 11:53:51 pm
content: and yet they claim "7x the charge of phone battery". Another one of those baits for investors.

author: sibeen
author_rank: Frequent Contributor
timestamp: August 27, 2020, 12:23:30 am
content: Start up company makes bullshit claims...news at 11.

author: greenpossum
author_rank: Frequent Contributor
timestamp: August 27, 2020, 01:37:30 am
content: Quote from: dybuk on August 26, 2020, 11:53:51 pmWell it may be true but you'd have to wait eons to extract that amount of charge.

author: Zero999
author_rank: Super Contributor
timestamp: August 28, 2020, 02:47:16 pm
content: Quote from: dybuk on August 26, 2020, 11:53:51 pmWhat do they mean by charge? It might store 7 times the charge of a phone battery, but if the voltage is one 7th, then it will store the same amount of energy.

author: tggzzz
author_rank: Super Contributor
timestamp: August 30, 2020, 03:08:23 pm
content: It is an updating of this 34-year old technology
Power supplies needed for DCDC - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 12, 2020, 01:57:34 pm
content: Dear EngineersWe need the following power outputs (isolated)24V, 5A; 12V,10.84A;These must come from a 14S Battery of voltage 42V-58.8VWe also need the same power outputs from a 24S Battery of voltage 72-100.8VI can find Vicor modules for this, but the Boss wants to find cheaper alternatives.PCB is 175 x 50mm approxWould you agree that this is basically Vicor territory?....And that almost nothing else would do

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 12, 2020, 11:54:33 pm
content: Quote from: zenerbjt on August 12, 2020, 01:57:34 pmThat's very common for telecom and IT equipment designed to run from 48V. Plenty of modules and designs for that.QuoteYou might be able to get a standard PSU with active PFC to run on that, although the low end might have problems with startup and you'll have to derate the power rating substantially.

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 13, 2020, 07:01:35 am
content: Yes, we need small size and so as you know we cant use custom design as standard transformers are big compared to the wee little integrated ones they use in these vicor modules.PCB is 150x75mm.I am just wondering if there are alternatives in DCDC modules to vicor?I searched digikey with a fine tooth comb but only found one flex power dcdc modules....but i never heard of them before and i wonder if they would have supply issues, whereas vicor can definetely supply parts

author: ahbushnell
author_rank: Frequent Contributor
timestamp: August 13, 2020, 03:34:30 pm
content: Quote from: zenerbjt on August 12, 2020, 01:57:34 pmWhen you compare Vicor to other options be sure to include the external components that are required. You can find the requirements in the Vicor data sheet.

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 13, 2020, 08:05:02 pm
content: Thanks, though i believe virtually all vendors DCDC modules at 100W+ will need external bypass caps at input/output, and also external fuse, as a minimum?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 29, 2020, 04:37:31 am
content: Meanwell power supplies have a name for having a good compromise between price and reliability.I don't know Vicor, nor what sort of quality and reliability your boss expects from a power supply.I can give you some pictures of cheap chinese garbage where thermal paste is smeared over the power transistors and diodes after mounting them, or where these components are not mounted flat to the outside for cooling. I do use these cheap things, but I would not dare using them without checking such details myself. This can easily cost half an hour for each power supply, which does not make much sense for a business model.
Measuring up to 400A inverter currents in BLDC drive (non invasive measurement) - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 19, 2020, 07:46:22 pm
content: Dear Engineers,We are using 10Kw BLDCs fed by 3 phase inverters. We wish to scope the current waveform in the battery supply cables to the inverter. We have selected the MLX91209 current sensor since it gives a non-invasive solution, and our current peaks will be some 400A. One must simply mount it into a gap in a ring torroid, and then run the conductor through that same torroid. The MLX91209 then gives a voltage output proportional to the current. It has the same bandwidth as a current sense transformer, near enough.https://www.melexis.com/en/product/MLX91209/250kHz-Programmable-Hall-Effect-Current-SensorHowever, the Melexis website doesn’t tell how we can get hold of the SUPRA 50 SP ferromagnetic cores for this useage.Do you know how much these cost? ..We don’t yet have a reply from MagLab, the named manufacturer.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: August 19, 2020, 07:58:47 pm
content: I would use a LEM current probe. Is this to go on a product our just for test.https://www.digikey.com/products/en/sensors-transducers/current-sensors/525?k=LEM&k=&pkeyword=LEM&sv=0&pv276=249171&sf=0&FV=1153%7C182102%2C1989%7C0%2C-8%7C525%2C222%7C1131&quantity=&ColumnSort=0&page=1&stock=1&pageSize=100This is an example. Not the current number you see is the RMS. It will measure higher peak currents. Dig into the specifications. We use them all the time.Andy

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 29, 2020, 04:13:40 am
content: Have you thought about using (a part of) the cable itself as a shunt resistor?You will have some drift when the temperature of the copper changes, but HALL sensors are not the most accurate either.

author: scrat
author_rank: Frequent Contributor
timestamp: August 29, 2020, 01:20:25 pm
content: Quote from: Doctorandus_P on August 29, 2020, 04:13:40 amThat's definitely not a reliable way to measure current. Wonder why so many people in the world uses Hall sensors and expensive shunts...I warmly second the LEM advice. Plenty of choice, well specified accuracy, bandwidth, etc.Plus, you can choose the current output type (the most common one), which ensures quite good noise immunity when you bring the output signal through few meters wire (in other words, the typical closed-loop LEM sensors work as 1:N Current Transformers, except they also work with DC).
50MHz "pickup" on scope on AC coupled output ripple voltage measurement? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 26, 2020, 07:59:43 pm
content: Dear Engineers,Today our contractor was doing a Vout ripple measurement on a scope on AC coupled setting. He was correctly using a “role your own" coaxial probe with narrow loop area. (no scope probe dangling ground clip).The SMPS was a 5Vout DCDC module by XP. It was only supplying a load of some 5W.I noticed his scope trace had the usual high frequency “pickup”, and the actual ripple voltage trace inside of this….kind of as in 4:33 of this video…https://www.youtube.com/watch?v=K0Mhj7MaOaI&feature=youtu.beThe high frequency pickup ringing pulses were at 50MHz. They had a peak-to-peak of 800mV…Anyway, he was recording the peak to peak level of the high frequency noise pickup. (The 50MHz) Therefore, I informed him that he should ignore this ‘pickup’ and just take the actual output voltage ripple which is considerably less in peak-to-peak…..He then informed me that I was wrong, and that he should indeed record the high frequency ‘pickup’ peak-to-peak, because it gave in indication of how noisy the DCDC module was…...So I then requested that he connect the scope ground and tip together, and then contact these to the 5V output terminal where he had been measuring the Vout ripple. I was expecting the high frequency ‘pickup’ to still be there…proving that it was simply ‘pickup’ induced into the scope probe…However, the “high frequency pickup” did indeed disappear from the scope trace….from which I had to conclude that the “high frequency pickup” was not actually induced into the scope probe, and that it was indeed a kind of “noise indication” pertinent to the actual DCDC module.I then took an AC coupled measurement of vout just downstream of a ferrite bead at the output of the DCDC module.(ie just downstream of the place where the first trace was taken. This second trace showed the peak-to-peak of the 50MHz ringing down 10 times to 80mV peak-to-peak)What do you think?This kind of thing is usually just “pickup”, and to be ignored?JTK3048S05 datasheethttps://www.xppower.com/portals/0/pdfs/SF_JTK30.pdfQuote ReplyReport Edit

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 27, 2020, 03:53:46 am
content: So I guess the VHF noise was more DM than CM, which is kind of interesting. Could be output diode recovery or such.It's ignored for ratings purposes ("ripple measured in 20MHz bandwidth") but that doesn't mean one can, or should, ignore it for system design. Some manner of filtering is desirable, yes, and an adequately rated ferrite bead (one each for + and -) will probably do.Tim
LP2981A linear regulator needs  resistor in series with its output capacitor? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 24, 2020, 09:02:56 pm
content: Dear Engineers,We are using the LP2981A linear regulator (5V input, 3V3 output)The load is a STM32F042K6T6 micro and a TCAN332 CAN transceiver.The LP2981A datasheet on page 8 says that a ceramic output cap must have a 1R resistor in series with it….….On our board, which just got sent off for manufacture, we don’t have this. We believe that since our load is only some 10mA, (nowhere near the 100mA full load), we should be OK with the 1uF Ceramic cap that we have on its output? (we didn’t place a series resistor)We’ve tried to change to a SOT23-5 linear regulator that is able to drive ceramic output caps (without needing a series resistor) but there’s none with the same footprint.Do you think we’ll be OK due to our light-ish load?LP2981A-33DBVR datasheethttps://www.ti.com/lit/ds/symlink/lp2981a.pdf?ts=1598302002553&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLP2981A

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 24, 2020, 09:09:50 pm
content: Fig.7, you need more than 20mohm at that load.TimP.S. Not using your primary account?

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2020, 04:57:18 am
content: The required series resistance increases as the output resistance increases which happens at lower currents, so greater series resistance is required at lower output current. Micropower regulators are very difficult to stabilize with ceramic output capacitors.Maybe you can replace the SMD ceramic output capacitor with a suitable solid tantalum capacitor?

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 25, 2020, 05:25:23 am
content: Would it solve things if we solder a 1R resistor in series with the output of the LP2981A?in fact.......there are multiple 0603 output caps. (five).......so can we say have a 1r in series with the 2u2 one...then the four 100n caps can do without this resistor?MIC5233-3.3YM5 seems to be ok with any Cout >2u2......i believe we will change to this.MIC5233-3.3YM5 datasheet:https://www.mouser.co.uk/datasheet/2/268/MIC5233-Data-Sheet-DS20006033D-1627563.pdf

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2020, 11:13:56 am
content: Quote from: zenerbjt on August 25, 2020, 05:25:23 amAbsolutely, and that is essentially what some regulators do internally. Discrete regulators sometimes take advantage of the same idea by placing the current shunt in series with the output of the transistor.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2020, 12:10:37 pm
content: Yes, ESR in the bulk cap, in parallel with smaller caps without much ESR, works as long as the ESR is dominant around the regulator's crossover frequency.Tim
Input capacitor to DCDC module could be over-ripple-currented? - Page 1
Forum section: electronics / general

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 16, 2020, 12:16:40 am
content: Dear Engineers,A contractor has done the attached prototype PCB for us using the JTK3048S05 DCDC module from XP Power.com.(spec is 48vin, 5V, 5A output.Would you agree that at the input, the 2u2 and 82u caps should swap places with each other?(it seems difficult to say, because there’s no way of knowing if there is already capacitance inside the DCDC module? If there’s no internal caps, then if it’s a BCM buck in the module, then the 2u2 cap will be heavily over-ripple-currented.)-----------------------------------*****************---------------------------------------------------------Datasheets...MSS1038 (12uH) datasheethttps://www.coilcraft.com/getmedia/3e03a7b4-3b1d-4f31-b1f3-e7c621695ac0/mss1038.pdfA759KK225M2EAAE685 cap (2u2) datasheethttp://www.farnell.com/datasheets/2...MIu9iI8a7j6gIVjO3tCh1plg7KEAAYAyAAEgL_bfD_BwEA759SZ826M2EAAE150 cap (82u) datasheethttp://www.farnell.com/datasheets/2...MIu9iI8a7j6gIVjO3tCh1plg7KEAAYAyAAEgL_bfD_BwEJTK3048S05 DCDC module datasheet 48VIN, 5V, 6A outputhttps://www.xppower.com/portals/0/pdfs/SF_JTK30.pdf

author: butech
author_rank: Contributor
timestamp: August 17, 2020, 09:25:05 am
content: Normally I would agree with you, but If you look at the datasheet of the JTK3048S05 DCDC module, you provided and look on the bottom of the last page, there a EMI input filter is shown with an inductor directly connected in series to the input of the DC/DC converter. Therefore I assume (educated guess) that there is sufficient input capacitance to handle to ripple current. But as mentioned it is only guessed.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 29, 2020, 04:30:44 am
content: Page 3 of the power suppies datasheet mentions a few times:"External input filter required, see applications note"So read it's application note for suggestions on filtering for this particular SMPS module.5V * 5A = 25Watt, which is 500mA at 50V.The links to the capacitor datasheets do not work so I have not checked if your capacitors can handle this.
How do I remove spikes (noise) in AC signal of inverter - Page 1
Forum section: electronics / general

author: radhika
author_rank: Regular Contributor
timestamp: August 13, 2020, 01:16:21 pm
content: Hi, I am working on SPWM inverter. I have generated 400Hz using switching frequency 20kHz. I made H bridge to get sine wave. I am using 2.2uF 400V and 1uH inductor in series with 10Ohm resistor to get sine wave.I am getting sine wave, but its not pure wave. Which components I add or remove to get the pure sine wave?https://postimg.cc/R60vYLX3

author: radhika
author_rank: Regular Contributor
timestamp: August 13, 2020, 03:32:02 pm
content: Anybody? any response?

author: Phoenix
author_rank: Frequent Contributor
timestamp: August 19, 2020, 10:52:37 pm
content: Can you post a complete schematic and photo of your board?

author: f4eru
author_rank: Super Contributor
timestamp: August 20, 2020, 07:00:45 pm
content: and oscillograms ?
How should I increase signal level with a transformer? - Page 1
Forum section: electronics / general

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 10, 2020, 08:35:55 pm
content: Helloit's very odd, but when I simulate the following circuit I don't get the right voltage at the output! why? the output should be sqrt(Ls/Lp)*Vin=sqrt(20/1m)*50=7071 V ,but the output is only 2.11 KvI have attached the LTspice file.trans_1.asc(0.94 kB - downloaded 54 times.)Actually I have a 50V sine wave, I want to apply it to a transformer to produce a 5KV sine wave.could you please help me to solve this odd problem?

author: Ian.M
author_rank: Super Contributor
timestamp: August 10, 2020, 09:01:25 pm
content: You are measuring it wrong. Change the .tran command to.tran 0 200m 100m 100uto start saving data after the initial transients have settled, then paste this as a directive:Code:.meas HV_1 RMS V(HV_1).meas n002 RMS V(n002).meas turns_ratio param HV_1/n002.meas ind_ratio param turns_ratio**2.error ; force Error Log displayn002 is the top end of L1.Results:Code:hv_1: RMS(v(hv_1))=4216.57 FROM 0 TO 0.1n002: RMS(v(n002))=29.8156 FROM 0 TO 0.1turns_ratio: hv_1/n002=141.421ind_ratio: turns_ratio**2=20000which is exactly as expected.N.B. There is a considerable voltage drop and phase shift due to R1.
Strange LiPo voltage curve.... free energy? - Page 1
Forum section: electronics / general

author: Kangurito
author_rank: Newbie
timestamp: August 10, 2020, 03:48:14 am
content: Can anybody explain this strange LiPo voltage curve?I have four wireless devices, each with a single cell LiPo battery. The batteries on three devices have a 'normal' discharge curve and don't exhibit the strange behavior I'm seeing on the fourth device.From 1:51pm to 8:09pm on the same day, the voltage 'slowly' drifted up from 3.77v to 5.07v. From there, it drifted back to 3.76v by 9:22am the next day.There are no other power sources, external or on the board.Voltage is measured using a resistor voltage divider into microcontroller ADC. I wasn't able to test the battery voltage using my meter but will do this if I see the voltage drift up again.Has anybody seen this happen with LiPo chemistry before? Can anyone explain it?'free energy'? (Joke)

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 10, 2020, 04:41:59 am
content: Most likely some problem with the divider causing bad readings, such as bad soldering or flux left on the board.

author: tom66
author_rank: Super Contributor
timestamp: August 10, 2020, 07:02:01 am
content: Alternatively, as the LiPo discharges, the ADC reference goes bad and the battery voltage looks high.