hybridfree/eevblog-posts huggingface dataset:
High isolation RF combiner for HF - Page 1
Forum section: electronics / projects

author: merseyless
author_rank: Contributor
timestamp: August 19, 2019, 12:49:50 am
content: Hi All,I've been beating my head against a image rejection mixer that just won't cooperate.I think the problem might be with the 10.7MHz lumped element quadrature coupler that I made which goes to the IF circuitry. I plan on adjusting the topology to place a prefabbed quadrature coupler on the RF input and use a high isolation RF combiner on the output of the two mixers.At the moment, I'm considering an opamp based solution. two opamps acting as buffers and a third as a summing amplifier. While it could work, the signal I'm looking at may still be at -30dBm. It shouldn't be a problem but I've never fed a signal that weak into an opamp. I'm also concerned that there would be an unwanted increase in noise from all those active components.Are there any other designs that I should consider?

author: DimitriP
author_rank: Super Contributor
timestamp: August 19, 2019, 02:37:51 am
content: You might want to show the design, the frequencies involved and in what way it refuses to cooperate.As for alternatives, from minicircuits to Analog Devices to another discrete contraption there are a few ....
high linearity, high speed DAC selection  - Page 1
Forum section: electronics / projects

author: xzswq21
author_rank: Frequent Contributor
timestamp: November 28, 2017, 02:28:56 pm
content: HelloDo you know a high speed DAC to produce sine signal with 90dB SFDR upto 10MHz? beyond 10MHz the SFDR should be around 50~60dB.Thanks

author: dmills
author_rank: Super Contributor
timestamp: November 28, 2017, 03:46:49 pm
content: LTC2107 is pretty much the most linear high speed part I have found in the above 125MHz space, at least according to the datasheet (ADC Datasheets lie)!What sample rate do you require?Regards, Dan.

author: xzswq21
author_rank: Frequent Contributor
timestamp: November 28, 2017, 04:32:45 pm
content: Quote from: dmills on November 28, 2017, 03:46:49 pmbased on my design and the RAM capacity (512MB DDR3) it should be between 100MSPS to 250MSPS...actually I want to generate a signal up-to 10MHz. above 125MSPS is good to generate a higher frequency that I'm eager to use it.

author: xzswq21
author_rank: Frequent Contributor
timestamp: November 28, 2017, 04:43:16 pm
content: LTC2107 is a ADC not a DAC.

author: dmills
author_rank: Super Contributor
timestamp: November 28, 2017, 06:14:56 pm
content: Yea... Bad day, and guess what datasheets I have been cursing over. One of the TxDac line maybe, they often have integrated interpolators and such which may be useful?Why can these bloody vendors not publish proper bloody datasheets? I don't really care what typical performance is, talk to me about worst case!Regards, Dan.

author: MasterT
author_rank: Frequent Contributor
timestamp: November 28, 2017, 09:56:30 pm
content: Seems you need 16-bits, 1-2 INL, settling time <100 ns. Here is search results on digikeyhttps://www.digikey.ca/products/en/integrated-circuits-ics/data-acquisition-digital-to-analog-converters-dac/701?FV=264000b%2C2640013%2C2640016%2C2640024%2C2640005%2C2640044%2Cf9400a6%2Cf9400b1%2Cf94018b%2Cf940193%2Cf940194%2Cf940195%2Cf940196%2Cf940197%2Cf940198%2Cf940199%2Cf94019b%2Cf94019f%2Cf9401a0%2Cf9401a1%2Cf9401a2%2Cf9401a3%2Cf9401a5%2Cf9401a6%2Cf9401a7%2Cf9401a8%2Cf9401a9%2C1ed800a1%2C1ed800e1%2Cffe002bd&mnonly=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&cad=0&datasheet=0&nstock=0&photo=0&nonrohs=0&newproducts=0&quantity=1&ptm=0&fid=0&pageSize=25Very pricey.

author: rsjsouza
author_rank: Super Contributor
timestamp: November 28, 2017, 10:40:32 pm
content: If I understood the original request, the intent is to generate a 10MHz sinewave. 100ns is not sufficient to do that.
High negative voltage  (-100 to -500V) switching with minimal current - Page 1
Forum section: electronics / projects

author: Saulius
author_rank: Newbie
timestamp: January 14, 2015, 07:29:38 am
content: HelloI am a final year bachelor in material science and i am quite a novice in electronics, but I have this project on my hands: for magnetron sputtering, on substrate we need to generate 10+ kHz switching 100-500v negative bias voltage ( we have wave generator and high voltage dc power supply, and we need middle part between these too), with minimal current, using only discrete components (i live in a small country and it would take a lot of time to obtain some intricate parts, and time is of essence here).Thank YouPS, sorry for broken grammar

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 14, 2015, 08:11:28 am
content: There are many MOSFETs capable of handling that voltage and frequency. However you will need a proper gate driver. For low frequency I use optical drivers but at this frequency I would look at a transformer based system like this.http://www.st.com/web/en/resource/technical/document/application_note/CD00003897.pdf

author: VK5RC
author_rank: Unknown
timestamp: January 14, 2015, 08:50:09 am
content: Sorry to take things back in time but have you thought about a valve (thermionic)?

author: fcb
author_rank: Super Contributor
timestamp: January 14, 2015, 09:34:22 am
content: I would probably use a small ferrite cored transformer.Drive it (transformer) with a square wave (probably drive it with an H-bridge made from junk-box transistors or MOSFET's), vary the DC supply to the H-bridge (say 10-50V) to get your 100-500V. Don't use a gapped core - you are using the transformer as a transformer, not a flyback transformer.Obviously use a fast rectifier diode to give you negative only pulses, probably load the secondary with a suitable resistor (this will reduce the ringing).

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 14, 2015, 09:43:50 am
content: photoflash style flyback -ve autotransformer?
High operating/quiescent current from buck converters? - Page 1
Forum section: electronics / projects

author: newto
author_rank: Regular Contributor
timestamp: October 27, 2021, 07:30:20 pm
content: Hello all!I'm having a smallish issue with the buck converters on my board, they're drawing a lot more operating/quiescent current than the specs sheet say they should be.I'm using twohttps://www.ti.com/lit/ds/symlink/tps562207s.pdfBuck converters to get 3.3V and 5V off two lithium cells. Since this is a prototype, the only stuff soldered on the board so far is the power converters (there are two more connected to the 3.3V) and the battery management. Unfortunate copy paste error, the R52 on the +5 rail should be 52.3k instead of 31k, at the moment they both make 3.3V. So if I say "5V" in this post, it's only outputting 3.3VIssue I'm running into is that with only a few chips and no actual loads, the board is consuming much more current than expected. With both chips enabled I draw about 24mA with some load on the 3.3V rail from an inefficient boost converter.The "5V" rail has no load and the 3.3V chip disabled, the board draws 11mA at 6.6V.If I attach a 33R resistor as a dummy load to the "5V" rail, it draws 64mA at 6.6V.If I remove the EN resistors on both chips, the board draws ~0mA, so it's not caused by anything else on the board.Also, if I increase the voltage to 8.4V with only the 5V and no load, the current goes up to 14mA, and with the load, the current goes to 54mA.So if I interpret this right, the chips should use less than 1mA each, even in the worst case, but they're draining 11mA+, and that amount increases with input voltage?Am I missing something with Buck converters, or have I done something horribly wrong? For a prototype, this isn't too concerning, but that eats up a lot of my power budget from the batteries
High output, small package waterproof sounders? - Page 1
Forum section: electronics / projects

author: mc172
author_rank: Frequent Contributor
timestamp: April 16, 2017, 10:49:41 pm
content: I'm looking to alarm a piece of remote equipment I'm building and I'm struggling to find a suitable sounder to serve as the alarm. Does anyone know of a relatively high output yet reasonably small for the purpose (given that I want to make a racket) sounders/drivers/whatever? Something like a waterproof smoke alarm sounder would do the job, but I can't find one. They are also a bit susceptible to being silenced by poking.My enclosure is a die-case aluminium housing which is about 8 inches square by 4 inches deep. It's passes my IP67, standard issue UK wheely-bin full of water test as-is (it has an O-ring type gasket around the sealing face) and I'd like the sounder to be at least IP54 if possible.I've got some old 1" compression drivers knocking about but I don't need the bandwidth and they're a bit on the large side, not to mention not being very waterproof.I'm not really bothered as to whether I have to give it an amplified signal or just power - anything would be a start.

author: Zero999
author_rank: Super Contributor
timestamp: April 16, 2017, 10:59:27 pm
content: What voltage does it run off?Do you need to vary the tone or is fixed fine?https://www.acornfiresecurity.com/ziton-as374-hazardous-area-sounder?gclid=CJvpna-KqtMCFUO3GwodD-ICHghttp://www.eibmarkt.com/gb/products/ABB-Stotz-S-J-Buzzer-90dB-CB1-630B.html?utm_source=Portalexport&utm_medium=CPC&utm_term=Produktaktion&utm_campaign=GoogleShopping_GB&userLocale=GB&gclid=CPHd-pKKqtMCFdTnGwodQ78GMAhttp://www.alliedelec.com/eaton-cutler-hammer-m22-amc-xamp/70239056/

author: mc172
author_rank: Frequent Contributor
timestamp: April 20, 2017, 11:31:15 am
content: It will run off 12 V.I don't need to vary the tone if I can command it on and off easily (thus generating a similar effect to changing the tone). I can't see why this would be a problem, just saying.The Eaton and ABB ones look promising, thanks for that.

author: max_torque
author_rank: Super Contributor
timestamp: April 20, 2017, 06:44:08 pm
content: How much of a racket? A hurt you ears >100db kinda racket or less?I've used pcb mount piezo sounders, firing out through Gore vents in a small ally enclosure for an operator alarm and it's reasonably loud?

author: mc172
author_rank: Frequent Contributor
timestamp: April 21, 2017, 11:53:19 am
content: I'd consider 90-93 dB at 1 m to be sufficient racket, but the high 80s would probably do the job. I don't want to do any damage.Not a bad idea. I've never heard of Gore vents (although I've heard of and used Gore) and will check them out. Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2017, 06:20:49 pm
content: Quote from: mc172 on April 20, 2017, 11:31:15 amWhat's your budget?I've just noticed that one of the links I posted previously was for ATEX approved (explosive atmosphere) and very expensive, as a result. If you want cheap a piezo disc tightly clamped and glued with silicone to the inside of an enclosure with a few small sound holes would do.
High pass filter in an op-amp - Page 1
Forum section: electronics / projects

author: microbug
author_rank: Frequent Contributor
timestamp: February 06, 2016, 11:20:58 pm
content: I know the title is vague but I couldn't think of how better to phrase it. I'm designing a small headphone amplifier for myself, using the op-amp circuit onthispage. I understand it except for how the value of C2 is calculated, and the importance of the value (what is the disadvantage to increasing it, which would better suppress power supply ripple?). As suggested on that page, I'm using R1=100k, R2=100k, R3=1M. Could someone explain?

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 11:30:30 pm
content: HiC2 is a bypass capacitor. It is a "bigger is better" sort of thing up to a point. If you make it big enough (relative to R1 parallel R2) the time constant could get nasty compared to your expected turn on time ( = why does it sound like crap for the first 20 seconds?). It is desirable to keep the R3 and C2 corner below 20 Hz. In any practical circuit that is not going to be a problem you run into.One other hint:It is common to try to pick one cap to be the one that sets the high pass for the amp and to keep the others "out of the way". That's not the only way to do it. In some cases it was done that way to make the math easy. In the days of LTSpice, there's no need for mathBob

author: microbug
author_rank: Frequent Contributor
timestamp: February 06, 2016, 11:33:12 pm
content: OK, thanks
High-performance (S/C/X/K band) FMCW/FSK/CW radar on sale - Page 1
Forum section: electronics / projects

author: lynnandsky
author_rank: Newbie
timestamp: March 02, 2016, 01:13:54 am
content: Hi there,Ancortek radar evaluation kit supports FMCW (Sawtooth, Triangle), FSK, and CW operation modes. If you are interested in FMCW SAR/ISAR imaging, FMCW radar for through-the-wall imaging and target detection/tracking, micro-Doppler analysis, or heartbeat/respiration sensing, this would be the perfect kit for you! We have fully tested our radars for these interesting applications.This sale event will end on March 31st, 2016.The main benefits of Ancortek radar are:1) Raw data could be streamed into Matlab for signal processing. You will have access to I and Q data, and implement your own signal processing algorithms. Matlab GUI could be provided.2) The processor module is compatible with all the RF modules. If you need S, C, X, and K band radars, you just need to buy one processor module and different RF modules.3) All the radars have a typical output power of 20dBm, which will meet your power requirements in most cases, without radiation concerns. Power amplifier could be added if larger detection range is desired.4) Light-weight, low power, and portable. It’s convenient for field trials. Raw data could be saved into either .mat file or .dat file for post-processing.5) You will have access to example Matlab processing codes for FMCW ISAR imaging, Range-Doppler map, and micro-Doppler analysis, etc.To learn more, please visitwww.ancortek.comproducts page. You could also find some application videos on youtube.Please don’t hesitate to contact me if you have any question. I could be reached at baokun.liu@ancortek.com. I will be very happy to help you.Best,Baokun LiuSenior Electrical EngineerAncortek Inc.
High performance DIY hotplate/stirrer [project log] - Page 1
Forum section: electronics / projects

author: Alex
author_rank: Regular Contributor
timestamp: October 30, 2013, 10:09:31 pm
content: Recently I was given a number ofcartridge heatersand was thinking of a project to put, at least a few of them, in good use. The etch tank idea on that thread would be better off with a low power, low power density immersible heater.What I have decided to use them for is as the heating elements of a hotplate/stirrer combo.Despite the classic chemistry lab applications, I know many use such hotplates to reflow SMT components. So I will keep a high level, mostly pictorial log of key stages in this project to chat over.Firstly to lay down a few requirements. I expect these to get 'massaged' during development.Must have:Heating area: 300x300 mmMax temperature unloaded: 450-500 degCMax temperature non-uniformity: 10 degCTemperature control method: PIDStirring speed: 100-2500 RPM (TBC)Stirring capacity: >= 10L waterSingle power outlet: 3kW (13A 240VAC)Would like to have:Coated surface for chemical splash resistanceHot surface indicator - Active when the surface is too hot to touchSecondary immersible process temperature sensorDesign drivers:Low profileSplit construction - plate and controller are separateRobustnessElectrical safetyFlexible on:WeightCostTimeHeat up/cool down durationAlready available components11x Watlow tubular cartridge heaters: 750W 240VAC each. Ceramic bead termination insulation and fibregalss wiring insulation1x K type thermocouple panel connector1x 10A and 1x 25A Celduc SSRsThe bar is quite high - there is a lot of work to be done and stuff to be purchased! So stay tuned for the next update where I plan to look at what is available and other peoples' hotplate design.Alex.
High Pitched whine under load - Page 1
Forum section: electronics / projects

author: ajp8868
author_rank: Regular Contributor
timestamp: February 18, 2023, 06:47:12 pm
content: A dual output PSU is making a high pitched whine on the 5v side (rated to 18a) but only when under load.I've used a sound meter to determine its 12403hzIs there any components specifically I need to check for this? The 12v side is fineThe PSU is a half bridge smpsThanks!

author: wasedadoc
author_rank: Super Contributor
timestamp: February 18, 2023, 06:51:11 pm
content: Drink enough of thewineit is producing and you won't worry about it.

author: ajp8868
author_rank: Regular Contributor
timestamp: February 18, 2023, 07:21:32 pm
content: Quote from: wasedadoc on February 18, 2023, 06:51:11 pmIf only 🤣

author: cantata.tech
author_rank: Regular Contributor
timestamp: February 18, 2023, 09:34:40 pm
content: Quote from: ajp8868 on February 18, 2023, 06:47:12 pmTransformer cores, most likely.But here is a hint, use a long (non-conductive_) tube (pvc?) say 50cm long x 10mm thick.Put it up to your ear and point the pipe at individual parts until you can isolate where the sound is coming from.

author: amyk
author_rank: Super Contributor
timestamp: February 18, 2023, 10:25:40 pm
content: The output inductors can also do that. Usually a blob of elastic glue will dampen them.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 18, 2023, 10:31:27 pm
content: If it's similar to your average ATX PSU (or actually one), it's 12V too, you maybe just aren't loading it enough to tell (why mention only 5V load and nothing else?).Which might be relevant, maybe both need to be loaded for compensation to behave.Maybe the capacitors are going and the compensation is off.(Singing may also happen by design at light load, but that seems out of scope here.)Tim

author: wasedadoc
author_rank: Super Contributor
timestamp: February 18, 2023, 10:38:13 pm
content: We've had wine and singing (song) in this thread. Who is going to complete the threesome?

author: cantata.tech
author_rank: Regular Contributor
timestamp: February 19, 2023, 02:53:11 am
content: Shouldn't this be on the "Repair" board ?

author: jonpaul
author_rank: Super Contributor
timestamp: February 19, 2023, 04:00:22 am
content: see other threads re SMPS noise, whines,this is sub cycle instability of certain types of control CCM, DCM, etc.For a 50 kHz controller, 12.5 kHz is 4th sub harmonic.Poor design of control loop, or noise in switch current sense.Typically will change freq with line or load or disappear.Many cheap Chinese PSU have this.the sub cycle instability causes the transformers or inductors to create sounds due to magnetostriction.No amount of potting, adhesive, mudffling will reduce the noise to inaudible, due to the high frequency.Even film capacitors can become transducers.Bon SoiréeJon
High Power Buck Converter Controller Selection - Page 1
Forum section: electronics / projects

author: ShaunAndFRED
author_rank: Contributor
timestamp: May 03, 2013, 07:25:43 pm
content: Hey EEVers!I'm working on designing a 2kW SMPS with an input from a PFC stage of 385VDC, output around 300VDC, and after reading a great book, Maniktala'sSwitching Power Supply Design & Optimization, I've got my component selection where I want it, but I'm running into issues selecting a controller.I was hoping to find an off the shelf poly-phase synchronous controller, but I'm not sure what I'm exactly looking for in the digikey parametric search... to the point where I'm seriously considering using an AVR XMega approach instead (Which I'm not opposed to! I think it would be very interesting to implement, and it's a garage project so there is no deadline to worry about). Most of the OTS synchronous poly-phase ICs are geared towards low voltage applications, but I was under the impression 385V was a standard PFC output voltage...I'm nervous using something geared for much lower power and just tweaking the feedback. Any Greybeards out there that have done this type of buck before? Did you go with an OTS chip? A micro solution? I've even read some papers of people using FPGA solutions! I though asking the community would be better than a coin flip.Thanks!Shaun and Robot.

author: ShaunAndFRED
author_rank: Contributor
timestamp: May 03, 2013, 08:33:28 pm
content: I know! Magnetics in higher power levels start to get quite pricey. I ended up getting some on sample for the PFC stage which saved me quite a bit. Did you mean the UCC3804? It looks interesting. I'm using off-chip drivers for SiCMOSFETS, so should be able to implement the synchronous drivers after. Right now the design is not isolated, but still entirely on paper.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 04, 2013, 04:21:19 am
content: Does the 300V output have to be isolated from the mains? If not, an easier solution would be to redesign the PFC using a buck-boost topology. Or if the input is 240V with a neutral (not 208V), center tap full wave rectify it and then run it through a boost PFC.300V is close to some typical EV battery voltages, so an EV charger design might be a good starting point.

author: Ghydda
author_rank: Regular Contributor
timestamp: May 06, 2013, 01:40:26 pm
content: You will not find wast numbers of high voltage polyphase synchronous controllers on this planet. AFAIK there are none.Most machinery in need for polyphase power controllers are usually large-ish and expensive-ish pieces of equipment and as such they usually have a fairly powerful microcontroller with an PWM hardware controller embedded. Just add glue-components to make your device go.For that reason there are quite a few high voltage synchronous polyphase drivers available. Like the IR2130.
High-Power Current Limiter for battery charging - Page 1
Forum section: electronics / projects

author: MooshooMatt
author_rank: Newbie
timestamp: June 05, 2020, 07:32:14 pm
content: Hello EEVblog forum! First post here. My name is Matt and I am a rising senior in university studying EE. I am working on a project and was hoping for some guidance from more knowledgeable people before I commit to this idea that I have.So I have a Li-Ion battery pack with a nominal voltage around 30 V and an off-the-shelf power supply. The battery has a maximum charge current of 10 A. I have chosen a power supply that can deliver 10.8 A before going into overcurrent protection (hiccup mode). (Before you ask, I have already worked out the details of the charging assuming proper current. There are provisions for preventing overcharging, etc)I want to design a circuit around this power supply that limits the current output of the supply when the load tries to draw more than 10 A, but otherwise leaves the operation affected.Minimal voltage drop is acceptable (let's say around 0.2V max when operating under 10 A).My first idea was to use a current sense amplifier and a feedback loop to accomplish this, kinda like this:In an ideal world this would work as is but as soon as I start replacing ideal parts with models, it becomes wildly unstable. The system oscillates between an overcurrent condition and turning completely off. Either this solution is impractical or my implementation is simply not stable as is. I am not familiar with how to stabilize feedback loops like this.How do you guys think I should proceed? Any guidance would be greatly appreciated!Best,Matt

author: temperance
author_rank: Super Contributor
timestamp: June 05, 2020, 07:59:41 pm
content: Hi,-you cannot simulate a battery charger with a resistor as a load. The load should be a voltage source with a resistor in series equal to the battery internal resistance.-The voltage dependent voltage source has infinite bandwidth while the real amplifier will have a limited bandwidth. Because of this, the phase around the loop might exceed 180° while the loop gain is still greater than 1.-Did you consider the power loss in the linear current source? A switching step down regulator might be a better option.

author: MooshooMatt
author_rank: Newbie
timestamp: June 05, 2020, 08:24:09 pm
content: Hi, thanks for the reply.1) Ok that makes sense, although I don't think it would make much difference in the simulation performance... (Edit: just checked, it does not make a difference)2) Yes I understand that. The voltage-dependent voltage source is just there to show what my idea is. That would be replaced by a high-side current sense amplifier in the long run. The frequency response of that amplifier simply introduces more stability problems which is exactly what I am hoping to fix...3) Yes, I have considered the power dissipation in the PFET. During normal operation power dissipation should be minimal. Worst case power dissipation would be in the tens of watts, which is manageable. I fail to see how a switching converter would help me here. I am trying to limit current, with as little voltage drop as possible.Matt
High power DC - DC converter - Page 1
Forum section: electronics / projects

author: ykurban
author_rank: Contributor
timestamp: September 23, 2016, 09:22:22 am
content: Is there any DC DC converter commercially avaible with this specsinput voltage : 12vdcoutput voltage : minimum 250vdc -or up to 500 vdcoutout power : >= 250 w

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 23, 2016, 09:59:54 am
content: Are you looking for a self-contained device (ie - in a box with input/output terminals, safety agency approval, EMC certification, etc.), or are you looking to hack something together? If the latter then look inside almost any automotive 12V to 220VAC inverter; at the 250W power level there is usually a two-switch forward stage that boosts and isolates the nominal 12V input to around 310V to 350V before an H-bridge chops it into 220VAC to 240VAC RMS.

author: ykurban
author_rank: Contributor
timestamp: September 23, 2016, 02:47:48 pm
content: i tried 12vdc to 220vac car invertes but, im more looking something lie self-contained device.

author: tszaboo
author_rank: Super Contributor
timestamp: September 23, 2016, 03:46:01 pm
content: I was researching something similar to a one off project. I ended up a with this setup :Bunch of step up isolated converter, connected in series. Not nice, very expensive, but works. Put a reverse diode on each output, some few Kohm resistor to dump the power when off, and capacitors separetaly. You dont need the capacitor if it is a complete power supply, but I would still put there the diode.
High power flashlights - Page 1
Forum section: electronics / projects

author: Jon86
author_rank: Frequent Contributor
timestamp: May 31, 2013, 09:32:12 am
content: So I've been looking for a keychain flashlight, like the one Dave uses, and I came across this:http://www.ebay.co.uk/itm/New-1000lumen-TrustFire-Mini-CREE-XML-T6-LED-Flashlight-Torch-Keychain-Battery-/271012893275?pt=UK_SportsLeisure_Camping_LightsLanternsTorches&hash=item3f19a0925bIs it really possible to have a 1000 lumen torch that's this small? Is this just another cheap Chinese scam?

author: Rufus
author_rank: Super Contributor
timestamp: May 31, 2013, 09:55:06 am
content: Look at the specification of the LED and the specification of the battery and you decide.

author: Jon86
author_rank: Frequent Contributor
timestamp: May 31, 2013, 10:09:15 am
content: Quote from: Rufus on May 31, 2013, 09:55:06 amWell if the battery can supply 3A then it seems feasible, but I guess it can't.But how many lumens REALLY is it then?

author: nukie
author_rank: Frequent Contributor
timestamp: May 31, 2013, 10:39:40 am
content: Assuming it is a real T6 flux, and you manage to feed 3A, 975lm from the LED, minus 20% light for regular mineral glass lens, minus 10% for reflector efficiency. Wait a few minutes you will see lumens drop as it heats up. Wait 10 minutes it will be burning your hands. A couple more minutes the Lithium PTC will kick in and you will be left in a total darkness.An XML gen2 U3 flux is closer to the 1000 lumens pipe dream from a 3.9 WHr lithium cell. Even if you got 1000 lumens from your keychain the heat and energy capacity will be the limitation to its usefulness.

author: SeanB
author_rank: Super Contributor
timestamp: May 31, 2013, 02:44:40 pm
content: More like 100 lumens initial, around 50 after an hour of operation.
High power IR LED driver - Battery powered - Page 1
Forum section: electronics / projects

author: Magnets
author_rank: Contributor
timestamp: August 14, 2016, 03:42:26 pm
content: I want to drive a 3w IR LED using AAs, I need a minimum of 3xAAs to power a micro.The LED is rated 1.4-1.6v 700mA but I don't mind if I only run it at 350-500mAI've tried using 3xAA (~4v) + a linear AMC7135 (PDF:http://led22.ru/ledcat/ledsource/amc7135.pdf) but obviously the power wasted through the driver is more than the LED uses.Using 4xAA (5.5v) + a small buck (mp1584) + AMC7135 is better but the AMC7135 needs 2.2v to work - it's rated at 2.7v (Vs) so it's still not very efficient. I get around 60%Are there any small linear drivers that will run from 1.5-2v supply? The only ones I could find are the BCR321U and BCR320U but I'm not entirely sure what their minimum supply voltage is, the infineon site says 1.4v min, but the datasheet doesn't mention it. Or maybe some off-the-shelf switch mode drivers?I think the best bet is to just get 2x3W leds in series and use 1xAMC7135 but I would rather just use 1 LED.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 14, 2016, 04:20:54 pm
content: When near empty 3 Alkaline cells is something like 3.3 V. This is well enough for 2 IR diodes in series with a linear driver. When not using the maximum current, the voltage should be more like 1.1-1.4 V. For linear current control one could also use an standard current sink circuit with OP and low level MOSFET.For just 1 LED one could used a switched mode current sink, not voltage regulator and linear current regulator. Many switched mode regulator chips can also work in constant current mode, preferrably those with a low voltage at the FB pin.

author: bktemp
author_rank: Super Contributor
timestamp: August 14, 2016, 04:32:40 pm
content: TS19377 should work fine at 3-4.5V and the LED brightness can also be controlled by PWM.http://www.taiwansemi.com/products/datasheet/TS19377_A11.pdfIf you look for other LED drivers, some boost converts can also drive LEDs with a low forward voltage by connecting the LED cathode to the input voltage instead to GND. There are probably more boost converts capable of running at 3V than buck converters.

author: Magnets
author_rank: Contributor
timestamp: August 14, 2016, 09:17:42 pm
content: The TS19377 looks good, I see there are clones (AX2002) which come in full modules
High power light source (waveguide + high power leds) feasibility? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 22, 2015, 10:36:57 pm
content: So the most powerful LED you can get on the market today would be some sort of cree LED (like the type that comes in flashlight, single diode). I'm not sure how big they make them.To make a focused directional source, is it possible to make wave guide which would accept light from a bunch of these LEDs and combine them to a single point? How easy would it be to make the optics (uv cureable resin + molds come to mind)? Or must it be glass ? Like accept the power of X amount of ultra bright LED's and then use a single reflector, to achieve an impossible light density at a small area.3d printing a mold that is filled with some highly transparant plastic resin would be rad. Or perhaps even using water??You could use a whole bunch of switchmode modules and many batteries, making it highly reliable.
High power manually-reset thermal cutout solution - Page 1
Forum section: electronics / projects

author: ab6014
author_rank: Newbie
timestamp: September 06, 2021, 11:05:42 am
content: HiI am trying to create a thermal cutout circuit to protect a large (10sqm) silicone heat pad table. The total heat pad load is around 30A (split between seven 1kW heat pads), running off a single phase 32A supply. The heaters are controlled with Eurotherms and SSRs, which fail in the closed position. Because of this I want to add thermal switches, but in a manually-resetting circuit. Due to the size of the table, the switches will be very hard to reach (wedged underneath a 500kg steel plate), hence why I dont want to just use thermal fuses.The max table temp is 90deg, so I was planning to use 110deg switches to switch off the power to the control box via a power relay, the power relay is initially switched on by use of a momentary switch. Once the relay is closed, the coil is powered by the mains supply, until a thermal switch breaks this circuit and powers off the relay. The control box will then not power back on until the thermal switches have closed again, and the momentary switch is manually pressed. See diagram below.However, I cannot find a power relay to these specs. The link below is the closest I could find, but contact rating is only 30A.https://uk.farnell.com/panasonic/he1an-ac240v/power-relay-spst-no-240vac-30a/dp/2503681I am slightly worried that the right components don't exist because my design is wrong in some way. So if anyone can help with the correct components or a new design that would be amazing.Thanks

author: Wolfram
author_rank: Frequent Contributor
timestamp: September 06, 2021, 11:48:32 am
content: Relays beyond some 20 - 30 ampere contact rating are often called "Contactors" and sorted in a different category, particularly if they have an AC-powered coil. The design itself looks very sensible to me.Edit: here's an example,https://uk.farnell.com/imo-precision-controls/mb09-s-10230/contactor-9a-230vac/dp/9939857?st=contactor, this is a four-pole one with a 20 A per-contact rating for resistive loads (AC-1), you could use all contacts in parallel for up to 80 A, or two and two in parallel to break both L and N up to 40 A. Smaller contactors are likely suitable, note that these usually have different current ratings depending on what type of load is used.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 06, 2021, 08:15:11 pm
content: As shown, the momentary on switch would have to power the heaters too. So one should use a seprate contact only for the contactor self holding function.
High Power Motor Controller (First Complex Design) - Page 1
Forum section: electronics / projects

author: henry85
author_rank: Newbie
timestamp: May 09, 2017, 01:57:58 pm
content: Hello,I'm writing as I'm designing this new dual channel controller for a robotic project. The thing is that it's my first ever project with such complexity. And I'm afraid there might be some flaw that me as beginner I wouldn't spot. Could you guys give me maybe some kind of advice on that?Please find attached the schematic. The whole idea of the design is to be able to handle the 70 A of stall current of my two motors that I'm using with my robot. Oh and the idea is that the user will only have to give a PWM signal and a HIGH or LOW signal (for direction) from an Arduino or similar for driving the motors.Also I've done some simulations and I see some small spikes of current of around 8 A. I'm wondering if I'm write to ignore them as they last only about 8-15 ns and the whole period of the PWM is about 50 us.Thank you!PS: You can check the board design here:https://1drv.ms/b/s!AljDQF12JgJdj_Ner8KKdz1oFIYWFg(3D PDF)

author: DBecker
author_rank: Frequent Contributor
timestamp: May 10, 2017, 05:47:44 pm
content: The board design link is useless. The document isn't empty, but it shows up as a tiny blank page.You might consider using a processor suited to the task. An AVR has a slow ADC. You won't be able to monitor current and respond quickly enough. An STM32 has a much faster ADC, with fewer limitations. It can be set up for continuous conversion and checking limits in hardware. Plus the timer units have hardware deadtime support.

author: Zero999
author_rank: Super Contributor
timestamp: May 10, 2017, 06:17:49 pm
content: Quote from: DBecker on May 10, 2017, 05:47:44 pmI couldn't view it either. It's probably because it's a 3d PDF which isn't supported by most 3rd party PDF viewers and requires Adobe PDF reader to work.I can see the schematic attached to the post though. What's the point of the logic gates? Can't their functionality be incorporated into the MCU software?
High power opamp current sinking  (OPA549) - Page 1
Forum section: electronics / projects

author: Spikee
author_rank: Frequent Contributor
timestamp: September 30, 2014, 05:29:37 pm
content: Hello,I was looking (again) to build a dc supply using the BB (TI) OPA549 chip. In an old topic of mine someone said that i could also sink current.So for example we want to use it as a dc load now , how would that be done ?Connect DUT to the OPA549 -> turn input voltage of opa549 to 0v ? and just set a current limit ? or how do such things work?Circuit:Datasheet:http://www.ti.com/lit/ds/symlink/opa549.pdf

author: Kevin.D
author_rank: Frequent Contributor
timestamp: September 30, 2014, 08:07:06 pm
content: Just seen the cost of those things.Youl cost yourself a fortune using those ,It's power dissipation capability is not that good if you look at thermal details .Stick to discreet transistors . If you want both source and sink capability then make a discreet mosfet push pull output stage ,study output stage of opamps for an idea.

author: Spikee
author_rank: Frequent Contributor
timestamp: September 30, 2014, 10:51:59 pm
content: 5/10 usd for 75W of current sinking is not that bad. If you do the current limiting using an external opamp and mosfet 100W should be possible.

author: Spikee
author_rank: Frequent Contributor
timestamp: October 01, 2014, 09:29:45 am
content: There is a lot of old stuck in russia/china. See ebay aliexpress. Thank you for suggesting mosfet push pull (never heard of it) it seems it can get pretty linear output with some tricks. The hard part is to get good output at low voltages.

author: ondreji
author_rank: Contributor
timestamp: October 01, 2014, 10:57:49 am
content: I was looking at it (OPA549) but I didn't like it for some reason... Maybe current limiting or something like that. Then I found nice LT1970 based 4 quadrant PSU application note:ftp://ztchs.p.lodz.pl/PRP/PRP_2006_2007/10804di.pdfI would like to build it soon - about to order the parts

author: Spikee
author_rank: Frequent Contributor
timestamp: October 01, 2014, 12:21:12 pm
content: Nice find, thanks for sharing!
High power server supply pinout - Page 1
Forum section: electronics / projects

author: VoidsWarranties
author_rank: Contributor
timestamp: October 08, 2016, 02:30:52 am
content: I have 2 hp 511778 power supplies rated at 12v 60A (750w). My goal is parallel them and before I start getting responses that this is overly complex and hard to do I have reasons why I think it will work. There are 2 of them in each server and they can run together (not just one running and the other on standby for redundancy). And for two I have read that some supplies have built in current sharing pins. If I could parallel them could I use 3 or more supplies to get ultra high currents(you can get used ones for 13$)? The only thing I know about the pinout is how to turn it on and the main output. If anyone has any experience with these please let me know. Other hp supplies also have voltage adjustment although most likely not over a large range that could be used for a bench power supply.Sent from my iPhone using Tapatalk

author: jitter
author_rank: Frequent Contributor
timestamp: October 08, 2016, 06:55:05 am
content: Might this PSU be very similar to HP's DPS-600PB?If so, fromthis threadthe current sharing pins in linked in image below.Please note that in that thread a series/parallel arrangement is used to get 24 V.
High-Power Split Rail DC-DC Options - Page 1
Forum section: electronics / projects

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 11, 2021, 07:23:29 pm
content: I have power source defined as 36-48V. I need to produce +-60V rails from this source, each rail capable of providing ~2A current.My initial thoughts are a standard boost controller (external FET power stage) for the positive rail (LM5122 perhaps), and a buck-boost controller (external FET power stage) for the negative rail (LTC3863 perhaps).F_sw must be >500kHz and disabling of light-load pulse skipping mode is required (so FPWM for LM5122, and Forced Continuous mode for LTC3863).Any clever suggestions beyond this proposed topology, or am I already on the right track?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 11, 2021, 07:42:13 pm
content: Minimal control method is, use a coupled inductor to do combined SEPIC and Cuk in one fell swoop. Gives good matching and cross-regulation (doesn't depend on load currents so much; the regulated output still needs enough minimum load to keep the other side going).Downside is, there aren't many coupled inductors available above 1515 sized SMT shielded-bobbin style parts; you'd probably need more than a few of those to get to 240W without melting anything. And the bigger ones that are available, tend to be more lossy, or poorly coupled (e.g. two windings on opposite sides of a toroid). So it may need a custom design. I think some 3637 PQ style parts are available though, which could do it.Mind, good luck finding 3+ winding inductors -- but you can always use a pair of duals and wire the primaries in parallel. Use double the design inductance, since they reduce in parallel (two uncoupled inductors in parallel).Otherwise, yeah, boost and invert is about as good as anything. Or multiple flybacks, which is basically the SEPIC-Cuk thing but worse (but it can be isolated, if need be). Or forwards.Tim

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 11, 2021, 07:59:53 pm
content: That reminded me of another constraint - avoiding custom magnetics. This isn't a high-volume thing, and definitely would prefer to avoid that route. Boost + buck-boost it is!
High Power Switching Circuit - Page 1
Forum section: electronics / projects

author: cpfeiffer55
author_rank: Newbie
timestamp: April 22, 2024, 08:22:47 pm
content: Hi All,I recently asked about a good IC for sensitivity switching circuit. I found that the 4093 would do the trick. It worked in my initial design but now I am driving a solenoid pulling about an amp at 12 volts and it kept letting the smoke out of the 4903 ( I am using a 2n3904 on the 4903 output to switch 12 volts off and on). I am thinking of swapping out the 2n3904 and using a NCP81074A Gate driver with a IRF540 Mosfet on the high side. I would appreciate any input from those more knowledgeable than I about this.Thanks,Chuck

author: max_torque
author_rank: Super Contributor
timestamp: April 22, 2024, 08:29:39 pm
content: Solenoids are inductive. How are you handling the stored magnetic energy when that load is switched off? If you haven't got a suitable over / under voltage clamp or a flyback current path, then the overvoltage generated is going to kill most things.These days for low voltage DC stuff (12 and 24vnominal) i pretty much never roll my own drivers as there is so much off-the-shelf ICs specifically targetted at automotive use, and they come with lots of useful features like overvoltage, overcurrent protection, current sensing feeback, logic level drive, over temperature limitation and fold back etc.Normally i'd use a smart high side driver from infineon:https://www.infineon.com/cms/en/product/power/smart-power-switches/They may at first glance look more costly than rolling something from a bare fet or transistor, but when you actually look at the protections and lack of necessary support services, i tend to find them very cost effective and more importantly, very robust

author: cpfeiffer55
author_rank: Newbie
timestamp: April 22, 2024, 09:13:54 pm
content: I was just thinking of bridging the coil with a diode. Not a good idea?

author: jbb
author_rank: Super Contributor
timestamp: April 22, 2024, 09:14:29 pm
content: I think the 2N3904 transistor is too small to handle a 1 amp load. How about changing it to a logic level MOSFET? Something with a 100 mOhm on resistance (or lower) should do the trick.Edit: logic level MOSFETs are designed to work with low gate voltages (eg 3V or 4.5V), and can be driven directly by logic chips. Just put a modest resistor (something around 50 - 100 Ohms I guess) between the logic chip output and the MOSFET gate.Also, max_torque is right about inductive kickback. When you turn the solenoid off it might well blow the switch up. This can be addressed with a simple diode, see:https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/inductor-commutating-circuits/
High Praise for the TI TPS6204X in a fault condition - Page 1
Forum section: electronics / projects

author: envisionelec
author_rank: Frequent Contributor
timestamp: April 11, 2019, 01:08:23 pm
content: A recent hand-built prototype turned up on my desk with "low voltage rails" tagged on it. It uses a 1.8V and 3.3V buck regulator formed by a pair of TPS6204X ICs. The rails were at 1.6V and 3.0V, respectively...odd, especially considering these are both fixed voltage devices. A quick FLIR image of the board showed some rapid heating of the two switcher ICs and local bypass tantalum capacitors. On further investigation, I found both SMD inductors were each turned 90 degrees on their pads, effectively sending the SW node straight into the bypass cap. What I found curious and quite impressive is that the devices held the rail voltage at a safe level in spite of this failure.What are some unexpected but "happy" failures you've experienced?

author: OwO
author_rank: Super Contributor
timestamp: April 11, 2019, 01:25:08 pm
content: I'm only surprised that the buck IC didn't blow up like other TI power management chips tend to doAll the cheap buck ICs with integrated MOSFET have cycle-by-cycle current limiting and would have been fine as well, these use analog circuitry which can respond fast to overcurrent and overtemperature while the TI chips tend to just be a MCU and power transistors slapped onto the same die.
High quality plain circular DIN plugs - Page 1
Forum section: electronics / projects

author: tooki
author_rank: Super Contributor
timestamp: December 16, 2024, 08:40:36 am
content: At work, I get a lot of heated magnetic stirrer plates in for repair, and one of the common failures is damaged cables to the thermostat units. Those are spiral cables with an overmolded 6-pin DIN plug. While we can get replacement cables from the manufacturer, they are spiral PVC, which gets damaged again because they come into inadvertent contact with the hot vessels. (And in one brand, the jacket just fails with age, with the PVC becoming brittle and just breaking off in chunks.)I can get unterminated replacement cables with PUR insulation (and I may switch to uncoiled silicone or teflon), but I haven’t had luck finding DIN connectors that tick all the boxes. I can’t use bayonet-coupled DIN connectors (like Amphenol C 091 B) because the bayonet interferes with the basic jacks on the units. Screw-coupled ones like C091 A and D can mate, but the coupling ring flops around in the breeze. The plain DIN connectors I have found are either the super cheap kind (like Hirschmann MAS) that are only held together by the plastic boot, or have some other deficiency (like the Deltron 610, which has a nice metal body with strain relief, but as far as I can tell, the actual contact insert isn’t retained by anything other than the solder joints onto the cable).I’d love something like the Neutrik/Rean DIN plugs, but they don’t make a 6 pin version.Good strain relief is a must because of the PUR insulation, as is a solid housing that holds the contact insert robustly. Something that doesn’t have a ton of gaps, nooks and crannies is desirable, since these get used in chemistry labs and so stuff gets dripped on them, so easy cleaning is a big plus.I’ll use screw-coupled plugs if I can’t find anything better, or maybe even modify them, but maybe someone knows of a plug model I haven’t come across?Thanks for any tips!