hybridfree/eevblog-posts huggingface dataset:
Power Supply for Jim Williams Pulse Generator - Page 1
Forum section: electronics / projects

author: Bryan
author_rank: Frequent Contributor
timestamp: July 28, 2015, 07:06:46 am
content: Hello:Would someone mind looking over the schematic for the power supply for the Jim Williams Pulse Generator. I am wondering what size of inductor is needed?. Was thinking of using a single 1.5v cell. Cheershttp://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/

author: Warhawk
author_rank: Frequent Contributor
timestamp: July 28, 2015, 07:17:54 am
content: Hi, on the picture below the schematic diagram there is TV1415-B inductor used.It should be 22uH 2.5 inductor.It is a strange coding explained here:http://electronics.stackexchange.com/questions/50582/help-reading-inductor-labelCheersJiri

author: Bryan
author_rank: Frequent Contributor
timestamp: July 28, 2015, 07:35:12 am
content: Thanks, I wonder if the inductor value is dependent on the input voltage. The author used a 4.5v supply where I wanted to use 1.5v. Maybe it doesn't matter?.

author: Warhawk
author_rank: Frequent Contributor
timestamp: July 28, 2015, 08:11:07 am
content: Quote from: Bryan on July 28, 2015, 07:35:12 amLet's have a look at it. It is a step-up converter with boosted output. In general, the energy calculation for one period is:(Energy-in) / (efficiency) = Energy-outEnergy-in is stored to the inductor only during tonphase.Ein=1/2*L*Ipeak^2and also Ipeak= Vin*ton/LCombining those two formulas gives meEin=Vin2*ton2/2*LLong story short, low input voltage must be compensated by longer tonor smaller inductor to keep output energy (power) constant. The IC chip by himself can work from 1.1V.If I were you I would start with the specified inductor.I Better wondering why author took feedback from the first stage and not from the output like Jim previously did.

author: Bryan
author_rank: Frequent Contributor
timestamp: July 29, 2015, 01:14:35 am
content: He explains in the blog as to the reasons why.Note that in Jim’s original HV circuit with LT1073, the feedback resistor was located at the HV output of the voltage multiplier, whereas in my circuit I left the feedback point at the primary output and leaving the multiplier voltage unregulated. The reason for this decision is that should R2 become unconnected the voltage input to the feedback pin will remain be within tolerance, avoiding any possible damage to the chip. Also, since the current requirement for the avalanche pulse generator is very low, regulating the HV output is not strictly necessary.

author: Warhawk
author_rank: Frequent Contributor
timestamp: July 29, 2015, 06:09:01 am
content: I should have read it firstThanks
Power supply for RD6006 - Page 1
Forum section: electronics / projects

author: bikeseat
author_rank: Newbie
timestamp: October 19, 2023, 06:22:27 am
content: I've ordered an RD6006 and am wondering if I can (or even should) use a USB Type C PD power supply with it?Adafruit has this device that I think would suffice:https://www.adafruit.com/product/5807(Adafruit USB Type C Power Delivery Dummy Breakout - I2C or Fixed - HUSB238)I don't need super high current for my projects, so if anyone has other suggestions, I'd definitely appreciate hearing them.Thanks for reading!

author: wrickert
author_rank: Contributor
timestamp: November 16, 2023, 04:33:01 pm
content: Sure, why not.

author: Jackster
author_rank: Frequent Contributor
timestamp: November 16, 2023, 10:40:59 pm
content: Just get the 65V 400W power supply that is designed for it?https://www.aliexpress.com/item/1005003036945650.htmlThey make for a nice little power supply.

author: Partizans
author_rank: Newbie
timestamp: November 20, 2023, 08:16:22 am
content: I'm curious, in the current model RD6006, for "curve display" are there Chinese characters on display right side (even in English language mode)?

author: jdev99
author_rank: Regular Contributor
timestamp: January 31, 2024, 01:48:41 pm
content: Quote from: PartizansTry updating the firmware.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 01, 2024, 09:34:08 pm
content: What are you using the RD for or on?One method is to park two motorcycle 12v batts in series under desk, send 24vdc to the RD.Then just attache a small "smart" batt-tainer to each batt, turn on the charging when you not using the RD.The dc-dc warts are gonna be noisy, but you can perhaps tack on a fat cap to the dc input of the RD, and add a few twists of the supply lines around some iron.
Power supply for servo motor - Page 1
Forum section: electronics / projects

author: cipicips
author_rank: Newbie
timestamp: May 26, 2021, 08:42:57 pm
content: Hello everyone,i have came across three servo motors (HDKJ D3015) specifications about them are listed below, and that is all I can find about them.My issue is powering them, all I have is 12V 5A power supply, what do you suggest I use to lower the voltage, linear regulator (LM7805, LM338, some DC-DC convereters.....)Operating Voltage:4.8-7.2VDead zone set:4usOperation Torque: (6V) 14Kg.cmOperation Torque: (7.2V) 15Kg.cmOperating Speed: (6V) 0.18sec/60°Operating Speed: (7.2V) 0.16sec/60°The rotation angle is 300 degreesNO-Load CURRENT:<500MARegards

author: thm_w
author_rank: Super Contributor
timestamp: May 26, 2021, 11:57:53 pm
content: You should have a few DC-DC buck modules in your parts kit for stuff like this.Do you not have an adjustable power supply at all?Can't seem to find what the max stall current of these is, but that would be good to know.

author: cipicips
author_rank: Newbie
timestamp: May 28, 2021, 10:36:16 am
content: Hello,thank you for your reply. I have done some measurment using Laboratory power supply and waveform generator. Since it is digital type of servo I've used 200Hz PWM frequency. Voltage applied was 6V and 5V.For my application there will be no load (it will only turn from one 0-300°) 5V will suit.Current in stady state was 0.1A. I was driving servo back and forth from 0-300° and current was varying from 0.33A-0.8A.Just to be sure i think it would be good to chose 1A per servo, in my case 5V 3A power supply.Since I have Meanwell LRS-150-12 (12V 5A) powering the board , i would like to use DC-DC so I can get 5V and 3A.Is it ok to power PIC microcontroler and servo from dc-dc buck converter ?Also, is there any recomendation what 5V buck should I use, or just buy something like Pololu step down converter D36V28F5 and solder it on board ?Regards

author: thm_w
author_rank: Super Contributor
timestamp: May 28, 2021, 09:46:28 pm
content: Quote from: cipicips on May 28, 2021, 10:36:16 amYes that is ok, assuming PIC is 5V version.QuoteThat is what I would do. I use generic cheap converters:https://www.aliexpress.com/item/1005001629723875.htmlhttps://www.aliexpress.com/item/32934802533.htmlBut D36V28F5 looks good, and being polulu I'm sure it meets the spec.
Power supply GND at different potential to scope gnd - Page 1
Forum section: electronics / projects

author: Sparky49
author_rank: Regular Contributor
timestamp: December 21, 2018, 12:53:42 am
content: HiI've recently purchased a Rhom BM92A12MWV-EVK-001 Power delivery dev board for examination. I also bought an Inatech 45W USB power supply which has PD3 capabilities. The Inatech has a plastic earth pin (in the UK) and is double insulated. When I connect the Rhom board to the Inatech, I measure open between the live and the output +V and gnd, and also with the neutral to +V and gnd.However, when I attempt to examine the output with my scope, I notice that a tiny spark appears when I connect the gnd lead of the scope probe to gnd on the dev board. This seems quite bad, what am I missing here?I've done some tests and the scope seems to have survived, but I'd rather double check what is causing this before continuing.

author: Ian.M
author_rank: Super Contributor
timestamp: December 21, 2018, 01:03:49 am
content: That's pretty much usual for non-grounded SMPSUs. Seehttps://www.eevblog.com/forum/chat/does-this-sound-acceptable-for-an-apple-product/for an explanation

author: Sparky49
author_rank: Regular Contributor
timestamp: December 21, 2018, 08:52:20 pm
content: Thanks Ian, I have to confess I'm still a little unsure about whether I should be able to probe.On one hand the scope gnd is connected to earth which is isolated from the potential on the circuit gnd, but on the other hand there is enough potential difference to create spark between the two. :/

author: Ian.M
author_rank: Super Contributor
timestamp: December 21, 2018, 10:11:02 pm
content: First check the leakage current to ground of the USB PSU is within the permitted limits for a double-insulated item of IT equipment (IIRC that's 0.75mA max.) - I described this test in the other topic.Then hook it up to the board under test and ground the circuit's 0V rail to the same mains ground as the scope using a separate wire securely connected at both ends *before* you plug in the mains supply to the USB PSU. Do *NOT* disconnect the extra ground wire while bench testing if the PSU still has mains connected.That will safely ground out the leakage current and eliminate the risk to the circuit and scope.

author: soldar
author_rank: Super Contributor
timestamp: December 22, 2018, 01:04:07 am
content: Floating PSU's can be a PITA sometimes with this kind of problem. I have modified many so as to ground the negative and that avoids this kind of problem. I have seen many PSU's and other appliances which have a small capacitive leak and I just add a ground to remove the problem. I have grounded many devices that came with no ground.These parasitic leaks can cause other problems. If the residence has GFCI's fitted in the individual outlets this is usually not a problem as it will not trip them but if the residence has a single differential breaker for the entire residence it can happen that a lot of capacitive leaks add up and the breaker trips very easily and it is a nuisance.
Power supply ground - Page 1
Forum section: electronics / projects

author: t_ryner
author_rank: Regular Contributor
timestamp: March 08, 2017, 05:48:05 pm
content: Hello! This is my first post here, and I just finished prototyping a audio amplifier on a breadboard. I plan on powering it with a power supply module I salvaged out of an old DVD player(I checked the power module's outputs with a meter). However on a previous audio amp, I had a problem with it not being grounded properly. I noticed that on most commercial power supplies, the ground planes are split internally, but are linked via a pair of optocouplers. Why is this? why not just bypass the optos and connect to a earth pin?( with a simular but smaller power module, it used a chasis ground to the metal case. when connected to power and earthed to the outlet, there was a sudden and violent release of magic smoke) Why is this?

author: Zom-B
author_rank: Regular Contributor
timestamp: March 08, 2017, 06:32:35 pm
content: Allow multiple power supplies to be put in series (create balanced +/- voltages)Inject voltage in the middle of a circuit that's already grounded

author: Codebird
author_rank: Regular Contributor
timestamp: March 08, 2017, 06:43:13 pm
content: As above, plus:- Ground loops and common-mode noise when two such devices are used together. Creates the annoying hum and puts out a ton of unwanted RF.
power supply grounding - Page 1
Forum section: electronics / projects

author: minibutmany
author_rank: Regular Contributor
timestamp: April 27, 2013, 05:01:14 pm
content: Hello,I have thought about building a bench power supply, as I have gone a long time without one. I wanted it to have both positive and negative 12V rails as well as a variable one, probably using an LM317. I wanted it to be as oscilloscope safe as possible, but i wasn't sure what needs to be done in terms of grounding. Is it possible to completely isolate the supply from ground while still having both positive and negative rails?Thanks

author: SebG
author_rank: Regular Contributor
timestamp: April 27, 2013, 07:02:57 pm
content: How will you be generating the negative voltage. If you are using a transformer with a center tap as the ground you will get a positive and negative voltage (after diode bridge). A transformer will isolate the AC Line (Hot and Neutral). As long as you don't connect the earth ground to your power supply ground you will have an isolated device. If you are using a switching supply to power your circuit, it might not be isolated from neutral or earth ground. You would need to isolate the voltage somehow (using an isolation transformer for example or use an isolated switching power supply)
power supply help please - Page 1
Forum section: electronics / projects

author: glinjik
author_rank: Regular Contributor
timestamp: December 07, 2019, 07:48:12 pm
content: hi guys im having a bit of bother with a power supply can anyone helpthis is what im building all seems good volt reg works current works my problem i used two 2n3o55 instead of tip3055 and e13005-1 instead of bd139 my problem is i get normal volts 17.7 on collector of 2n3055 but only 10v on emmiter any ideas? lm317t shows 17v input only 10.1 output

author: xavier60
author_rank: Super Contributor
timestamp: December 08, 2019, 12:34:31 am
content: A properly functioning LM317T should produce an output voltage With Respect To ground that cause the R1,R2 divider to apply 1.25V the Adjust pin WRT the Output pin. If the layout is very poor, oscillations can alter expected voltages.I can't see how the current setting section can ever work properly.

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2019, 01:35:31 am
content: Yes, that design is ludicrously bad. There is no compensation for the varying output transistor Vbe drop with load current, nor for the emitter resistor drop, using Ib as a proxy for Ie for the current limit is a dumb idea in the first place due to the large variation of hFEwith Ic, and the current limit circuit doesn't - its just an overloaded Vbe multiplier.Boosting its output with an emitter follower is just plain dumb - see Figure 23. High-Current Adjustable Regulator Circuit in the Texas Instruments LM317 datasheet for the right way to go about it.However, adding variable current limiting to a LM317 that works right down to 0V out isn't easy, so its probably best to throw it out and start from a regulator that's easier to apply limiting to, or has it built in or drop back to the classic two opamp CC/CV control loop solution.

author: David Hess
author_rank: Super Contributor
timestamp: December 08, 2019, 01:51:29 am
content: If it worked, that sort of current limiting is called beta current limiting. It relies on limiting the current into the base to control the maximum collector current. But since beta (hfe) is not well controlled and varies significantly with temperature, it is really only suitable for short circuit protection and often not even that.If you can do without the current limiting, consider starting with a circuit like that shown below.
Power supply kits  - Page 1
Forum section: electronics / projects

author: daniel123
author_rank: Regular Contributor
timestamp: April 26, 2016, 09:22:57 pm
content: Hi daniel here. Today I was wondering if anyone knows who makes kits to make a bench top power supply. Heathkit has been is buisness it still is but the sad thing is that they don't make the good stuff anymore it's all ha gear. The problem with ham gear is that the homeowner asscociations these days are so stupid. Their are like no kits for our side of the hobaby we like have to design our own pcb and the general population can't really do that but the general population well most of it can solder. That's the problem I just am looking for kits like in describing because I think it would be cheaper than buying one of the same type prebuilt.SincerelyDabiel vrolijk

author: daniel123
author_rank: Regular Contributor
timestamp: April 26, 2016, 09:29:42 pm
content: I still think these kits should still exist

author: AustinEngy
author_rank: Regular Contributor
timestamp: April 26, 2016, 10:35:34 pm
content: Could you give more specifics on your needs for a power supply? There are plenty of basic kits that would be good for tinkering and things, but I doubt you'll find a high quality DIY kit out there, at least, not from what I've seen. This is about the only one that even looks decent that I've been able to find:http://www.amazon.com/Elenco-Triple-Output-Power-Supply/dp/B0002DT0GU/ref=sr_1_1?ie=UTF8&qid=1461708950&sr=8-1&keywords=bench+power+supply+kitEverything else I've seen looks even cheaper. Honestly, you'd end up saving money and have a better supply buy just picking up a reasonably cheap chinese supply like this one:http://www.amazon.com/Tekpower-TP3005T-Variable-Linear-Supply/dp/B00ZBCLJSY/ref=sr_1_2?ie=UTF8&qid=1461709836&sr=8-2&keywords=power+supply+benchI've got one of these, it works really well aside from a lingering petroleum smell.If you really just want to put it together yourself, there are multitude of DIY projects out there.Good luck!
power supply low v dc&ac - Page 1
Forum section: electronics / projects

author: RDSK
author_rank: Newbie
timestamp: January 03, 2017, 01:07:06 pm
content: I want to replace a power supply to a gadget, The gadget requires these inputs:32 VDC 100mA7.5 VDC 150mA4.25 VAC 350mAPlease could you suggest best way to build such a supply both using... mains 240 VAC inputand/or... using 5VDC USB ideally with a pass thru battery

author: BrianHG
author_rank: Super Contributor
timestamp: January 03, 2017, 01:50:22 pm
content: Do you know if the 4.25vac needs to be isolated from the other supplies?Are you allowed a common ground for the 32v and 7.5v?What is you price budget?

author: RDSK
author_rank: Newbie
timestamp: January 03, 2017, 02:37:04 pm
content: Thanks. I am unsure if the 4.25VAC needs to be isolated or why if it does? The measured Voltage was higher and perhaps a 5VAC is OK.I think its common ground since old adapter is earthed.Could I get 5VAC from 5VDC cheaply? Have small budget of $20. Perhaps square wave would work?

author: jeroen79
author_rank: Frequent Contributor
timestamp: January 03, 2017, 03:29:58 pm
content: It would be useful to know what this gadget is.When powered from mains a simple transformer plus regulator will do fine.Just get a separate transformer for each line.When powered from USB you can use DC-DC boost converters to get the higher DC lines.Without knowing what the VAC line is for it is hard to tell what get for it.Possibly it will work fine on DC as well, possibly not.If a square wave will do then an H bridge from the USB can make that.An inverter could be modified by changing it's transformer or adding another transformer.Or simply generate mains AC with an inverter and then follow the second paragraph.

author: Zero999
author_rank: Super Contributor
timestamp: January 03, 2017, 07:27:25 pm
content: Quote from: RDSK on January 03, 2017, 02:37:04 pmThis simplest circuit I could think of. It's basically an astable multivibrator (Q1 & Q2, R1 & R2, C1 & C2) but with two additional transistors (Q3 & Q4) to act as a pull-up, forming an h-bridge. Q5, D1 & D2 and RS form a crude current limiter (maximum current = 0.6×RS = 0.6×1 = 600mA) which guards against temporary overloads and limits the current drawn when both the PNP and NPN turn on at the same time. If you need it to be able to withstand a continuous short circuit Q3 & Q4 will need to be able to dissipate 1.5W. If current limiting isn't required (not recommended, since this circuit does short circuit the power supply when all transistors are on simulataniosly) replace Rs with a short and omit Q5, D1 & D2.https://en.wikipedia.org/wiki/Multivibrator
Power supply making help needed - Page 1
Forum section: electronics / projects

author: dave_j_fan
author_rank: Regular Contributor
timestamp: March 11, 2025, 03:52:01 pm
content: I made this circuit with YouTube channel kasyan tv. But I don't have 2.7v zener.Can I replace initial 10v reference with TL431?I have 5v zener.. Can I use in place of 2.7v zenerWhat is the purpose of 2.7v .. Is it maintaining the bc557 pair in 12.7v to prevent damage.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: March 11, 2025, 04:08:03 pm
content: Can I swap 5v

author: Kleinstein
author_rank: Super Contributor
timestamp: March 11, 2025, 06:13:56 pm
content: The 2.7 V reference is there to get some headroom for the differential amplifier to work. If the input voltage is high enough, one could use a 5 V zener there. It is not so much to protect the transistors, but more to have a stable supply for the amplifier part and less ripple at the output.For the 10 V zener one could use the TL431 or 2 x 5 V zener in series.The circuit looks really old. Today one would more like use an OP-amp for better accuracy and less drift. Even an LM358 is more stable than the pair of transistors running at rather different currents and thus with quite some offset.The claimed power rating is rather optimistic. The 2N3055 (especially the modern ones) are not that happy with 2.5 A and 40 V for the worst case. So I would suggest reduceing the maximum current more to some 3 A.The supply may need some capacitance (like > 10 µF electrolytic) at the output to ensure stability.

author: Benta
author_rank: Super Contributor
timestamp: March 11, 2025, 07:38:23 pm
content: Seems to be an old Elektor/Elektuur circuit (I'd guess 80s).For the power transistors, use 2N3773 instead. You never know what kind of 2N3055s you'll get.

author: PGPG
author_rank: Frequent Contributor
timestamp: March 12, 2025, 12:39:32 am
content: Quote from: dave_j_fan on March 11, 2025, 03:52:01 pmAt picture I don't see 2.7V but 2.4V.I think that you can use 4 x 1N4148 (or 2x BAV99) in this place (or even a green LED).

author: dave_j_fan
author_rank: Regular Contributor
timestamp: March 12, 2025, 05:42:31 am
content: Thank you all.. I will opt 4148 option. Also making another one with 358.but this circuit seems erroneous... There must be 1k needed for 5200 base. I feel some pins are not correctly connected in Lm358 circuit( new build) see attached image

author: PGPG
author_rank: Frequent Contributor
timestamp: March 12, 2025, 11:29:21 am
content: Quote from: dave_j_fan on March 12, 2025, 05:42:31 amSchematic is totally unreadable. You should not assume that everyone knows what pin is what, or expect that someone trying to understand you will search for datasheet. Even there is probably standard how two op amps in one IC are connected I simply don't remember. I was playing with OpAmps 40 years ago.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 12, 2025, 02:53:39 pm
content: Yes, and I have that issue somewhere in the attic.I think its very early 80s. Too much dust to check!
Power supply module (AC to 12VDC @ 2A) for project: cheap and low ripple - Page 1
Forum section: electronics / projects

author: asilva10
author_rank: Contributor
timestamp: November 25, 2013, 03:35:33 pm
content: Hi,I need to integrate a small power supply device (12V@2A) for one of my projects.The voltage line will be further regulated programmatically via MCU (2-9V range). The maximum output current is 1A (peak), 0.3A (average).My plan is to include, at the last stage of the power solution, an additional ripple filter.Anyway, it would be better to have as the first stage of the power solution a commercial module with a relative small ripple in order to improve the quality of the MCU control.Price and size are also important and I started looking for cheaper solutions at ebay, such as this one:http://www.ebay.com/itm/Power-Adapter-12V-2A-DC-Regulated-Power-Supply-Transformer-New-/120951137560?However, it seems that such devices are used for LED applications with non-critical ripple requirements.Can you suggest a balanced solution for this case?Thanks
Power Supply: Output On/Off - Page 1
Forum section: electronics / projects

author: DavidDLC
author_rank: Frequent Contributor
timestamp: September 14, 2011, 05:51:08 pm
content: How is the output on/off perform in a good power supply ?Is is opening a connection ? Like opening a relay or any other element ?Changing the voltage to zero ?The transition should be smooth ? or it does not matter ?David.

author: Freighternut
author_rank: Regular Contributor
timestamp: September 15, 2011, 12:36:35 am
content: Hi,On my AIM-TTi QL355T Power supply (Great supply!), the output voltage is set to zero to effectively turn the output off. There are no relays etc.Cheers, Roger...

author: Gall
author_rank: Frequent Contributor
timestamp: September 15, 2011, 06:57:07 am
content: Usually the whole idea is to make the output perform better than being operated just by mains switch and/or physical output wire (dis)connectiion.The desired effects are:1. In case of emergency, be able to turn off the power quickly, without residual capacitor charge but without any inductive spikes, too. The best way to do that is to set output to zero smoothly in fractions of second. Not at instant, not with a relay since the device under test connected to the PSU may have a choke at its input.2. When mains switch is just turned on, do not turn on output power and allow to check output settings first. Any kind of switching is Ok to do that.3. When output is turned on, the output voltage and current should grow to desired values but without overruns. This is done by turning on the output slower than the output regulator works.4. On multi-output PSU, turn all outputs on/off at once (excatly at the same time). Relay is not good (random delays between diferent contact groups).Depending on the construction of the regulator itself, different methods may be used. The simpliest one is to set reference voltage to zero smoothly in fractioons of second (0.05 sec should be Ok). In some cases additional output switching (shortening?) may be used to guarantee 0.000V output.It does not matter if you short the output or let it float unless you have any special requirements. Both are useful in some cases. I personally prefer shortening to discharge capacitors in the device under test (if any).
Power Supply Output Switch - Page 1
Forum section: electronics / projects

author: Custom
author_rank: Newbie
timestamp: March 12, 2015, 11:44:07 pm
content: I am still quite new to electronics so in my quest to learn I have decided to design and build a power supply.I don't think all the specs and schematic will be nessessary for my question other than it does not have a micro controller and all analog circuitry. The output is capable of 24V @ 2A. My question is about the Output On / Off switch and how it should be done. My first few thoughts were either to actually disconnect the output via a switch or relay (would I need to disconnect both V+ and V-??) or to pull the drive voltage down to ground like my current limiting circuit does?I want what ever is on the output to not be bothered and want to try and avoid any kinda overshoot or switch bouce if possible.... Any ideas? also, let me know if more info is needed. Thanks

author: ajb
author_rank: Super Contributor
timestamp: March 13, 2015, 03:01:34 am
content: Well, a relay has the advantage of immediately and completely isolating your power supply from the circuit it's powering. If you're going to do a relay, may as well disconnect both + and -. Inhibiting the pass transistor would allow you to soft start, which will be much kinder to your circuit under test, and give more time for your overcurrent protection to kick in before you fry the load.Why not do both? Have the switch that controls the relay also pull down your voltage set point, that way you get the fast disconnect of the relay, but can do a soft start at turn on. Maybe have another switch to disable the soft start, for when you want to see how a circuit handles hotplugging or something.
Power Supply OVP Protection - Page 1
Forum section: electronics / projects

author: echen1024
author_rank: Super Contributor
timestamp: July 13, 2014, 06:54:43 pm
content: Hi,So I have designed an HV supply with the Ultravolt modules, which output a 0-2.5v signal proportional to the output signal. For OVP protection, I have a comparator configured as a discriminator, with the reference divided into the non inverting pin of the comparator, and the output signal into the inverting pin. Thus, when the output is above the reference, the comparator pulls the output low and sinks the secondary reference, thus pulling the HV out low.In this circuit, once the voltage is lowered, the HV out is enabled again, and operation returns to normal. I want it to require a hard reset before the output returns to normal. Anyone here have any suggestions?Thanks.

author: Rerouter
author_rank: Super Contributor
timestamp: July 14, 2014, 10:19:01 am
content: add some biasing to make it more of a schmitt trigger, (diode and resistor adding into the signal to make it stay higher than the reference,) that way when it trips it will stay tripped,

author: rob77
author_rank: Super Contributor
timestamp: July 14, 2014, 10:30:53 am
content: make an RS flip-flip out of a comparator - i did a over-current protection with hard reset exactly that way (for H-bridges - CNC).so in fact one comparator as RS flip-flop - it's output pulling down the reference and a second comparator watching the output voltage and triggering the RS. + a button to reset the RS flip-flop of course - to manually return back to normal.
Power supply problem - Page 1
Forum section: electronics / projects

author: pannitan
author_rank: Newbie
timestamp: January 19, 2015, 07:15:36 am
content: We are designing a PCB with two section 1stwith 3.3v (for microprocessor,ADC) and 2ndwith 24V. Now the problem is we have input supply voltage of 28V. We can use LDO for one section(24V ) but for 3.3v section using LDO is kind of suicide because of the amount of heat generated and there is no option of fan or cooling. But we also want to avoid using switched power supply as this section has lot of sensitive ICs like ADC ..Can somebody help in this regards.. Thanks in advance

author: void_error
author_rank: Frequent Contributor
timestamp: January 19, 2015, 07:56:35 am
content: Use a switchmode regulator to drop 28V to something more manageable for the a 3.3V linear regulator input? Something like 28V - 5V - 3.3V... with the switchmode regulator output well filtered, or drop the 28V using the switchmode regulator low enough so you don't dissipate too much in the linear regulator but higher then the dropout voltage.

author: pannitan
author_rank: Newbie
timestamp: January 19, 2015, 08:01:39 am
content: Thank you .. It seems this is only way ..Even we were thinking of cascading DC-DC with LDO .But I was hoping for some single IC solution

author: penfold
author_rank: Frequent Contributor
timestamp: January 19, 2015, 11:59:14 pm
content: You will have to bare in mind that the practice of cascading an LDO with a switch-mode does not directly take advantage of the intrinsic low noise nature of the LDO. It allows you to make a switch mode which operates slightly higher than the intended output voltage with so much filtering that its noise becomes acceptable but its transient response and regulation becomes poor... the LDO can take care of regulation. Regardless of what most data-sheets for LDO regulators state, you'd have to be quite lucky for all your noise to magically not get passed its internal capacitances

author: dannyf
author_rank: Super Contributor
timestamp: January 20, 2015, 12:36:51 am
content: QuoteYou probably want to get some sense as to how much current is consumed by the 3.3v section to truly figure out if a linear regulator (LDO or otherwise) makes sense here.As to noise for Vadc, there are a lot of ways of dealing with that.
power supply problem - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: April 25, 2014, 04:25:53 pm
content: Hi ,I attached the schematics that I have found in the web. It work nicely expect that when the input is 12V the minimum supply is going down only to 3.5V it don't go below that. can anyone please tell me why it is . I have checked the CC source and the current sink but I cannot find the problem. please help

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 25, 2014, 05:57:15 pm
content: that usually means that you need a negative rail connected to something or that yoou need a rail to rail op amp
Power supply question - Page 1
Forum section: electronics / projects

author: Dan Moos
author_rank: Frequent Contributor
timestamp: April 30, 2016, 02:55:18 pm
content: My project requires a 5 volt supply for the digital stuff, and a +/- 6 volt supply for analog (audio) stuff.For now, the power source is a bench PS set at 15v.Which of the following topographies sounds best?An LM7805 feeding the digital, an LM7812 feeding the analog, with a resister voltage divider (pair of 100k's) providing a reference voltage for all my opamps (this is what is currently up and running)OR an LM7812 feeding the same voltage divider, and using the center point of the divider as the zero reference, so I have +/- 6 volt rails. I would feed this to the LM7805, again using thecenter point of the voltage divider as my zero reference. As I right this, it occurs to me that 6 volts isn't enough to feed the LM7805, so lets say I have dealt with that (say, +/- 10v rails instead for the higher voltage reg). Is this a bad way? My biggest worry is noise on the analog signals.Method 2, if its even viable, allows me to not have to send a reference voltage to each of the 32 opamp buffers my design requires. Maybe that's no big deal.Its possible (likely actually) that my final design will run of mains, in which case getting a +/- supply is a little easier, and I just ditch the voltage divder.But I at least want to know the best way right now when I'm running on the DC bench supply. Also, It would be nice to not need any parts beyond what I already have if possible. I'm open to that though.+
power supply replacement  - Page 1
Forum section: electronics / projects

author: _THEON_
author_rank: Newbie
timestamp: May 24, 2019, 05:07:46 pm
content: Hi everyone,i have an old device with separate power supply which i would like to replace since it does look very worn down and humms.Since i dont have a datasheet, is there a way to know the max amp rating so that i can find an fitting replacement?I measured +/- 12 volts at the outputs with multiple +12v and ground connections. Is it safe to assume they are the same?Further more, there seems to be a floating pin connected to the frame.Are there any other things that i should look out for?Thanks in advance.

author: ocset
author_rank: Super Contributor
timestamp: May 25, 2019, 08:53:20 am
content: to replace the power supply.....can you borrow a bench power supply.?..set it up for +12/0/-12 output and hook that up to your device...then measure the current in the wires to it...and then from that work out what power is used...then buy a power supply of that power level or more

author: _THEON_
author_rank: Newbie
timestamp: May 25, 2019, 09:35:03 am
content: Sadly my power supply only has a single output, so i can't provide +12/0/-12

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 25, 2019, 09:54:48 am
content: Hi,Does the original supply have any labels on it?Can you tell us what is being powered by this supply?Can you tell us the manufacturer of the equipment?Regards,Jay_Diddy_B

author: radix
author_rank: Contributor
timestamp: May 25, 2019, 11:27:46 am
content: You can try to work out a very approximate upper limit based on components that are in there.I can see a 2.5 mF electrolytic and a C 5000/3000 bridge rectifier. If I recall correctly, the bridge rectifier is rated for 5 A/3 A and the electrolytic would imply something between 0.5 A - 1 A, or more depending on which rule of thumb you follow (these numbers are for 2-4 mF/A).

author: _THEON_
author_rank: Newbie
timestamp: May 25, 2019, 01:41:25 pm
content: Thanks for your replies.I have no information on the device since the manufacturer is no longer around.The supply drives a CRT.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 26, 2019, 03:57:10 am
content: Quote from: _THEON_ on May 25, 2019, 01:41:25 pmBy "CRT" do you mean the entire monitor ?"CRT" normally refers to the big glass device that your display appears on.
Power supply ripple measurement - Page 1
Forum section: electronics / projects

author: santoshgurral
author_rank: Contributor
timestamp: October 22, 2019, 09:23:19 am
content: HiI am trying to capture the power supply ripple on my PCB with a 50ohm co-axial cable(just coax cable only no additional DC block). I have an R&S RTO2024 oscilloscope. My doubt is, in order to capture the ripple should I set the oscilloscope coupling to50ohm DC or 1Meg DC or AC coupling?ThanksSantosh

author: Kleinstein
author_rank: Super Contributor
timestamp: October 22, 2019, 10:31:05 am
content: To capture the ripple one likely needs to use AC coupling, unless the ripply is really high (e.g. more than some 5%).Using the 50 Ohms DC mode can even be dangerous to the scope (the 50 Ohms termination) if the voltage is too high.

author: santoshgurral
author_rank: Contributor
timestamp: October 22, 2019, 10:41:43 am
content: Thanks for the reply...but when I use an active differential probe RT-ZD10 from R&S to measure ripple scope mask out AC coupling option. By default, only 50ohm DC coupling mode is set when a differential probe is connected. Why is it so ? Differential probes can not be AC coupled? If not then how to measure ripple (very small ripple in range of 10mVs) using a differential probe?ThanksSantosh

author: Kleinstein
author_rank: Super Contributor
timestamp: October 22, 2019, 12:00:20 pm
content: The differential probe seems to have a 50 Ohms output. At this low impedance AC coupling would only work for high frequencies. Anyway with a differential probe AC coupling would be at the probe input. So there is no more need for AC coupling behind the differential probe.

author: Zero999
author_rank: Super Contributor
timestamp: October 22, 2019, 12:08:07 pm
content: Quote from: santoshgurral on October 22, 2019, 10:41:43 amBecause a differential probe is really an amplifier, with a high input impedance and will be designed to drive a 50Ohm load. As far as your circuit is concerned, it will only see the high impedance of the differential probe's inputs, not the 50 Ohm oscilloscope input.

author: prasimix
author_rank: Unknown
timestamp: October 22, 2019, 03:57:02 pm
content: I'm using the method that is described in some HP/Agilent/Keysight power supply manual (have to find out which one) as describedhere. Actually, I it's a half way to complete setup since I have just one AC coupling capacitor + inline terminal instead of two (another has to go to Vout-), but that is better then nothing. Also please note that is a huge difference between "$1 per meter" coax and scope probe cable. Therefore scope probe is used (set to x1) and scope input now can be set to DC safely (because of inline capacitor) but gain has to be set to x2 to have accurate reading because of 50 Ohm inline terminator.
power supply safeguard relay logic  question - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: July 12, 2024, 04:38:16 pm
content: Hello , I have the attached schematics which i am trying to understand the logic of it.I have a problem understanding J29 and J27 role in opening the V23105A5476A201 relay described in a photo below.The current suppose to flow from 1 to 16 , so there needs to be voltage drop between legs 1 and 16 to open .Why leg 1 in J29 connected both to pin16 and pin1 (threw a diode) and J27 leg 1 is connected to leg1 of J29.What could be the logic of that?Thanks.https://eu.mouser.com/ProductDetail/TE-Connectivity-Axicom/V23105A5476A201?qs=KKrrU%252baSadI5%2FocrT%2FYCiw%3D%3D
Power supply schematic input - Page 1
Forum section: electronics / projects

author: ahnuts72
author_rank: Regular Contributor
timestamp: May 06, 2013, 03:30:48 pm
content: Was wondering what everyonestake on this supply is.I want to replace my lm338 supply.Sent from my Milestone X using Tapatalk 2

author: penfold
author_rank: Frequent Contributor
timestamp: May 06, 2013, 03:51:10 pm
content: Looks like it should work pretty well.The only few things to comment are perhaps:The lack of compensation on the opamps, but that will depend a lot on the exact amps you end up using and what sort of response you're afterAnd lack of variable current limit, I'm assuming you considered that but went for the more elegant solution

author: ahnuts72
author_rank: Regular Contributor
timestamp: May 06, 2013, 05:25:02 pm
content: Im still looking for one with current limiting that I might try to build.I would like to have current controlas well.Im looking at some Power Designsupplies on ebay but I want to build this as a learning experience.Sent from my Milestone X using Tapatalk 2
power supply schematics - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: May 06, 2014, 03:07:44 pm
content: hi guys,Please somebody send me any bench top power supply schematics of standard company expect agilent. I just want to know what is going on inside. please

author: liquibyte
author_rank: Frequent Contributor
timestamp: May 06, 2014, 03:15:46 pm
content: Google is your friend.

author: owiecc
author_rank: Frequent Contributor
timestamp: May 06, 2014, 03:19:28 pm
content: Find some service manual on ElektroTanya.

author: miguelvp
author_rank: Super Contributor
timestamp: May 07, 2014, 03:05:23 am
content: also a lot of schematics here:http://bama.edebris.com/manuals/just type power supply in the search if you don't know the vendor/model you are looking for.

author: cellularmitosis
author_rank: Unknown
timestamp: May 09, 2014, 12:30:04 am
content: Circuit specialists lists the schematic for their $50 18V 2A linear supply.http://www.circuitspecialists.com/pdf/1802X_schematic.pdf

author: kizzap
author_rank: Unknown
timestamp: May 09, 2014, 08:10:45 am
content: Quote from: cellularmitosis on May 09, 2014, 12:30:04 amthat is the first time I have ever seen a schematic label their passives with the codes that they would commonly be marked with, i.e. 472 for 4.7k on a resistor.

author: mariush
author_rank: Super Contributor
timestamp: May 09, 2014, 11:56:25 am
content: Here you go.

author: dcsleep
author_rank: Newbie
timestamp: May 10, 2014, 09:31:32 pm
content: @mariush: The schematics you posted labeled as 'agilent 36xx psu' don't appear to be Agilent schematics - especially since they appear to use an ATmega MCU. Are the schematics from a derived design? If so, is there a site with additional information - BOM, notes, etc.? I find the design interesting as I've been toying around with the same thing.

author: mariush
author_rank: Super Contributor
timestamp: May 10, 2014, 10:09:33 pm
content: I had those three pictures in a folder with lots of schematics. I probably saved them there when I noticed them in a thread about power supplies, on this forum or some other forums I frequent. Unfortunately, I did not make notes regarding the thread i downloaded the pictures from so can't help you further..
power supply schematics - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: April 25, 2014, 04:29:07 pm
content: Hi guys ,please somebody please post me any bench power supply schematics expect agilent . please guys

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 25, 2014, 05:53:17 pm
content: You won't find a better explained power supply then dave jones u-supply video series. Not only does he give you schematics BUT he also has a 6 part video series explaining the rational that went into designing the supply and real life tests that helped him hone in on his design.http://www.eevblog.com/projects/usupply/
Power supply scheme for MCU-controlled garden lights - Page 1
Forum section: electronics / projects

author: resistor
author_rank: Regular Contributor
timestamp: September 26, 2013, 10:50:31 pm
content: Hi folks,My front yard has walkway lights that are powered by 12VAC (from a big transformer in my garage). I'm trying to build an bulb replacement for them that will use an MCU + yellow/orange LEDs to make them look like flickering torches. I think I have a good idea of how to do the flickering and the interfacing to the bulb socket, but I'm having some issues designing the power supply system.Obviously I'm going to have to rectify and regulate the 12VAC down to 5V or 3.3V for the MCU. The question, then, is how to power the LEDs. I can use an LED driver IC powered by the the logic Vcc, or I could do a DIY constant current source powered by the (rectified and filtered, but unregulated). Maybe there are other options to consider?My biggest constraint here is area. The enclosures of these lights aren't too big, and don't have a lot of air circulation. I've nervous about dissipating too much heat (I haven't picked the LEDs yet, but I suspect they'll be 1-2W total), as I don't really have the space to add heat sinks.Thanks!

author: mariush
author_rank: Super Contributor
timestamp: September 27, 2013, 12:10:20 am
content: reuse the 12v acbridge rectifier, capacitor, mc34063 buck regulator to get 3.3v or 5v.. power the leds from the same 3.3v or 5v you use for the microcontroller. the microcontroller can even drive the leds directly from its I/O pins if neededIn theory, I suppose you could use a few 555 timer chips to get the leds to flicker and simulate the fire... this may save you the trouble of getting 3.3v and 5v, as the 555 chips can usually work with up to about 16v, so you could just use a single diode and a capacitor for half wave rectification (and get 5-16v)

author: Harvs
author_rank: Super Contributor
timestamp: September 27, 2013, 01:12:44 am
content: Just something to consider if you need a bit of light, I got some of these for some wood shed lighting thinking they'd be crap but worth a try:http://www.ebay.com.au/itm/400498138585?var=670099942444&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649To be honest I'm pretty stunned. At just over $1 each they're awesome. Not really a pleasant enough colour for indoor use (a bit yellow), but fine for general outdoor lighting.