hybridfree/eevblog-posts huggingface dataset:
-12V A - ATX PSU Bench PSU - Page 1
Forum section: electronics / beginners

author: kr15_uk
author_rank: Newbie
timestamp: November 18, 2016, 03:28:18 pm
content: Ladies and gents,I've built ATX Bench PSU some time ago, all good, but never had a chance to play with -12V or soNow I'm working on one small project where I'll finally need my 24V out of +12V and -12VBut... I'm a bit lost with AMP rating for this combination.+12V1 is rated for 15A max but -12V 0.5ASoooo.... My 24V in theory will be ??A... And I'm stuck here...Thanks.Kris M

author: TheAmmoniacal
author_rank: Unknown
timestamp: November 18, 2016, 04:12:28 pm
content: CORRECTION: you're limited to 0.5 A because the current has to go through both rails (and thus you will be limited to the rail with the lowest rating).

author: kr15_uk
author_rank: Newbie
timestamp: November 18, 2016, 04:30:06 pm
content: Thanks for the reply.Do you mind to share how you've calculated this so I don't bug people next time when I get something similar?!Like next possible option +5V 16A and -12V 0.5AI've tried to figure it out myself but none of the options were even close to 967mA...Thanks.Kris

author: MarkF
author_rank: Super Contributor
timestamp: November 18, 2016, 04:51:05 pm
content: I assume you intend to connect your projects +V to the supply +12V and -V to the supply -12V. The current out of the +12V must equal the current into the -12V (i.e. You're limited to 0.5A).I don't recommend doing this as your final solution. Your project will be referenced to -12V. Therefore, your project MUST be isolated from ground to prevent a short of your power supply.

author: kr15_uk
author_rank: Newbie
timestamp: November 18, 2016, 05:02:13 pm
content: Thanks Mark.0.5A makes more sense to me.24V is only for testing. If I'll find that 24V is way to go then I'll get proper bench PSU.Thanks.

author: raspberrypi
author_rank: Frequent Contributor
timestamp: November 18, 2016, 11:19:11 pm
content: The only way I know of is to read the label on the side of it. To generate the -12 volts requires dedicated circuitry that they don't beef up like the +12 because computer mother boards don't use alot of - voltage. I built one ofthose and was all excited to play with the negative voltage until I realized it was such little current. A crude way is to count how many wires come out for that voltage, lots of wires are to carry lots of current.

author: MarkF
author_rank: Super Contributor
timestamp: November 18, 2016, 11:19:49 pm
content: Quote from: kr15_uk on November 18, 2016, 05:02:13 pmCareful with scope probes during testing. That ground clip on the probe WILL short your ATX supply.
12v Automotive relay trigger - Page 1
Forum section: electronics / beginners

author: andrewlapham
author_rank: Contributor
timestamp: July 01, 2019, 09:28:59 am
content: hey,I drew up a diagram of what I think would work but need some input. Basically, I need to trigger a 12v relay from an Arduino pin. I'm just not sure if the 2N222 is going to feel the pain and let the magic smoke out or not.

author: digsys
author_rank: Unknown
timestamp: July 01, 2019, 10:35:43 am
content: The 2N2222 has a current gain of ~ 100-150X, so if the relay coil is 100mA, all you need is ~2mA. Even if you said 5mA for certainty. Assuming 3V3 op / .005 = 660RI'd just increase your resistor to say 560R and put a 10K from Base to Emitter. You can tweak values depending on coil current.

author: Ian.M
author_rank: Super Contributor
timestamp: July 01, 2019, 12:25:16 pm
content: Please ignore this if you are just using a car battery as convenient portable power for some gadget in a field somewhere!However if your gadget is going to be fitted to or used in a vehicle, I'd be very wary of transient ground potential differences in an automotive environment. If the transistor emitter, Arduino Ground and buck regulator ground aren't all connected to the same point by relatively short wires, you are likely to have trouble.Also, is the buck regulator rated for automotive use? The transients it may be subjected to are absolutely vicious, and even on a modern well maintained vehicle are not nice and well outside the abs. max. ratings of most commodity switching and linear regulators. Google:"ISO 16750-2"or the superseded standard"ISO 7637"which may be easier to find the full text of as ISO charge for access to their standards.

author: andrewlapham
author_rank: Contributor
timestamp: July 01, 2019, 11:42:23 pm
content: One thing I'm not so sure about now is the ground connections, Should they all be common? Can the 12v and 5v lines share the same ground?

author: ptricks
author_rank: Frequent Contributor
timestamp: July 02, 2019, 12:19:48 am
content: Quote from: andrewlapham on July 01, 2019, 11:42:23 pmYes and they have to be for the circuit to work correctly.

author: digsys
author_rank: Unknown
timestamp: July 02, 2019, 07:27:07 am
content: As good practice, keep all grounds referenced at one point, preferably nearest the power source or inlet. This is especially important if you are using it in a vehicle.At the very least make sure the highest current devices are closest to power source 0V.
12v dc "breathing" lamp dimmer - Page 1
Forum section: electronics / beginners

author: BlueFan100
author_rank: Newbie
timestamp: March 17, 2022, 02:37:30 am
content: HelloI'm looking to build a simple circuit to automatically increase and decrease the brightness of a 12v incandescent bulb so it seems like it's "breathing" for example the light would fade up from zero to full brightness over about 5 seconds then reverse and fade out to zero over the same time period.I found a simple dimmer circuit that uses a variable resistor that seems like a good place to start, however I'm not sure what components would be necessary to replace the variable resistor, I am guessing I would need some sort of capacitor connected to the transistor and as it charges it would switch the transistor to increase the brightness, but not sure where to go from there. Can anyone suggest something simple?

author: amyk
author_rank: Super Contributor
timestamp: March 17, 2022, 03:22:42 am
content: "Simple" as in lowest BOM cost: MCU + transistor."Simple" as in pure analog: relaxation oscillator (at least half a dozen parts).

author: james_s
author_rank: Super Contributor
timestamp: March 17, 2022, 05:49:58 am
content: Using a transistor as a linear element is a terrible way of dimming an incandescent lamp, you're going to burn up all the extra voltage as heat in the transistor. I agree with the suggestion to use a microcontroller with a PWM output and just do it in software, unless you really want a retro approach. Either way you want PWM, not linear, unless it's a very low power lamp.

author: Renate
author_rank: Super Contributor
timestamp: March 18, 2022, 06:31:14 pm
content: Are you really sure that you want to use an incandescent bulb?Even if it's for something bright, there are tons of bayonet base 12V LED assemblies.Whether you end up with an LED or bulb you will probably find that you need a compensation curve to make it look natural.If you use 0/255 to 255/255 PWM and ramp it up/down at a constant rate in a loop it will look like it doesn't spend enough time off/dim.You need a cube law compensation.

author: Kim Christensen
author_rank: Super Contributor
timestamp: March 18, 2022, 07:01:34 pm
content: If you are just goofing around, something likethis circuitcould work with some modifications to drive a 12v incandescent lamp. You could replace the 2N4403 with a PNP darlington to drive a bulb that'll draw more current than the LED shown.As other have mentioned, you'll waste a bit of heat in the transistor. If it's a small lamp it's fairly manageable heat wise. For higher power you'll be better off with a PWM type which makes the circuit a bit more complicated.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2022, 08:08:02 pm
content: PWM is the best way to do it and if you want simplicity use a micro controller.It's possible to do it the old way using comparators. Here's a circuit using the LM339. It fades two LEDs alternately. If you just want to fade a single incandescent lamp, omit U1d and the associated components and replace Q1 with a MOSFET
12V DC MOTOR  - Page 1
Forum section: electronics / beginners

author: gsingh11
author_rank: Contributor
timestamp: January 26, 2023, 05:35:50 pm
content: I AM LOOKING FOR A DC MOTOR THAT IS CHEAP AND WITH GOOD FLOW THAT CAN BE USED FOR FILLING OR EMPTYING A TANK

author: BillyO
author_rank: Super Contributor
timestamp: January 26, 2023, 05:48:36 pm
content: What are you pumping? Water, gasoline, alcohol, oil, acid, caustic fluids, acetone, toluene, MEK, DMF, xylene, ..etc?Isn't this triple posting?Is this an electronics question?Is your philosophy to just keep asking the same question until you get the answer you like?

author: Zero999
author_rank: Super Contributor
timestamp: January 26, 2023, 06:20:50 pm
content: You need to fix that broken capslock key.Please provide more information.What voltage?How big is the tank? How far does the fluid need to be pumped and to what height?A car fuel pump can be used to pump hydrocarbons, but not water, or anything which will mix with water. A car windscreen washer pump can be used for water.Is it drinking water? If so, the pump must be approved for potable water use, so don't use anything automotive or industrial, as it might be contaminated with poisonous chemicals.

author: Gyro
author_rank: Super Contributor
timestamp: January 26, 2023, 06:29:46 pm
content: Sigh...https://www.eevblog.com/forum/beginners/need-dc-water-pump/Another duplicate thread already removed.
12V DPDT device (except relay) - Page 1
Forum section: electronics / beginners

author: mitrynicolae
author_rank: Contributor
timestamp: May 13, 2019, 04:38:20 pm
content: Hello everyone,I need a DPDT device (like a relay) that should meet the following restrictions:- the switching mechanism should accept 12V or more on the input- the switching mechanism should not sink more than 1mA ( which mean roughly 100mW)- the output pins should accept voltages from 0 to 20V (being able to drop to 0 is a must)- the output pins should not have an resistance greater than 100 mOhms- should be small enough to fit in a 8x7 mm rectangleThe following relay meet all the conditions except the size :https://www.tme.eu/ro/details/ftr-b4ca012z/relee-electromagnetice-miniatura/fujitsu-takamisawa/.If you believe that this can be achieved using transistors or other ICs please let me know how would you do it.Just as a reference, this relay should switch between a voltage input on board and a calibration circuit.

author: MarkF
author_rank: Super Contributor
timestamp: May 13, 2019, 06:57:07 pm
content: Maybe theV23105A5003A201 Low Profile Relayfrom TE ConnectivityORDigiKey:https://www.digikey.com/products/en?keywords=V23105A5003A201NEVER MIND. MUCH BIGGER.

author: mitrynicolae
author_rank: Contributor
timestamp: May 13, 2019, 07:01:45 pm
content: Thank you for the answer, but the suggested relays are double in size then the one I suggested.

author: Benta
author_rank: Super Contributor
timestamp: May 13, 2019, 07:31:35 pm
content: Analog switches are available for this, check Vishay/siliconix for instance. But you left out an important parameter: do need you isolation between control input and the switch?

author: Zero999
author_rank: Super Contributor
timestamp: May 13, 2019, 08:13:46 pm
content: Analogue switches tend to have a much higher resistance than an Ohm. The only sub-Ohm ones I've seen are limited to much lower voltages: typically < 6V.I dare say, the original poster's specification is impossible to full-fill, without designing a custom IC. Even solid state relays will be too big and a photo-coupled MOSFET will use too much current.This doesn't mean that the original poster's problem is impossible to solve. There might be other ways of solving it, which they haven't considered.
12v ignition trigger curcuit - Page 1
Forum section: electronics / beginners

author: bborisov567
author_rank: Regular Contributor
timestamp: August 11, 2021, 09:12:51 am
content: I am trying to make a device that switches a relay when engine is started (voltage going from 12v to 13.5v). I am using the circuit below. Zener is 8v. I have a problem with the standby current - it's about 10-12mA which is a lot for a device that is connected to the battery all the time. I tried making R10, R30 and the trimmer pot around 3 times bigger but current is still the same. I believe what happens is since the threshold is quite small both transistors are already saturated at 12v. Could you give some suggestions or another relatively simple circuit for the task.

author: Renate
author_rank: Super Contributor
timestamp: August 11, 2021, 11:36:02 am
content: Using a voltage reference and a comparator could work with less current.TL431 needs a mA or two.Going whole hog, a INA226 (at 0.5 mA) and an AVR8 will give you 15 bits of measuring voltage.I simply poll the OBD from the ECM to see if the engine is running.That way I can see running time and schedule my coffee breaks.Checking voltage is not the most reliable way to tell if the engine is running.Do you really need to differentiate "ignition on" from "engine running"?If your alternator has a separate "Stator" (S) output, that would be more reliable.If your coil/ignitor pack has a tach output you could monitor that.
12v interupt - Page 1
Forum section: electronics / beginners

author: VIC
author_rank: Newbie
timestamp: October 05, 2014, 05:32:35 am
content: Hi GuysI am sure you will be able to help with the following.I recently fitted a new flip front head unit to my car which is great except for the following problem.When starting car (key turn between ACC and START) there is a split second power supply interupt tostereo which makes the unit reset eg. fold in then fold out Really annoying. Is there anything i can putin the acc lead to prevent thisYour help would be greatly appreciated.Thanks in advanceVIC

author: reportingsjr
author_rank: Contributor
timestamp: October 05, 2014, 06:19:24 am
content: This is likely caused by voltage sag on the 12v system. Starting a car can make it drop down as low as 3v. You can try to add a filter inductor in series with the positive line into the radio and a big capacitor after that from positive to ground. Even that may not help though. Good luck!

author: Whales
author_rank: Super Contributor
timestamp: October 05, 2014, 06:44:54 am
content: That should solve your issue, but it hints are other problems with your car (assuming the radio is stock)- Your battery is not behaving correcty. Eg too old or not big enough for your car- Your starter motor might not be healthy- Your engine might have a larger than normal mechanical resistance to startupHope it goes well

author: Whales
author_rank: Super Contributor
timestamp: October 05, 2014, 06:46:17 am
content: Quote from: reportingsjr on October 05, 2014, 06:19:24 amIt's probably easier to source large diodes than large inductors.
12v L.E.D Light Bar  - Page 1
Forum section: electronics / beginners

author: thorthor
author_rank: Newbie
timestamp: April 27, 2021, 07:07:28 am
content: I have a 12v L.E.D light bar it has 60 leds(20 in series and 3 of those in parallel if im not mixing that up). The center 20 leds just barely light up, so I poked around with my multimeter like one does, every led works when tested, but when I measured everything while 12v was applied the driver circuitry for the center measured 55-60v but the other 2 drivers only went to 12v. I compared sections and everything measure the same till I get to 2 caps where I get the 55-60v, am I wrong in thinking its a bad inductor. ....... Its an old light bar that was on a truck it did have water work its way in. I did clean everything up with a nylon brush and alcohol, to my eye no leads or pads broke/rusted off. Thanks for any help/advice etc.

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2021, 08:06:41 am
content: Could be anything . A bad driver chip , transistor , shorted cap even a burned resistor can exhibit higher resistance than it should . 60V for 20 white LEDs in series seems about right . 2.7 to 4 forward volts is typical of white LEDs . If you could check the Forward voltage of one of them with diode setting on your DMM and multiply that with 20 that will give you the total forward voltage of the string.Could you take some clear pictures of the driver board ?

author: thorthor
author_rank: Newbie
timestamp: April 29, 2021, 06:47:02 am
content: You're absolutely right, forward voltage hadn't even crossed my mind. And yea I can take one quick. Sorry for the late reply btw.is this one good? Its from 1 of the working ones there's 3 driver circuits on the board in total all 3 are copies of each other, the one shown is the one I could get the best picture of due to how my work space is set up. I no some of the silkscreen is flecking up in places but I think there's another layer beneath cause its not conductive at all.
12v latching relay/switch from momentary switch. - Page 1
Forum section: electronics / beginners

author: central3
author_rank: Newbie
timestamp: March 07, 2021, 02:00:13 am
content: I am working on an 80's era ford concept car and trying to figure out how to fix some of the electronics.The relay/switch pictured is not good. I am looking to replace it with something that works the same.It is triggered by a momentary 12v pulse.Can someone recommend a simple replacement for this relay or switch.

author: bdunham7
author_rank: Super Contributor
timestamp: March 07, 2021, 02:47:28 am
content: It would help to know what its function is! Is it a turn signal sequencer?

author: central3
author_rank: Newbie
timestamp: March 07, 2021, 03:58:09 am
content: All they control are 5-7 lights. They just turn them on and off. Fairly low amp.

author: Psi
author_rank: Super Contributor
timestamp: March 07, 2021, 04:28:48 am
content: Quote from: central3 on March 07, 2021, 03:58:09 amIt has a cam system, there must be more to it than that

author: calzap
author_rank: Frequent Contributor
timestamp: March 08, 2021, 07:11:28 pm
content: A few more views would be helpful. But good chance a programmable timing relay, like the Macromatic TE8812U/TD8/THR3 series or Selec 600XU, can duplicate the functions of this device. It might take two. These relays are versatile and relatively inexpensive.Mike in California

author: antenna
author_rank: Frequent Contributor
timestamp: March 08, 2021, 07:30:40 pm
content: There are latching push button switches in the electrical isles of nearly every auto parts store. Some even light up. I am curious how the original failed though. Looks built too well to ever fail. If necessary, the switch could control a relay. Is there a reason for a momentary button and a complicated solid-state latching circuit?
12v power supply, output fluctuating when NOT under load - is this normal? - Page 1
Forum section: electronics / beginners

author: xboxgamer
author_rank: Contributor
timestamp: February 09, 2022, 06:07:46 am
content: Hi everyoneSo I have a weird "issue". My satellite receiver wouldn't turn on so I did basic troubleshooting with measuring voltage coming out of my cheap, chinese AC to DC power adapter. It was fluctuating 0-9-10-12-0... very fast so I said - it's broken. Also it was giving this very quiet hissing sound every second like it's trying to power on and shuts down. I spent 2 days replacing capacitors and checking inside and it was still happening.Then I discovered that there was a lose cable inside receiver itself and after fixing that I powered it on using another power adapter that was giving stable 12v on the output when not connected to anything besides multimeter. Just for fun I connected the "broken" adapter back only to discover that when connected to device, it gives stable 12.35V on the output. But as soon as I disconnect it from device it fluctuates again.What gives!? All my life I thought that power supply MUST keep stable 12v even without connecting to anything.Is this a fault? Is there a way to stabilize it in case it's not normal?Power supply looks like thishttps://m.media-amazon.com/images/I/61JAjYzklDL._AC_SL1000_.jpg

author: johankj
author_rank: Contributor
timestamp: February 09, 2022, 10:00:30 am
content: Voltage for any power supply will change with load. I'm not surprised a cheap Chinese brick is all over the place when unloaded. I've seen this behavior too.

author: JohanH
author_rank: Frequent Contributor
timestamp: February 09, 2022, 10:37:43 am
content: Some power supplies need minimum load to give stable output. Put a resistor as load to draw 5-10 mA current if you are concerned.Besides, many devices don't need a precise input voltage because of internal regulators. Cheap devices often come with a 12V adapter that isn't regulated and have higher voltage when not loaded. Also, I have accidentally powered "12V" devices with 5V adapters and they have worked fine.

author: Gyro
author_rank: Super Contributor
timestamp: February 09, 2022, 11:27:14 am
content: The hissing sound is a dead giveaway that the PSU isn't stable under zero load. It is either cycle skipping or just generally instability depending on quality. As others have said, put a load on it and it will settle down.

author: Zero999
author_rank: Super Contributor
timestamp: February 09, 2022, 01:38:06 pm
content: As mentioned above, some power supplies need a minimum load to be stable.It's possible it's a cheap, unregulated power supply. Most switched mode power supplies are regulated, but some really cheap ones aren't, or are very poorly regulated. Your satellite receiver probably doesn't need a regulated power supply. It will have various regulators on its power inputs to five different voltage i.e. 5V and 3.3V.
12V relay back feed  - Page 1
Forum section: electronics / beginners

author: Millsner
author_rank: Newbie
timestamp: February 08, 2022, 04:48:11 pm
content: Hello, new to forum. Trying to wire up an override switch for my electric fans on my hot rod but for some reason I keep getting back feed from the battery circuit to the ignition circuit on my override relay. I can tell the back feed is coming from the 85/86 side of the override relay as when either side of this is unplugged, the back feed stops. Also if I unplug the 30 on the override relay this will also stop the back feed. Looking for some help on how to properly wire this up. I want the fans to work on ignition normally but when i push the fan override switch, I would like that fan relay to then be powered off of battery power. I have attached a quick schematic.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 09, 2022, 08:50:28 pm
content: The Truck Forum is not here anymore.
12v sealed lead acid battery has low volts - Page 1
Forum section: electronics / beginners

author: jonovid
author_rank: Super Contributor
timestamp: May 02, 2018, 02:25:07 am
content: I have a 12v 1.2Ah sealed deep-cycle lead acid battery that now has 8 volts.charging has not fixed the problem, the battery still holds 8 voltsits like 2 calls are non-existentelectrolyte levels?the battery is 3 ys old and is charged one a week for 12 hrs.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 02, 2018, 02:48:36 am
content: It certainly sounds dead. Two of the cells might have shorted out.You say it is charged 1/week for 12 hours. Are you deep discharging it between then? Are you sure it is actually being charged?

author: Gregg
author_rank: Super Contributor
timestamp: May 02, 2018, 05:21:57 am
content: The best way to test it is to check the voltage with a load. Something like an automotive brake light bulb that draws a couple of amps would work well. If the voltage drops to almost nothing, there is an open circuit either within a cell or between cells. If it maintains something over 7 volts, one cell is shorted internally; probably from plates warping and contacting each other.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: May 02, 2018, 07:24:52 am
content: In my experience, if a SLA won't hold charge it is knackered. Attempts to revive them are rarely successful. Small sizes are cheap to replace and not worth the effort anyway.

author: jonovid
author_rank: Super Contributor
timestamp: May 02, 2018, 07:58:22 am
content: yes it looks knackered did have it under 1 amp load. the voltage sits at around 8Vthe problem only showed, up after a deep and full discharge when I left the equipment on.with deep cycle batteries they do not say how many deep cycles you get. no guarantees you get the full nine lives.- thanks

author: tautech
author_rank: Super Contributor
timestamp: May 02, 2018, 08:22:41 am
content: Quote from: jonovid on May 02, 2018, 07:58:22 amSLA's particularly don't like that, less so with a bit of age on them.I've seen figures for 1000 charge cycles although you'd want to treat with with kid gloves in order to get that.I use 12V 7A ones for night time pest spotlighting and even if you run them til the light dims repeatedly you're gunna shorten their life.Once they start only holding a short charge, they're stuffed. You can piss around steady cycling/recycling them and desulfating them but you're only

author: Gyro
author_rank: Super Contributor
timestamp: May 02, 2018, 09:07:39 am
content: Quote from: jonovid on May 02, 2018, 07:58:22 amIn your case it sounds like a combination of sitting fully discharged for a significant (I'm guessing) period of time and discharging below 1.8V per cell. A situation that is pretty much guaranteed to cause irreversible sulphation and drying out. They will tolerate full discharge but then requireimmediaterecharging.
12v stable from a 4S5P li-ion pack - Page 1
Forum section: electronics / beginners

author: Ozzyfr
author_rank: Newbie
timestamp: June 04, 2018, 03:36:45 pm
content: Hi,Is there a small module capable of stabelising a 12v output out of a 4S5P battery pack that delivers around 14.8V and drawing at max 20A?Thank you!

author: innkeeper
author_rank: Unknown
timestamp: June 23, 2018, 03:45:54 am
content: Hi,The problem is that a lipo under that kind of load will likely drop in voltage to 3v per cell and even lower as it discharges depending on the cell.to handle that, you would need something called a boost/buck converter, that will raise and lower the output voltage depending on need, however, i've never seen one at 20A... it doesn't mean it doesn't exist or that you couldn't design one.life would be easier if it were 5S then you would be at 18.5v and maybe 15v under heavy load.There are plenty of circuits out there that could do that by just regulating the output.

author: Audioguru
author_rank: Super Contributor
timestamp: June 24, 2018, 04:20:14 am
content: If your battery can supply 20A continuously then each cell provides 4A. It has 4 cells in series so its fully charged voltage is 4 x 4.2V= 16.8V. The poor voltage regulator will heat with (16.8V - 12V) x 20A= 96W. Do you have a voltage regulator powerful enough and a heatsink large enough?The voltage regulator has a minimum input voltage of about 14V but your battery will drop to 12V. Then when the battery is 14V each cell is 3.5V which is almost only half a discharge.

author: sleemanj
author_rank: Super Contributor
timestamp: June 24, 2018, 08:03:23 am
content: Quote from: Audioguru on June 24, 2018, 04:20:14 amThe poster didn't say he wanted a linear regulator.Assuming there is a suitable DC-DC converter found with around an 85% efficiency, which is reasonably typical, the dissipation as heat at 20A 12V output would be, ((12*20)/0.85) - (12*20) = 42W, still a sizeable amount but not that large, although active cooling is probably advisable.The primary problem to solve though is finding a suitable SEPIC that can handle the demands. I'd say that going to a 5S pack would be better then it becomes easier to find a capable buck converter, rather than a SEPIC.

author: Audioguru
author_rank: Super Contributor
timestamp: June 24, 2018, 04:56:45 pm
content: Quote from: sleemanj on June 24, 2018, 08:03:23 amHe said, "a small module capable of stabelising a 12v output" which sounds like a voltage regulator. I don't know the dropout voltage of a 20A switching regulator.
12V to 12.6V boost with current limit for 1Amps - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: August 29, 2020, 11:26:38 am
content: Input is 12V, output I need is 12.6V with 1Amps current limit.Output connected: Lithium battery 8.1V to 12.6V range and a resistive load in parallel.Since battery is also connected at the output, so current limit is required. Otherwise battery drains huge current, if limit is not there

author: Zero999
author_rank: Super Contributor
timestamp: August 29, 2020, 10:27:02 pm
content: What are you trying to do? Charge three lithium ion batteries from a 12V supply? You'll need a SEPIC converter and a specialised lithium ion charging IC.

author: ledtester
author_rank: Super Contributor
timestamp: August 30, 2020, 04:06:43 am
content: You should tell us more about what your application is -- I'm sure there are some assumptions not being stated.For instance, do you want your load to be powered by the battery when the input power is taken away -- i.e. like a uninterruptible power supply? Do you want to charge the lithium 3S battery in a balanced fashion?Some ideas:- "Balanced 3S Lithium Cell Charger using the TP4056"https://youtu.be/rpRYNMrVCk0- The "ESP32 ESP32S For Wemos For Raspberry Pi 18650 Battery Charge Shield Board V3 Micro USB Port Type-A USB 0.5A For Arduino Charge" module:https://youtu.be/joAkJ9QA2bw

author: ledtester
author_rank: Super Contributor
timestamp: August 30, 2020, 07:44:34 am
content: An updated video to the battery charge shield board review:10 Battery Power Boards and “SuperPower” project (incl. selection table)https://youtu.be/-SJbdPvgQnE
12V to +/- 12V - Page 1
Forum section: electronics / beginners

author: Nickk2057
author_rank: Regular Contributor
timestamp: April 29, 2016, 02:48:09 pm
content: what i want to do is make a circuit to run a amplifier circuit like a TDA2050. but i see that it uses a + and - volt rail with center common. how do i achieve this?Thanks.Nick

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2016, 03:01:31 pm
content: for low current use, dc/dc converters would be the way.most audio guys hate those, though.otoh, the tripath or class-d you have in mind is already digital and extra dc/dc noise isn't going to hurtbest way is to go with a center tapped trafo. ct goes to gnd and the 2 ends go to a bridge rect, which gives you the plus and minus rails.you could also use 2 single ended FLOATING psu's and make a center tap; either at the ac level or at dc.finally, you could use a diode trick to convert a single winding trafo output into dual rail dc output, but it adds twice the amount of hum (half wave config, iirc) and under current draw, the hum gets even worse.

author: Dave
author_rank: Super Contributor
timestamp: April 29, 2016, 04:05:10 pm
content: Inverting switch mode power supply. Just set the frequency well above 20kHz and make sure that it never goes into pulse skipping mode.

author: danadak
author_rank: Super Contributor
timestamp: April 29, 2016, 07:11:49 pm
content: You can run that part single supply, primary drawback is need for largecap to DC isolate speaker from part. Datasheet shows this.Just a thought.Regards, Dana.

author: Zero999
author_rank: Super Contributor
timestamp: April 29, 2016, 10:44:04 pm
content: What are your power output requirements?If it's under a couple of watts you can use run the TDA2050 off a single 12V power supply.Otherwise why not simply buy an IC designed for single 12V operation such as the TDA2005, LM4950, LM1896 etc?http://www.ti.com/lit/ds/symlink/lm4950.pdfhttp://www.kitsrus.com/pdf/tda2005.pdfhttp://www.ti.com/lit/ds/symlink/lm1896.pdf

author: uncle_bob
author_rank: Unknown
timestamp: April 30, 2016, 12:13:54 am
content: HiThe simple answer is : buy a +/- 12V supply and use that. They are out there and it's the simple solution.A bit more complex: Spend $5 on a center tapped transformer (I just bought some at that price) and build a +/- 13 to 20V supply.Either way, it will be cheaper than trying to fiddle with DC-DC converters and then quiet things down.Bob

author: Nickk2057
author_rank: Regular Contributor
timestamp: April 30, 2016, 05:38:54 am
content: well really a DC-DC converter is the only way to go with me cause i am making a suitcase boombox with aiwa speakers in it.

author: jitter
author_rank: Frequent Contributor
timestamp: April 30, 2016, 09:06:20 am
content: Might I suggest you look into something likethis?It's rated to output +/- 20..32 V, in the lowest setting comfortably within spec for the TDA2050.Don't worry about the 350 W being overkill, they are most likely "Chinese Watts".Edit:You gotta love the Chinese for adding some important details:QuoteYeah right, Taiwanfamousbrand...What's that then, CrapXon?
12v to 3.3v logic lvl start oscillating  - Page 1
Forum section: electronics / beginners

author: bestrider14
author_rank: Newbie
timestamp: September 17, 2023, 10:30:26 pm
content: Hi,Im new here but I need your help. I try to implement a circuit that will detect if my 12v as been switch on via a STM32 but via a logic gate to block a NFET to be activated at the same time. my circuit have 3 input that comings from my STM32 (on my image is done by a switch). So 1 input active the PFET to give me 12v. An other input activate an NFET to connect the circuit at the GND. The last input allow me to put a low current 3.3v (5v on my image) to test a fuse. So I made a logic circuit that if the 12v and the 3.3v is active at the same time I cant activate the NFET. Before 1 of my input of my XOR gate was at the input of my PFET but after I realise, I think, that it will be safer if a really check after the PFET and see the 12v. And now ho boy when I try to simulate this if I active my PFET and NFET to blow the fuse my circuit start oscillating and I dont know why. Im sorry if my schematic is not clean. I try so many thing and is getting worst every time I try something new. (my complet schematic is done on Kicad). So its where the node TES all my problem begin, I done 1000x test so my resistor value, diode might be wrong in this now. (I made it on 5v on my image cause the simulation need 5v too see an logic high but on my real schematic im on 3.3v with the right logic IC.)thank you

author: bestrider14
author_rank: Newbie
timestamp: September 18, 2023, 02:31:04 am
content: I even try a simple voltage divider with a 100k, 36k resistor instead of the Zener and resistor. I still have the same result. I have a cap, it change nothing.Edit: Ok I found what cause the oscillation. When the NFET is activated the line between the 2 FET go to 0v so it disactivate the NFET and now the loop begin. So now I need to isolate this node to stay at 3.3v when the FET become active.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 18, 2023, 04:43:04 pm
content: oscillating how fast?

author: bestrider14
author_rank: Newbie
timestamp: September 18, 2023, 04:46:05 pm
content: On simulation I cant let it run cause the simulation crash. But I think if I could setup a low pass filter on the node TES it could work.

author: bestrider14
author_rank: Newbie
timestamp: September 19, 2023, 04:37:50 am
content: I almost get rid of my problem but I dont think this is the best solution. So in the 12v isolation I made a voltage divider to get my 3.3v after the Zener 6.2v. After in the pyro circuit (its 2x the same circuit) I add a resistor PYR_R15/R16 so it create a voltage drop there. so my logic see the voltage before the resistor so it keep the logic HIGH. In the screw terminal its where I put my igniter (1ohm and need 1.25A). The problem now its my resistor take a lot of power for almost nothing so that's why I think its not the best solution.

author: bestrider14
author_rank: Newbie
timestamp: September 21, 2023, 03:13:32 am
content: I put a flip flop problem solve.
12v to 5v usb multi port - Page 1
Forum section: electronics / beginners

author: Ranger14
author_rank: Regular Contributor
timestamp: February 25, 2016, 03:11:01 am
content: I want to build a dc-dc converter that can supply 5v 2amps to say 4 or 6 usb ports.. What would be the best way ?? I am a noob and trying to work out the best way . Also would it be better to make separate circuit per usb port or combine some ???Oh I want to build not buy if possible..Thanks

author: prawncrackers
author_rank: Contributor
timestamp: February 26, 2016, 08:31:29 am
content: id think its easy to use a dedicated buck converter IC for thisthis one is really famous but the is also a bit oldhttp://www.ti.com/lit/ds/symlink/lm2596.pdfive had a lot of wireless routers that have that IC converting 12v or 5v down to 3.3v or somewhere.i guess it would be easier just to just wire all the ports to one supply but i think you want to make each of them separate from the other so that a circuit fault in one port will not affect the others...build a working circuit first then lets explore the protection thing.
12VDC to 12V 3 Phase? - Page 1
Forum section: electronics / beginners

author: optionen100
author_rank: Contributor
timestamp: June 14, 2014, 09:15:32 am
content: Hello,I need to power a Power Steering Unit from an Fiat Punto.The motor has 3 phases and needs 12V.Sadly I dont have the CPU/ECU unit for it.So heres my question:How can I get 3 phases out of 12VDC?I cant find any data about it (I THINK it needs 12V and these motors usually need around 60A)Are there any Cheap (under 50€ ) solutions?(sorry for my english)

author: Legit-Design
author_rank: Frequent Contributor
timestamp: June 14, 2014, 09:28:54 am
content: Brushless motor controller? BLDC. Do you need to spin the motor or have it operating as electric power steering assist? Or is it some kind of stepper motor style?

author: Psi
author_rank: Super Contributor
timestamp: June 14, 2014, 10:01:31 am
content: Hobbyking sell lots of 3phase 12v 60+A ESCs for under your pricelimitHowever i'm not sure if they will work with the timing of your power steering motor, it's likely a bit different to a model RC motor.

author: optionen100
author_rank: Contributor
timestamp: June 14, 2014, 10:24:13 am
content: I was building a REAL RC Car.I used a simple 12V motor for steering.Now i got this steering assistant.Controlling it will be no problem-and its strong enought to steer on its own.Sadly I dont know what king of motor this is.http://www.reluctantmechanic.com/images/punto-steering/punto-steering-motor.jpg

author: Legit-Design
author_rank: Frequent Contributor
timestamp: June 14, 2014, 10:31:43 am
content: 3 phase wires and 5 wires for maybe hall effect position sensing?

author: optionen100
author_rank: Contributor
timestamp: June 14, 2014, 10:36:47 am
content: The other 5 wires are there to change polarity.There are 2 Relays in it. And 2x3 cables inside the motor short the left 3 cables= motor turns left...short the right....Thats how i will control it.Relayshttp://www.fiatforum.com/attachment.php?attachmentid=89419&d=1302976393Motorhttp://www.fiatforum.com/attachment.php?attachmentid=89418&d=1302976369
12vdc to 4.5vdc - Page 1
Forum section: electronics / beginners

author: rvprepperwayne
author_rank: Newbie
timestamp: September 28, 2015, 06:12:21 am
content: First time poster here but a long time watcher to the YT channel. I have a light that runs off of 6 AAA batteries but it runs off of 3 and the other 3 are in series. Here is a link to the light-http://www.harborfreight.com/household/lighting/four-head-led-under-cabinet-light-96794.htmlI would like to wire them into my RV 12v system but I need a way to drop the voltage down to 4.5 or 5v MAX. I scrap electronics for gold recovery and I keep all the parts that Is on a board in case I ever need something or want to tinker. I'm not electronics savvy by no means but I can fix some things that don't need major work. How and what can I use to drop the voltage down? I'm sure the draw is less that 1A. Thanks Wayne

author: Psi
author_rank: Super Contributor
timestamp: September 28, 2015, 06:19:41 am
content: Get one of those cheap stepdown DC/DC modules from eBay.They are like $3 and have a pot to adjust the output voltageThey are switchmode which is good. You want to avoid the opposite which is a linear regulator because it will get hot.http://www.ebay.com/itm/2pcs-DC-DC-3A-Buck-Converter-Adjustable-Step-Down-Power-Supply-Module-LM2596S-/200964337125?hash=item2eca686de5

author: rvprepperwayne
author_rank: Newbie
timestamp: September 28, 2015, 06:35:42 am
content: something like this one?http://www.ebay.com/itm/DC-DC-LM2596-Step-Down-Adjustable-Converter-Power-Supply-Module-1-3V-35V-LE-/251980864576?hash=item3aab3adc40or would this one be better-http://www.ebay.com/itm/5A-XL4015-DC-DC-Step-Down-Adjustable-Power-Supply-Module-LED-Lithium-Charger-/221888411623?hash=item33a99477e7

author: rvprepperwayne
author_rank: Newbie
timestamp: September 28, 2015, 01:12:01 pm
content: Ok I didnt see your link in the post. I did order one. Thank You for the input. Wayne

author: nbritton
author_rank: Frequent Contributor
timestamp: September 28, 2015, 04:42:16 pm
content: http://www.amazon.com/s/ref=nb_sb_noss?field-keywords=buck+constant
12Watt FU50 single ended mono block amp running from 12V DC supply??? - Page 1
Forum section: electronics / beginners

author: gb243
author_rank: Contributor
timestamp: April 02, 2019, 08:15:31 pm
content: Errr. No. So the heaters are lit up and the rest of the 12V powers a hidden semiconductor amp in each block. That is just blatant. Sold everywhere of course but for goodness sake.https://www.iwistao.com/products/iwistao-1pc-mono-tube-amplifier-fu50-power-stage-class-a-signal-ended-small-300b-12w-preamplifier-2-x-6j4p-hifi-audio?variant=42938228748
13.8v psu - Page 1
Forum section: electronics / beginners

author: Gazeddy
author_rank: Newbie
timestamp: April 13, 2014, 01:41:39 pm
content: been looking at building a 13.8v psu for my cb radio in the house. ive been looking at lm317 and using a pair of 2955 pass transistors to boost the output up to around 30a. ive seen various diagrams and schematics. the bit i dont understand is why the pass transistor goes pre reg instead of post reg?

author: Simon
author_rank: Unknown
timestamp: April 13, 2014, 01:43:21 pm
content: As far as I know they go in parallel to carry the current the reg can't handle. but the current sensing that keeps them conducting just right does go in front of the reg as far as i know, that way any voltage drops on resistors don't affect the output voltage.

author: Gazeddy
author_rank: Newbie
timestamp: April 13, 2014, 01:45:25 pm
content: ahh ok sort of makes sense now.
14W linear bench power supply - Page 1
Forum section: electronics / beginners

author: Wytnucls
author_rank: Super Contributor
timestamp: October 08, 2012, 11:27:23 am
content: Here is my first project:A compact linear bench power supply, based on the LM317. Limited to 14V and 1A.I still have to install a constant current limiter, but am a little unsure of how to do it, considering the lack of space in the enclosure.The first thing I want to do is to add a small push button on the front plate, to display mA on the same Volt LED display. Then limit the current to 1A with another LM317 in line with a 1 Ohm resistor.My question is: How would you implement a simple constant current feature in this particular case?

author: ptricks
author_rank: Frequent Contributor
timestamp: October 08, 2012, 12:04:30 pm
content: You got a lot in such a small space. You might be able to get enough space to add current limiting if you re-route some of the power wires. I noticed the wires on the power transformer seem to be crossed and look taught, might want to give some slack on that. Shorten all the wires to as short as possible and that would free up some space too. One other tip, you have the AC side of the power supply in different parts of the case, generally that isn't a good layout , it is best to keep all the mains stuff in one area so you can keep that isolated.The lm317 will work for what you need, it just requires a low ohm resistor placed somewhere it can keep cool.

author: Wytnucls
author_rank: Super Contributor
timestamp: October 08, 2012, 12:35:55 pm
content: yes, the wiring is a bit of a mess, to say the least. I will shorten and clean that up once the design is finalized.

author: Tepe
author_rank: Frequent Contributor
timestamp: October 08, 2012, 01:22:40 pm
content: It's an interesting enclosure and front panel. Where did you pick it up?

author: Wytnucls
author_rank: Super Contributor
timestamp: October 08, 2012, 01:51:33 pm
content: Conrad in Germany. Great for small projects.No screws, everything snaps into place.http://www.conrad.com/Half-shell-caseCadmium-free-polystyrene-%28L-x-W-x-H%29-135-x-95-x-45-mm-Red.htm?websale7=conrad-int&pi=523105&ireusocl=1

author: Wytnucls
author_rank: Super Contributor
timestamp: October 08, 2012, 02:05:11 pm
content: Here is the back of it:
15v 500mA ower supply questions - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: August 30, 2019, 04:39:56 pm
content: Hello guys, I want to know what is purpose of the transistor T3(BC547B) in this circuit. I understand it provides base current to the series pass transistor T5(2N3055). Also i want to know1. what is the function of transistor T4(BC557B) and T2(BC547B) and T1(BC547B)??2. Here D1 (1w,15V) is a zener diode?3.What is BZ1(24V) in this schematic?

author: Zero999
author_rank: Super Contributor
timestamp: August 30, 2019, 10:08:06 pm
content: T3 forms a Darlington pair, with T5T4 compares the reference voltage set by the potentiometer with the output voltage. it's in common base configuration. It turns T2 on, when the reference is exceeded by 0.6V, thus cutting off T3.Yes, D1 is a zener diode.BZ1 is a buzzer, which is turned on by T1, when a the current flowing through R1 exceeds a certain threshold, set by R1.
15V to 5V circuit modification (RC)? - Page 1
Forum section: electronics / beginners

author: BlueBill
author_rank: Regular Contributor
timestamp: February 03, 2015, 09:39:09 pm
content: The circuit below works great at 15VDC, what changes do I need to make to get it to operate at 5VDC. Should I just decrease the cap size by a factor of three? Ideally I'd like to use a 0.01µF cap and adjust the other resistor values accordingly.The input to the diode is from a comparator at 120Hz with a short negative going pulse width of 1.8ms and a high of 14.9ms. The comparator can sink 20ma.Thanks in advance.Bill

author: lapm
author_rank: Frequent Contributor
timestamp: February 04, 2015, 12:18:26 am
content: So input its that sort of pulses, what you need output from this circuit? Similar pulses? Also second pamps negative signal is going to have effect on where it will output high...

author: Kdog44
author_rank: Contributor
timestamp: February 04, 2015, 12:42:46 am
content: What is the output of the circuit suppose to look like?What is the second input to the most right op-amp?

author: BlueBill
author_rank: Regular Contributor
timestamp: February 04, 2015, 03:11:42 pm
content: Quote from: Kdog44 on February 04, 2015, 12:42:46 amI'll post the waveform today, as for pin 6 it's a trimpot (voltage divider).Here's the signal (yellow) I'd like to replicate at with a 5V supply. The purple trace is the pulse that pulls the diode to near ground.