hybridfree/eevblog-posts huggingface dataset:
Switch mode power supply problems. - Page 1
Forum section: electronics / projects

author: and101
author_rank: Contributor
timestamp: December 30, 2014, 12:53:07 pm
content: I am trying to design a 12V smart USB charger based around the TPS54394 step-down switcher from TI and I have run into a problem. I based the switching circuit off of a design from TI using their power supply workbench tool and it is supposed to work between 9V and 16V input. Up to 12V it works fine with a stable 5V output but above 12V the power output starts to get erratic with glitches like the ones in the screen shot I have attached from my scope. The higher the voltage gets the worse the output becomes. It also increases as the load on the output increases, with no load the output is smooth.The circuit also includes a 3V supply using the other half of the TPS54394 and this side of the supply is working properly but that could be due to the fact that it is only powering a microcontroller and bluetooth module so the current draw is only a few milliamps and possibly not enough to cause the erratic behaviour that the 5V side is showing.I don't have much experience with designing switching supplies, I normally use off the shelf modules so I am not sure if it is a problem with the circuit or the PCB layout. I have attached the schematic for the power supply part of the circuit as well as the PCB layout. Hopefully someone with a bit more experience in switching PSU design can tell me where I have gone wrong.

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 30, 2014, 03:05:03 pm
content: Hi,What frequency is the PWM running, and what are the full load currents?Robert

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 30, 2014, 03:35:52 pm
content: Hi And101,On page 15 of the datasheet, it says that a 1 uF ceramic capacitor must be connected between the VREG5 and GND pins for proper operation. It is recommended to use a ceramic capacitor with a dielectric of X5R or better.Robert

author: and101
author_rank: Contributor
timestamp: December 30, 2014, 04:33:08 pm
content: Hi RobertThank you, I added a 1 uF capacitor onto the VGREG5 and ground pins and it is now smooth on the 5V output.Next time I will read the datasheet instead of just believing that TIs webbench designs are correct.

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 30, 2014, 04:55:45 pm
content: Quote from: and101 on December 30, 2014, 12:53:07 pmTPS54394Fixed Soft Start : 1 ms, The erratic waveforms shows the controller resting itself, a short maybe ?700 kHz Switching Frequency, what's your frequency ?You show a 3D model, is your design on an actual PCB? if so post your rig.
Switch-Mode Supply Driving Servo Motors - Page 1
Forum section: electronics / projects

author: Fratink
author_rank: Contributor
timestamp: November 17, 2017, 03:34:03 pm
content: Hi All,We've been working on a design for a few months now and we keep coming across a potential stumbling block. We're building a robotic device for agricultural work, with 120V generators for power. Since we don't have much excess power we're also using switchmode supplies. We have 1750W 48V supplies (meanwell RSP-2000) that drive 4 motors each (2 steering, 2 drive). I'm hoping that by setting low acceleration profiles I can limit the problems but that might not solve everything. I'm curious if anyone has suggestions for how to deal with power regen and motor startup?Some other info:Total vehicle weight: 500kgDrive motors (4): Allied Motion EMI-095G9004 (750W)Drive gear reduction: 67:1Steering Motors (4): Moog Animatics SL17406DSteering Reduction: 100:1Top Speed: Maybe 2m/s

author: fourtytwo42
author_rank: Super Contributor
timestamp: November 17, 2017, 05:21:14 pm
content: Quote from: Fratink on November 17, 2017, 03:34:03 pmI should think that is going to be very dependent on the motor controllers but you dont mention what your using ?

author: Fratink
author_rank: Contributor
timestamp: November 17, 2017, 05:46:27 pm
content: The motors are actually integrated controller types, so each has a CANOpen interface directly on the motor. I'm using that for vehicle-wide control.I guess I'm just curious about what strategies people usually take when dealing with regen power and switchmode supplies. I've read about using batteries, capacitors, or voltage level triggered shunts, but I'm not sure what would make the more reliable system.

author: jmelson
author_rank: Super Contributor
timestamp: November 17, 2017, 08:39:31 pm
content: Quote from: Fratink on November 17, 2017, 03:34:03 pmAt low speed, although the motors may be drawing a lot of current, the switching motor drives (You ARE using a motor drive, right, not just connecting the motors to the 48 V supply with a relay??) will draw low current. With a switch-mode motor drive, the power IN is slightly greater than the power OUT. So, with a modest acceleration profile, the peak current can be limited.Jon

author: Fratink
author_rank: Contributor
timestamp: November 17, 2017, 10:13:11 pm
content: Haha, no, I'm not just connecting the motors to a relay, that would end poorly. They're fully smart servo motors with integrated drive electronics. You basically just tell them the motion you want and they'll handle the commutation of the brushless motor to create that motion profile.
Switch Question - Datasheet Incomplete (I think) - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: January 10, 2024, 01:47:28 am
content: Recently I obtained a none working Variac. The fuse was good, windings didn't look burned (I assumed the fuse would have blown before anything smoked anyway), and power switch light was illuminated. I measured the wires on the output receptacle and found they didn't have any voltage on them (I initially thought the receptacle was broken.In any case, at this point, I sensed the switch was bad, so I replaced it with a spare from the same model Variac that was junked months ago due to taking a fall, and it worked.The original switch is part number (no manufacture shown on switch): QY603-101 T125. The replacement switch is from Soken and is part number: RK1-15I tried finding the datasheet for the broken one without success and resorted to assuming the switches are the same since they came from the same model Variac, same footprint, etc... but the datasheet I found for the Soken didn't have a pin out.Since the switches are the same footprint, and came from the same model Variac, I really don't need a datasheet, but I'm interested to know how someone would know which way to wire this (without measuring) since the pins aren't labeled; nor does it show on the datasheet.It's wired with one of the outer pins as hot from the input plug, the middle pin is hot out to one side of the windings (when the switch is closed), and other outer pin is neutral to the output receptacle/input plug/other side of the winding.
Switch spark on turn on - Page 1
Forum section: electronics / projects

author: laejf
author_rank: Regular Contributor
timestamp: December 30, 2020, 10:21:59 pm
content: How do I avoid sparking in my cheap slide-switch when I turn on the circuit? Is it a sign of too large capacitance? It does not spark when turned off.

author: bob91343
author_rank: Super Contributor
timestamp: December 30, 2020, 10:26:26 pm
content: The problem is that C1 draws a lot of current when you connect power to it. You can add an inductor in series with the switch but then you may have sparks when you switch it off. Add a resistor if you can afford the voltage drop.

author: laejf
author_rank: Regular Contributor
timestamp: December 30, 2020, 10:33:53 pm
content: Perhaps a charge resistor for the cap with a parallel discharge diode? Never seen that being used really so perhaps there are more elegant solutions. Thanks

author: bob91343
author_rank: Super Contributor
timestamp: December 30, 2020, 10:47:35 pm
content: That won't work. The capacitor needs to charge and discharge frequently so a diode will not allow that. A series resistor will destroy the capacitor's function; it needs to be low impedance.

author: jaycee
author_rank: Regular Contributor
timestamp: January 03, 2021, 02:41:02 pm
content: Do exactly what you would do to spark suppress a relay. Put an R-C snubber across the switch terminals.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 03, 2021, 02:46:24 pm
content: Quote from: jaycee on January 03, 2021, 02:41:02 pmThe damper does not save from the charging current of the capacitor.

author: jananetha
author_rank: Newbie
timestamp: January 05, 2021, 08:34:06 am
content: Finally what is the best method to suppress the sparks

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2021, 10:40:41 am
content: Quote from: laejf on December 30, 2020, 10:21:59 pmAs you've said, it's a sign of too larger capacitance. The data sheet for the LM1117 shows a 10µF, on the input, and you are using 470µF.https://www.ti.com/lit/ds/symlink/lm1117.pdfWhy are you using 470µF, rather than 10µF? If it's powered from a power supply, with a lot of ripple, such as rectified mains frequency AC, then put the switch between C1 and your circuit and use another, lower value capacitor, right next to U5 and U6. If the wires to the switch are short, you can use an even smaller capacitor than 10µF.

author: laejf
author_rank: Regular Contributor
timestamp: January 05, 2021, 12:16:26 pm
content: I thought that it couldn't hurt having a large tank-capacitance, especially for the DC-motor/pump. The power supply has a bit of ripple, but I could try a smaller capacitor. Thanks!

author: laejf
author_rank: Regular Contributor
timestamp: January 05, 2021, 12:30:21 pm
content: I replaced the 470u cap with a 10u and now there is no sparking!Thank you for the help!
Switchable Input Resistance - Page 1
Forum section: electronics / projects

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: March 15, 2021, 04:35:29 pm
content: Please find attached schematic snippet of THS4531A fully differential amplifier. I’ve used this part in many designs as an ADC driver.A new project requires a switch-able input impedance. My attached schematic has a flaw though, the Q9/Q11 transistors will conduct thru body-diode with negative input voltage on PREAMP_M/PREAMP_P nets.The signals seen on PREAMP_M & PREAMP_P are ground centered, with a +-2.5Vpp max swing (I know this signal level will clip on outputs of THS4531A, that’s okay). I AC couple the inputs because I need some HPF.Does anyone have any clever ideas or ICs that would allow me to completely isolate the input resistors without requiring bipolar power supplies? Everything on the board is unipolar, and I don’t want to have to add a second supply.The design is quite space constrained – I would like to stick to a similar SOT23 size of BSS138K if possible.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: March 15, 2021, 05:01:21 pm
content: Without knowing other constraints an analog switch should work:https://www.digikey.com/en/products/detail/on-semiconductor/NL3S22SMUTAG/6684813It seems to take less space than your 2-transistor solution at around the same total cost. I does seem to specify analog input down to -2.5V.

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: March 15, 2021, 05:06:41 pm
content: Quote from: Tomorokoshi on March 15, 2021, 05:01:21 pmSlick part, thanks! I need signal bandwidth up to ~256kHz (ADC sample rate is 512kHz). The THD plot in spec sheet only goes up to 100kHz. I suspect it's probably okay, but not sure.

author: gamalot
author_rank: Super Contributor
timestamp: March 15, 2021, 05:25:18 pm
content: Try 2 MOSFETs back to back.

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: March 15, 2021, 06:03:15 pm
content: Quote from: Evan.Cornell on March 15, 2021, 05:06:41 pmThe ON Semi hint led me to peruse their other offerings with "negative swing", and they have another part showing bandwidth >200kHz:https://www.onsemi.com/pdf/datasheet/nlas2750-d.pdf.TI also has something similar in TS5A22362.Thanks!
Switchable USB Hub - Page 1
Forum section: electronics / projects

author: dicky96
author_rank: Regular Contributor
timestamp: October 27, 2019, 11:28:45 am
content: Hi guysI bought this switchable USB hub thingy at the car boot sale this morning. To be honest I don't know why I bought it, I don't have any particular use for it, it just looked kinda.... cool... and I had 5 euros lying around in my pocket.Now I don't have 5 euros - I have this thing instead lolIt has 7 individually switchable USB sockets and an external PSU connectorSomehow I think this must be useful around the workshop but I have no clear idea why it would be lol.Any ideas (good or otherwise) what it would be really useful for?

author: soldar
author_rank: Super Contributor
timestamp: October 27, 2019, 06:52:05 pm
content: I suspect that is not really a data hub but just a bunch of USB charging ports. Can you confirm that?

author: dicky96
author_rank: Regular Contributor
timestamp: October 27, 2019, 08:01:25 pm
content: No it's notMy PC detects it as Generic USB Hub.If I plug a flash drive in and then turn the corresponding switch, the blue LED over the switch turns on and it detects the flash drive and I can access it.If I then turn that switch off the light goes out flash drive disappears againWhat's this thing meant for?

author: soldar
author_rank: Super Contributor
timestamp: October 27, 2019, 08:10:10 pm
content: So it is a hub which can be used the same as any other hub with the added convenience that you can disconnect a device without having to physically unplug it.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 27, 2019, 08:17:32 pm
content: It only switches power. So self-powered devices still work.

author: dicky96
author_rank: Regular Contributor
timestamp: October 27, 2019, 10:49:25 pm
content: Quote from: soldar on October 27, 2019, 08:10:10 pmAgreedAnd for sure it's nice gadget for €5 and it lights up in blue over the switch(es) you turn a switch on and looks as cool as f#ck But why?
Switchable voltage doubler for AC square wave circuit - Page 1
Forum section: electronics / projects

author: aiq25
author_rank: Regular Contributor
timestamp: December 03, 2018, 05:24:51 am
content: Hi. I'm working on a voltage doubler using the capacitors on the output of the bridge rectifier. I found the attached concept online.I have a square wave output though, around 12Vpeak with 85% duty cycle as my AC source. I don't always need the voltage doubler, only when the input voltage drops. My idea is to use a MOSFET as the switch and switch in the doubler when I need it. My question is, since the body diode of the MOSFET will cause current to follow when I don't want to, can I use two MOSFET's (with the body diodes pointing at each other, so that one it will cancel out) or is there an easier circuit I can use?I have tried this circuit in SPICE and it seems to work but I'm worried about the real life implementation of it. My goal is to be able to boost the voltage and power around 50W load. The input will be a battery with voltage range 6-12V. I want the doubler to work below 9V.Any feedback is appreciated.

author: JackJones
author_rank: Regular Contributor
timestamp: December 03, 2018, 05:45:19 am
content: Using dual MOSFETs is a common configuration for switching AC. You do need an isolated driver for the gate though. They do make photovoltaic drivers just for that.Why not just use a relay though? Would be much simpler to implement.

author: aiq25
author_rank: Regular Contributor
timestamp: December 03, 2018, 05:57:11 am
content: Quote from: JackJones on December 03, 2018, 05:45:19 amThanks.I'm using MOSFET's to create the square wave, so it's easier to use just those (one less part count). I agree relay is easier to use though.
Switched capacitor filters  - Page 1
Forum section: electronics / projects

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 20, 2020, 10:11:51 pm
content: Just a curious question;Is anyone here actually still using switched capacitor filters?I remember when I first played around with the MF10, and felt it was the best thing since sliced bread.National and many other started to offer a large portfolio of devices, but nowadays the offerings have been pared down.Are they still viable building blocks?

author: tggzzz
author_rank: Super Contributor
timestamp: October 20, 2020, 10:20:29 pm
content: Quote from: schmitt trigger on October 20, 2020, 10:11:51 pmThe Tayloe mixer (as used in SDR dongles) is one form of switched capacitor filter.Apart from that, the relentless improvement in ADC speed/resolution means that it is often easier to filter samples in the digital domain.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 20, 2020, 10:20:45 pm
content: I would say their heyday is firmly in the past...https://www.tinaja.com/glib/muse91.pdf

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 21, 2020, 12:18:49 am
content: Quote from: Alex Eisenhut on October 20, 2020, 10:20:45 pmThat is my feeling, based on the reduced availability of types.Regardless, I feel a little nostalgic about this nifty building block.A similar fate occurred to the bucket-brigade devices. Nowadays audio delays and reverbs are implemented in DSP.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 21, 2020, 01:45:33 am
content: I would be perplexed and nonplussed if I saw one in a modern design. For hobby stuff, have at it!

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 21, 2020, 03:15:11 am
content: Agree, OK for hobby use.Because isn’t that what a hobby is all about? Indulging in obsolete technology for the sake of it?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 21, 2020, 10:15:35 am
content: Why would you want something discrete-time that you can't reprogram endlessly -- like a DSP?They're good for fixed filtering applications with monolithic integration I think, and the clock variable response is a neat trick -- but other than that, I don't think there's much point. With DSP-capable MCUs being so common these days (yes, even the humble ATMEGA is capable of a small amount of DSP) I'd much rather plop in one of those.Tim
switched capacitor power supply - Page 1
Forum section: electronics / projects

author: sagnikbasu
author_rank: Contributor
timestamp: February 07, 2017, 02:58:03 pm
content: How can we control the output voltage in switched capacitor power supply ? Is it by adjusting the switching frequency ?

author: Kleinstein
author_rank: Super Contributor
timestamp: February 07, 2017, 03:38:37 pm
content: Usually the no load output voltage of a switched capacitor supply is fixed. That is there is a fixed ratio (usually integer or simple fraction) to the input voltage. Usual factors are 2, -1 and 0.5. Only under load the voltage will change significant with a frequency change. The frequency has a direct influence on the output resistance and thus the voltage drop due to a load current.

author: David Hess
author_rank: Super Contributor
timestamp: February 07, 2017, 11:29:15 pm
content: The output voltage is adjusted via pulse frequency modulation or by operating in burst mode. Check out figure 23 on page 16 ofLinear Technology application note 3for an example of a 5 volt 1 amp switched capacitor voltage regulator.
switched current limiter - about 10A - Page 1
Forum section: electronics / projects

author: rr100
author_rank: Frequent Contributor
timestamp: May 06, 2013, 10:05:06 am
content: Hi, I need some ideas/links about a really small and dumb project. Basically I want to charge a 12V lead-acid battery from a 20-30V DC supply, without burning too much energy in the process. Not interested in charge termination/voltage limiting, just the charge current should be limited at something like 8-10A (and sure I'll use fuses but I also want the design to be as bulletproof as possible).I have some schematics in mind but I don't have the needed FET and inductor anyway right now so if there's some part that's best suited for this I'll appreciate any pointers. Ebay links are welcome as well, I've seen some LED drivers but they are either for much smaller currents or really expensive.

author: G7PSK
author_rank: Super Contributor
timestamp: May 06, 2013, 10:33:14 am
content: You can get DC to DC converters on ebay that will do what you want for about £5-00. I use a boost one to charge a 24 volt wheel chair in a car, its rated at 150 watt as is and greater with extra cooling so I put a small fan in the box. Both boost and buck are available.

author: rr100
author_rank: Frequent Contributor
timestamp: May 07, 2013, 09:49:10 am
content: I have as well some DC-DC converters but they don't really do what I want. I might be able to tweak them to do constant (or limited) current instead of voltage but I'd rather have something simpler, bulletproof and especially designed for this application.

author: envisionelec
author_rank: Frequent Contributor
timestamp: May 07, 2013, 03:32:07 pm
content: Quote from: rr100 on May 07, 2013, 09:49:10 amI think you're going to find this is a rather specialized application that will require the tweaking of another design to get what you want. You're after a current controlled (aka Current Mode) SEPIC or Buck/Boost power supply. I just did one based on the newer Linear Tech LT3862, but it's a Step Up (Boost) design. Very reliable. You'll find something similar.
switched preregulated 500V DC tube powersupply 1963 - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 20, 2023, 10:02:49 am
content: i am sure you will enjoy to see thisfantastic design by Danish Radiometer from 1963 a few transistors and diodes, but the rest is tube based, a few cool design ideas in this one : pre-regulator done using PL6574 tetrode thyratron, this means the main series regulator E235L power pentode can deliver a lot of power much colder.https://youtu.be/bSxdYC324E0
Switched Regulator, Frequency settings - Page 1
Forum section: electronics / projects

author: luiHS
author_rank: Frequent Contributor
timestamp: June 14, 2019, 10:40:40 pm
content: Hello.I am using recently the LM25085, to replace the XL4015 and XL4016.I only have a problem. At 12v input, the voltmeter of the power supply varies constantly and rapidly (mA and tenths of mA). If I raise the voltage to 18v that problem ends. In addition, to 12v, approaching the ear to the circuit you hear a hum or continuous beep.I put the oscilloscope and I see a signal of about 400Hz mixed with the DC, it is very dim but it affects the circuits that I connect the regulator.I used the Texas configurator, which works quite badly because every time you enter, with the same configuration, it gives you different values ​​for the input capacitor, even for another circuit capacitor. According to the configurator, for the frequency I selected (the one offered by default) I was instructed to put a 15uF capacitor, but I finally put 3 x 10uF in parallel. But sometimes you go into the configurator, and it tells you to put 3 x 15uF (in parallel I understand), if this is the right thing, my 30uF could be the problem.Is it possible that the malfunction is due to the low capacitance of the input capacitor? I have thought of putting another two or three capacitors of 10uF in parallel, to rise to 50 or 60uF.On the other hand, I thought about raising the frequency of the oscillator to 700 or 800Khz, so the inductor will be much smaller and cheap, and I could put it on a Reel in my Pick and Place machine.What advantages and disadvantages does the oscillator of a switched regulator have to work at a higher frequency? As advantages I see that the inductor is smaller, of value and size, also cheaper if the size is reduced.
Switcher pre-regulator + LDO or just switcher? - Page 1
Forum section: electronics / projects

author: shadewind
author_rank: Frequent Contributor
timestamp: March 19, 2011, 04:00:34 pm
content: I'm powering an ARM MCU (TI/Luminary LQFP thingie, among some other things) from 9V - 12V (somewhere around there) and I'm wondering what the best way is to do this. My first thought was to simply use an LM2675-3.3 switcher to simply bring that down to 3.3V. But then I'm starting to think I might want +5V on the board as well.Is using an LM2675-5.0 for the +5V and then an LDO to 3.3V a good idea for this? If so, any LDO you can recommend? If I didn't want 5V, would there still be a point in using an LDO for cleaner power for the MCU?

author: Simon
author_rank: Unknown
timestamp: March 19, 2011, 05:08:52 pm
content: 5t all depends on the conversion efficiency you require and the current draw, if you only need a few mA at 5V then just use a regular linear reg from the 9/12V supply. more information will help make a better recommendation on your supply "logistics"

author: AdShea
author_rank: Contributor
timestamp: March 19, 2011, 05:30:51 pm
content: Do you have analog stuff on any of the rails? If so, I'd usually use a linear regulator and a few ferrites for those rails.

author: Zero999
author_rank: Super Contributor
timestamp: March 19, 2011, 06:27:40 pm
content: Yes, it depends on what you're doing.Where are you getting 12V from? If it's an automotive system and only powered when the engine is running and you need under 0.5A from both 3.3V and 5V, you might as well just use a linear regulator for the whole thing.
Switches - Page 1
Forum section: electronics / projects

author: Jazzyrick
author_rank: Newbie
timestamp: February 26, 2024, 12:46:26 am
content: I'm working on a timer of sorts...just design as I am not an engineer. Here's the premise.Picture a LCD watch/timer, but mounted to a hard surface. Basically I'm looking for a switch/mechanism to activate momentarily when you press the entire watch/timer. Is this a specific type of switch that exists or more than likely there are many ways to skin this cat?

author: Jazzyrick
author_rank: Newbie
timestamp: February 26, 2024, 12:49:47 am
content: Preferably as low a profile as possible and with some tactile feedback...like a click sound, but looking for all ideas.

author: aeberbach
author_rank: Regular Contributor
timestamp: February 26, 2024, 01:05:14 am
content: 3d print a mount for your timer that is hinged to a base, sits atop a microswitch (with appropriate extra spring to compensate for weight - though may not be needed)?
switches  - Page 1
Forum section: electronics / projects

author: merlin
author_rank: Newbie
timestamp: November 13, 2016, 05:00:58 pm
content: hi there i would like to know if its possible to ha key have 4 key switches and a number key bap to work togetherbasically you have to turn all 4 within 3 seconds or so witch can then power the key pad where i can enter a 6 digit pin witch can then power a relay until the key switches are turned offbut if all the switches were NOT turned on at the same time or within 3 seconds or so system will need a restart to work again and would be nice to have like an emergency witch when pushed it re-locks the system in a seance (basically when the button is pushed it will unpower the relay and require a restart to try and work again) i would also like a failsafe feature were the system will not start unless allswitches are off if you need any more info pleas ask
Switching 12v 5a load  - Page 1
Forum section: electronics / projects

author: kamaangir
author_rank: Contributor
timestamp: March 29, 2016, 12:38:56 am
content: HiI would like to build a programmable controller to switch 8 relays (about 5a 12v) in different sequence. I have an arduino mega but could use any other micro or any other circuit. I would like to vary the sequence of the relays energising, all 8 outputs need to activate from less than a second to 5 seconds ( I would like to control that also)My question is whether to use relays or mosfets?I have had a look and could not see a project like this using an arduino.Many thanks

author: ez24
author_rank: Super Contributor
timestamp: March 29, 2016, 12:43:50 am
content: My vote - solid state relays

author: rx8pilot
author_rank: Super Contributor
timestamp: March 29, 2016, 12:56:50 am
content: SSRs are MOSFETs with a controller. How much do you want to design/build/troubleshoot? An SSR is super easy and not hard. Building a custom circuit is more of a challenge, wil probably take longer and might blow up a few times. Once you get it through, it feels pretty good.Sent from my horrible mobile....

author: digsys
author_rank: Unknown
timestamp: March 29, 2016, 01:07:19 am
content: Quote from: kamaangirA nice logic-level FET (NPN) with LOW Rds-on, say 10mR ish. A nice S/Mount package. Perfect ! No bulky items, no contact arc or switching delay, no ageing,and NO noise.

author: kamaangir
author_rank: Contributor
timestamp: March 29, 2016, 01:09:26 am
content: Thanks for the replies, I have about 3 ssrs somewhere from a previous project, just need to buy some more.I would like to get it working using a micro so I can program them to energise in different sequence.
Switching an unknown DC voltage with a LVTTL signal - Page 1
Forum section: electronics / projects

author: hamster_nz
author_rank: Super Contributor
timestamp: June 24, 2020, 10:07:23 pm
content: What is a good way to switch an known DC voltage (between 2.4V and 24V) with unknown polarity using a 3.3V CMOS logic signal? The controlled signal will usually be driving low voltage DC motors. If the polarity was known I would just use a logic level MOSFET.A relay would be the ideal, but energizing it uses too much power - I want to drive it for many hours from a CR2032 cell.

author: langwadt
author_rank: Super Contributor
timestamp: June 24, 2020, 10:29:50 pm
content: Quote from: hamster_nz on June 24, 2020, 10:07:23 pmif you supply is isolated, back-to-back mosfets?or maybe a latching relay?

author: hamster_nz
author_rank: Super Contributor
timestamp: June 24, 2020, 10:57:52 pm
content: Quote from: langwadt on June 24, 2020, 10:29:50 pmSupply is definitely isolated (battery powered device). So something like this attached schematic?Hummm - can't see how I would reference the 'smart switch' to the load being switched...

author: langwadt
author_rank: Super Contributor
timestamp: June 25, 2020, 02:34:58 pm
content: Quote from: hamster_nz on June 24, 2020, 10:57:52 pmbasically this:https://www.homemade-circuits.com/wp-content/uploads/2020/01/SSR-concept.pngthe two sources are "ground" for your control circuitry

author: hamster_nz
author_rank: Super Contributor
timestamp: June 25, 2020, 09:43:35 pm
content: Quote from: langwadt on June 25, 2020, 02:34:58 pmPerfect. Thanks for your help.
Switching between two voltage sources for LDO - Page 1
Forum section: electronics / projects

author: pebcac
author_rank: Contributor
timestamp: February 10, 2023, 10:07:55 pm
content: Hi folks, I'm designing a circuit that powers an ESP32 and some peripherals from USB-PD, which starts out at 5V but can go up to 20V to power a boost converter for a battery pack charger.The ESP32 takes in 3.3V and I have a fan that takes 5V. Currently, there's an XL1509 5V buck converter (1.5V dropout) from USB-PD VBUS which can be 5-20V. From the 5V output, I've put an AMS1117 3.3V LDO (1.1V dropout) for the 3.3V.At 20V, the supplies should work as intended. However at 5V, before the 20V USB-PD negotiation is done, if the buck IC drops 1.5V and LDO drops 1.1V, we'll have 2.4V out of the LDO, which is too low for the ESP32 and other 3.3V peripherals.I've thought of some alternatives:-Use a lower drop out buck IC and LDO--I'd like to stick with the XL1509 and AMS1117 because they're considered basic components so JLCPCB doesn't require a $3 surcharge.-Use a one buck IC for 5V from VBUS and another buck IC for 3.3V from VBUS--I don't know how good the line regulation XL1509 has when jumping from 5V to 20V, so I'd like to have an LDO after the buck converter.Is there a BJT/FET circuit that can switch from USB VBUS when it's at 5V, to the XL1509 5V output when VBUS jumps to 9/15/20V? I was thinking a PFET switch driven by an NPN BJT biased with a 5.6V zener but didn't end up going far.The ESP32 will be triggering the voltage change so it can drive the switch circuit, but I'd prefer a discrete solution without the ESP32.Let me know what you guys think!

author: Hiemal
author_rank: Regular Contributor
timestamp: February 12, 2023, 02:44:12 pm
content: IIRC, the dropout voltage of a regulator isn't necessarily the voltage it drops by itself; it's the voltage required by the device to maintain regulation, and with that regulation, all of the other associated things go out the window with it. So you'd lose out on PSRR, accuracy, noise reduction, etc.That being said, if the supply itself is already fairly well regulated, then you might not have a problem at all. It's something you'd have to experiment with and see how it performs in regards to current output and voltage drop.Otherwise... buck-boost converter/sepic/cuk might be good.

author: pebcac
author_rank: Contributor
timestamp: February 15, 2023, 08:45:04 pm
content: Thanks, I've decided to go with the Torex XC6206 LDO instead of the AMS1117 because it has a much smaller dropout voltage of 200mV due to the use of a FET instead of a BJT as the regulator.With 1.5V drop from the buck and 0.2V from the LDO, we should have enough headroom for 3.3V out.
Switching Boost converter drops voltage when connected to the load. - Page 1
Forum section: electronics / projects

author: Pariston
author_rank: Contributor
timestamp: December 03, 2021, 08:19:20 pm
content: Hi,I am working on the boost converter circuit (5 to 9 Volt) and having some difficulties. Open circuit voltage is set at 10-11 Volt. At the same time, voltage drops to 4.5 Volt when connected to the 100-ohm load. I've attached some schematic and scope pictures.Related components:Boost IC: PAM2423 (https://media.digikey.com/pdf/Data%20Sheets/Diodes%20PDFs/PAM2421,22,23.pdf)Inductor: PQ2614BHA-6R8K (6.8uH, +-10%, Saturation Current 34.5A)Schottky Diode: SB240-E3/54 (Forward voltage 0.5V)I would appreciate some help.

author: eblc1388
author_rank: Frequent Contributor
timestamp: December 04, 2021, 02:51:51 pm
content: At a glance I would say the main problem will be the DIP-8 IC adaptor PCB. It has very thin PCB trace to connect between the IC and the 8 DIP pins on the breadboard. Secondary problem would be testing such SMPS on breadboard in general instead of layout a proper PCB according to manufacturer's recommendation.If you are just testing the design as a quick proof of concept only, you could try soldering wires directly to PAM2423 IC pin1 for supply negative and 2,3 for supply positive. This will greatly improve the situation. However, this cannot eliminate the effect of the thin PCB traces between the power inductor connections. The best way is to solder wires also to the inductor and connect them directly to the IC pins.

author: Pariston
author_rank: Contributor
timestamp: December 04, 2021, 06:53:10 pm
content: Thanks a lot. Took me some time to solder all the components in the midair, but performance improved drastically.
Switching circuit for a power supply - Page 1
Forum section: electronics / projects

author: BRetonDP
author_rank: Contributor
timestamp: May 22, 2015, 12:47:58 am
content: Hello, EEVBlog community!I am currently building a very cheap power supply which I want to have backed up by a 5V power bank.I was going to use an integrated circuit that did the switching for me, and I found the LTC4412, which is exactly what I'm looking for but in a very inconvenient package (I am using DIP and that comes in TSOP-23, which is way too small). The datasheet of the IC can be found here.http://cds.linear.com/docs/en/datasheet/4412fb.pdfI'm only going to be handling 5 volts. Do any of you know of another integrated circuit (or a circuit I can build) which does approximately the same and comes in an easier to handle package? Thanks in advance!

author: BRetonDP
author_rank: Contributor
timestamp: May 22, 2015, 01:06:31 am
content: Hey, evb149. Thanks for your reply. The currents I will handle are well below 1A, so I think it wouldn't hurt me to try the diodes.And true, the packaging isn't so bad, but I'd rather work with something else; I don't really want to risk damaging the IC by accidentally burning a pin off or something.
Switching circuit with input clock - Page 1
Forum section: electronics / projects

author: sri2014
author_rank: Newbie
timestamp: June 11, 2020, 06:18:01 am
content: i have attached the timing diagram. I want something similar to monostable multivibrator but with so additional features. don't know how the circuit will be.Case 1:I want the output to go high at the rising edge of the input, output stays high as long as the input is high but output will be pulled down after 500ms even if the input is high.Case 2:Output should go low if the input is less the 500ms, i.e. if the Input is of 300ms the output will also be of 300ms.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 11, 2020, 02:29:03 pm
content: If I get it right, what you want is basically some pulse width limiter.One simple way of achieving this with discrete parts would be to just "AND" the output of a monostable with the input signal.

author: Benta
author_rank: Super Contributor
timestamp: June 11, 2020, 05:32:03 pm
content: CD4538/MC14538 set up as edge triggered MMV, plus an AND gate at the output.
Switching controller that goes above and bellow Vin? - Page 1
Forum section: electronics / projects

author: Korken
author_rank: Regular Contributor
timestamp: May 09, 2013, 02:43:46 pm
content: Hi all!I've been working on a PSU where I need a switching controller that can with one inductor go above and bellow Vin.I've been searching night and day but I'm unsure of what this type of switching controller is called so I'm unable to find one on Digikey.Could someone help me with a push in the right direction?If possible I'm looking for one with internal witching transistors and one with external.Regards, Emil

author: oPossum
author_rank: Super Contributor
timestamp: May 09, 2013, 02:51:49 pm
content: SEPIC: Single ended primary inductor converter

author: aep9690
author_rank: Regular Contributor
timestamp: May 09, 2013, 02:52:26 pm
content: I think you are looking for a buck boost converter. It can either boost a voltage above VIN or buck it down below. They are typically used for uncertain input voltages but I think it will work for what you want as well.http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converterhttp://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=753&uiTemplateId=NODE_STRY_PGE_TThere are also other solutions such as SEPIC or Cuk converters
Switching device address lines of I2C EEPROM? - Page 1
Forum section: electronics / projects

author: c4757p
author_rank: Super Contributor
timestamp: February 16, 2015, 05:55:11 am
content: I'm working on a system with multiple cards on a backplane, and I'd like to put a small EEPROM on each one to identify the card and, in some cases, provide some calibration memory for it. The easiest seems to be the usual cheapo I2C EEPROMs. Problem is - with six slots, I can't assign all of them an address (even if they had enough address lines - some do, though most have only two - I don't have the available pins on the backplane). I do haveoneline available on each slot that I could use to individually address its EEPROM. Obviously, I could put a switch on the I2C lines to completely gate them, but it might be easier.Can I just tie this line to one of the address bits, so that only the selected device will respond to the address I call out? That is, changing the device addresses and calling out the same address, rather than keeping the addresses static and calling out different addresses. None of the datasheets seem to indicate whether there is any latching on those pins, or for that matter anything resembling a delay after changing their values, because they obviously don't intend you to do this. Butcanyou?

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: February 16, 2015, 07:11:11 am
content: it's seem totally possible to me, anyway i simulated that with 24LC512 and it work.

author: Christopher
author_rank: Frequent Contributor
timestamp: February 16, 2015, 06:23:46 pm
content: Why not bring the address lines out to the backplane and set each backplane connector an address?

author: c4757p
author_rank: Super Contributor
timestamp: February 16, 2015, 06:25:18 pm
content: Lack of pins, I said that. I'm trying to "abuse" an existing control signal so I don't have to find space for some more pins if I don't have to.
switching gain with 4052 multiplexer on audio output - Page 1
Forum section: electronics / projects

author: jmibk
author_rank: Regular Contributor
timestamp: June 06, 2020, 07:52:38 am
content: I'm designing a dsp board and like to have a switchable gain output, schematic for two outputs in the link down there:http://www.audiowerk.at/downloads/temp/eev/dsp_output_stage/Schematic_ADAU1701_4x4_2020-06-06_09-39-04.pdfVOUT0 and VOUT1 are voltage outputs of an DAC, 0 - 3,3V, zero line is on 1,65V.MPXo1_0 and MPXo1_1 are coming from an 74HC595 shift register that is controlled by an mcu.Now the problem - maybe I oversee something (just mention channel 1, other have the same problem):- feeding the system with a 1kHz sinewave- CHo1_0 views the sinewave at it should- CHo1_-10, CHo1_-20 and CHo1_+10 are either clamped on positive or negative rail dc, often fragments of the sinewave are visible, but mainly there is this huge dc offset.- If i short CHo1_0 to ground and open it after that, everything works as aspected.- changing the value of R80 to a smaller value like 200 ohms doesnt change anything.If I remove the 74HCT4052D (U5) the offset is gone, lines CHo1_-10, CHo1_-20 and CHo1_+10 are zero volts.Why does the 4052 pull the line to + or - 12V?I know that it is not ideal drive the OPs with 12V and the 4052 with 5V but it should do right if the signal isnt greather than 5V.Thanks for any hint or solution!

author: Kleinstein
author_rank: Super Contributor
timestamp: June 06, 2020, 08:30:50 am
content: The 4052 supplied with +-5 V should not cause clamping to 12 V levels.One may have to take care of the other channel - to high a voltage at channel 2 may also effect channel 1.CMOS MUX tend to be sensitive to latchup, if the voltage goes beyond the supplies. Transient on turn on could go beyond the planed +-5 V signal level. As a protection I would have resistors in the +-5 V supplies. The static supply current is very low, so some 10 K would not matter, but can limit the worst case current and the chip should recover from a latch up.There are a few not directly related points:The TL074 OPs don't like driving capacitive loads - even 2 m of cable can be too much. So there should be some series resistance (e.g. 50-100 Ohms) at the outputs.The circuit is rather low impedance. R80 is more like not needed at all. R118 - R120 already provides enough DC path to ground. R5 and R10 give quite some load to the switch. The switch on resistance is not that linear at higher current. So R5 and R10 should be higher value, more like >10 K each. Even than it would still effect the -10 dB setting a little (more like -11 dB).
Switching HV to a load with? - Page 1
Forum section: electronics / projects

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 13, 2017, 08:12:49 pm
content: So I'm looking to switch a HV source to a load, but otherwise remain in a infinite open condition when off. The load will be switched to ground, LV or HV or open.Think of a SP10T rotary switch.I've tried to work out the permutations in my head and on paper, but it all looks like an impossible feat. Does anyone have an idea on how to accomplish this?

author: daqq
author_rank: Super Contributor
timestamp: November 13, 2017, 09:28:13 pm
content: Depending on the requirements (and your budget) you may want to look at Behlke devices - basically high voltage (up to 150kV) solid state switches with insane parameters.http://www.behlke.com/

author: langwadt
author_rank: Super Contributor
timestamp: November 13, 2017, 09:32:11 pm
content: Quote from: Quarlo Klobrigney on November 13, 2017, 08:12:49 pmwhat voltage?

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 13, 2017, 10:20:11 pm
content: Too much in the amperage department, but nice stoof: "Look at Behlke devices"I'm looking for no more than 1KV at say 1/2 amp and less. A see-saw arrangement, i.e. low V high A, high A low V.If you folks don't think it viable, I may have to go to a switch...

author: whatsthegeek
author_rank: Contributor
timestamp: November 13, 2017, 10:43:48 pm
content: Hi, how fast would you need to switch the HV ?If it's doesn't need to be realy fast, you could just use a couple of HV relays (one to ground, one to HV and one to LV):http://www.gigavac.com/catalog/high-voltage-relays/single-pole-single-throw-SPST

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 14, 2017, 01:31:57 am
content: I followed the link, although no pricing is given and one must contact one of their sales reps (and answer all those questions) no thanks. However they do have a solution. I've been down the sales rep rabbit hole before and wasted lots of time to come up with "sorry no stock".As far as switching time, not fast at all. DC to 1 second. Not fussy at all.Quote from: whatsthegeek on November 13, 2017, 10:43:48 pm

author: texaspyro
author_rank: Super Contributor
timestamp: November 14, 2017, 05:51:33 am
content: Search Ebay for "high voltage relay". Here's a 5KV 10A relay. Looks like he has 98 of them available...https://www.ebay.com/itm/KILOVAC-H-4-S1-5-KVDC-HIGH-VOLTAGE-SPDT-RELAY-100-ohm-8-15-VDC-coil/261813426254?epid=1048349097&hash=item3cf54bd84e:g:PFgAAOSwNSxVBhuY