hybridfree/eevblog-posts huggingface dataset:
Switching Buck Regulator against Constant Current Driver. - Page 1
Forum section: electronics / beginners

author: Harsh Chandola
author_rank: Contributor
timestamp: March 09, 2017, 06:38:48 am
content: Hello All,I am designing a tube light that can switch between warm white, cool white and both warm and cool white depending on the way push button is pressed, single short press toggles between warm and cool white and long press turns both ON. For this circuit I am using Atmega328P as the micro controller to perform the task. The circuit I have designed will be fed with existing tube-light LED driver. Now the specification for LED Tube light would be in the range of 48-72 volts and upto 250mA for each cold white and warm white strip. My first hurdle is how to feed 5volts to Atmega328P chip. While I designed the circuit I didn't take into account the driver I'd cascade with my circuit would be a constant current driver. So assuming constant voltage driver I choseMAX5035 BUPA+Switching Buck Regulator that can regulate voltages up to 76 volts to 5Volt and rest of the circuitry is easy.Now suddenly I thought, I might have to use constant current driver and now I am confused about how will my Regulator be regulating voltage if it's constant current that comes out of the driver. Is there a simple work around that can be implemented.I'd be obliged if somebody explains me constant current drivers and constant current source's concept in detail and in almost layman's terms if possible, with schematic and all.Please find attached the schematic for my design.D1 and D2 are Zener diodes.Kind Regards,Harsh Chandola

author: danadak
author_rank: Super Contributor
timestamp: March 09, 2017, 11:56:41 am
content: The Atmega wants to be driven with a constant V. That takes care ofdevice to device and I/O load variation, eg. if load changes device Vstays the same, in spec.A constant I driver, for load changes, supplies a fixed current. LEDslike to be driven as constant I so that led to led in a given strip putout roughly same brightness, and are invariant to led to led manu-facturing parameter differences.Note your tube may incorporate internally a constant current driver.Hence its input, a V, feeds constant current driver input. Some reallycheap strips just use a R to effect a crude constant current. But LEDdevice threshold, led to led, vary all over the map.Regards, Dana.

author: Harsh Chandola
author_rank: Contributor
timestamp: March 15, 2017, 05:59:55 am
content: Quote from: danadak on March 09, 2017, 11:56:41 amI understand that, my other question is can I use switching buck regulator like MAX5035 to convert current to voltage and then snap it down to 5Volts so that I'll be able to power Atmega? Is that possible? or is there a work around to get that done?
Switching ground, but need to switch positive side - Page 1
Forum section: electronics / beginners

author: mickc
author_rank: Contributor
timestamp: October 28, 2018, 12:58:54 pm
content: HiI have some real aircraft cockpit warning lights that are in a flight simulator. These run on 28v DC, and are controlled by some USB cards that sink to ground to activate the light, ant the other side is powered with 28v.This is fine, and all works as it should, but there are some that use a different power setup, where they are grounded all the time, and use the 28v positive to activate the lamp.My USB boards can only sink to ground, not to the source. Also the warning lights have internal diodes for protection and the push to test function so I can change them.Bottom line is, what is the easiest way to change a low side switched circuit to a high side switched circuit? I have used small 28v relays for this in the past but thats quite tedious to wire into the panel.Im thinking some sort of transistor array etc? Each warning lamp draws 80mA at 28v DCOpen to any ideas, Cheers.

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2018, 01:19:52 pm
content: P-MOSFET, source to +28V, drain to load, and gate driven by the tap of a potential divider (2x 4K7) between +28V and your card output.

author: mickc
author_rank: Contributor
timestamp: October 29, 2018, 12:12:35 am
content: Quote from: Ian.M on October 28, 2018, 01:19:52 pmThanks Ian,Are there any P-Mosfet array chips available that you know of?

author: Ian.M
author_rank: Super Contributor
timestamp: October 29, 2018, 06:46:38 am
content: Nothing I've actually used. You could hit a major component distributor's parametric search and look for dual or quad P-MOSFETS with suitable voltage and current ratings, but I'd bet on the result being more expensive and far more difficult to lay out a board for than using individual 'jellybean' SMD P-MOSFETs and individual resistors, as you wont be able to simply layout one channel and clone it N times.
switching & ground isolation question - Page 1
Forum section: electronics / beginners

author: salviador
author_rank: Regular Contributor
timestamp: April 25, 2016, 12:03:42 pm
content: Hi,Looking various diagrams of swiching power supplies, I noticed that the ground of high-voltage is not completely isolated from the ground of the low voltage! But is coupled with capacitor!This a problem because when apply the ground of my dso (in "isolated low voltage") I have small earth shock!!!Why?Example of power supply

author: michaeliv
author_rank: Frequent Contributor
timestamp: April 26, 2016, 08:00:59 pm
content: Have a look at this:http://www.edaboard.com/thread207482.htmlhttp://www.arpnjournals.com/jeas/research_papers/rp_2010/jeas_0210_300.pdf

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 27, 2016, 09:09:44 am
content: The capacitor provides a path for high frequency AC.It should be a small enough value that you cannot feel the current flow.Sometimes, the capacitor is placed on the AC input side of the common mode choke. Sometimes, a common mode choke is also needed on the secondary side. The exact combination of chokes and capacitors, and their placement, is hard to figure out until testing.If you have a three-prong AC cord, the neutral wire should be consistent, and a capacitor to neutral should not deliver any ground leakage current. This would be a better location than across the transformer.Tim
Switching Lab supply design - Page 1
Forum section: electronics / beginners

author: Alakis
author_rank: Newbie
timestamp: February 06, 2024, 05:57:59 pm
content: Hello,I am in the process of designing a programmable 0-24V, 0-3A lab supply. I am planning to drive it from an existing 12-48V DC supply. I would like it to be a small form factor so I am thinking about a switch mode topology. I am a little bit confused on how to pick the inductor sizing for such a wide parameter range. Are there any simple to understand reference designs I could take inspiration from? Ideally they would have some sort of explanation attached to them as well.What I have planned so far:1) Input buck-boost converter taking input voltage and converting it somewhere near 24V (maybe a little more to adjust for possible drop out)2) CV part of the circuit, which I still haven't worked out well. I would take a reference voltage as input to convert the 24V to some desired level.3) CC part of the circuit, similar to the CV part, just controlling the max current.4) Current and voltage feedback would be done by some simple opamp circuits. For that, I am planning to add a split rail SMPS circuit. (something like here:https://www.digikey.at/de/articles/design-tips-for-generating-split-rail-power-supplies)5) I am planning on using an INA219 or some other IC to read the output voltage and current, this would be separate from the CV and CC mode monitoring, as I don't want to rely on MCU response time for controlling the output.6) MCU to communicate with PC via USB, display output values and control reference voltage DACs.I am mostly confused and need guidance on the CC and CV parts. As I said before, switch mode component values change a lot depending on the output voltage and current. The reference designs always seem to be some crappy LM317 circuits, which work better as heaters than power suppliesI would like to design something more efficient and without giant heatsinks.Thank you in advance!

author: LinuxHata
author_rank: Frequent Contributor
timestamp: February 07, 2024, 04:16:08 am
content: Here you go, use this circuit as basis for your design.

author: Gyro
author_rank: Super Contributor
timestamp: February 07, 2024, 09:38:06 am
content: The OP double posted here...https://www.eevblog.com/forum/projects/switching-lab-supply-design/which now has more replies.@OP Please don't double post, it annoys people through duplicating each others' replies, and ultimately gets you banned.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 07, 2024, 05:50:22 pm
content: while it is a good schematic provided earlier, do note it doesn't provide any isolationit act like a buck boost / buck down converter, you will need an x-former with filtering caps etc ...

author: coromonadalix
author_rank: Super Contributor
timestamp: February 08, 2024, 12:17:03 pm
content: and you double thread ... not nice

author: Simon
author_rank: Unknown
timestamp: February 08, 2024, 06:05:20 pm
content: https://www.eevblog.com/forum/projects/switching-lab-supply-design/msg5319897/#msg5319897Please don't double post
Switching Low Voltage with High Voltage - Page 1
Forum section: electronics / beginners

author: Memphetic
author_rank: Newbie
timestamp: June 03, 2013, 08:22:19 am
content: Hey guys. The problem is this: I need a source of 5V OR 12V (it has the ability to be both, depending on the application) to switch 5V.I would use a LDO regulator, but I don't believe they switch fast enough - the source voltage is actually a digital data signal at 15k baud.Another thing out the window would be a voltage divider - it would work if I was only working with 12V, but obviously, I wouldn't want it to divide the signal voltage if it's only a 5v source.I can't think of a way to make an NPN work either... Perhaps I could use a voltage divider on the base to drop the voltage to 1/4 (so we'd be dealing with 1.25v and 3v instead).Any ideas? Thanks!

author: David_AVD
author_rank: Super Contributor
timestamp: June 03, 2013, 08:41:39 am
content: Input switches an NPN transistor that in turn switches a PNP transistor to get you back to +ve switching. Pretty standard arrangement.

author: daveatol
author_rank: Regular Contributor
timestamp: June 03, 2013, 09:35:20 am
content: Or simply use a series resistor (to control max current) and clamping diodes (to clamp it to 5V).

author: Paul Price
author_rank: Super Contributor
timestamp: June 03, 2013, 02:59:21 pm
content: If you take a minute to sketch and carefully describe what your circuit needs to do on a piece of paper and scan it into your computer you can easily create a .jpg or .png picture that would carefully explain what you are trying to do if you can bother attach it to your reply.Your description of the problem is very vague and part of you description are very hard to understand, but a diagram like this with some words would help to very quickly solve this problem..
switching-mode PSUs: looking for theory and design guide materials (books?) - Page 1
Forum section: electronics / beginners

author: 0db
author_rank: Frequent Contributor
timestamp: May 24, 2020, 10:29:04 pm
content: From "simple" single rail switched mode PSUs, to complex ones, I am willing to learn the theory from the scratch. Can you suggest some good book or course?

author: JustMeHere
author_rank: Frequent Contributor
timestamp: May 25, 2020, 03:46:23 am
content: Check this video out:

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 25, 2020, 04:03:09 am
content: no pun intended (this is how i learn)...https://lmgtfy.com/?q=switch+mode+power+supply+pdfhttps://www.google.com/search?q=switch+mode+power+supply+pdf&ie=utf-8&oe=utf-8&client=firefox-b

author: tautech
author_rank: Super Contributor
timestamp: May 25, 2020, 04:10:44 am
content: Study SMPS controller IC datasheets and particularly their typical application circuits.

author: Weston
author_rank: Regular Contributor
timestamp: May 25, 2020, 06:10:40 am
content: "Fundamentals of Power Electronics" is theory heavy and really starts from square one. If you work your way through it you will understand how to derive most of what you see in power electronics, it's used in a lot of grad level college courses.The material is available in slide form from the course website of one of the authors:https://ecee.colorado.edu/~ecen5797/notes.html, a full PDF is available on all the usual sites.Fundamentals of Power Electronics is a good fallback if you want to understand how everything is derived but is a bit dense. If you are mainly interested in SMPS design and topologies that are currently commercially popular you would best be served by manufacture app notes, as stated by others. TI has a lot of good material you can find. As an arbitrary example, the "Power Topologies Handbook" pretty exhaustively covers all non-resonant topologieshttps://www.ti.com/seclit/ug/slyu036/slyu036.pdf.

author: Benta
author_rank: Super Contributor
timestamp: May 25, 2020, 10:09:59 am
content: A good place to start is the book "Switch-Mode Power Supply Reference Manual" from ON Semiconductor (ref. no. SMPSRM-D.PDF).It's downloadable for free fromwww.onsemi.com

author: 0db
author_rank: Frequent Contributor
timestamp: May 25, 2020, 05:18:20 pm
content: thisone? Just downloaded. Thanks!

author: Benta
author_rank: Super Contributor
timestamp: May 25, 2020, 05:35:53 pm
content: Yep, that's the one, I had a slash instead of a dash in the reference number, sorry. Now corrected.I see you're in Zambia. I lived two years in Kitwe(69...71).
Switching MOSFET - Page 1
Forum section: electronics / beginners

author: Thepunydiode
author_rank: Newbie
timestamp: May 03, 2020, 11:42:04 am
content: I am currently working on DIY buck converter, and I am using IRFZ44N (N- Channel Mosfet) as a switch. I tried to switch it at 37kHz. The problem I had noticed that the mosfet is not producing sqaure wave it's waveform looks like the charging of capacitor. But at low frequency everything works fine. I am giving 12v gate supply. If I am making any mistake please correct it.

author: xavier60
author_rank: Super Contributor
timestamp: May 03, 2020, 12:00:05 pm
content: There might not be enough Gate drive current. You will need to post the schematic.

author: Simon
author_rank: Unknown
timestamp: May 18, 2020, 06:59:06 am
content: https://www.eevblog.com/forum/beginners/switching-mosfet-242488/msg3072134/#msg3072134
Switching negative voltages  - Page 1
Forum section: electronics / beginners

author: PerpetualConfusion
author_rank: Newbie
timestamp: April 03, 2018, 10:46:20 pm
content: Hi,I have a few of these ssr’s (https://www.mouser.co.uk/datasheet/2/205/Lcc110-444.pdf) in my supply but there’s one thing I don’t know about them... can these, or any SSR, switch negative dc voltages? For instance, given that the voltage rating of this particular SSR is 350v dc, does that mean it can also switch -350 dc? If this is not the case then any suggestion would be welcome.Thanks in advance

author: BrianHG
author_rank: Super Contributor
timestamp: April 03, 2018, 11:07:47 pm
content: Yes, those do both AC and DC, meaning negative and positive.It's the LED which has only 1 polarity.
Switching on Dual Supply Rails with an opto isolator. Advice Needed - Page 1
Forum section: electronics / beginners

author: Romanizer
author_rank: Newbie
timestamp: September 12, 2020, 04:49:18 pm
content: I am trying to rebuild the infamous Objective 2 Headphone Amplifier as a Balanced unit. The old Power supply consisted of a positive and negative 12V regulator, a on switch, and a power conditioner. the conditioner waits for the switch to stabalize the rails and then pass clean +/-12v to the op amps. My design is going to replace the last two components with a mosfet switch for both rails (see picture). my question is if this is going to work. I want a mcu to switch on the opto isolator to turn on both mosfets at the same time, exactly. the 10k resistors should create a crude virtual ground (doesnt need to be precise at all) and the mosfets should turn on at the same time. Are there any mistakes?The rails +12V and -12V are coming right off the regulators.The rails V+ and V- are going to the Op Amps.

author: rohmeooo
author_rank: Newbie
timestamp: September 13, 2020, 09:45:25 pm
content: That should work.You'll get roughly ~0V at each gate (+/- VCE of the opto) which should be enough to turn it on. Make sure those gates are safe with ~12V between G-S.Bear in mind that there will be some leakage through the opto which could turn one/both of the FETs on when it's supposed to be OFF. With 10k/1k resistors it can probably be negligible. Same issue exists if it's not exactly +12 & -12V. eg if one is 13V and the other is -11V the opto will find the middle around ~1V (+/- VCE of opto). Could be some funny business when 12V/-12V are turned on or loaded down.Also bear in mind that insufficient drive on the opto-input (and thus insufficient current sink thru opto C-E) will result in a half-on FET.Finally, the actual value voltage at each gate won't exactly be zero--leakage through the gates will draw one side or the other up/down. Again, 10k/1k are nice and low values that it should work fine.I'd personally use the opto to drive a NPN/NMOS + PNP/PMOS to pull the gates of the PFET+NFET respectively. No funny business with resistor values because you'd tie the (eg) NPN collector directly to GND so you know exactly what voltage it will pull to.

author: David Hess
author_rank: Super Contributor
timestamp: September 13, 2020, 11:47:17 pm
content: Usually switching the regulator itself is better because the output can be more closely controlled, but that should work.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: September 13, 2020, 11:48:56 pm
content: Use 2 low-power solidstate relay if the current is small and a resistance of about 1 Ohm is acceptable. Or use 2 MOSFETs that are controlled by an cpecial optocouplers with a group of LEDs generating a control voltage for the MOSFET of about 9V Toshiba TLP3905/3906.
Switching or Linear Power Supply? - Page 1
Forum section: electronics / beginners

author: Tech77997
author_rank: Contributor
timestamp: March 18, 2020, 12:36:53 am
content: I am a beginner and would like to purchase a power supply; why would it matter whether I purchase a switching or linear power supply?

author: WattsThat
author_rank: Frequent Contributor
timestamp: March 18, 2020, 12:43:44 am
content: It probably would have been best to ask the question in this thread so people had some idea of your intended use.https://www.eevblog.com/forum/beginners/is-this-multiple-triple-power-supply-a-good-buy/msg2968870/#msg2968870FWIW, linear supplies tend to have lower noise figures, especially when discussing inexpensive units, which makes them a better choice for analog use.

author: Tech77997
author_rank: Contributor
timestamp: March 18, 2020, 12:49:17 am
content: Thanks for your reply. You're right I should have asked in that thread.
Switching power supply - 0.5V between GND and Earth - Page 1
Forum section: electronics / beginners

author: andering
author_rank: Newbie
timestamp: September 17, 2016, 10:18:02 pm
content: Hello,I just got switching (LED) power supply (220V -> 24V) and tried measure voltage between Earth and GND(24V) and got 0.5V - 1V ,is that vital ?Thank you.

author: Psi
author_rank: Super Contributor
timestamp: September 17, 2016, 10:57:07 pm
content: Does it have any current behind that voltage? or are you just picking up random noise that happens to be showing as 0.5-1V on the DMM.I think you will find it's just noise/leakage and becomes zero the instant you load it a little. (eg 470R resistor between earth and negative)
Switching power supply - Cambridge Audio Magic Streamer 6 - Blue smoke - Page 1
Forum section: electronics / beginners

author: Andy-Polok
author_rank: Newbie
timestamp: January 26, 2023, 03:24:00 pm
content: Hi , before i start i would like to thank you all of you People for sharing Knowledge here and on EEvblog videos on YouTube , learn a lot and still learning Big thanks .im working at power supply from CA Stream magic 6 power supply , its a switching power supply with controller ICE3BR0665J , initially was dead completely , i have replaced main controller ( maybe 6 times) also all diodes around resistors and caps , what happen is after repair i can power up power supply and i have standby voltages - all correct : - +19 , 3.3 and 5V but when i press power on on front panel , Controller ICE3 just smoke or exploding after like 3 second , i have check for shorts before and after transformer and all good i mean only 5 V line have around 550 ohm with ground ( is that to low ? )so to summarize in standby mode resistance to ground :- + 19 lines - Megaohm3.3 V line - kilohm5V line - around 550 ohmso i did repair /replaced components on that power supply 3 times and always blue smoke , i have no idea what is going on , can i ask for a bit of help ? i can upload pictures , schematicthanks

author: m k
author_rank: Super Contributor
timestamp: February 05, 2023, 03:47:47 pm
content: Your controller seems to be trying too hard.Maybe it's the feedback.Pictures and schematics are always positive.

author: AdrianE
author_rank: Newbie
timestamp: January 28, 2025, 03:36:57 am
content: Did you ever find out what was causing this? I have the same issue.
Switching power supply grounding question on PCB - Page 1
Forum section: electronics / beginners

author: Muku
author_rank: Contributor
timestamp: August 31, 2020, 03:31:20 pm
content: Hello everyone,This is my first time design a PCB with a switching supply on it. Board is small and has RF components on it. So I want to keep the power supply noise as low as possible. Below is the schematic.I have few question for the grounding of such supplies and I also need to confirm if I am doing things right.First, As you can see in the schematic, I have GNDREF which is the main ground from input DC source. Then I have GND1 which is the ground for the IC. I am connecting GND1 and GNDREF with a 0ohm resistor. Is this the right way to do it?Second, the input DC source may itself be a switching supply, so do I need to separate ground for every IC ground as GND2, GND3 and then connect them all to GNDREF using the 0 ohm resistor? Or I can just create GNDREF plane and connect everything else to this GNDREF plane? What is the best practice?
Switching power supply input and output voltage and current tester - Page 1
Forum section: electronics / beginners

author: Giuseppe Concezio Pisciel
author_rank: Newbie
timestamp: November 10, 2023, 04:21:20 pm
content: Hi everyone!I'm here to ask for some advice and clarifications about something I want to make as my first non-beginner project: I'd like to create a testing set up to measure voltages and currents of both the AC input and the DC output. The power supply can be adjusted from 90 Vac to 270 Vac for the input and from 24 Vdc to 36 Vdc for the output, and the load has to be 15 Ah. My first question is about the load: when I read "Ah" I immediately thought about a battery charged by the supply, but I was told that Ah can also be applied to purely resistive load. I've looked for an explanation for days because I found that so strange (a resistive load doesn't store charge, it only lets charge pass in the form of current), but I didn't find anything. Can anyone have a clue about that? Maybe it was a mistake and it was 15 A, and assuming that things simplify, and looking for a 15 A dummy load I found this blog and Dave's video (), it' s interesting because of the display that allows to get rid of a multimeter like in this other test bench (http://www.fraw.org.uk/meir/work/handouts/elv_dummy_load.pdf): I think that I can be inpired by the Dave's one once transistors, heatsinks (or cooling in general), and the other components are carefully chosen, can't I? And is it possible to integrate the measurement on the AC side in the same PCB or should I put that (as I think) on a separate PCB? Feel free to ask if something is not clear, it's important to be understood properly. I'm still relatively unexperienced, so every advice is more than welcome. Thanks in advance for the answers.
Switching power supply Mean Well RT85B - 12V no load, 13V with a load - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: April 03, 2021, 01:30:51 am
content: Switching power supply Mean Well RT85B - 12V no load, but when I connect it to the Tandy 1000 I am powering it with, the +12V goes up to 13V! I had the 5V trimmed to exactly 5V, but I had to turn it down to 4.75V to get the +12V to drop to +12.5V. Both are now with +/- 5%. Is it normal that a voltage would go up under load?

author: drvtech
author_rank: Regular Contributor
timestamp: April 03, 2021, 01:45:45 am
content: Yes, the reason is that the 5V is the main output and it is regulated by a proper feedback loop (5V goes down under load, power supply detects this and turns itself up to maintain 5V). There is no control loop on the two 12V ouputs - they just go up and down as the 5V is turned up and down. So what happens is that when you load up the 5V the 12V gets turned up as the power supply starts working harder. The solution)if you need one) is to put a separate regulator on the 12V output or to load the 12V to bring it down.

author: PKTKS
author_rank: Super Contributor
timestamp: April 03, 2021, 01:11:23 pm
content: or... putting a dummy load on the 5V rails .. say about 1A .Just to keep the regulator busy on point at the expense ofwasting this extra load.Blame the poor design probably by supervising 5V and not 12V ?Paul

author: TimNJ
author_rank: Super Contributor
timestamp: April 03, 2021, 01:33:19 pm
content: This is a matter of multiple output “cross-regulation”. With only one feedback loop, it cannot be entirely avoided but there are certain ways the designers could have made it better. Nonetheless, it doesn’t sound too bad.

author: TimFox
author_rank: Super Contributor
timestamp: April 03, 2021, 03:58:33 pm
content: These supplies were designed for digital systems where the +5V needed to be controlled, and the 12 V outputs were not critical. Therefore, the feedback loop sensed only the +5V output.

author: alank2
author_rank: Super Contributor
timestamp: April 04, 2021, 12:04:37 am
content: Thanks for the explanations everyone!

author: Photoman
author_rank: Regular Contributor
timestamp: April 04, 2021, 05:18:19 pm
content: I had a similar issue with a Mean Well QP-320F. In my case the 24v line jumped up to 25v.I put a 6 amp general purpose rectifier diode (P600M) in series with the 24v output.That drops the voltage within the spec of the load. The diode does get a little toasty but not enough that im worried.The load is 3-4 amps so its within the safety margin.
Switching power supply not working  - Page 1
Forum section: electronics / beginners

author: electron_misfire
author_rank: Contributor
timestamp: July 20, 2014, 01:09:26 am
content: Hello all,I've built a switch mode power supply using a laptop P/S incorporating 5v and adjustable lm2576 switching regulator. The problem with mine is that the adjustable output is 3v no matter how I adjust the pots. The only strange things I've noticed is that the 5v output is 16-17v and before the inductor it is 5-6v. The schematic attached is what I built it on. One thing to note is that the 5v inductor is 380uh and adjustables is 220uh.Thank you in advance.

author: mij59
author_rank: Frequent Contributor
timestamp: July 20, 2014, 03:39:39 am
content: Hi,There's no feedback, check the data sheet how feedback works.
Switching Question  - Page 1
Forum section: electronics / beginners

author: Lewham5115
author_rank: Newbie
timestamp: May 24, 2024, 04:53:26 pm
content: I've got a project where I want to be able to switch 3-5 potentiometers between two different banks of them. So an A bank of between 3-5 pots, then a B bank of 3-5 pots.Could someone point me in the direction of how I should look to implement this?The signal going through these pots are all very low voltage. And I need to be able to switch between these two different banks with just a single switch.Is there some sort of chipset that will allow me to accomplish this? Should I look at using relays?Any help would be appreciated.

author: themadhippy
author_rank: Super Contributor
timestamp: May 24, 2024, 05:59:57 pm
content: How are the pots wired? worst case your after 15 pole 2 way switching,if however the pots are commend at one end or both youll only need 10 or 5 pole 2 way switching.

author: xvr
author_rank: Frequent Contributor
timestamp: May 24, 2024, 07:55:03 pm
content: 3-5 SPDT analog switches.https://www.digikey.ie/en/products/filter/analog-switches-multiplexers-demultiplexers/747?s=N4IgjCBcpgnAbABiqAxlAZgQwDYGcBTAGhAHsoBtEAFkQFYEB2EAXRIAcAXKEAZU4BOASwB2AcxABfEnAAcsFCHSRs%2BYmUohkLaSAC0AJkXLBAV3XlIVOq116F0JVDMXNEHbqNWQWEblJiAAR4AO5CnKgAFrZAA6 channel:https://www.digikey.ie/en/products/filter/analog-switches-multiplexers-demultiplexers/747?s=N4IgjCBcpgnAbABiqAxlAZgQwDYGcBTAGhAHsoBtEAFkQFYEB2EAXRIAcAXKEAZU4BOASwB2AcxABfEnAAcsFCHSRs%2BYmUohkLaSABMiWNUXLVhEuUhV4rDt0ggAIqQCuAIxwEpJALR6TUIIu6pZUdKy6PgrQSoECwRaaEDq6-lYgWCK4pGIABHgA7kKcqAAWEUAThis one for example:https://www.digikey.ie/en/products/detail/texas-instruments/TS3A27518EPWR/2075716
Switching RC delay network in and out of circuit - Page 1
Forum section: electronics / beginners

author: JBourke
author_rank: Contributor
timestamp: December 02, 2021, 10:19:24 pm
content: Hi all,I have an existing RC network in a digital circuit to delay a certain signal by ~70ns. The resistor value is 10R and the capacitor's is 680pF.The delay does its job, although I know there are better ways to delay digital signals but anyway that is not an option right now.I would like to be able to switch this delay network in and out of circuit with a mechanical switch but I have found that if I add any additional wiring the circuit no longer works. I understand the wiring will add capacitance and resistance but I didn't expect this to have that much influence; beginner here obviously, I must be violating some fundamental principles :-)Would changing the combination of R an C help in this?Your help and expertise is much appreciated,John

author: Ian.M
author_rank: Super Contributor
timestamp: December 03, 2021, 12:07:14 am
content: No. The problem is stray capacitance, and you are already at minimum R, less than the output impedance of most logic families, so cant increase C to swamp the stray capacitance. Wire inductance may also be causing problems.There are a couple of possible approaches. Use your mechanical switch to apply a DC control voltage to control:a SPDT analog switch, choosing the delayed or non-delayed signal.small signal N-MOSFET, with its drain providing a switched ground to the capacitor of the RC. Add a 1Meg pullup to logic Vcc to bias the drain so the body diode doesn't conduct on falling edges of the signal when the MOSFET is off.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 03, 2021, 12:35:48 am
content: Your whole approach is defective by design. Using RC delays in combination with logic gates is a dubious and amateurish approach. With an IC like a "retriggerable monostable mutivibrator" such as for example the 74xx423 you will get much more reliable results.I also do nut understand why you want to use a mechanical switch. Long wires add inductance and capacitance and this does not combine well with high speed signals. A better option would be to use your switch to adjust a logical gate that reroutes your signal.But if you want to proceed with your RC approach.For a "quick" solution I pretty much agree with Ian.M.First increase the resistance, so it does not draw more current from the output pin then it can deliver, and adjust the capacitor to get your time constant.Then, you can insert a small MOSfet between the capacitor and GND.

author: JBourke
author_rank: Contributor
timestamp: December 03, 2021, 01:15:14 am
content: Thank you both, I learned something and have useful solution suggestions to boot.
Switching Reg - Page 1
Forum section: electronics / beginners

author: whatchitfoool
author_rank: Contributor
timestamp: July 27, 2012, 06:05:49 am
content: Ive got a Maxim MAX630 CMOS DC-DC regulator, wired up deadbug style, that is putting out a little less voltage then I'm putting in it.Here's the FullData sheetI can't get this to work right for the life of me. I'm putting between 6.6 - 8.2v input, looking for anywhere between 12-15v out (150ma peak).I'm using -D1 : 1n5819 schottkyL1: low esr 19r474c 470uh power inductor (1.1A rating)C1 : 470uf electrolytic in parallel with a 22uf tantalumCx: 47pf ceramicR1: 91kR2: 10kCc: 10nf mlccDon't have R3,R4, pin 1,or pin 8 connectedIve spent the better part of 3 hrs looking over this, and cant find any visible reason it should be working like i want.i thought it was maybe the esr on the 470uf, added the 22 in parallel. then CC. Then considered it could be a dirty power supply. dug another one out. Then used batteries.I did have it powered on with R1 & R2 reversed - could i have toasted the comparator op-amp?I'm under the opinion that the chip is bad, but the thing is like 8 bucks (and i don't have another handy).Does anyone see something i missed?

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 27, 2012, 11:26:39 am
content: What voltage does it output? I guess it's the input minus the voltage drop over the diode? If so, you will have the same 'output' without the MAX630.The thing doesn't look very complicated, it should adjust the output so that the voltage on pin 7 equals Vref, 1.3 volts.If you reversed R1 and R2 it tried to output something like 1.5 volts, you would not kill the comparator but just stop switching completely because your Vout will be above that.What do you measure on pin 7?Is the oscillator running? (put the scope on pin 2)Is it trying to switch? (scope on pin 3)Did you connect pin 5 and 6 together?

author: whatchitfoool
author_rank: Contributor
timestamp: July 27, 2012, 06:38:27 pm
content: it was outputting about .3v less then the input. (diode).yes, pin 5 and 6 are tied together.I do not have a scope. Been looking to get one for years, have never been able to do it.I haven't messed with it too much after finding this, but i was assuming some things and didn't read the whole data sheet.i was also putting the input to pin 5, but the chip actually does its thing with the output voltage, not the input.I'm going to fiddle with it some more, but the first impression is that the circut still isn't working

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 27, 2012, 10:04:23 pm
content: If you don't have a scope you could try a multimeter on AC. You should at least be able to measure some AC on pin 2 and pin 3.But yes, get a scope...
Switching regulator for low power worth it? - Page 1
Forum section: electronics / beginners

author: Foxxz
author_rank: Regular Contributor
timestamp: May 22, 2022, 01:20:49 am
content: I want to run a low power FPGA off a coincell battery. I will need 1.2 and 2.5v for my application. I don't know the current draw yet (hopefully below 25ma). Is it worth exploring a switching regulator? Are there any meant for low power operation that have the inductors built into a single surface mount package?

author: Foxxz
author_rank: Regular Contributor
timestamp: May 22, 2022, 04:58:51 am
content: I am well aware of the limitations of the coin cell. I'm not looking for continuous operation for days or even hours. Intermittent operation for minutes.But I think I was able to eventually answer my own question. The RM590 line seems to do what I'd like. But the juice probably isn't worth the squeeze.
Switching regulator output current - Page 1
Forum section: electronics / beginners

author: Nogtail
author_rank: Regular Contributor
timestamp: December 01, 2016, 04:45:02 am
content: Most switching to regulators seem to need the desired output current to determine the values of supporting components. In my situation I want to use a MC34063 to drive a device that is often sleeping and only consuming a few uA, but when awake can use tens of mA. What value should I be putting into the calculations? Average current? Max/min current? Is the MC34063 badly suited to changing output loads and should I use something better suited for the task?

author: mariush
author_rank: Super Contributor
timestamp: December 01, 2016, 05:35:32 am
content: mc34063 is a cheap switching regulator with minimal input and output protections, which can be damaged easily, too easily.In addition to that, it's also relatively low efficiency, with high quiescent currents, requires a lot of extra components etc..There are far better switching regulator chips out there these days, just a bit more expensive but in some cases with the added benefit of saving you money by allowing you to use smaller inductors and ceramic capacitors and resistors.You would design your circuit for the maximum current it would have to give to devices plus some margin for safety ... ex if your circuit won't use more than 100mA, maybe design it for 125 mA max. Usually, the more you tweak it to be able to do higher currents, you lose efficiency at low currents.For very small current amounts, sometimes it may make more sense to use LDOs, as their efficiency won't be much different than the most a mc34063 would be capable of (maybe 75%-80% with perfectly picked parts)
Switching solar panels with MCU - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: May 13, 2020, 09:48:07 pm
content: tl;dr can I switch 2.6KW of solar panels between two different inverters using an MCU and relays for under $500.Hi All,This is not a "current" requirement I have, I'm not going to be playing with this amount of amps myself.So say I have eight 325w panels in a string, two strings, these string feed into charger/inverters which supply power to the batteries, it's an off-grid setup. I also have a seperate grid-connected inverter, let's say that this inverter has no panels connected.When the sun is beating and I have excess energy production (the batteries are charged), I would like to use an MCU to switch a string of panels to the grid-connected inverter to feed-in.Obviously this isn't ideal and I should buy a fancy grid-tie charger/inverter but let's just say I inherited the current setup and it works well.I'm guessing it's an MCU controlling a little relay that's controlling a much bigger relay scenario.So I guess the question is can you safely switch this connection with an MCU for under $500, I think it would be a maximum of 60A at 48V right?CheersRichard

author: wizard69
author_rank: Super Contributor
timestamp: May 14, 2020, 03:46:07 am
content: Given enough time and money you can do anything you want. How much damage you cause before you have a working system is the big unknown. There may be easy approaches to this but that is highly dependent upon what your current system is made of.The obvious question here is why not just buy a grid tied inverter / charger that already has the required certifications? I'm generally all for DIY but sometimes the wall to a finished project is just too high for an individual. That is unless you have lots of time It is sort of like the guys that spend years, even decades, building hot rods in their garages. it can be done but most people just go out and buy a Corvette.
Switching supply PSA... - Page 1
Forum section: electronics / beginners

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 18, 2016, 07:28:09 am
content: http://imgur.com/gallery/SoYtht4Feel free to write your own of the (or related) memes!Tim

author: Rerouter
author_rank: Super Contributor
timestamp: March 18, 2016, 10:25:15 am
content: I'm sorry, but i don't really understand,The chip from its datasheet appears to have decent specifications, and the layout doesn't look that bad?Well apart from 35V caps used on a 40V max chip.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 18, 2016, 11:44:32 pm
content: Decent in 1980, perhaps! It's dreadfully slow, barely ultrasonic; the control scheme is undefined (you have an "oscillator" block with apparently some means of current sense), the behavior is hysteretic so not only is the ripple massive from the low operating frequency, but it's several times worse due to pulse skipping and chaotic limit cycles; shall I continue?All of the alternatives listed are modern CMOS devices, with operating frequencies up to a few MHz, and excellent stability, efficiency, and current limit performance. You will literally save more on capacitors and inductor alone than the chip cost.Tim

author: xygor
author_rank: Regular Contributor
timestamp: March 18, 2016, 11:54:12 pm
content: Is that the stupid chip with the error amp gain inversion when the common mode voltage range was exceeded. (i.e. negative feedback turned into positive feedback.) I got burned by that figuratively and the parts literally. Die! mofo Die!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 18, 2016, 11:55:03 pm
content: Dunno, but that's characteristic of many older chips!Tim

author: SeanB
author_rank: Super Contributor
timestamp: March 19, 2016, 06:03:02 am
content: 1 billion ultra cheap and nasty mobile cellphone chargers use it though. I have repurposed a few as cheap and nasty buck converters to charge batteries, or as simple LED drivers for a single LED. Put a decent cap and inductor on them and they do work well enough.
Switching to backup power - Page 1
Forum section: electronics / beginners

author: Moriambar
author_rank: Unknown
timestamp: September 03, 2018, 06:28:11 am
content: Hello,I'm bit in a pickle with this one.i have a battery powered circuit with very low quiescent power consumption,that spends most time in this mode. Some components in this have an inbuilt "backup battery switch" that, when the main power is too low, switches them to the CR2032 battery automatically.The problem arises with the LT2956-1 which is featured to occasionally wake up part of the circuit: the LT2956 must always be powered, in order to retain its time frequency, even when the ordinary batteries are substituted. So I need to switch the LT2956 power when the main goes out.I actually don't know how to implement this, except than with two diodes at V+ pin of the 2956 (which I don't think is the best), connecting both power supply rails to it. Hence I came here.Please mind that neither an RTC nor a micro can be part of the solution...Is there any other way?Thanks

author: capt bullshot
author_rank: Super Contributor
timestamp: September 03, 2018, 06:54:10 am
content: Either connect the LT2956 to your backup battery only - its power consumption is low enough,or just use the diodes. Using diodes to provide backup supply is rather common and was widely used before the advent of all these fancy controllers with built-in power switch.

author: Moriambar
author_rank: Unknown
timestamp: September 03, 2018, 07:26:10 am
content: Quote from: capt bullshot on September 03, 2018, 06:54:10 amAh, ok, thanks!
Switching voltage reference using analog switches - Page 1
Forum section: electronics / beginners

author: DanKalc
author_rank: Newbie
timestamp: March 07, 2014, 07:31:41 pm
content: Hi,Can i use an analog switch do change reference voltage to ADC converter? Will the switch affect my performance and what parameters should I consider?

author: valentinc
author_rank: Regular Contributor
timestamp: March 09, 2014, 08:02:04 pm
content: What ADC you are using ? And why you need to change the reference voltage ?

author: tszaboo
author_rank: Super Contributor
timestamp: March 09, 2014, 09:04:49 pm
content: Quote from: Dawgie on March 09, 2014, 08:11:04 pmDigital pots usually have horrible Tempco. Maybe a multiplying DAC would be a better solution?I believe you can switch the voltage reference, with some restrictions. First, you need to know, what bandwidth the vref of the ADC can have. it is possibe that you need to skip several conversions before the ADC is usable. Also, you might need to buffer the vref after the switch, if you use capacitive loading ADC. This is what comes into my mind, but can you describe why it would be useful?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 09, 2014, 10:53:09 pm
content: Why not switch the input signal level instead?ADCs usually draw a little VREF current, so you wouldn't want to use a naked analog switch; it would have to have very low R_on, and then leakage (or switching transients) may screw things up.You can use two switches (of almost any R_on) and an op-amp follower, but then Vref depends on the op-amp's precision level. So you incur more cost there too.Tim
switching/routing data signals only ddoable with relays? - Page 1
Forum section: electronics / beginners

author: somuchtyler
author_rank: Contributor
timestamp: December 04, 2018, 10:38:30 pm
content: Lets say I am working on a project that requires me to switch between 5 different headphone jack sources to one headphone. The only way to accomplish this is to use a set of two relays per source and design my project to power on the set of relays of the source that i want to listen to?My question is, is this only achievable through relays? Is there a less expensive option?

author: Wimberleytech
author_rank: Super Contributor
timestamp: December 04, 2018, 10:54:09 pm
content: Quote from: somuchtyler on December 04, 2018, 10:38:30 pmThere are many ways to do this. Take a look at MAX4908. Maybe use two of them? You could roll your own with FETs/analog mux circuits.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: December 05, 2018, 12:16:32 am
content: Can or do the sources share a common ground? That's really going to drive the design.
SWR for ham radio VU-meter input to an arduino  - Page 1
Forum section: electronics / beginners

author: pitpat
author_rank: Contributor
timestamp: September 09, 2021, 09:02:31 am
content: Hi guys, thanks for checking in!So, I've recently scored on eBay a nice VHF-UHF SWR PWR meter that unfortunately my local "parcel handler" manage to break, the panel meter thingy specifically.Since the actual circuitry is fine, I was wondering if an Arduino could replace the old needle meter. (SD-312A) a 630 ohm VU-meter that the manufacturer seems to have molded to display SWR and PWR.I do have some dummy loads to do some approximate calibration but I'm not quite sure about the actual output that a needle meter requires (something about uVolt I guess).I'd love to hear your thoughts!Cheers 73Federico

author: m3vuv
author_rank: Super Contributor
timestamp: September 09, 2021, 08:08:30 pm
content: what current did the old meter movement need for fsd?

author: Benta
author_rank: Super Contributor
timestamp: September 09, 2021, 08:45:22 pm
content: I remember those.They usually had germanium rectifiers to provide an approximate logarithmic response on the scale, and were mostly also magnetically non-linear.You'll need to plot the output of the circuit to get an idea of what your MCU has to do.

author: pitpat
author_rank: Contributor
timestamp: September 10, 2021, 09:22:16 am
content: Hi! Thanks for the reply.I did put the output through an oscilloscope and it does look like a normal variable DC voltage.I've also discovered that the circuitry is actually divided in 2 sections, The meter and the Directional coupler.From my understending the Dir. Coup. Should give forward and reversed voltages that could easily convert to an approximate form of SWR with some arithmetics.I've found thishttp://kk5jy.net/swr-meter-v1/and got some reasonable results also on the power readings, quite a nice project btw, I now have to figure out how to calibrate the actual SWR and PWR readings.Do you guys have some ideas?I'll post some photos of the circuits as soon as I get back to home.PS. Maybe I should change the thread title...