hybridfree/eevblog-posts huggingface dataset:
Voltage follower circuit - Page 1
Forum section: electronics / beginners

author: cowasaki
author_rank: Frequent Contributor
timestamp: February 13, 2018, 10:49:33 pm
content: What voltage follower circuits do people use with a 1:1 voltage amplifier that is accurate, very stable and capable of 1-2 amps from maybe a 30mA input? Both for a positive and negative output and a constantly changing positive/negative circuit. The reason I am asking is that I have a few alternatives but the only one I've actually used tended to drift (I can't find it at the moment) and I would like to use a voltage reference as the input for one circuit, the output of a resister tree ADC circuit for another and an adjustable DC voltage for the third one (which might be adjustable from -28V to +28V.Preferably not using a negative input voltage (unless the reference is also negative) if at all possible. I will be using a 2 x 30v+12v transformer so would have -30 and 30 but I want the option to use flip the -30 and use it as a second 30v rail if I want to.

author: Audioguru
author_rank: Super Contributor
timestamp: February 14, 2018, 05:21:18 am
content: You need to design a DC power amplifier with a gain of 1.

author: drussell
author_rank: Super Contributor
timestamp: February 14, 2018, 05:24:22 am
content: Yeah, pretty much any differential amplifier with the feedback taken direct, not divided.Even an unity-gain op-amp (a high enough voltage one) circuit with pair of transistors on the output, inside the feedback loop, would do it.

author: danadak
author_rank: Super Contributor
timestamp: February 14, 2018, 12:16:16 pm
content: Power OpAmp ?http://www.ti.com/amplifier-circuit/op-amps/power/overview.html?utm_source=GOOGLE&utm_medium=cpc&utm_term=Power%20Op%20Amp&utm_campaign=ASC_AMP_US_N_E_OpAmps&utm_content=bf2b2f3a-5a00-4217-a7ba-ce436c55d7b7&gclid=EAIaIQobChMIx62_47Cl2QIVRh6GCh3kKwA9EAAYASAAEgKXL_D_BwERegards, Dana.
Voltage follower WTF? - Page 1
Forum section: electronics / beginners

author: int2str
author_rank: Regular Contributor
timestamp: April 09, 2015, 04:45:21 am
content: I put a simple voltage follower circuit on a breadboard using the TL972 "rail to rail" op-amp (datasheet).Powered the op-amp using 5V and put a 0-5V on the input. The result was the attached chart. Blue is in, yellow is out.Looks like the op-amp is NOT rail-to-rail?Is this normal? I can make the top go away by supplying more power. But how do I fix the bottom?

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: April 09, 2015, 05:02:05 am
content: Yep, that's normal. You have to read the datasheet to know what "rail to rail" actually means, but I don't think it will ever mean you can actually go to both rails on the inputs and get all the way to the rails on both outputs. Relevant parts of that datasheet:QuoteQuoteYou "fix" the bottom by giving the opamp a negative supply that is sufficiently lower than the lowest you want it to output in this case, same as how you "fixed" the top. You can do that by lowering the negative supply or raising the input voltage. Suppose the opamp was supplied with 0V and +10V and your input came in at 3V to 8V, for example.

author: cyr
author_rank: Frequent Contributor
timestamp: April 09, 2015, 05:40:33 am
content: The claim is "outputrail to rail", which in reality is always going to mean "really close to the rail".You usually have some gain, so not having the inputs go rail-to-rail is less of a problem. If you really need that, get another part.

author: Zero999
author_rank: Super Contributor
timestamp: April 09, 2015, 10:40:13 am
content: This is known as phase inversion and occurs when the common mode range of the input is exceeded. The inputs exchange functions, so the inverting input becomes the non-inverting input and vice versa.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: April 09, 2015, 02:05:22 pm
content: As mentioned above, that op-amp has rail to railoutputs, not rail to railinputs. For what you're trying to do, you need both.

author: macboy
author_rank: Super Contributor
timestamp: April 09, 2015, 02:16:59 pm
content: Not trying to beat the dead horse here (the consensus is of course, R-R outputs does not imply R-R inputs), but if you look at the Vout vs Vin in section 9.1.2 of the datasheet, you will see a curve that demonstrates the exact behavior that you see when the input reaches within ~1 V of either rail.

author: int2str
author_rank: Regular Contributor
timestamp: April 09, 2015, 05:41:09 pm
content: Awesome! Thank you guys for really helping me understand and co-relating the datasheet!Much appreciated!
Voltage from factory Ni-Mh Batteries - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: February 01, 2016, 06:13:05 pm
content: Hello all,I recently bought 24 Ni-Mh batteries from a seller on ebay (seethis post).13 have a voltage of close to 1V (around 0.95V), 1 has around 0.67V and 11 have voltage close to 0.2V.What should be the factory voltage? Should there be a factory charge? Are the 0.2V Ni-Mhs dead?

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2016, 06:48:41 pm
content: That does sound like quite a variation for new(?) batteries. If NiMh behave the same way as NiCd the it is ok to discharge them to 0V (In fact large capacitysingle cellaviation cells used to be supplied with a shorting clip fitted)..What kills them is where you have multiple cells in series and one cell gets forced reverse polarity by the other cells as the whole pack gets discharged.The important thing (I assume you're going to be using them in series stacks) is that their capacities match well. If not, the above situation can occur. They will at least need constant current charging at C/10 rate for longer than 14 hours to ensure that they all become fully charged and the cell voltages equalize.Edit: To answer your middle question - always assume that new batteries are discharged and require a full charge before use. There are some special 'low self-discharge' cells that are retail packed as 'pre-charged' now, but that's not what you have bought.

author: DivineChaos
author_rank: Regular Contributor
timestamp: February 02, 2016, 11:04:33 pm
content: If they are AA nimh batteries, you can refresh them with a LaCrosse BC-700. Best Nimh charger and restorer period. Keep in mind that it will in some cases take DAYS to restore them.The charger will also tell you the capacity of the batteries so you can pair them up
Voltage increase with LED driver current resistance? - Page 1
Forum section: electronics / beginners

author: steveggz
author_rank: Contributor
timestamp: October 13, 2017, 12:03:02 am
content: Referencing the HLG-240H-C1750B, would adding a resistor between DIM + and DIM - increase the voltage of the driver?It's rated to output 143v at 1750mA. But if I added a resistor between the DIM terminals decreasing the current to let's say 1500mA would I get more voltage? If so how much?

author: Zero999
author_rank: Super Contributor
timestamp: October 13, 2017, 08:05:06 am
content: Quote from: steveggz on October 13, 2017, 12:03:02 amPlease keep it to one thread per topic.https://www.eevblog.com/forum/projects/led-driver-and-component-requirements-(remote-phosphor-light)/msg1322903/#msg1322903
voltage injection BPS - Page 1
Forum section: electronics / beginners

author: jackx
author_rank: Newbie
timestamp: October 31, 2024, 12:31:12 pm
content: Dumb noob question....Linear is said to be better than switching and a must have. I haven't seen a reason for this.Can someone tell me?I have a switching 30v10a, with on/off and an output switch. It can be shorted.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 01, 2024, 02:21:07 pm
content: Said by who?Well, it depends on the situation and how old you are.A lot of old buggers are still profoundly traumatised from the switcher encounters (alien probing mostly) that they had in the 70's and 80's.I had me some therapy and have moved on now.Modern switchers can outperform many linear supply dseigns on all fronts.I've seen a lot of crappy linear supplies down the years.I've also seen more bit of kit destroyed by linear supply failures than by supposedly satanic switchers.Engineers often regard the linear PSU part of their project as trivial, and it aint.Of course, there are good and bad and ugly switchers out there- you get what you pay for, by and large.Switchers are more reliable, cheaper to buy/ make and can very efficient and compact.Applying them requires you to be a bit more inteligent about your wiring or layout though. Filtering and shielding too.Most consumer (and pro) AV products work just fine with their switchers.Recording studio and broadcast gear is almost entirely smps powered now.But if you're not well informed about psus you can fall into the Trumpian nightmare of audofoolery misinformation.These days I only use linear for low level and precision stuff. Horses for courses

author: u666sa
author_rank: Frequent Contributor
timestamp: November 01, 2024, 06:16:32 pm
content: Linear is more reliable, but switching is cheaper and good enough.The only time I had trouble with switching, is when I connected my switching PSU to 5 watt radio and jammed a frequency. Power supply would shut down if it was near the transmitter. I had to move it further away from transmitter for proper work.

author: TimFox
author_rank: Super Contributor
timestamp: November 01, 2024, 07:00:57 pm
content: I used to build large arrays of x-ray detectors, and we used linear power supplies for noise reasons.The younger engineers wanted to use switchers, and I replied that it was possible but that they had to budget engineering time to ensure noise performance, since the switching frequencies were in a range that our analog electronics was susceptible to.Hand-waving doesn't count: the switching noise can be radiated, imposed on the DC outputs, and conducted back to the AC mains.There are engineering solutions for all of these problems.Linear power supplies have lower efficiency and generate more heat, but can be more quiet if properly built.
Voltage level detector with one pulse output  - Page 1
Forum section: electronics / beginners

author: mnt22
author_rank: Contributor
timestamp: June 30, 2021, 08:03:34 am
content: Hi everyone please help me out, I need circuit that at specific (adjustable) input voltage outputs one pulse with adjustable width, but only using basic components (opamp/resistors/capctors/diodes... etc.Thanks for the help

author: fcb
author_rank: Super Contributor
timestamp: June 30, 2021, 09:11:05 am
content: Input voltage range? Pulse width? Supply available? Output level & load? Skill level???

author: mnt22
author_rank: Contributor
timestamp: June 30, 2021, 09:37:33 am
content: Input Voltage 0 to 24Output level 0 to 24Pulse width in millisecondsSupply available 0 to 24Output current max 500 mASkills BingerThanks

author: Zero999
author_rank: Super Contributor
timestamp: June 30, 2021, 10:49:51 am
content: Can we please see the bigger picture. What project is this circuit being used for?Use the LM393. One half as a comparator circuit to sense the threshold and the other as a monostable. See figure 35, page 11 of the data sheet, attached to this post, for how to build the monostable.More information on op-amp monostables, but bear in mind it's better to use a comparator, such as the LM393, which has an open collector output, so the circuit is slightly different.https://www.electronics-tutorials.ws/opamp/op-amp-monostable.htmlMore information on comparators.https://fscdn.rohm.com/en/products/databook/applinote/ic/amp_linear/common/opamp_comparator_tutorial_appli-e.pdfVarious comparator circuits.http://www.circuitous.ca/Comparators.htmlAs you require an output current of 500mA, you'll need another circuit. In this case, Q1's base should go to the output of the monostable circuit.

author: Ian.M
author_rank: Super Contributor
timestamp: June 30, 2021, 11:14:17 am
content: The specification still needs clarification.O.P: "... at specific (adjustable) input voltage output ..."*AT* a voltage isn't practically achievable. You'd need to implement it as:'. .. when input voltage crosses a specific (adjustable) threshold, output ...'You'd also need to specify if the pulse is to be generated when the input is rising, or falling, or both, when it crosses the threshold, which would require different trigger arrangements for Zero999's proposed monostable.

author: mnt22
author_rank: Contributor
timestamp: June 30, 2021, 11:53:11 am
content: The input is 5v acThe threshold is 2vAnd the output when crossing the threshold

author: Zero999
author_rank: Super Contributor
timestamp: June 30, 2021, 12:35:38 pm
content: Quote from: mnt22 on June 30, 2021, 11:53:11 amIs that 5VAC RMS, or peak?You obviously haven't read my previous post properly, including clicking on the links. Please do that and either come up with a rough sketch, or ask specific questions, relating to my previous post. Failing that, count me out, of this thread.
Voltage measurement/display of a battery WHILST being charged. - Page 1
Forum section: electronics / beginners

author: antong
author_rank: Newbie
timestamp: January 29, 2018, 09:21:57 am
content: HiI am new to the forum and a newbie regarding Electronics. I have a question regarding devices that displaythe current voltage of a battery whilst being charged. How is that done exactly?If you connect a voltmeter across the terminals of battery (e.g. a car battery) it would measure approx 12Vdepending on the state of charge. That is fine. However, when the battery is connected to a charger (conventional orsolar charger), it charges at a high potential difference e.g. +14V. But how does the charge controller reflect the truevoltage (12-13V) and not the higher voltage whilst being charged?Does it stop charging for a split second, measure the voltage, display it, and then resume charging or what?Any info/reference would be appreciated.I have also heard of the term Battery Driver. Is this similar to a charger except that you could leave it connected or is thatanother device?RegardsAnton

author: amspire
author_rank: Super Contributor
timestamp: January 29, 2018, 09:35:30 am
content: You certainly can stop charging, let the voltage settle and measure the voltage, but the old-style chargers with analog meters just had a green region that was the normal discharge range, and say an orange region above the green that was the charging voltage range. They didn't try to show the actual zero current battery voltage while charging at all or even estimate the percent charge. They often had a line in the orange region for "Float Charge". When you see the normal charge cycle is complete and the battery is sitting on the float charge line, you know the battery is fully charged.You also have to take into account the fact that the battery voltage changes with temperature - the charger should change its voltage with temperature too.

author: danadak
author_rank: Super Contributor
timestamp: January 29, 2018, 11:58:06 am
content: Some basics on charging Lead Acid batteries -https://www.powerstream.com/SLA.htmRegards, Dana.

author: David Hess
author_rank: Super Contributor
timestamp: January 29, 2018, 08:41:25 pm
content: One trick that may be used is to modulate the charging current slightly and read back the modulated voltage. Between these two things, it is possible to calculate the battery's resistance and from there, the "open circuit" battery voltage can be estimated. Offhand I do not know of any commercially available chargers which bother doing this though.Usually just the charging current and voltage at the battery terminals are good enough.
Voltage mode vs current mode signalling  - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: March 02, 2019, 03:44:45 am
content: For current-mode drivers, why is it easier to control output impedance ?For voltage-mode drivers, why "0.25 to 0.5" of the current needed for a given output voltage swing ?

author: RoGeorge
author_rank: Super Contributor
timestamp: March 02, 2019, 03:59:07 am
content: An ideal current source have infinite internal impedance.The only way to get a 50 Ohms total out of an infinite impedance is to put a 50 Ohms in parallel with the infinite impedance of the current source.An ideal voltage source have zero internal impedance.The only way to get a 50 Ohms total out of a zero impedance is to put a 50 Ohms is series with the zero impedance of the voltage source.

author: promach
author_rank: Frequent Contributor
timestamp: March 02, 2019, 04:24:40 am
content: What is the purpose of the two opamps in the voltage-mode driver shown the first post ?How do the two opamps contribute to current amount reduction ?

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2019, 12:51:53 pm
content: Quote from: promach on March 02, 2019, 03:44:45 amWith the voltage-mode drivers, the resistance of the output transistors is in series with the source termination. With the current-mode drivers, the resistance of the output transistors is in series with a constant current source making it irrelevant except in lowering the output compliance voltage.Note that in both cases, it is not absolutely necessary to use source termination which would halve the current required for the current-mode driver and halve the voltage required by the voltage-mode driver but the series resistance of the transistors in the voltage-mode driver would still be a problem.QuoteThat is incorrect. For a given output voltage, the voltage-mode drivers only require 1/2 the current because they are driving twice the output resistance from the double termination but they also only produce 1/2 the voltage.Quote from: promach on March 02, 2019, 04:24:40 amThe operational amplifiers just represent the regulated supply voltages. Note that the second operation amplifier is providing twice the output voltage because half is lost in the source termination which is inexplicably not shown.QuoteThey do not. That is a function of the double termination (not shown) used with the voltage output drivers. They author may have been suggesting that a second supply voltage of twice the value is necessary to get the same output as the current-mode driver.

author: promach
author_rank: Frequent Contributor
timestamp: March 04, 2019, 03:17:25 pm
content: SeeCurrent-Mode vs Voltage-Mode Summary
voltage multiplier - Page 1
Forum section: electronics / beginners

author: Pirateguy
author_rank: Regular Contributor
timestamp: July 23, 2018, 07:10:45 pm
content: how do i chose the caps and diodes for this?i presume the capacitance doesn't matter much but i am wondering about voltage ratings.

author: David Hess
author_rank: Super Contributor
timestamp: July 24, 2018, 02:19:50 am
content: The series arrangement of the common Cockcroft-Walton voltage multiplier shown means that the diodes and capacitors only need to be rated for greater than the peak-to-peak input voltage.

author: Pirateguy
author_rank: Regular Contributor
timestamp: July 24, 2018, 03:21:53 am
content: ok lol that changes things considerably.thanks for the help.

author: Raj
author_rank: Frequent Contributor
timestamp: August 09, 2018, 04:30:31 am
content: i'd say, tripple of input voltge for safety.Even in simple bridge rectifiers,we use overrated diodes and caps

author: Pirateguy
author_rank: Regular Contributor
timestamp: August 13, 2018, 12:02:26 am
content: nevermind, scrapping this idea in favor of a marx generator.

author: Wolfgang
author_rank: Super Contributor
timestamp: August 13, 2018, 09:36:44 pm
content: Why dont you simulate one and see how it works and what voltages and currents you can expect ?Like here:https://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-1kv-50ma-linear-power-supply/Just to be on the safe side, ...- At very high voltages, caps and diodes need equalizing resistor chains- The bottom side caps get the most ripple current. This can be considerable, and if you use electrolytics you need to check for ripple current ratings- dont forget bleeder resistors so that stored charge does not stay there forever and kills the operator long after the beast has been switched off- watch isolation distances- use HV fuses only, check for ratingHV can kill. Have fun but dont be silly !

author: Pirateguy
author_rank: Regular Contributor
timestamp: August 13, 2018, 11:59:03 pm
content: i ordered some 1kv ceramics and looking at this schematic:i saw another where the first resistor on the left was 10M.the scope of the project is to incorporate this into a miniature diorama,and to produce visible sparks. i intend to limit current as much as possibleand in the end it should be no more dangerous then a stun gun module.(hell, if things get too hot or whatever i might just end up faking it with one of those modules)anyhoo i still have some reading to do on this one, it is one in a long list of miniaturization experimentsi have lined up.the bleeding resistor, it can be the same watt rating as the rest?
Voltage multiplier for use with benchtop dc power supply - Page 1
Forum section: electronics / beginners

author: Version 7
author_rank: Newbie
timestamp: September 23, 2016, 12:39:24 am
content: I have a 0-30 volt, 0-3 amp adjustable DC power supply which works fine for most of my needs, but I recently came across the need to be able to test LED strings from televisions and using 9 volt batteries in series is kind of a pain. I'm wondering if I can build a voltage multiplier to use with my current power supply to get me up to the voltages I need. I can't imagine needing any more than 110 volts at 800-900 mA max.Thank You

author: danadak
author_rank: Super Contributor
timestamp: September 23, 2016, 01:30:08 am
content: Based on DC values your supply generates a max of 90W, yourLED string ranges from 88W to 99W."Normally" you could think of a boost regulator, its efficiencymaybe around 85% which says you input to it ~ 117W worstcase.One way. relatively cheap, is a auto inverter, 12V to 110, and rectifyits output and filter.Regards, Dana.

author: Ammar
author_rank: Regular Contributor
timestamp: September 23, 2016, 01:41:08 pm
content: If you can deal with an unregulated supply, perhaps a step down transformer and rectifier will do the trick.
voltage multiplier problem - Page 1
Forum section: electronics / beginners

author: justin66
author_rank: Regular Contributor
timestamp: August 09, 2015, 08:57:51 pm
content: i build voltage doubler circuit and it worked out perfectly but when i have built voltage tripler circuit it doesnt work i both tried with dc and ac why tripler is not working? i checked if everything ok 2 timesmy setup:17V 6A transformeredit: when i connect my transformer to tripler my multimeter report 8v dc and 0 volt ac but when i connect a speaker i dont need i clearly hear nasty sinewave

author: retrolefty
author_rank: Super Contributor
timestamp: August 09, 2015, 09:15:25 pm
content: An 8 ohm speaker will present quite a large load for that circuit and the ripple voltage will rise significantly. A O-scope is a better means to evaluate your voltage multiplier circuits.

author: lapm
author_rank: Frequent Contributor
timestamp: August 10, 2015, 12:26:42 am
content: Downfall of these diode-capacitor voltage raisers is you cant really load them significantly. 8 Ohm speaker is big load. Like already mentioned, use oscilloscope...Lets see, you have 17 V transformer, triple that should be 51 volts. Put that to 8 Ohm load and you should get 6,3 Amps of current flowing. Way too much for this sort of voltage raising circuit. No wonder its failing.

author: justin66
author_rank: Regular Contributor
timestamp: August 10, 2015, 10:06:52 am
content: with no load multimeter reported 8 volts dc instead of suposed 75v dc my voltage doubler gives me 50v dc with quite a good load lm3886t rocking at full blast but because i dont have split lane psu im spliting that 50v into a 25v. btw im using 2200uf capacitors in my circuit. and it still make no sense why is that trippler is not working? osciloscope is on queue to buy

author: mikerj
author_rank: Super Contributor
timestamp: August 10, 2015, 02:59:56 pm
content: Quote from: justin66 on August 10, 2015, 10:06:52 amDouble check the polarity of your diodes, and that none of them are shorted.However, even with large caps you can't draw much current from a doubler (and especially a tripler) running at 50/60Hz without the ripple becoming very large. The peak diode currents will also be very high, so you'd better have some heavy duty diodes in your circuit.
Voltage Noise Density of Resistor - Page 1
Forum section: electronics / beginners

author: vim831
author_rank: Newbie
timestamp: February 06, 2014, 11:59:57 pm
content: Hello,I want to gain a proper understanding of what thermal noise in a resistor really is. I have a basic understanding but i was hoping someone could explain it in better detail.Yes, this is a homework question, however I really want to understand this more than I want to get the answer correct. My current solution is attached.V = sqrt (4kTBR) explain what this equation means and how it is derived.Thanks.
Voltage on LED driver chasis - Page 1
Forum section: electronics / beginners

author: CranberryFire
author_rank: Contributor
timestamp: January 17, 2022, 03:01:13 am
content: I have some meanwell HLG drivers and I am measuring about 1.3v from me to the chasis(touching it with a sensitive part of the skin like the wrist gives a slight shock). Chasis is grounded, and live and neutral are not reversed. Any ideas whats going on?

author: Munyua44
author_rank: Contributor
timestamp: January 17, 2022, 04:37:32 am
content: i think there is a discontinuation of the grounding somewhere in the chassis. You should try doing it at random places in the chassis and see the reactions that you get.

author: magic
author_rank: Super Contributor
timestamp: January 17, 2022, 07:48:54 am
content: Sounds like it's not grounded or maybe grounded to neutral or your mains ground is not actually grounded?That being said, I wouldn't touch random parts of the chassis to see where it kicks you the most but inspect the device and/or check continuity with DMM (disconnected from mains).

author: Zero999
author_rank: Super Contributor
timestamp: January 17, 2022, 10:28:49 am
content: Have you checked the earth connection? If it's good, then don't worry. It's normal and is due to the tiny leakage current through the Y-capacitor.

author: CranberryFire
author_rank: Contributor
timestamp: January 17, 2022, 06:17:29 pm
content: Quote from: magic on January 17, 2022, 07:48:54 amThe chassis is grounded to the ground prong of the plug, I had checked that already with my DMM.

author: magic
author_rank: Super Contributor
timestamp: January 17, 2022, 09:24:13 pm
content: That's weird, I would expect to feel nothing when touching a truly grounded object, unless simultaneously touching some other ungrounded object with some voltage on it.I had one of those "tingling" ungrounded power supplies and it only tingled when I touched it with one hand and grounded stuff with the other.
Voltage on sensors vs. voltage on board. - Page 1
Forum section: electronics / beginners

author: roffvald
author_rank: Unknown
timestamp: March 27, 2016, 10:13:11 am
content: Please excuse my noobishness(if that's a word), but I've been getting into the hobby of electronics over the last months, mostly putting together kits or simple circuits from schematics.However now I have an actual project on hand where I will be using an ESP8266 12-E to connect 6x temperature/humidity sensors(DHT11) for use in a server room.I have ordered this board through OSHPARK(Not designed by me) (https://oshpark.com/shared_projects/9CsYq2PY+https://github.com/8n1/ESP8266-Breakout-Adapter/tree/master/Breakout%20Adapter%20v1.1%20-%20LM1117) and will be soldering the ESP8266 module to that. The board has an onboard 3.3V regulator for the EPS8266, however I would like to run the sensors on the 5V i plan to input to the board. Will this work or do I need to also run the sensors on 3.3V? Is a pull up resistor needed for the signals from the sensors and would 4.7k do?I will be soldering and putting everything together, my friend who is a coder is doing the coding.Sorry if I left something out, and thanks for any help. This forum has provided me with hours of interesting reading, so thanks for that too

author: Alex Trofimov
author_rank: Contributor
timestamp: March 28, 2016, 10:46:44 am
content: I think, it may work. In this case don't forget that low state on the I/O line should be 0 volts, but high state should be Hi-Z, because the pull-up resistor is the sourse of high logic level. The last one should be connected to 3.3V in this case. And 4.7k resistors would do the buisiness, if your cable from board to sensor is less than 20m, according to the datasheet on DHT11.But, why bother. :-) 3.3V is within valid DHT11 power supply voltages range. LM1117's power capability is weeeeell enough to power 6 DHT11's. So I'd use onboard 3.3V supply for everything.

author: roffvald
author_rank: Unknown
timestamp: March 28, 2016, 01:52:33 pm
content: Thanks for the feedback, it makes sense. The wiring will be at most 10m. And I've been reading some more datasheets so as you said I'll just stick with the onboard 3.3V.
Voltage Potential vs. Rating - Page 1
Forum section: electronics / beginners

author: nathon
author_rank: Contributor
timestamp: August 23, 2015, 04:59:54 pm
content: I have an odd question. In my (limited) understanding of voltage and current, it seems it's really the potential (difference) between the ground and VCC states that make a circuit operate.This being said, are ratings also simply a function of that difference? I give two examples below with my assumptions. You can tell me if I'm wrong.1: Ground is 50V, VCC is identical to GND (50V). I assume the circuit will do nothing. Any components rated below 50V won't care since there is no difference between GND and VCC.2: Ground is 50V and VCC is 5V higher (55V) on a circuit designed to operate at 5V. I assume it will operate as intended. Components rated for 5V will function normally.Can anyone tell me if I'm mistaken or not and why? Of course I'm ignoring Earth ground references in these examples. These would of course have to be floating.Thanks for satisfying my curiosity. I don't have any electronics education and am trying to determine if I understand things correctly. This is one question I've been asking myself for a while.

author: retrolefty
author_rank: Super Contributor
timestamp: August 23, 2015, 05:17:15 pm
content: As an example certainly say 3 5vdc power supplies can have their outputs wired in series to make available +5, +10, and +15 volts relative to negative terminal of the 'bottom' supply, as long as the supplies have isolated outputs relative to their AC input terminals.Your use of 'ground' term is taking on a more important role then it is in reality. In the above series supply example one could use the positive terminal of the 'bottom' supply be called and used as 'ground' and therefore have available -5vdc, +5vdc, and +10vdc. What you use and call 'ground' should rather be called 'circuit common' or just 'common' to make it clear that you, the circuit designer, is the one that determines what circuit point is to be common and all other voltages are relative to that circuit common point.Ground, earth, circuit common terms can be confusing to newcomers (and some old-timers) and usually requires more 'system context' to best describe what is trying to be confided in the circuit schematic.

author: Neilm
author_rank: Super Contributor
timestamp: August 23, 2015, 05:22:13 pm
content: You have that understanding correct. It is the potential difference across a component that causes it to work. It does not matter if the reference (0V) voltage is connected to earth, 50V or 50kV. It will also work if the 5V is connected to earth, with the 0V being at -5V. (indeed, that is the way some inverter circuits work).

author: nathon
author_rank: Contributor
timestamp: August 23, 2015, 06:46:43 pm
content: Thanks guys! I'm picking this stuff up as I teach myself. That topic was one that I was sure must be true, but I wanted to put it to the smart people here to make sure.I'm kind of nutty in that I have a need to know every microscopic detail of something before I'm satisfied. Thanks for helping me get a little closer. :-)
Voltage rating of SMD tantalum cap - Page 1
Forum section: electronics / beginners

author: XantheFIN
author_rank: Contributor
timestamp: February 10, 2021, 09:55:28 am
content: I need 1uf rated cap in one project and found this from this old pcb. But i am slightly unsure what is this Voltage rating or week code plus old letter voltage rating from the past. The symbol at the end confuses.I tried to search but i can't find.Thank you in advance for your knowledge and time.

author: KT88
author_rank: Frequent Contributor
timestamp: February 10, 2021, 10:23:29 am
content: They are 25V and 35V. But I won't salvage tantalums for a new circuit - you'll never know which abuse they have taken so far and when they eventually might blow up...A rule of thumb is to operate them at half of the rated voltage and avoid high current transients. If you could tell if the used caps were treated well, you might still be fine to use them...CheersAndreas
Voltage ratings on Relay - Page 1
Forum section: electronics / beginners

author: Jesper
author_rank: Newbie
timestamp: March 05, 2017, 02:59:24 pm
content: Hi,I have a relay where the coil is rated 230VACand a relay where the contacts is rated 250VACAre these values peak or RMS ? I've been looking at some datasheets, but can't find that information.kind RegardsJesper

author: grumpydoc
author_rank: Super Contributor
timestamp: March 05, 2017, 03:16:20 pm
content: They will be RMS

author: Jesper
author_rank: Newbie
timestamp: March 05, 2017, 07:42:30 pm
content: Thanks

author: Zero999
author_rank: Super Contributor
timestamp: March 05, 2017, 09:22:31 pm
content: Just beware that the ratings are for 50 or 60Hz AC only, not DC.
Voltage Reference. - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: September 14, 2015, 04:16:10 am
content: Scullcom did a reviews of a couple cheap eBay voltage references any has anyone ever played with one and has it stayed in calibration and was it worth it

author: Wisnaeme
author_rank: Unknown
timestamp: September 14, 2015, 02:15:37 pm
content: If you mean discrete parts for self calibration/matching I use TL431A parts.They're pretty stable adjustable references for day to day use in circuit and as a stock calibration.Maybe not accurate enough for exacting use, but it's my favourite "Power Zener" type reference at <$1 eachR

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 14, 2015, 02:20:33 pm
content: Quote from: TorqueRanger on September 14, 2015, 04:16:10 amI do have one of these 4-channel China refs.I was able do check it with calibrated test gear @ Makerfaire in june 2015 in Germany after 7 Month of ownerchipThe result was excellent.So I ca recommend it strongly.
Voltage Reference from a Battery Charger IC - Page 1
Forum section: electronics / beginners

author: ziggyfish
author_rank: Regular Contributor
timestamp: December 01, 2016, 11:35:11 am
content: Hi,I am currently looking for an IC to charge a 6S battery when I plug an adapter into it. The one I am thinking of using is thebq24630.The great advantage of using this IC is that it comes with a 3.3 output voltage reference (VREF), with a regulation voltage of 3.267 to 3.333 which is stable enough for my purposes. However, it only supports a 35mA current draw. However, I need a 1-2A current output to run the rest of the system. (the output of the charger IC voltage will be used directly to other components of the system, i.e., I need 3.3V and a VBAT(22V to 28V @ 13A) rail).My question is considering that the I already have a 3.3 VREF and in the interest of cutting down the component costs (and possibly better efficiency gains too), is it wise to use this VREF, and if so is there a way to use this VREF to power larger loads?Would using this VREF be better than using say a buck converter?
Voltage reference max6070 - Page 1
Forum section: electronics / beginners

author: bogdant
author_rank: Regular Contributor
timestamp: January 24, 2020, 07:03:08 am
content: I have the voltage reference max6070 the 3.3V variant used in my new power supply schematic. It is hooked to Vref from the microcontroller stm32f767. The schematic implemented is the one recommended by datasheet. But the output voltage is 4.6V, if the input is 5V. This is the first time when I use an voltage reference.Here is the link to my schematic:https://github.com/bogdan-tirzioru/Powersupply/blob/master/factory/sampleB/Job2.PDFI have also tried a new chip soldered on an empty board, without any load, but I have the same voltage on the output of reference 4.6V.The layout can be found on the location:https://github.com/bogdan-tirzioru/Powersupply/tree/master/factory/sampleB/GerberAny idea what could be the problem? Does anyone used this chip ?

author: aheid
author_rank: Regular Contributor
timestamp: January 24, 2020, 08:46:47 am
content: Just for kicks did you connect a load resistor testing it alone? Also, is this part from reputable dealer or random Chinese seller?

author: bogdant
author_rank: Regular Contributor
timestamp: January 25, 2020, 05:23:36 pm
content: Initial did not connected any load, but after you tell me about it, I did connected 22k resistor and make it worse , now I have a short between In and Out.
Voltage Reg dropping out - Page 1
Forum section: electronics / beginners

author: ikrel
author_rank: Contributor
timestamp: February 08, 2014, 03:12:22 am
content: I'm trying to setup a voltage regulator and every time I put a load on it the voltage drops out. It goes from 24v to 15v with 100mA of load, and I don't know why. I eventually want this to handle 6A of current. Can anyone explain this?This is what I have going:

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2014, 03:25:05 am
content: It's regulating to a ratio of VCC, which assumes VCC is regulated to begin with.It may be oscillating too. 1N4007s and 2 x 470uF aren't even in the ballpark for 6A, of course.Read up on: power supply design, source impedance, voltage reference, loop stability and so on.Tim

author: ikrel
author_rank: Contributor
timestamp: February 08, 2014, 03:52:33 am
content: This is just the "get it to work stage." Once I have it working I'll work on getting the actual output current i want.I've also just figured it out. The value of the 1K resistor on the base of the transistor was too high and was not allowing the current needed to keep the transistor turned on.

author: c4757p
author_rank: Super Contributor
timestamp: February 08, 2014, 03:55:47 am
content: Quote from: ikrel on February 08, 2014, 03:52:33 amDude, when you want to build a car, you don't start by throwing a lawn chair on a wheelbarrow, then fix the problems. Start with the end specs in mind.

author: ikrel
author_rank: Contributor
timestamp: February 08, 2014, 05:30:31 am
content: The diodes fit in the bread board(I have higher current ones that I will use for the PCB), the TIP41C is good for 6A(I've now switched to a FRP50N6 MOSFET).I still have to Research how to size the filter caps properly(suggestions?)Also any suggestions on reducing/filtering the noise on the output? I'm currently getting 200mVp-p of noise and would like to reduce this.EDIT: no worries about the noise, just need to connect the ground lead the ground. do'h

author: Unknown
author_rank: Unknown
timestamp: February 09, 2014, 12:51:44 am
content: The point is that your circuit isn't a voltage regulator. At best, you've got a slightly complicated voltage follower.What happens to the 16.2v 'reference' on the wiper of the pot when the unregulated Vcc drops (e.g. when you load up the supply)? How does that affect your output voltage?
Voltage regulation - Page 1
Forum section: electronics / beginners

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 09:38:00 am
content: Question: I would like to make a digitally controlled 10V supply, starting from 5V from Arduino. If I were not to increase the voltage to 10V, I would use an R-2R ladder, controlled by digital pins. Is there any better way than introducing a voltage step-up regulator for each digital pin when using an R-2R ladder approach?

author: ggchab
author_rank: Frequent Contributor
timestamp: November 05, 2024, 09:49:31 am
content: I would create a reference voltage with the R-2R ladder/digital pins and then use an op amp to obtain the right voltage.I guess you don't need high currents ?

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 09:51:20 am
content: Good idea!Quote from: ggchab on November 05, 2024, 09:49:31 am

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 10:08:07 am
content: A follow up question: would the amplification stage work with a boost converter in case one should go to higher voltages (let's say 50V)? I am not sure how linear the response of the boost converter is in terms of output/input voltages.Quote from: ggchab on November 05, 2024, 09:49:31 am

author: tooki
author_rank: Super Contributor
timestamp: November 05, 2024, 11:50:15 am
content: A boost converter is not an amplifier. Its output voltage is regulated, and not a fixed multiple of the input voltage.The way to make a digitally-controlled boost converter is to manipulate the voltage on the feedback pin.Texas Instruments has a Java power supply design tool that includes a calculator specifically for how to design this:https://www.ti.com/tool/POWERSTAGE-DESIGNERSee page 18 of the user guide:https://www.ti.com/lit/ug/slvubb4b/slvubb4b.pdf

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 12:33:01 pm
content: Thank you very much!Quote from: tooki on November 05, 2024, 11:50:15 am

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 03:52:42 pm
content: Sorry again, trying to understand the circuit (in the screenshot below).I have the output voltage of 50V in my case, which I would like to digitally control. What is Vref and Vout here? I initially thought Vref can be e.g. 5V and Vout is 50V, but it does not seem it applies like this.Quote from: elki on November 05, 2024, 12:33:01 pm

author: elki
author_rank: Regular Contributor
timestamp: November 05, 2024, 04:02:32 pm
content: Sorry, I get it now!Quote from: elki on November 05, 2024, 03:52:42 pm
Voltage regulation recommendations(Vin=5-24V, Vout=5V,500mA) - Page 1
Forum section: electronics / beginners

author: EAvMx
author_rank: Newbie
timestamp: August 10, 2021, 03:09:59 pm
content: Hello, I'm looking for a circuit capable of receiving 5-24V in its input and output 5V and a maximum of 500mA.As far as I know, for LDOs worst case scenarios are Vin=24V where the LDO would waste too much power dissipated and Vin=5V where Vout would be lower than 5V because of the voltage dropped by the LDO.The latter being the same problem I'm facing while searching for Buck Switching Regulators.I found the TPS55165-Q1 but unluckily, its Vin needed to startup is 5.3V and it wouldn't work for me.I've been told that what I need is a SEPIC IC that boosts/bucks the input voltage to a fixed output voltage but so far after reading lots of datasheets I haven't been able to find a proper IC. Can someone please help me out recommending one?Thanks!

author: magic
author_rank: Super Contributor
timestamp: August 10, 2021, 03:42:10 pm
content: There are "low dropuout" buck regulators with P-cannel MOSFETs out there. For example, the common on auction sites XL4016 advertises 300mV dropout, presumably at full 8A load, which appears to be solely due to 40mΩ Rds(on) and could become 20mV at 0.5A. Because it's PMOS, it can be switched on 100% of time. But it needs 8V to run.Another potential alternative to complex switching topologies could be paralleling an ordinary linear LDO with an ordinary buck and adding some hack to turn on the linear reg when the buck can't work. But with linear LDOs it seems to be "cheap, ultlra low dropout, high input voltage range, pick two".

author: Hamelec
author_rank: Regular Contributor
timestamp: August 10, 2021, 03:48:29 pm
content: maybe something like that:https://www.ebay.de/itm/272638443626https://www.ebay.de/itm/311568532268

author: Benta
author_rank: Super Contributor
timestamp: August 10, 2021, 03:53:42 pm
content: Easiest is one of the small isolated DC/DC modules, eg, from Tracowww.tracopower.com.
voltage regulator - Page 1
Forum section: electronics / beginners

author: Cali-Sam
author_rank: Contributor
timestamp: August 14, 2014, 11:58:11 pm
content: my understanding is that you can basically make a voltage regulator out of a pot, an op-amp and a transistor, just like Dave's dummy load but without the load resistor..... the problem is that everywhere i look, i see a voltage reference being used and connected to one of the op-amp's inputs.....why do i need a voltage reference? can i get away with a pot instead?without a reference, you can drive the voltage down to 0 volts, why doesn't everybody use this? why do people use a regulators IC's that have 1.2v minimum voltage?.......

author: c4757p
author_rank: Super Contributor
timestamp: August 15, 2014, 12:06:45 am
content: The voltage reference is what the output is regulated with respect to. If you use a pot, an op amp and a transistor (assuming I'm picturing what you're picturing), the output will always be some fixed ratio to the input. If you use a reference, the output can be fixed no matter what the input does.Now, typically, a voltage regulator "contains" an op amp (in its block diagram, at least), and the voltage reference is connected to the (+) input, and the output is divided by a voltage divider and that goes to the (-) input. This gives you voltagesabovethe reference voltage. If you move the voltage divider to the reference side, you get voltagesbelowthe reference. This topology can be used for the very few times when you need a voltage under 1.2V.And I suppose the best answer to the "why" would be "almost nothing needs voltages under 1.2V".

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: August 15, 2014, 12:43:52 am
content: Getting 1V via linear regulation is pretty inefficient since your regulator (and rectifier, if you're starting from AC) will likely be dissipating at least as much power as the load. It's much more efficient to get low voltages using a DC-DC converter instead, and if you go to thePMIC - Voltage Regulators - DC DC Switching Regulatorsarea of digikey, you'll find a lot of options that support <1V output.Variable linear bench power supplies do use something like an op-amp and transistor as the regulator element so they can generate low voltages with low noise. But they are generally quite bulky, partly to deal with the heat generated in that scenario.
Voltage regulator 4th pin connection - Page 1
Forum section: electronics / beginners

author: robsims
author_rank: Frequent Contributor
timestamp: December 22, 2022, 11:55:27 pm
content: Hi,Attached is a datasheet of a voltage regulator i want to use. Voltage regulator is a PQ09RA11 with 9 volt output. I want this voltage regulator to further smoothen the voltage coming out of a self made power supply, after the bridge rectifier and capacitor. Output voltage of the power supplyis 20 volts so input voltage of the voltage regulator will be 20 volts. Question is can i connect the 4th pin at the + input for it to work? I don't want to use it with a separate voltage source.

author: BillyO
author_rank: Super Contributor
timestamp: December 23, 2022, 12:11:57 am
content: That should be fine.

author: argentas
author_rank: Newbie
timestamp: December 23, 2022, 12:39:30 am
content: Yes, it will be fine to use the supply voltage to trigger the switch input.How much current will your load be drawing? Bear in mind that regulating down from 20V to 9V will involve dissipating the rest as heat, so you'll need a heatsink unless your output requirements are very small.

author: robsims
author_rank: Frequent Contributor
timestamp: December 23, 2022, 09:11:33 am
content: Quote from: argentas on December 23, 2022, 12:39:30 ammany thanks guys. I was afraid to ruin the regulator. My load will be drawing 20 mA