hybridfree/eevblog-posts huggingface dataset:
Voltage indicator circuit, thoughts and suggestions - Page 1
Forum section: electronics / projects

author: darko31
author_rank: Regular Contributor
timestamp: April 08, 2013, 09:47:24 pm
content: Hi everyone,I'm in a need of simple voltage indicator of lead acid batteries, and I've came up with a simple circuit with LM324 op-amp and some LEDs. Resistors at the inputs of the op-amp serve as voltage dividers, and some trimpots for fine tuning of voltages. The main goal is to keep it cheap and simple.Does anyone have any suggestions?Is using a microcontroller with an ADC better idea?

author: kxenos
author_rank: Frequent Contributor
timestamp: April 08, 2013, 10:09:30 pm
content: Hello. Normally you would use a comparator for an application like this, except if there is an extra op-amp you can spare. If you use an op-amp normally you would want to drive your LED with a small MOSFET to avoid drawing a lot of current from your op-amp. You can add a feedback resistor to create hysteresis as this will make your transition cleaner. Also you can take a look at LM3916 if you want a fancy bargraph or coarse voltage measurement indication. Cheers!

author: audiffred
author_rank: Newbie
timestamp: April 09, 2013, 02:25:05 am
content: Consider a TL431 device. Figure 29 in the data sheet should get you started. The device can act like a simple precision comparator, and it's inexpensive when pennies matter.http://www.ti.com/product/tl431

author: 6502nop
author_rank: Regular Contributor
timestamp: April 12, 2013, 08:59:14 am
content: Sorry for the late reply...A while back, I posted this circuit based on the LM339 quad comparator chip. I tweaked a few things, and applied it to read the battery that powered the circuit. Hence, I came up with the name "Battery Under Test Tool/Sniffer", or "BUTT/Sniffer". All notes are included in the diagram, along with the simple math to calculate the values for your particular application. The whole thing should draw no more than 60mA (100mA if you cascade two LM339s).If you have any questions not covered, holla back.nop

author: darko31
author_rank: Regular Contributor
timestamp: April 12, 2013, 10:38:29 am
content: Thanks everyone for replies, I've took advice and used LM339 in some simulations, everything is working perfectly, I've designed something similar as 6502nop, now I just need to order some parts and get the thing working.LOL, BUTT Sniffer, funny name 6502nop, and good one, too.
Voltage insulation with Prepreg PR2125 of 0.2mm - Page 1
Forum section: electronics / projects

author: SwissEngineer
author_rank: Contributor
timestamp: February 29, 2016, 10:43:44 am
content: Hello everyone,I am designing a board with 1000V in 6 layers with Eurocircuit. But I don't now if the internal insulation of the board is enough..... (stackup attached)It says Prepreg - PR2125 0,1mm X2. But I can't find any information on the prepreg about voltage insulation....Thanks for the help
Voltage Inverter? - Page 1
Forum section: electronics / projects

author: negativ3
author_rank: Regular Contributor
timestamp: October 13, 2015, 10:14:02 am
content: Hi all,I have a linear sensor which acts like a pot in that +24V supply across it gives an output 0-2.5V at the wiper.Is it possible to invert the output (somehow) so that it runs 2.5V to 0V instead of 0 to 2.5V?So 0V out of the sensor I want 2.5V and 2.5V out of the sensor I want 0V.I have tried reversing the supply however the sensor must have some built-in clamping going on to prevent reverse supply connection.http://www.regal.se/data/prodfile/ktc_ktf_ktp_en_2015.pdfMany thanks.

author: negativ3
author_rank: Regular Contributor
timestamp: October 14, 2015, 02:22:39 am
content: Thanks blueskull.

author: mikerj
author_rank: Super Contributor
timestamp: October 14, 2015, 10:02:03 pm
content: The datasheet suggests the sensor can either be supplied as a simple potentiometer or with a 4-20mA output. If you have the basic potentiometer model, why are you only getting 2.5v maximum at the wiper with a 20v supply? Do you have the 4-20mA version?

author: negativ3
author_rank: Regular Contributor
timestamp: October 15, 2015, 12:58:55 pm
content: Good question mikerj, I shall confirm what is here with a meter in series with the output.

author: mikerj
author_rank: Super Contributor
timestamp: October 15, 2015, 09:28:59 pm
content: You could just read the model code of the device (assuming it's readable/still present) and check against the datasheet.

author: negativ3
author_rank: Regular Contributor
timestamp: October 25, 2015, 06:50:18 pm
content: Turns out it indeed is a 4-20mA output. Good call. No label available unfortunately.
Voltage is dropping down !!! - Page 1
Forum section: electronics / projects

author: shaikss
author_rank: Newbie
timestamp: June 19, 2013, 07:42:54 am
content: Hi Folks,I have designed a rectifier and regulator for RFID Tag. Both are working fine when they are simulated independently.When I gave 500mV as input to 4-stage rectifier, I got 1V output for open load ckt condition.Now, I have connected rectifier to regulator. Rectifier output is 500mV. What may be the reason? Because of the load, current decreases. That is fair. But why voltage is decreasing? Any clue. When regulator has run independently, it consumes 836nW of power. I am in desperate need of help. Pls help me.

author: rkupka
author_rank: Regular Contributor
timestamp: June 19, 2013, 08:38:06 am
content: how about posting a schematic first ?

author: vk6zgo
author_rank: Super Contributor
timestamp: June 19, 2013, 08:47:43 am
content: The fact that the output voltage is halved implies that the input impedance of the regulator is equal to the output impedance of the rectifier.Do you have any figures for these impedances?My first reaction was that your input voltage was too small to turn a diode on,but when I Googled for 4 stage rectifier I found the following which may be helpful.:ftp://202.196.33.229/NSTL-english/2010/20100105/zx94333767_02.pdfIt lost me on the second page!
voltage limiter - Page 1
Forum section: electronics / projects

author: bpwmd
author_rank: Newbie
timestamp: November 26, 2013, 09:06:15 am
content: ok so heres the details guys.Im making a Boba Fett helmet and i want the rangefinder to move electronically.i used to be a mechanic and a typical window motor has a circuit that turns off the circuit when the window reaches its mechanical limit causing the motor to draw more voltage.id like to make the circuit like that. i have no problem if it involves a IC chip. id like to run it off 3 max 9v's in parallel for longevity and dont mind if i need a voltage limiter to supply it. i want the power to later power a audrino later for some other projects in the helmet. i need it to move up and down with a corresponding direction momentary switch with no need to hold the switch during operation, and stop at 0 and 90 degrees. size is limited due to limited area in the helmet. i want to stay away from limit switches due to the complexity of all the parts. i wanna use either a small electric motor or a RC servo as the part is very light.i hope i have enough info here to get some help

author: fcb
author_rank: Super Contributor
timestamp: November 26, 2013, 09:46:09 am
content: Stepper motor or model servo. Both are simple/hard to drive depending on who you know.Stepper motor would be my choice as it is mechanically more robust but perhaps heavier. Have a look at someone like zappautomation or similar.

author: bpwmd
author_rank: Newbie
timestamp: November 26, 2013, 09:49:54 am
content: i would need help with the diagram. i havent the slightest idea how to design it.

author: BravoV
author_rank: Super Contributor
timestamp: November 26, 2013, 10:03:30 am
content: Don't hang you expectation too high, I just don't think people will come out with a complete circuit ready to build just for you, my 2 cents.

author: bpwmd
author_rank: Newbie
timestamp: November 26, 2013, 10:04:59 am
content: lol that i know but help would be wonderful!
Voltage Limiting - Page 1
Forum section: electronics / projects

author: MSD
author_rank: Newbie
timestamp: August 30, 2018, 04:30:45 am
content: Hi.I'm a beginner in circuit design. I've got a switching power supply that can be adjustable between 4 and 6 volts at 9A powering an atmega328p microcontroller and 4 max7219 display driver ic's. At 6 volts the max7219 ic's fail its operating range is 4 to 5.5 volts.How can i limit the voltage to the operating range of the max7219 at the circuits maximum current draw of 2A at the lowest cost in case the power supply is set to its maximum?I've tought about using a diode for its voltage drop. Would this be recommended? If so how would I go about selecting a diode for this purpose?

author: aju11
author_rank: Contributor
timestamp: August 30, 2018, 06:59:00 am
content: Option 1: A series resistor and zener across supply of MAX7219 ICs to clamp the supply.Option 2: I would prefer to use a series pass regulator set to around 5 V.http://www.circuitstoday.com/voltage-regulatorsUsing a diode won't be a reliable solution. The drop will change as per the current drawn.
Voltage limits of TECs - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: October 07, 2016, 03:14:39 pm
content: I'm in a bit of a bind.On one design we have a TEC that has a bit of a lead time and was hoping to substitute it in case we run out. Dimensions, delta-T and everything else are the same but the voltage ratings are slightly different. The old part has a maximum voltage rating of 4.3V, while the new one is 3.8VNow, the TEC driver does have a 5V supply but it only peaks up that high very briefly at initial boot, then it's just temperature stabilizing. It's regulating the temperature of a small piece of metal. Steady state operation is <1V.I would say that current 4.3V TEC is a bit under-speced and it would be ideal if the driver was running off of 3.3V.How bad is it for the TEC to receive a voltage larger than it's rating? With motors you can overdrive them a bit as long as it isn't prolonged. Am I playing with fire by checking off that the 3.8V TEC is a suitable substitute in a pinch? It looks like it's driving fine, but could the voltage rating cause serious issues down the line?

author: Kleinstein
author_rank: Super Contributor
timestamp: October 07, 2016, 04:12:54 pm
content: Usually the current is the more important factor, not the voltage. If you use more than the so called optimum current (which is about the same as the specified maximum), the cooling effect will go down again. Otherwise it should be no problem to use a higher current / voltage as long cooling of the hot side is sufficient and the temperature is not close to the upper limit. It is more like a practical limit and than due to possible thermal effects. So short pulses should not be that bad. If cooling of the hot side is not perfect, the optimum current will be reduced - so the turn over to lower cooling usually comes earlier than the optimum current specified in the DS.For regulation one should avoid going higher, as the curve will change slope, so simple regulators will not work in the range well above the maximum. If you need to work close to the maximum current one should take into account the nonlinear (about an parabola) relationship of current to cooling power.A lower supply or TEC with a higher rated voltage could ease on the inductor for smoothing.

author: Pack34
author_rank: Frequent Contributor
timestamp: October 07, 2016, 04:25:21 pm
content: Thanks!
Voltage logger  - Page 1
Forum section: electronics / projects

author: kentfielddude
author_rank: Contributor
timestamp: May 29, 2025, 05:43:15 am
content: I want to make a simple device that records the voltage level of a car battery and logs it to an SD card. It needs to have precision of 0.1v and a voltage range of 5-17 volts.I'm going to be using Arduino.Can I just use a stm32 blue pill with a SD card module. Will a simple voltage divider work?

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 29, 2025, 09:36:31 am
content: Sounds ok to me, no reason why it shouldn't work. Just remember to put your STM32 on sleep power mode (3uA iirc), then wake up, sample ADC, write to SD card and sleep again. Wouldn't want to contribute to the voltage drop

author: CaptDon
author_rank: Super Contributor
timestamp: May 29, 2025, 01:32:16 pm
content: I wouldn't call .1v 'precision logging'. You could certainly easily do .01v resolution with a 10 to 12 bit ADC and adjusting the low reference pin to make 5VDC equal a zero count and adjust the divider and scaling so that 17VDC is full scale FFFh.

author: tooki
author_rank: Super Contributor
timestamp: May 29, 2025, 02:43:22 pm
content: Quote from: kentfielddude on May 29, 2025, 05:43:15 amYes. But an even more elegant solution is something like an INA226 or INA219 breakout board. More resolution, no voltage divider needed, and much more resilient to automotive voltage spikes. Really easy to use, too, thanks to ready to use libraries.

author: mawyatt
author_rank: Super Contributor
timestamp: May 29, 2025, 03:10:50 pm
content: Don't some of the cheap DMMs already log data?Best
Voltage mirror circuit - Page 1
Forum section: electronics / projects

author: garvind25
author_rank: Regular Contributor
timestamp: May 04, 2025, 03:42:59 pm
content: Hi,Does anyone know of voltage mirror circuit topologies? I need to replicate the voltage at one node of the circuit to another node. I can’t short these two nodes. A 1:1 transformer will be a bulky option. I tried searching the internet but did not come up with anything useful. Any pointers will be useful and gratefully acknowledged.Thanks.Arvind Gupta

author: Benta
author_rank: Super Contributor
timestamp: May 04, 2025, 03:46:48 pm
content: Isolation amplifier? Check Broadcom.

author: TimFox
author_rank: Super Contributor
timestamp: May 04, 2025, 05:24:48 pm
content: Please clarify:You have two circuit nodes. Do you want to mirror the voltage at those two nodes (each a point) with respect to the same reference node (e.g. “ground”), or do the two nodes have separate references?

author: garvind25
author_rank: Regular Contributor
timestamp: May 04, 2025, 05:56:30 pm
content: Thanks for the replies. Here is the clarification. The gnd is common. I have a node A whose voltage 'v' needs to be same at another node B. In other words the voltage 'v' generated at A should be replicated at B.

author: TimFox
author_rank: Super Contributor
timestamp: May 04, 2025, 05:59:05 pm
content: Is a simple op-amp “voltage follower” suitable?Node “A” connected to the non-inverting input, node “B” connected to the output and inverting input.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 04, 2025, 06:02:16 pm
content: Hello garvind25,Check out thisbuilding block.

author: Benta
author_rank: Super Contributor
timestamp: May 04, 2025, 06:23:21 pm
content: Quote from: garvind25 on May 04, 2025, 05:56:30 pmThat's called a wire. Perhaps with a buffer in between.Your description is imprecise, sorry.

author: TimFox
author_rank: Super Contributor
timestamp: May 04, 2025, 07:02:07 pm
content: Quote from: Benta on May 04, 2025, 06:23:21 pmFor some unstated reason, he can’t short the two nodes, which a wire does.The usual four-resistor op-amp diff amp can tolerate different references for the two nodes, but that’s not his problem either.

author: Benta
author_rank: Super Contributor
timestamp: May 04, 2025, 07:17:43 pm
content: Quote from: TimFox on May 04, 2025, 07:02:07 pmYeah. But it's also stated that the ground node is common. Very odd.

author: SteveThackery
author_rank: Super Contributor
timestamp: May 04, 2025, 09:00:43 pm
content: @garvind25: could you give us a bit more detail about the device? Obviously a piece of wire would do what you've described, so there is clearly more to your question. Could you give some context?
Voltage Monitor with Logging - Page 1
Forum section: electronics / projects

author: Mike Warren
author_rank: Unknown
timestamp: June 25, 2015, 03:57:37 am
content: I need to be able to log a nominal 12V system for up to a week. What Ineedto know is what the lowest and highest voltage was during the test, with 0.1V accuracy. It needs to be reasonably small, powered from the supply its measuring, must start automatically when connected and remember the data if power is disconnected. (manual clear only)It would, however, be nice to have some sort of record of how often the voltage dropped below or raised above a set range (say outside 10V to 14.4V).Also nice would be time stamps of the events, but neither of these things are required.Before I potentially reinvent the wheel, I thought I'd ask here if there is already something available that could be used to do this for less than about $200.If not, it will be a fun micro based project. Should be able to get away with a small AVR, regulator, a display, and a couple of buttons. Probably a voltage reference as well. Not sure the AVR built-in VRef is good enough, even for this simple job, although, since it's a one-off, I could calibrate it.

author: Mr.B
author_rank: Unknown
timestamp: June 25, 2015, 04:02:22 am
content: There are a bucket load on fleabay in that price range.Depends on the logging frequency you want, data points, etc.example:http://www.ebay.com/itm/USB-DC-Voltage-Data-Logger-32-000-Data-Recorder-LED-Alarm-DGraph-0-30V-BDV01-/360886321882Material: ABS, PCColor: BlueDC voltage measurement range: 0~30VAccuracy: ±1%±1countResolution: 0.04VMemory capacity: 64KBytesSample rate: 1 second to 12 hoursEdit:powered from the supply its measuring - NOTmust start automatically when connected - DON'T KNOW

author: dadler
author_rank: Unknown
timestamp: June 25, 2015, 04:11:13 am
content: Perhaps?https://moosh.im/mooshimeter/

author: Mike Warren
author_rank: Unknown
timestamp: June 25, 2015, 06:48:48 am
content: Thank you both for your replies. That eBay one looks particularly interesting, considering the price. I also found an Australian made one that doesn't appear to need a diver installed to read the data.http://www.ebay.com.au/itm/USB-Voltage-Data-Logger-Volt-DC-Recorder-Switch-Flash-Memory-Windows-Mac-/121678406965?pt=LH_DefaultDomain_15&hash=item1c54992535I hadn't considered a device without a display, which is why my eBay searches only turned up logging multimeters.None of these quite fit my specs, but I can be a bit flexible. Certainly worth looking into further.

author: dom0
author_rank: Super Contributor
timestamp: June 25, 2015, 08:11:04 am
content: One of the cheapest things you may be able to pull this off with is a chart recorder. Price: free to a few bucks (at most).

author: David_AVD
author_rank: Super Contributor
timestamp: June 25, 2015, 08:55:01 am
content: One thing to consider with a logger is are you interested in capturing transient values? If these occur between samples (1 per second at best) they won't be recorded.
Voltage monitor. - Page 1
Forum section: electronics / projects

author: daddario
author_rank: Regular Contributor
timestamp: May 09, 2016, 11:13:40 am
content: Hi folks!I'm having a bit of an headache here - I need to monitor the highest of two voltages, the region of interest is around 200mV, but it doesn't have to have a great deal of accuracy.Due to the low voltage just two diodes wouldn't suffice, so I threw together the simplest of active rectifiers. You know - a voltage follower with feedback taken after a series diode from an op amp's output. One for each source and then just two outputs combined - almost like an OR gate, but for analogue. I used an LM258 and a dual schottky, since there is some speed - rise/fall times around tens on ns and pulse widths of a few µs - nothing out of this world, but not exactly audio, either.Works as intended - bit slow, but I already knew that was going to happen. Has a bit of an issue, though - seems to kill opamps.I can only suspect excessive current in the negative input during switching low, but haven't figured out a proof for it that I could put in numbers.Here's a rough sketch to look at:

author: danadak
author_rank: Super Contributor
timestamp: May 09, 2016, 11:33:03 am
content: Nothing seems improper from schematic, even issuessuch as supply sequencing do not seem to matter sinceyour currents are limited.The only possibility I see is possible phase reversal if inputs takenoutside CM range. I think LM358 series is subject to this if mymemory serves me.What is observed behavior of OpAmp when it is "killed" ?You testing them in a different circuit ?You could get rid of the schottkys if you use an open collector comparitor,just a thought.Regards, Dana.

author: StillTrying
author_rank: Super Contributor
timestamp: May 09, 2016, 01:19:06 pm
content: I can't see anything in normal use there to kill the op amps.If external things are regularly connected and disconnected to the output the -ve inputs are vulnerable.1K to 10K in the feedback from output to -ve inputs ?

author: void_error
author_rank: Frequent Contributor
timestamp: May 09, 2016, 06:46:52 pm
content: You might want to check for any (unwanted) oscillations. Or take a quick lookhere- first thing that comes to mind - second circuit. I think Analog Devices has some neat app notes about precision rectifiers too.Or just try sticking a ~100p cap between OUT and IN- for each op amp. It'll slow it down but it'll also probably kill the oscillations. Note that this is not the proper way to do it so put a scope on the op amp output and check for any stuff that doesn't belong there.
voltage multiplier design - Page 1
Forum section: electronics / projects

author: alireza7
author_rank: Regular Contributor
timestamp: October 11, 2017, 05:54:35 am
content: hii have a flyback transformer which i want it to makes me 400v ac and i want to make it +-1600v dc by a four stage voltage multiplier circuit and i want it to give me 6maso i connected a 267kohm load to it.i get 2000v at no load but when i connect the load to the circuit the voltage drops to +-800 volt.i tryed frequency from 1khz to 100khzi use 220nf polyester capacitor and uf4007 diodesgenerally can i draw such current at such voltage with a four stage voltage multiplier circuit?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: October 11, 2017, 06:10:28 am
content: Show your schematic please.Andy

author: David Hess
author_rank: Super Contributor
timestamp: October 11, 2017, 11:58:53 am
content: What is the turns ratio on your transformer? If that is a flyback transformer from a CRT, then you are using way to many voltage multiplier stages.What are the output voltage with just the first stage of the multipliers?Did you use suitably fast and high voltage diodes?

author: alireza7
author_rank: Regular Contributor
timestamp: October 11, 2017, 06:22:45 pm
content: Quote from: David Hess on October 11, 2017, 11:58:53 amturns ratio is about 13:510first stage voltage about 250yes uf4007 is a fast diode

author: Etesla
author_rank: Regular Contributor
timestamp: October 12, 2017, 07:41:06 pm
content: Generally the higher value capacitors you use in your multiplier, the more your output voltage and current will act like you expect them to. You can also put a high voltage, high value capacitor across the output. So use bigger capacitors, and put a capacitor across the output if possible. Also, traditional flybacks by nature create a higher voltage output than will be reflected by your input voltage and turn ratio, at a lower than expected max current. I recommend running your flyback with a push pull configuration if possible, or with a full or half bridge if you only have one primary winding. This will solve that problem. On the note of safety, any HV circuit that has capacitors is inherently dangerous for obvious reasons. I recommend having something like a half meg bleeder resistor across the output at the very least.
Voltage rating of safety capacitors (x/y) - Page 1
Forum section: electronics / projects

author: pulse
author_rank: Contributor
timestamp: May 13, 2016, 02:21:53 pm
content: Hi!I'd like to build a transformerless power supply, but I'm not sure if I can use 250V rated standard film capacitors (x2 for example). Mains voltage in my country is 230VAC, which means 324V peak DC, so this looks like not so good idea, but since those capacitors are used directly on mains or phase to earth / neutral to earth for Y capacitors, I think there shouldn't be any problem with this, although voltage rating is only 250V. So, would that work?Thanks

author: wraper
author_rank: Unknown
timestamp: May 13, 2016, 02:43:51 pm
content: Their rating is 250VAC(safety approval) and they are specially made for mains AC voltage and to fail safely. Their DC rating usually is above 600V. If you use regular 400V DC cap, it will usually fail within a few years.

author: pulse
author_rank: Contributor
timestamp: May 13, 2016, 03:05:13 pm
content: @wraperThanks for that! I have only one more question: what about capacitors that don't have much data on them (only voltage and capacitance), how could I tell if they're safety capacitors? I have a couple of dark-brown capacitors that look just like ordinary film capacitors, but I don't know if they're x/y or just ordinary film capacitors. It says ob them "JR or TR" and 105K 250V. I know they are 1uF +/- 10%, but as I said, it doesn't say whether they're standard or safety capacitors.Best regards!

author: wraper
author_rank: Unknown
timestamp: May 13, 2016, 03:39:09 pm
content: Safety capacitors are covered with various certification logos, also X2/X1 or Y2/Y1 should be marked somewhere too. Voltage rating should be with "~" symbol, or "AC", "VAC" or something like this.Quotemost likely regular caps with DC rating

author: pulse
author_rank: Contributor
timestamp: May 13, 2016, 04:11:20 pm
content: Ok, thanks again!
Voltage rating of solar inverter transformer - Page 1
Forum section: electronics / projects

author: Circlotron
author_rank: Super Contributor
timestamp: June 07, 2016, 12:26:41 am
content: The day is coming where people will begin to discard non-working solar inverters. May of them have a honking big toroidal transformer. Does anyone know what is the typical inverter side voltage of these transformers is? Next step is to think of a project using one.

author: uncle_bob
author_rank: Unknown
timestamp: June 07, 2016, 02:03:34 am
content: Quote from: Circlotron on June 07, 2016, 12:26:41 amHi273.8328 VA at 281.68962 uH using a material that is optimum at 73.892 KHzThere are roughly a zillion different designs for these gizmos out there. They run to a wide variety of output voltages and loads. The inductors in them are going to be all over the place. Simple answer is to pull it off the board, measure it, and see what you have.Bob

author: Seekonk
author_rank: Super Contributor
timestamp: June 07, 2016, 05:11:12 pm
content: You will be waiting a long time. Any broken solar electronics still brings big bucks on ebay and that is likely to continue.
Voltage rating on scope - Page 1
Forum section: electronics / projects

author: eponte5
author_rank: Newbie
timestamp: March 15, 2016, 04:09:18 pm
content: I have a Rigol DS1062CD that shows on the BNC "all inputs 400V Max"I'm pretty certain that if I use a differential probe like the one Dave sells in his Amazon store, (B&K Precision PR-60 Active Differential Probe) which the data sheet states 700V max, I'd be ok to use it on my scope since it's an isolation probe.My question is what about a X100 scope probe that says it's safe for 2000V max. Because its directly connect to my scope without isolation should I still only use it to 400V Max?The conservative/safety conscience me says 400V max.I don't have at this moment a voltage higher then 400V to measure, but if it where to come up, I don't know if I could use the X100 times probe on it or go with a differential probe.Thanks in advance.

author: klr5205
author_rank: Regular Contributor
timestamp: March 15, 2016, 04:19:29 pm
content: Check out page 42 of this document from Tektronix:http://circuitslab.case.edu/manuals/Probe_Fundamentals-_Tektronix.pdf

author: Fungus
author_rank: Super Contributor
timestamp: March 15, 2016, 06:35:49 pm
content: Quote from: eponte5 on March 15, 2016, 04:09:18 pmAssuming it's from a reputable source: You can use it for 2000V.Because the probe attenuates by a factor of 100 the oscilloscope will only see 20V. That's well inside the 400V rating so it's safe to do that.OTOH be very careful - you're poking bits of metal at a 2000V source. Observe general electrical safety precautions.
voltage reducer for dc dc converter - Page 1
Forum section: electronics / projects

author: rezrezrez
author_rank: Newbie
timestamp: December 10, 2014, 01:57:26 pm
content: Hi every oneI have an isolated dc to dc converter where it's rated input is 430v.However in my application the dc input voltage is 580v. Is there any way to bring this voltage down to 430 other than using zener diodes or voltage divider. The reason is these two options are really lossy. Thanks for your help.

author: Paul Price
author_rank: Super Contributor
timestamp: December 10, 2014, 02:39:20 pm
content: Yes, all you need is to design an efficient buck converter to drop the voltage, otherwise you must deal with high power loss.In other words, yes you can, but the solution is much more complicated and certainly more costly.

author: rezrezrez
author_rank: Newbie
timestamp: December 10, 2014, 02:43:36 pm
content: Thanks for your reply. The problem is buck converter becomes very less efficient due to the high conversion ratio and very low duty cycle. The optimum solution is go for a flyback but I want to save time and use the standard isolated dc to dc converter ICs.

author: Paul Price
author_rank: Super Contributor
timestamp: December 10, 2014, 02:55:48 pm
content: Doesn't seem to me to be a high converston rato, but obviously the operaton voltages are very high though. A low duty cycle doesn't necessaryily mean a lot of power is being wasted..quite the opposite compared to resistor or resistor-zener solutions.

author: rezrezrez
author_rank: Newbie
timestamp: December 10, 2014, 03:02:00 pm
content: Sorry Paul. I meant conversion from 580v to low voltage say 15v.But you meant from 580 to 400ish.
voltage reference distribution / multiple ADCs - Page 1
Forum section: electronics / projects

author: rounin
author_rank: Regular Contributor
timestamp: September 25, 2016, 07:45:04 pm
content: Hi all,I'm trying to make DAQ with 4 simultaneous differential sampling channels, using 4x analog devices 24bit AD7175-2, and either a MAX6220 or MAX6126 5V reference, with the hope of getting maybe 19-20 noise free bits the first go-around. I'm planning to use a PGA280 as the input amplifier.Is it possible to have all the ADCs share 1 voltage reference? Would they need to be separately buffered? Is it easier just to use a seperate 5V reference per ADC? (I'll be calibrating the channels separately anyway, so not too worried about a little bit of offset between them). It seems simpler to just use a reference per ADC, but if I can avoid that without causing a bunch of other layout headaches, it would be nice.Anyone ever distributed voltage references across a board?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 25, 2016, 08:01:03 pm
content: The mentioned ADC has differential inputs for the reference and internal buffers for the reference too. So there should be no problem just wiring the ref. inputs in parallel. Filtering / noise reduction at the reference might be a good idea with such fast ADCs.

author: rounin
author_rank: Regular Contributor
timestamp: September 25, 2016, 08:30:53 pm
content: OK cool, I'll hook the REF inputs up in parallel, and look into filtering. Thanks

author: ebclr
author_rank: Super Contributor
timestamp: September 25, 2016, 09:05:34 pm
content: May be this IC will cleanup your designhttp://www.ti.com/product/ads1274

author: rounin
author_rank: Regular Contributor
timestamp: September 25, 2016, 09:35:54 pm
content: Interesting. I had also been considering the AD7768-4, and was drawn to the 7175-2 for possibility of sub uV noise at low sample rates, if everything else gets to that point.The ads1274 looks interesting, seems to have similar performance at high sample rates? I'll dig through the datasheet some more. It looks like the settling time might be longer on the ads1274, I guess due to the deeper digital filter.

author: ebclr
author_rank: Super Contributor
timestamp: September 26, 2016, 01:14:36 am
content: Note that AD works in parallel at the same time, this means you will have all 8 channels sampled at the same time with 8 independent adc inside the chip. That's the main point on this chip
Voltage reference drift direction - Page 1
Forum section: electronics / projects

author: AlfBaz
author_rank: Super Contributor
timestamp: July 06, 2013, 02:56:53 am
content: I'm messing around with an LM399. I have it hooked up on a bread board as per the data sheets "Portable Calibrator" application example, except the only decent op-amp I had laying around is an LT1007Most drift charts I've seen for various voltage refs show upward drift. I'm seeing consistent downward drift. Is this normal or is drift direction just luck of the draw?

author: AlfBaz
author_rank: Super Contributor
timestamp: July 06, 2013, 02:59:56 am
content: Hmm It just struck me, I think I need to verify what's actually drifting
Voltage Reference for DMM Check - Page 1
Forum section: electronics / projects

author: balu
author_rank: Regular Contributor
timestamp: July 03, 2014, 01:46:55 pm
content: Often I found a used or old DMM on peddlers market, garage sale or at the internet. To check the basic functionality of these devices I made this simple, easy and cheap voltage reference. Heart of the voltage reference is an easy to get (here in Germany -> Reichelt) MAX6325. This circuit provides 2.5V with an initial accuracy of +/-0.02% and a TEMPCO of 1ppm/K – this is more than I need. However, with an op amp (LT1037), some resistors and a rotary switch I made a small and handy device with a 2.5V voltage reference and 2.5µA, 250µA, 10mA and 25mA current references.The PCB will have a size of 5x5cm (1.96”x1.96”), because I will use the design/layout to check “Dirt Cheap Dirty Boards” for PCB production. I will provide my experience later;-) I made the schematic and layout with eagle v6.6.
Voltage reference on multiple chips? - Page 1
Forum section: electronics / projects

author: JorgeCarbajal
author_rank: Contributor
timestamp: June 08, 2012, 12:58:16 pm
content: Hi, I'm trying to use a pair of DACs which needs a 10v reference, and i was wondering can i use a single vref chip for both of them, i mean its not a big deal but it may lower the cost a bitany help appreciated, thanks!

author: digsys
author_rank: Unknown
timestamp: June 08, 2012, 02:03:52 pm
content: QuoteAs long as the VRef chip can supply enough current, you can supply as many DACs as required. Just make SURE you tie all DACs 0V Ref to ONE point.ie don't have the DACs at opposite ends of the PCB layout, unless you really careful with the 0V layout.
Voltage reference shoot out / market overview of the day. - Page 1
Forum section: electronics / projects

author: 0xFFF0
author_rank: Regular Contributor
timestamp: June 29, 2024, 05:07:01 pm
content: LM336-5.0: 20 ppm (0.70€)REF195E: 2 .. 5 ppm (8€)LT1236A-5: 2 .. 5 ppm (13€)LT1021B-5: 2 .. 5 ppm (17€)MAX6250AC: 1 .. 2 ppm (14€)LT1027A/B-5: 1 .. 2 ppm (17€)MAX6350CA: 0.5 .. 1 ppm (22€)LM399A: 0.3 .. 1 ppm (21€)

author: Terry Bites
author_rank: Super Contributor
timestamp: June 30, 2024, 02:01:20 pm
content: Ah! Bargain basement stuff.........
Voltage refrences - Page 1
Forum section: electronics / projects

author: OM222O
author_rank: Frequent Contributor
timestamp: November 30, 2018, 06:40:01 pm
content: HelloI purchased a few different voltage reference ICs (2.048v) and I'm quite happy with their initial accuracy value, but they have a TRIM pin which they recommend to connect to a voltage divider circuit. I was wondering if I must connect it to a circuit in order for the chip to work or if I can just not connect it to anything(or maybe connect it to the Vout pin or ...)I'm specifically asking about ADR440BRZ (https://www.analog.com/en/products/adr440.html) but I also have a few from TI (for example the REF5020).They don't mention it anywhere so a bit of help would be great. Thanks!

author: JackJones
author_rank: Regular Contributor
timestamp: November 30, 2018, 06:45:08 pm
content: Usually trimming would be optional, unless specifically stated that it is needed. If you look at page 15 and figure 36 it shows a basic configuration with trim not connected. So you can leave it unconnected unless you want to get fancy.
Voltage regulator (dc power supply+ inverter) - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 15, 2018, 11:17:14 am
content: Would this make for a very good voltage stabilizer/power conditioner?I am only asking for theoretical applications since it will cost a lot to buy a high output dc power supply and a quality inverter but would it be the best way to clean up AC line voltage?

author: Ian.M
author_rank: Super Contributor
timestamp: February 15, 2018, 11:43:08 am
content: It depends on the reliability, power quality and KVA you need. The inverter would need *VERY* good filtering for its output to be cleaner than that from a ferroresonant transformer. However the gold standard for power quality would be a common shaft or direct coupled synchronous motor generator set driven by a crystal controlled VFD so its output frequency doesn't fluctuate with grid frequency variations.

author: Benta
author_rank: Super Contributor
timestamp: February 15, 2018, 01:03:14 pm
content: If it's for cleaning up fluctuating/noisy mains voltage, an "always-on" UPS could do the trick.
Voltage regulator delayed start - Page 1
Forum section: electronics / projects

author: Halban
author_rank: Contributor
timestamp: January 22, 2021, 11:09:10 am
content: Hi Guys,I'm new and happy to be here!I'm starting a little circuit based on a voltage regulator, to convert 12V to 11V. This LM2941SX regulator has an ON/OFF pin that I want to use to delay the 11V power on (for example, when 12V is present at the input, the 11V output will be ON after around 500ms).The ON/OFF pin enables the regulator at low state (under 2V).My idea was to add a RC model to controls the ON/OFF pin, so when the 12V appears, the RC output will be 12V, then slowly decreasing until reaching 0V.Do you think it's a good idea? Seems too easy for meHave a nice day!Halban

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2021, 11:57:33 am
content: It seems sensible to me, as long as the time delay isn't critical. You might want to put a diode across the capacitor, so it discharges quickly, when the power is disconnected, preventing it from powering the input, with no power connected.
Voltage Regulator Power Good Signal - Page 1
Forum section: electronics / projects

author: veryevil
author_rank: Unknown
timestamp: November 14, 2011, 12:09:13 pm
content: Hi, Im looking to use aMCP1825in a project im working on. This LDO Regulator has a POWER GOOD signal. I thought it would be a nice feature to use this output to delay the switch on of the board.However I have not found a single example of someone doing this and I am not sure why?My first thought would be to use the PWRGD signal to switch on a MOSFET which would go across Vout and the load so the load would not receive power until PWRGD went high, would this work and how would I design the FET part as I am not overly familier with FETS?Vin = 5vVout = 3.3vImax = 500mAThanksSteven

author: ivan747
author_rank: Super Contributor
timestamp: November 14, 2011, 12:30:14 pm
content: Use a P channel MOSFET with a 10K resistor going to the output of the voltage regulator and going to the transistor's gate. Connect the transistor's gate to the Power good signal. Connect the source (the pin with an arrow pointing outwards) to the output of the voltage regulator. The drain pin will give 3.3V when power is good.Remember the pinout (this is NOT the circuit I am talking about):A more efficient way of turning digital circuits off with a power good signal is to attach all the reset lines to the power good signal and a pull-up.

author: Balaur
author_rank: Unknown
timestamp: November 14, 2011, 12:43:42 pm
content: The Power Good signals are not intended to be used to switch ON/OFF the power rail.A soft start such as indicated in figures 2-25 and 2-26 is actually better for nicely starting up the attached devices.As ivan747 said, the Power Good signal can drive reset inputs to allow the circuits to reliably start at the correct state when the power is stable.Another use is for chaining the start-up of multiple regulators (i.e Power Good of the first regulator to an Enable/Shutdown of the following one) in order to ensure the correct sequence of the power domains for devices (FPGAs, MCUs, CPUs, etc) that are sensitive to this aspect.Cheers,Dan

author: ivan747
author_rank: Super Contributor
timestamp: November 14, 2011, 12:54:06 pm
content: Quote from: Balaur on November 14, 2011, 12:43:42 pmI never though of that use. I guess you can also add a simple R-C delay and a schmitt trigger (unless the Enable pin has one) to produce a time delay if required.
Voltage regulator that sinks current - Page 1
Forum section: electronics / projects

author: shpavel
author_rank: Newbie
timestamp: May 18, 2017, 06:46:40 am
content: HiI am lookin some solution for a circuit I am designing. I have 5 volt and I need to create adjustable low voltages in the output. Something below 1.2 volt and above 0.3. The problem is that I need the circuit to be able sink and source current (something in the range of 50 mA). I have looked the web but my knowledge in vr is limited. Where do I start? Can buck step down solution do the work? Can linear vr do it?

author: Kalvin
author_rank: Super Contributor
timestamp: May 18, 2017, 07:05:39 am
content: Op amp.

author: shpavel
author_rank: Newbie
timestamp: May 18, 2017, 07:09:56 am
content: The DDR termination ldo are usually not adjustable. The come with constant voltage.

author: tszaboo
author_rank: Super Contributor
timestamp: May 18, 2017, 11:11:45 am
content: If you take a voltage regulator, and add a resistor on the output, you get a voltage regulator that can source less current than the maximal, it will waste energy continuously, but it can also sink some current. For 0.3V, 50mA you need 5 Ohm. Maximum waste is 1.2V 5 Ohm = 300mW, not too bad.Or an opamp.

author: cjm
author_rank: Contributor
timestamp: May 20, 2017, 09:37:52 am
content: Quote from: Kalvin on May 18, 2017, 07:05:39 am+1...although sourcing 50mA at 0.3V might be challenging unless you have a negative supply rail for the opamp. Some rail to rail ("RRIO") opamps might just work with just 0v-5V rails - e.g. OPA340, AD8531 or similar.
Voltage Sense Input for High Current PSUs - Page 1
Forum section: electronics / projects

author: FxDev
author_rank: Regular Contributor
timestamp: January 23, 2020, 08:00:42 pm
content: Hello,I designed 24V 250A PSU. In this project I used TL431 for feedback but one of my customer wants to use Sense Input for long distance voltage drop.Can you suggest me any schematics or app notes about that?

author: jbb
author_rank: Super Contributor
timestamp: January 23, 2020, 10:57:49 pm
content: That’s quite a big supply you’ve built there; I can see why remote sense is an issue.I haven’t done one myself, but you could have a look at the EEZ BB3 design (schematics available on Github).My guess about things to look out for:- swapped leads- don’t blow up if a lead falls off (ie don’t have output voltage suddenly go to max!)- how much cable voltage drop will you support? (Note, someone working on batteries might want to put a diode in series)- how much current will you draw from the load if the power supply is off? (Batteries again)- will long leads (ie inductance) cause oscillation?- will the supply be OK if the mains input is removed and there’s still voltage at the output? (Eg capacitor banks and batteries)
Voltage Sensing - Page 1
Forum section: electronics / projects

author: EMIRGIN
author_rank: Newbie
timestamp: January 25, 2022, 07:14:16 am
content: Hello everoneI measure 24-12v from MCU.I have a circuit there is a cap and 5 v zener paralell to out of circuit.However, The output of the circuit is very variable.I choose 100n cap.What should I change to fix this problem? İs there any cap callculation this type circuit or Am ı added filter(what kind of)

author: bob91343
author_rank: Super Contributor
timestamp: January 25, 2022, 06:27:18 pm
content: I read your message several times and was unable to understand it. Be more careful about your grammar and please attach a diagram of what you are working with.
Voltage shifting ideas 12V -> 0V turned into 0V -> 5V - Page 1
Forum section: electronics / projects

author: VermontEE
author_rank: Contributor
timestamp: March 21, 2016, 03:41:22 pm
content: I've got to convert the output of an integrator that sits nominally at 12V and goes to 0V for maximum drive. I have to scale this to 0 to 5V (so invert and scale). i have designed a Deboo integrator and realized that I would now have a reset problem so I designed a voltage scalerI have an opamp that has +12/-12V supplies and the bandwidth of the circuit doesn't need to exceed 10kHzHere's the LTspice circuit - With out a zener to clamp the 0->5V outputI can clamp the output with a zener and get the effect that I wantAre there better ways to do this?What issues might I run into with this implementation?

author: ZeTeX
author_rank: Frequent Contributor
timestamp: March 21, 2016, 06:22:29 pm
content: I might be very wrong, but I think you should put a resistor in series with the cathode, because the op amp output resistance is pretty much zero, and the diode sinks all the curent the op amp can supply.

author: Marco
author_rank: Super Contributor
timestamp: March 21, 2016, 06:33:38 pm
content: Why do you need a second integrator? Why can't you just do -5/12*(Vin-12)?

author: VermontEE
author_rank: Contributor
timestamp: March 21, 2016, 06:44:42 pm
content: Quote from: Marco on March 21, 2016, 06:33:38 pmI was going to replace the current integrator with the Deboo but there is the reset issue I don't want to deal with. I'm trying to keep the current integrator and simply scale the voltageI could just power the amp with +5V/0V and then the output would be limited and I would be done with it. But then I would have to add parts to generate the +5V ref.I have been working with a FET amplifier that could do the trick