hybridfree/eevblog-posts huggingface dataset:
Abusing gate drivers as voltage level translators to +15V logic - Page 1
Forum section: electronics / projects

author: daqq
author_rank: Super Contributor
timestamp: January 12, 2017, 08:53:54 am
content: Hi guys,I've been looking into the standard solutions for low->high level shifters such as the 4104 (http://www.farnell.com/datasheets/1758136.pdf). They have a very large range of long delay times, and the transition time isn't that awesome either. Basically you can get around 10MHz max out of the whole thing. Other similar devices are similar in terms of speed when going from +5V logic to +15V logic.On the other hand, gate drivers for MOSFETs or IGBTs, such as the UCC27519DBVT (http://www.ti.com/lit/ds/symlink/ucc27519.pdf), have very fast rise and fall times, as well as very low propagation delays, in addition to cool stuff like undervoltage lockouts, enable pins, etc. They are pricier, but other than that there seems to be no downside to abusing them as simple voltage level translators.The +15V side device has a +8V logic treshold, it's a simple logic input of no extreme requirements.So, is there any downside to using similar devices as a simple level translator?Thanks,David

author: tautech
author_rank: Super Contributor
timestamp: January 12, 2017, 09:14:25 am
content: 4066 is somewhat faster than a 4104.

author: tautech
author_rank: Super Contributor
timestamp: January 12, 2017, 09:53:30 am
content: And this little chap: IRF5851
AC 100W Dimmer - Page 1
Forum section: electronics / projects

author: raul320
author_rank: Newbie
timestamp: January 15, 2013, 11:31:38 am
content: Hi!Can anyone explain, how exactly works AC -Triac dimmers like this one:http://blog.savel.org/2011/12/24/dimmer/? What is the serial choque for?and why is this white cap every time on it? (see pic:http://blog.savel.org/stuff/20080306b.jpg)Best Regards! O0

author: SeanB
author_rank: Super Contributor
timestamp: January 15, 2013, 03:15:02 pm
content: The choke is there to reduce radiated noise from the fast switching edges of the triac, by reducing the rate of rise of current. Thus it is not a high power noise source generating harmonics every 100/120Hz from 50/60Hz to over 100MHz. the wjhite item is a 130c one time thermal switch, there for safety by disconnecting the power if the board gets too hot.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 15, 2013, 03:46:27 pm
content: That fuse is overcurrent, not thermal.Ther reason you need fuses in dimmers is what sometimes happens when an incandescent bulb blows.An arc forms at the break, and this can spread back along the filament so that you end up with an arc between the two filament supports, or between part of the filament and a support. This can draw a lot of current, and trip breakers or blow dimmers (sometimes the fuse protects the triac, sometimes the triac blows to pretect the fuse...).This why you sometimes hear a pop and/or see a flash when a bulb blows.Some better quality bulbs include a simple internal fuse of some sort.

author: raul320
author_rank: Newbie
timestamp: January 15, 2013, 07:07:04 pm
content: Thank you Guys for quick reply! What is the simplest way to calculate the parameters of such chokes?

author: lewis
author_rank: Frequent Contributor
timestamp: January 15, 2013, 07:16:47 pm
content: Quote from: mikeselectricstuff on January 15, 2013, 03:46:27 pmI think he means on top of the toroid.

author: SeanB
author_rank: Super Contributor
timestamp: January 15, 2013, 07:22:58 pm
content: You can buy modules ( expensive though) that have everything on one small encapsulated substrate. you just add the pot and the inductors and capacitors, it is the complete unit in a 15 by 15mm package with 3 leads.

author: G7PSK
author_rank: Super Contributor
timestamp: January 15, 2013, 09:47:45 pm
content: That white thing looks like a ceramic cap or filter unit to me.

author: lewis
author_rank: Frequent Contributor
timestamp: January 15, 2013, 10:55:11 pm
content: Quote from: G7PSK on January 15, 2013, 09:47:45 pmIt's one of these:http://dgyujie.en.alibaba.com/product/467380843-212272649/50Pcs_New_M30_TF125C_Thermal_Fuse.html
AC and DC voltage ratings on pushbutton switches - Page 1
Forum section: electronics / projects

author: eecook
author_rank: Regular Contributor
timestamp: February 08, 2019, 11:38:29 pm
content: Hi All,I was looking for a simulated roller lever type switch on Digikey and noticed that there is a huge difference between the AC and DC ratings for each part. I am wondering why that could be?Digikey results page:https://tinyurl.com/y52fknblThe only things that come to mind are:1. Tracking.2. Finite probability of low voltage switching with an AC waveform.But neither 1 nor 2 could explain it. Tracking is related to the RMS voltage, doesn't matter if it's AC or DC. Regarding the finite probability, the average switching voltage will be the voltage of a rectified sine wave which is very similar to it's RMS value.Any clue?

author: ataradov
author_rank: Super Contributor
timestamp: February 08, 2019, 11:57:27 pm
content: This is the similar to relays. Connecting and disconnecting AC current is easier, since it naturally goes to 0 very often, so there is no arcing, or arc gets extinguished fast.
AC Chopper circuit - Page 1
Forum section: electronics / projects

author: nimit393@gmail.com
author_rank: Contributor
timestamp: November 28, 2013, 07:09:07 am
content: i am designing a AC chopper circuit -buck type.max 230AC 5A.i am using IGBTbut can it be used for negative half cycleor should the IGBT be connected to bridge rectifier so that in any case it sees a potential drop and at any moment at which i give i pulse, the igbt conduct the AC voltage.suggest any other method if the above stated method isnt valid.

author: Zero999
author_rank: Super Contributor
timestamp: November 28, 2013, 02:09:25 pm
content: Why do you think spamming the forum, by posting the same question 4 times, will improve the quality of the response?
AC Chopper circuit - Page 1
Forum section: electronics / projects

author: nimit393@gmail.com
author_rank: Contributor
timestamp: November 26, 2013, 02:41:58 pm
content: Designing a AC (50 hz)chopper circuitWhat would be a decent PWM FrequencyWhat thyristor should i use for switching....SCR or IGBT or TRIAC??pls help

author: KJDS
author_rank: Super Contributor
timestamp: November 26, 2013, 03:29:27 pm
content: You've just done the equivalent of asking people to recommend a good car and asked if petrol or diesel, a 2 seater convertible or a 50 seater coach would be best.Perhaps if you could clarify your requirements it would enable people to provide a slightly more focused answer, unless you want to be told that a road train will carry enough load and a 1.2 petrol engine will give the best economy.

author: nimit393@gmail.com
author_rank: Contributor
timestamp: November 26, 2013, 03:48:43 pm
content: 230 VAC -5Ausing it for AC-AC buck-boost converter
AC coupled Differential op amp bias gain -100 Vcc/2 resistor dependencies? - Page 1
Forum section: electronics / projects

author: beduino
author_rank: Regular Contributor
timestamp: April 02, 2019, 09:36:39 pm
content: Hello,I'm a little bit confused why in this quite good intro (AC_coupleddifferential_amplifier_Vbias_Vcc2-marked) to AC coupled differential op amp, there is some kind of dependency between R2 and R3/R4 voltage divider for Vbias?I've R1=1k and looking for gain x100 to saturate opamp to have pin change interrupt on MPU input pin, so I do not need measure amplified voltage difference, but just generate interrupt - in owrst case scenario no problem if I will not be able distinguish between pin change from 0/1 nor 1/0.I'd like to connect to this differential op amp a few loops of wire to detect magnet crossing nearby inducing voltage peaks - it will be clamped by to anti-parallel shotky diodes to limit input voltage difference to less than 0.7V probbaly depending on how many loops of wire, its crosssection area, distance and speed of magnet etc...Any idea howto properly choose value for R3=R4, while it looks like R2 should be 100k and by rearanging this formula for R2=R*R/(R+R)=0.5*R -> R3=R4=R=2*R2R3=R4= 200k ?I've already designed PCB with op amp in differential amplifier configuration like shown here, but before testing real circuit,I'd like to ensure those resitor values makes sense?I watched great Dave opam tutorial and also spotted similar differential aamplifier circuit, but probably without bias, or maybe a I missed something?I'm interested in AC signal difference multipled by gain at bias voltage Vcc/2, so I assume R3=R4 in split resitor example linked below.Regards.
AC coupled gate drive vs negative bias to driver, pros and coins?  - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: October 27, 2020, 01:30:13 pm
content: Hi folks,I need a negative turn off voltage for gate driveWonder is here any main disadvantage for capacitor coupled with clamp vs more complicated generating negative voltage and then have gate drive supporting negative voltage directlyDuty cycle limitation is not a concern here as this is for boost converter-5 to 15V swing shall be enough, so max drive voltage is also not a problem here
AC Coupling Analog-to-PWM Converter - Page 1
Forum section: electronics / projects

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 09, 2021, 01:39:30 pm
content: I am trying to implement simulation of TI's app note SLAU508 - Analog Pulse Width Modulation (https://www.ti.com/lit/ug/slau508/slau508.pdf), but modifying it for ac-coupled input to avoid having any DC offsets that would cause problems when driving a full-bridge power stage.I removed R2 from the circuit, per app note, but then the output only generates PWM output on the negative-going half of the input sinewave. It seems the signal on the error-amplifier side of the ac coupling cap is now biased around VCC instead of VCC/2 (VREF). Does anyone know how else can I modify the circuit to enable proper ac-coupling of the input signal?FYI - cross-posted on TI's e2e forum.

author: MasterT
author_rank: Frequent Contributor
timestamp: August 09, 2021, 04:51:37 pm
content: Do not remove R2 . Set s cap in series with input (R3). Value C depends on frequency of operation

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 10, 2021, 12:16:21 am
content: I may have had a simulation error previously. I just checked now, and doing what the app note said, remove R2, works fine.
AC coupling/DC blocking - is this math valid? - Page 1
Forum section: electronics / projects

author: seamusdemora
author_rank: Regular Contributor
timestamp: November 04, 2020, 08:03:17 pm
content: I asked a question re a simple circuit earlier:The question had to do with the cause of someasymmetryin the V&I curves of my LTspice simulation. That's mostly resolved now, but in thinking through the operation of this circuit, itseemsthere's a relationship that controls the amplitude and duty cycle of the current waveform. That relationship is that if one integrates the current through the "load" (R1 in this case - ref attached schematic) over time, this integral/sum will always be zero.Is this a valid statement, and if so, does it have a name?
Ac Current control - Page 1
Forum section: electronics / projects

author: anishkgt
author_rank: Frequent Contributor
timestamp: November 29, 2016, 11:01:42 am
content: How can the current be controlled ? i was readinghttps://erg.abdn.ac.uk/users/gorry/eg3576/power-control.htmland thishttps://openenergymonitor.org/emon/mk2/switchdev. I am trying to get some clarity into the subject.I have Microwaveoven Transformer, rewound the secondary to get about 1100A @3VAC. I was hoping to control the current that it outputs through an arduino. I've coded it control switching time but the current is something that require a little more expertise.

author: woodchips
author_rank: Frequent Contributor
timestamp: November 29, 2016, 11:41:39 am
content: Use a choke?Connect some suitable gauge cable to the secondary, say 1m long, and measure how much current the transformer will supply. Repeat with the cable tightly twisted together, repeat with the cable spread as far apart as possible. The inductance changes with the cable layout, increased inductance means lower current. This is why you run a spot welder with the minimum possible length of arms.

author: anishkgt
author_rank: Frequent Contributor
timestamp: November 29, 2016, 01:09:52 pm
content: QuoteHow is the measurement taken ? So twisted together meaning in a spiral way ? and with secondary shorted ? and with a DMM probe the twisted cable ?Sorry about the silly questions.
AC current sense with comparator ideas? - Page 1
Forum section: electronics / projects

author: dobsonr741
author_rank: Frequent Contributor
timestamp: September 16, 2023, 03:02:28 pm
content: I’m looking for build ideas for detecting 25mA AC current with a clamp on/split core detector. The current will be present for minutes, few second delay in detection does not matter. The output should tell the observed wire is over the 25mA AC, regular 50/60Hz, with a nice single edge transition, so I can power up an MCU. The monitored system is a solenoid of an irrigation system.It should be low power, so it’s can run for months on from a single LiPo cell. I have a few LM4250 at hand, as a starter low power opamp. Ended up getting YHDC SCT-013 5A/1V split core sensor.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: September 17, 2023, 03:23:08 pm
content: The question comes down to a low power full wave rectifier with single supply, linear down to 50mV. Maybe I just can not have it all?

author: soldar
author_rank: Super Contributor
timestamp: September 17, 2023, 05:04:51 pm
content: You might get better response if you explain it better and with more details.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 17, 2023, 06:51:30 pm
content: Quote from: dobsonr741 on September 17, 2023, 03:23:08 pmAn alternate approach would be to make a mV window detector with two low offset opamps.You then OR the outputs. No diodes needed at mV levels.That should work down to even 1mV with modern uV offset opamps.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 17, 2023, 07:17:24 pm
content: As the sensor only detects AC, one can likely get away looking at only one polarity. It may help to wait for a longer signal or multiple pulses in a row and not just a short spike. To avoid false alarms the µC may have to than do a quick check if there is really a signal and not just a glitch (e.g. lightning somewhere). Depending on the µC it may be lower power to accept a few more starts of the µC instead of adding more analog HW to do a better check before the start.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: September 17, 2023, 09:01:00 pm
content: This is where I'm at the moment:Power wise:A single 2000mA/h 18650 expected to power it for 6 months: so the average current allowance is 450uA. Half of the budget set aside for RF bursting out the status, so ~225uA remains for the analog rectifier/comparator and timekeeping.Timekeeping with MCP79401 is ~1uARectifier:Peak vs full vs half wave: I tend to think for full or half and against peak, as peak would not suppress noise. Nice op-amp choices exist, however the only feature today that beats the old LM4250 is output going rail to rail. Depending on layout, 3 or 4 opamps will cover amping 50mV to ~1V, rectifying and comparing against a set level. Good that LM4250 can be adjusted to optimize quiescent current.Voltage reference:REF35 is <1uA, @2V it can provide common voltage to opamp and act as comparator reference.
AC current sensing relay - Page 1
Forum section: electronics / projects

author: phaseform
author_rank: Regular Contributor
timestamp: February 19, 2018, 05:36:40 am
content: Looking for a very simple AC current sensor to trigger a 240V AC relay.I have a pool pump which will cycle the power off every so often, this is a problem if the solar pump is also running.. So rather than replace the pool pump, is there a way I can sense current flow into the pool pump, and have that trigger a relay to allow the solar pump to operate. I'm looking at current sensing boards on ebay, but they have very little info in the description..Something likethis current sensorwiththis relayI am thinking?

author: viperidae
author_rank: Frequent Contributor
timestamp: February 19, 2018, 06:02:24 am
content: Why not just put a mains voltage relay in parallel with the pump? Or if you can't find a relay with a mains operated coil, a transformer and a relay.An option of you don't want to touch the mains wiring is a current transformer. You could feed it into a peak detect opamp circuit to trigger a relay for your solar pump.

author: phaseform
author_rank: Regular Contributor
timestamp: February 20, 2018, 02:15:56 am
content: I boughtthisrelay with inbuilt zero crossing - for under $10...viperidae: I think the cheap ebay current sensor should suffice from my understanding where it will trigger 5v high when a specified current is met..

author: phaseform
author_rank: Regular Contributor
timestamp: May 15, 2018, 09:39:22 am
content: Building this circuit and having agreattime linking the sensor output to the SSR input - having some difficulty finding a transistor value..So I've been able to get the current sensor board (as above) to output 0.2v low, and 2.2v high, corresponding to a fan heater (test current) being off/on. That results in the SSR not being stable, as it's minimum voltage is around 3v. -I haven't been able to find a datasheet for the sensor board so those results are the best I can make from the ebay instructions....Going to run this signal through a transistor - figuring this part out now. I have a BC639 (datasheet) I've found, which seems like overkill but I don't really understand transistor function that well...I measured the SSR current at 5mA, which is around what the specs say on the ebay page (max for BC639 is 1A). Vbe is around 2.2. I've been readingthispage which has an equation for finding a base resistor value.. using that equation I got a single digit number. I'm so confused by this, does this mean I don't need a base resistor..?heres the current version
AC-DC Power Supply Module with widely Adjustable Output Voltage - Page 1
Forum section: electronics / projects

author: Muny
author_rank: Contributor
timestamp: March 19, 2022, 01:52:37 pm
content: Hi All!I'm toying around with a design that I'd like to make reasonably compact. The design has a fairly constant resistive load, through which I'd like to pass a varying amount of power based on a temperature reading.In my current prototypes I'm using a chassis-mount AC-DC converter (120/240VAC to 24VDC), which feeds into a buck regulator that I can give a signal to vary the output voltage of. This solution works, but the combined size of the two modules is larger than I'd like.(I should state now that I don't want to PWM power to the load)I understand that the efficiency of the buck conversion is not great when the output voltage is much lower than the input, but I believe it's better than using a linear regulator (which I also would like to avoid using for this, as the power to the load is somewhat high).I'm wondering if there are parts available that combine the AC-DC and adjustable DC-DC. As in, a 120/240VAC input and an output adjustable from <4V to 24VDC (~100-200W when at 24V). I've looked around on DigiKey but it's pretty hard to filter for something like that. Just curious if anybody knows of any parts like this.TLDR: I'm looking for an embeddable adjustable bench power supply.

author: mariush
author_rank: Super Contributor
timestamp: March 19, 2022, 02:16:29 pm
content: So you basically want to a programmable power supply.You could try to get an existing design and change the potentiometers to digital ones, but there are some restrictions about maximum voltages on digital potentiometers so you have to be aware of that.Not sure what "compact" means. I was thinking you could use a 18-24v toroidal transformer, unwind the secondary winding and rewind it with multiple taps, for example 0-4.5v-9v-13.5v-18v or 0-6v-12v-18v-24v AC then you could simply use a couple mechanical relays to switch between taps to change voltage
AC-DC transformers and feedback calculations - Page 1
Forum section: electronics / projects

author: okw
author_rank: Frequent Contributor
timestamp: July 25, 2025, 10:10:58 pm
content: I'm trying to understand the mechanisms of the transformator and the feedback windings.The example below is an old-school cell phone charger. Primary 300T, secondary 8T and feedback 8T.I guess the secondary and feedback doesn't have to be identical, as long as it's compensated in changing some of the values in the feedback loop?Let's say I have a p=170T s=21T and f=17T. Which components would need to be adjusted to get the same 5V out (though schematics say 5.5V), and to which values?Where do I turn (pardon the pun), to find the math behind it?In this 220V-5V application, are there any pros/cons of 300:8 vs. 170:21? The latter will be further off 5V, so is this about efficiency?In practical use (not as a cell charger, but powering an MCU++), would it be better to regulate to 6V, then an 5V LDO? Would the output be more stable?Also, what are the benefits of using an PWM m like THX208 or THY275 found in many cheap AC-DC modules, instead of this simple BJT solution?

author: moffy
author_rank: Super Contributor
timestamp: July 25, 2025, 10:36:35 pm
content: It's a flyback converter the turns ratios are not the absolute determiner of output voltage, it works by energy transfer, the primary is charged to 0.5*Lp*Ip*Ip then that energy is dumped into the output load on the discharge part of the cycle. The energy transfer times frequency and the load reach equilibrium and that is the output voltage, in simplistic form. The feedback winding is part of a self resonant topology, there is a lot going on there.

author: Mj12
author_rank: Contributor
timestamp: July 25, 2025, 10:46:21 pm
content: I think ZD1 sets the voltage here, When voltage increases in the secondary, same but negative voltage is induced across the feedback winding, during transistor Q1 turn off.This voltage is sampled into C3 and when it goes to negative more than 5v, base signal on the Q1 is decreased. There does not seem to be any other proper feedback loop. This might mostly operate in hysteresis mode, so periodic switching followed by periodic idle stateFor 21 turn secondary and 17 turn feedback you would need 5 something like 17*5.7-0.7=3.9V zener diode 5.7V because the voltage drop of D5 and -0.7V from the final result because of the D6

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 26, 2025, 01:07:23 am
content: These simple bricks have terrible load regulation.Quote from: okw on July 25, 2025, 10:10:58 pmOf course, post linear regulation is better, but the cheap chargers are built to a price.Quote from: okw on July 25, 2025, 10:10:58 pmThe older designs have given way to low-cost ICs which can give better performance.In the continual chase of every last cent, some ICs now try to 'regulate' without any secondary feedback at all, and some ICs try to compensate for cable resistance.
AC fan motor - direction of rotation - Page 1
Forum section: electronics / projects

author: Miti
author_rank: Super Contributor
timestamp: March 03, 2021, 01:26:21 am
content: What gives the direction of rotation in an AC fan motor, for example ebm-papst 4606N vs 4606Z, and can it be easily reversed?Cheers,Miti

author: wraper
author_rank: Unknown
timestamp: March 03, 2021, 01:36:43 am
content: Most of such fans use shaded pole motor. Due to their construction rotation cannot be reversed. Nor fan would work properly even if you manage to do so because blades are designed for one direction only.

author: themadhippy
author_rank: Super Contributor
timestamp: March 03, 2021, 01:47:17 am
content: QuoteFlemings left hand rulelooking at the picture of the model mentioned just turn the whole thing around

author: Miti
author_rank: Super Contributor
timestamp: March 03, 2021, 02:18:25 am
content: Quote from: wraper on March 03, 2021, 01:36:43 amLooking at the blades, they look almost flat to me. What about turning the stator upside down?

author: Miti
author_rank: Super Contributor
timestamp: March 03, 2021, 02:31:55 am
content: Quote from: themadhippy on March 03, 2021, 01:47:17 amThat can be an option, but I would prefer not to. This fan would be used to suck hot air from the T962 reflow oven and probably the label on the other side would melt or deteriorate anyway.I found a relatively cheap T962 on Kijiji, a local classifieds site for 120CAD and I couldn't resist. Even though I did all the upgrades that are well documented, I have quite an uneven heating left to right. I figured out that the fan in combination with the shape of the vents that are punched at the back side of the tray compartment, are causing more air flow on the left side compared to the right side. I think the manufacturer found a solution for that by reversing the flow, sucking instead of blowing. Looking at the BG T962, they added an exhaust to the back. That doesn't make sense unless they suck the air from the oven and blow it through that exhaust.The fan is ebm-papst 4606N and is made of steel with aluminum casing, so I think it can take the short punch of heat during cool down. I could simply replace it with 4606Z but it is quite expensive at 76.36 CAD.https://www.banggood.com/T-962-Infrared-IC-Heater-Desktop-Reflow-Solder-Oven-BGA-SMD-SMT-Rework-Station-Reflow-Wave-Oven-p-1707182.html?cur_warehouse=CN&ID=47184

author: Medved
author_rank: Contributor
timestamp: March 09, 2021, 07:35:18 pm
content: You can look into the coil and core assembly around the rotor, if you were able to disassemble it.You will see there on one side of the pole, there is a kind of shorted turn across part of the core. The rotor will then turn so it will pass this side last, so towards this shorting turn.You may see it on the fan disassemble video above...
AC in filters. Good idea? - Page 1
Forum section: electronics / projects

author: mkiijam
author_rank: Regular Contributor
timestamp: April 06, 2024, 03:24:15 pm
content: I have a bunch of random devices that I build / tinker with. They all use AC mains for power. The all consume less than 1 amp. I've been building linear supplies. Transformers / 78XX regulators etc. I'm wondering how meaningful / useful / necessary the little silver box I see in other devices that I believe are AC filters of some sort?In other words, is there a universally good "AC IN" system / circuit / topology that I really should implement on all devices that run on wall power? Currently there is only a FUSE and AC switch "before" the primary of the stepdown transformer, if that makes sense.

author: bdunham7
author_rank: Super Contributor
timestamp: April 06, 2024, 04:16:58 pm
content: Quote from: mkiijam on April 06, 2024, 03:24:15 pmWith a basic linear power supply those filters really aren't necessary. They're typically called AC input filters or something like that, but AFAIK their primary purpose is keeping EMI from gettingoutvia conducted emissions. So you see them on things with an SMPS. They're a reasonably cheap way to incorporate a switch, fuse and C14 inlet socket so you might see them in places that don't really need the filter feature.
AC line transients suppressor - Page 1
Forum section: electronics / projects

author: Mikaelin
author_rank: Contributor
timestamp: January 12, 2024, 11:24:07 pm
content: Hello,This is my first deal with transients.I have a sensitive device that detects under and over voltage plugged in a wall socket (230V). I have observed that this device switches off in the same time when my fridge is switching off. Very interesting. Why? I plugged my scope into AC line and I have captured this moment and I could analyze it. That's how I discovered the transients in real life.I have seen spikes off -860V, +1.48kV, -1.30kV. The duration is about 320usNow, for testing and learning, I would like to insert a filter to suppress these transients. What options we have?

author: moffy
author_rank: Super Contributor
timestamp: January 13, 2024, 02:42:46 am
content: You could use an LCR filter, but it is important to know how much power/current the filter has to pass as that is important for choosing the inductor. The spike is probably due to the current to the fridge compressor being turned off under load, because of line inductance that energy will cause a voltage spike.

author: floobydust
author_rank: Super Contributor
timestamp: January 13, 2024, 02:56:17 am
content: I had this problem with a fridge and the proper fix is adding a capacitor across the thermostat in the fridge. Like 10-33nF mains-rated. It can be located in the outside bottom.Otherwise the switch arcing causes the thermostat to not last, and the compressor motor gets this spike and it can damage the winding's insulation.You can use MOV near the fridge but I found the switch arcing still happened, just at a bit lower voltage on mains.
AC Motor Control With Relays and MCU - Page 1
Forum section: electronics / projects

author: baget
author_rank: Contributor
timestamp: April 09, 2016, 07:24:45 pm
content: HiI have the AC Motor SPDT switch (Up and Down) that control my blinds.I would like to add relays to control it using MCU (like ESP8266) but I also want a failsafe override switch control, i.e. that if the mCU set Down the blinds, I would like to override it using switch to make it go up.can someone suggest my a circle for that?i attached the basic schematics of my blinds current control

author: Paul Moir
author_rank: Frequent Contributor
timestamp: April 09, 2016, 07:32:53 pm
content: My preference is to use a three position switch. The centre contact connects to L, and the position contacts either the relay's (C)ommon terminal, the Up line or the Down line. This gives you a switch with Up Down and Auto controls.Do you need a neutral position where no power is applied to either up or down?

author: baget
author_rank: Contributor
timestamp: April 09, 2016, 07:52:43 pm
content: Quote from: Paul Moir on April 09, 2016, 07:32:53 pmto stop the blinds, I just don't give power for up or down.so I don't need neutral position.
AC Motor direction control (Triac) - Page 1
Forum section: electronics / projects

author: John80
author_rank: Contributor
timestamp: February 15, 2022, 07:50:37 am
content: Hello all!I want to make a circuit to control the direction/movement (Clockwise, Counter Clockwise, Stop) of a small AC Motor. The AC Motor has this tag on it:and I've made this schematic:Is this ok? Is there any problem?

author: Benta
author_rank: Super Contributor
timestamp: February 15, 2022, 11:36:50 am
content: What makes you think that an AC motor like that can be reversed? DC, yes.

author: themadhippy
author_rank: Super Contributor
timestamp: February 15, 2022, 11:55:14 am
content: might want to consider some form of interlock so the motor cant try and go both ways at once

author: John80
author_rank: Contributor
timestamp: February 15, 2022, 11:57:44 am
content: Quote from: Benta on February 15, 2022, 11:36:50 amSimple! Put the live on the one side of the start capacitor and it goes CW. Put it on the other and goes CCW!

author: Ian.M
author_rank: Super Contributor
timestamp: February 15, 2022, 12:10:20 pm
content: Any PSC motor with *identical* windings can be reversed that way. Their wiring diagram will show if that's the case. If you can tolerate a double normal duration starting surge, as they change direction, and the load inertia isn't too high, they can even be 'plug' reversed while running.However its far more usual to have a main winding and a significantly higher impedance auxiliary winding as although that provides less starting torque, it allows the use of a much smaller cheaper capacitor. PSC motors of this type can only be reversed by swapping connections to the ends of ONE winding and if running must be allowed to fully stop before re-powering in the opposite direction.@John80,Do your TRIACs have adequate current capability for the locked rotor current of your motor, *after* derating them for operating temperature? A genuine BT139-800E, properly heatsinked, should be OK up to max. 16A starting surge, but 'off-brand' ones may only be good for half of that, which your motor may exceed.

author: strawberry
author_rank: Super Contributor
timestamp: February 15, 2022, 12:36:02 pm
content: reverse main winding to run in opposite directionneed access to 4 connectionsif both windings are identical then 3 connections enough
AC on electrolytic capacitors - Page 1
Forum section: electronics / projects

author: MRMILSTAR
author_rank: Contributor
timestamp: December 04, 2018, 04:40:06 am
content: A few months ago I bought a used DRSSTC (dual resonant solid state tesla coil). There was no documentation with it, so no schematic. Upon studying the circuitry, I noticed that there are three 1500 uF electrolytic capacitors connected in parallel for a total of 4500 uF. The mysterious thing is that the 120 volt 60 Hz AC power line is connected directly across the terminals, so for each half cycle the polarity is wrong. The DRSSTC works well, so apparently this odd arrangement works. My question is, why don't these capacitors explode from the reverse polarity?

author: Jwillis
author_rank: Super Contributor
timestamp: December 04, 2018, 07:05:50 am
content: They are probably Bipolar Electrolytic Capacitors.Do they have BP or NP on them anywhere?

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2018, 07:13:13 am
content: 4500uF would have a reactance at 60Hz of 0.59 ohms, and if wired between Line and Neutral would draw a current of 195A from a 115V AC line. Even if you consider their possible ESR, its unlikely the impedance would be over 1 ohm so the current would be significantly over 100A.That's patently ridiculous, so either your capacitors are *NOT* of the value you think they are and probably not electrolytic (e.g. could they be 1500nF oiled paper, in aluminum cans?), or you've traced the connections incorrectly and they are *NOT* directly across the AC supply.

author: aju11
author_rank: Contributor
timestamp: December 06, 2018, 10:47:24 am
content: A photo of the capacitors might help.
AC output plugpack design needed - Page 1
Forum section: electronics / projects

author: scottb721
author_rank: Contributor
timestamp: December 30, 2017, 12:59:01 pm
content: Howdy allMy GF has lost the powerpack for a lamp which holds sentimental significance to her. Unfortunately the socket label says 6VAC.Inside it powers a 5W lamp and a 0.5W motor, both 6V. pic hereAny help with a cct for making a PSU would be greatly appreciated. Had it suggested to base it around this txhttp://www.altronics.com.au/p/m7252-powertran-10va-6+6v-pcb-transformer/Thanks very much.

author: janoc
author_rank: Super Contributor
timestamp: December 30, 2017, 01:06:22 pm
content: Almost any small mains transformer rated for 6V output will likely do. There is not circuit to deal with, just the primary of the transformer wired to the mains plug (with a fuse in series, if required) and the secondary to the output jack.But I would first search for a ready-made plugpack - shouldn't be that hard to find something.

author: scottb721
author_rank: Contributor
timestamp: December 30, 2017, 01:16:40 pm
content: I could not find anything off the shelf.I did think the cct would be quite straight forward but then people started talking about power factors and that's beyond my mostly V=IR DC experience. I'm fine with knocking something up, I just want to make sure it's safely fused.

author: fourtytwo42
author_rank: Super Contributor
timestamp: December 30, 2017, 02:44:53 pm
content: Hi Scott that trafo you linked will do the job but you have to case it etc, there are tons of 6V adapters herehttps://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1311.R1.TR3.TRC0.A0.H1.X6vac.TRS0&_nkw=6v+ac+adapter&_sacat=0BUT most of them are DC output (no good to you) and quite a few to low output current, you need 6V AC at an amp or more, happy hunting and just ignore anybody who tries to blind you with junkspeak!

author: chendragon
author_rank: Newbie
timestamp: January 21, 2018, 02:42:10 am
content: https://www.ebay.co.uk/itm/GENUINE-TRANSFORMIC-MR-CHRISTMAS-TRANSFORMER-POWER-SUPPLY-TEL-481-6-VAC-7-2A/192427171650?hash=item2ccd8d9f42:g:SV0AAOSwfoNaW8pXThis one looks like it would be perfect, maybe.
AC Panel Meter Advice - Page 1
Forum section: electronics / projects

author: TheFloyd
author_rank: Contributor
timestamp: September 08, 2025, 02:27:36 am
content: Hi Folks, I am hoping that someone might have had the same issue as me, and be in a position to offer some advice. I am thinking of a little project to create a light bulb current limiter and instrument panel for my variac. My cheap variac has a wildly inaccurate volt meter on it, so i was going to include both a volt and ammeter on my instrument panel. This got me looking for AC panel meters to do the trick. I do love the look of the analogue panel meters and they are relatively inexpensive, however if it want it to have a FSD of 0v-300VAC, there isnt a great deal of granularity on the dial. So ideally, using a digital meter would provide values to a decimal place.The issue is that I am really struggling to find any digital meters that have independent power sources, so they generally have a minimum operating voltage of 50VAC or more. This is pretty useless for when i want to dial the variac way down and test with very low voltage.I have arrived at the point where I think my only option is to build a custom solution, using an Arduino, a Hall sensor, and an LCD screen. I mean, that sounds like fun too, but surely there are some digital AC meters out there that dont cost the earth, and will allow me to independently power them, so they can display a range of 0v-300v ?Any expert tips on this would be a huge help!

author: floobydust
author_rank: Super Contributor
timestamp: September 08, 2025, 02:56:19 am
content: Seehttps://www.eevblog.com/forum/beginners/power-meter-for-variachttps://www.eevblog.com/forum/projects/digital-mini-0-56-inch-ac-voltage-panel-replacement-meter-for-variachttps://www.eevblog.com/forum/projects/using-a-fixed-range-ac-voltmeter-with-variable-input[https://www.eevblog.com/forum/projects/digital-power-meter-mod-for-voltages-down-to-zero/

author: TheFloyd
author_rank: Contributor
timestamp: September 08, 2025, 07:10:03 am
content: Thanks a bunch for this! I shall get reading!cheers

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 08, 2025, 11:41:34 am
content: Quote from: TheFloyd on September 08, 2025, 07:10:03 amFor the next time: Turn that around.First do the reading, then report back whether it was useful to you.Forums are not like "regular conversations" that require (nearly) instant answers during a conversation.
AC power measurement design not working right - Page 1
Forum section: electronics / projects

author: electrotwelve
author_rank: Contributor
timestamp: May 11, 2016, 07:21:46 pm
content: I built this design to measure AC power (attached). The voltage is measured pretty much the normal way only its stepped down to show about 1.4Vpp for 240V. The current is measured by measuring the voltage across the 4 milli-ohm shunt. The output that goes to the MCU has a DC offset of 0.7V which is then removed in the software. I simulated this in LTSpice and it showed the expected results.I built this design today and while I was testing it I observed the following:The VSENSE-N and ISENSE-N is where the DC offset of 0.7V is added however I measured -2.9V DC here. Also I see only the positive half of the AC voltage at the V-MCU pin and I'm not sure why.The AC waveform at the I-SENSE-P pin is also offset by about -3V DC but I do not see any waveform at the I-MCU pin.I used a 40W bulb as the AC load. The LMV324M is powered by a +/- 3.3V supply. The -3.3V comes from a charge pump dc to dc converter TC7660S.What am I missing here?
AC power measurement query - Page 1
Forum section: electronics / projects

author: electrotwelve
author_rank: Contributor
timestamp: April 27, 2016, 11:05:36 am
content: I'm trying to understand and tweak thissmartplug reference designfrom TI. I'm stumped on the Metrology Analog Filters section on page 1. What I do not understand is why is there a 0R resistor on the Neutral line and more importantly why is this line grounded?Also since the shunt method is inherently unsafe, can I simply replace the shunt with the primary of the current transformer? In the attached schematic the current source and the terminating resistor essentially mimic the secondary of a current transformer. If I can replace the shunt, can I simply do away with the instrumentation amp in the reference schematic and simply put the attached bit in and feed the signal to the MCU?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 27, 2016, 01:23:15 pm
content: Using a current transformer can work. After the current transformer the filter can be even easier, as it does not need to be symmetric any more. It can also save on the amplification, so less amplification, if any is needed.The ground looks like the signal ground for the circuit. So the circuit is tied to the neural line and not fully isolated. So even with a current transformer for current sensing the voltage sensing part still needs the connection. So there is not much gain in safety from the current transformer alone.

author: Jeroen3
author_rank: Super Contributor
timestamp: April 27, 2016, 01:40:19 pm
content: You can use an AMC1200 differential isolator.But a shunt is the most accurate way to measure the full range. From small to large currents. A transformer or isolator will make measuring small current difficult.It is also the least expensive way.As this application note is from a fully enclosed unit where the only terminals are Mains IN and Mains OUT you don't need isolation of the sensing. If it featured USB it was a different story.Just use an USB isolator when attaching the debugger when it's live.

author: electrotwelve
author_rank: Contributor
timestamp: April 27, 2016, 03:47:58 pm
content: Thanks @Kleinstein and @Jeroen3!
Feedback on an AC power measurement design - Page 1
Forum section: electronics / projects

author: electrotwelve
author_rank: Contributor
timestamp: April 28, 2016, 07:38:18 am
content: Here is an AC mains power measurement schematic that I tweaked from one of TI's smartplug designs. This simulates well in LTSpice and I was hoping you could give feedback on this. What improvements could be made, what could be eliminated etc. There is no user interaction anywhere here and hence no isolation.The first section across the voltage source is the voltage measurement bit. The resistor divider step the voltage down and then through filters its offset by 0.7V. The current measurement is about the same except here the voltage is measured across a shunt resistor. The maximum current measured is 15A and the max voltage measured is 240V AC. I thought about using the ACS712 for current measurement (and I'm still in two minds) but it bumps up the cost and I have not read good feedback about working with the chip.
AC Power Relay IoT Dinglehopper: Design Advice - Page 1
Forum section: electronics / projects

author: waymond91
author_rank: Regular Contributor
timestamp: January 11, 2024, 01:40:28 am
content: Hello!For reasons out of my control, I have been tasked with design an IoT controllable AC power relay (with some surge protection built in).This is my first PCB design that will have AC power coursing through its veins, so I was just hoping to solicit some general advice.This thing is supposed to work on 120VAC with 10-12 Amps for max current draw.I worry at this power level, the issue is no longer just with trace widths, but also with diaelectric of the board itself, and therefore the spaces between traces.I also worry about KiCADs default thermal reliefs for the componens pads, as there is also quite a bit of power moving through these now.Does anyone have some general guidance for this?I also was working on a small protector circuit for the AC power.My understanding is that we need to protect for over-voltage and over-current conditions.To that effect, I have chosen some fuses, movs, and a thermal fuse to help protect the whole thing. Again, this is my first time spec'ing these components - so any tips are welcome.I also am trying to use an off the shelf ac to dc converter, although I worry my approach here is also too simplistic.I have attached the schematics so far, really just looking for feedback on the ac power components (not the esp32 or w5500).I will also link in the parts pages for the components down below:Main fuse:https://www.digikey.com/en/products/detail/littelfuse-inc/0215012-MXP/777451?s=N4IgTCBcDaIAxgIwFY6LAOgLIA0AKIAugL5AAC to DC fuse:https://www.digikey.com/en/products/detail/bel-fuse-inc/RST-250-BULK/809314MOV:https://www.digikey.com/en/products/detail/littelfuse-inc/V14E150P/1009240Thermal Fuse:https://www.digikey.com/en/products/detail/bourns-inc/SA72SB0/6830067?s=N4IgTCBcDaIM4EMDsY4CMAMIC6BfIAAC to DC Converter:https://www.digikey.com/en/products/detail/mean-well-usa-inc/IRM-02-5/7704628Power Switching Relay:https://www.digikey.com/en/products/detail/cit-relay-and-switch/J114AF1CS3VDC-53/14002301?s=N4IgTCBcDaKP9-CBSBGZAWAggMWQYQMoDMAagCK4B0ArISALoC%2BQA

author: liaifat85
author_rank: Regular Contributor
timestamp: January 12, 2024, 02:58:42 pm
content: At 120VAC and 10-12 Amps, you're correct in considering trace widths and spacing. You can make a PCB with FR-4 for a high dielectric strength to prevent breakdown at high voltages.
AC Servo Motor Help - Page 1
Forum section: electronics / projects

author: nick.sek
author_rank: Regular Contributor
timestamp: February 28, 2013, 04:24:33 am
content: Hey,I need an AC servo motor for a project; which needs to be fairly low wattage (between 100 W and 200 W) preferably 100 W with an encoder built in;I was wondering if anyone knew of an online supplier with a good reputation and a reasonable price tag. Any leads would be greatly appreciated.My searches online have been very on promising.ThanksNick

author: daedalus
author_rank: Regular Contributor
timestamp: March 05, 2013, 03:53:09 pm
content: if its a one-off then I would recommend a second hand motor off of ebay, its going to be far the cheapest option. You will also be able to pick up cheap motor drives there. Another drive option iswww.granitedevices.fi, who produce a pretty reasonably priced FOC AC servo drive.If you want new motors at a reasonable price, then its places like alibaba and the like, but reputation is a bit hit or miss, and you have import to deal with.
AC surge protection - Page 1
Forum section: electronics / projects

author: gogoman
author_rank: Regular Contributor
timestamp: June 25, 2015, 01:17:09 pm
content: Hi , I would like to implement a surge protection circuit on the AC(120-250v), it must pass the IEC 61000 4-5 2000v test.One thought is to place MOV at the input of the line filter. The connections are Line to neutral, Neutral to Gnd and Line to Ground.The protection is the front end for a Switching power supply and micro controller stuff.My concern is resetting of the controller and other nasty things.What Works? Are there any golden rules to follows? does the gauge of the ac line cord matter?thanks