hybridfree/eevblog-posts huggingface dataset:
MOSFET reverse polarity protection + crowbar circuit combined - Page 1
Forum section: electronics / beginners

author: Zhenek
author_rank: Newbie
timestamp: August 14, 2019, 05:55:35 pm
content: I'm trying to combine two well known circuits, one is reverse polarity protection with MOSFET, another is crowbar circuit against overvoltage. Before trying to make the real circuit on the breadboard, I've decided to simulate it in TINA. However, I can't make it working. Separately both snippets work. Below is schematic and simulation result. It seems that SCR is always on for the reason I cannot explain.In real application I supposed to place a fuse where ammeter is on my schematics. Zeners are rated 15V.What am I doing wrong?

author: Zhenek
author_rank: Newbie
timestamp: August 14, 2019, 09:38:18 pm
content: Ok, changing SCR to TRIAC makes all the difference, now it's working as expected. Still I cannot explain, any ideas?
MOSFET Selection for HV DC Application - Page 1
Forum section: electronics / beginners

author: 97hilfel
author_rank: Regular Contributor
timestamp: October 11, 2016, 07:35:25 am
content: Hello guys,currently I am trying to build a Nixieclock, but I dont want to use those old russian driver ICs,so I decided to use MC14028 BCD to Decimal decoders, in combination with a MOSFET to drive the cathode.I am using IN-14 tubes with about 160V. In a Mr. Carlson's Lab video the MSPA42 NPN Transistor is suggested, but this transistor does not exist in SOT23 (which I want to use). So I found the BSS131, but are there better choises?Felix

author: bktemp
author_rank: Super Contributor
timestamp: October 11, 2016, 07:41:11 am
content: MPSA42 in SMD: FMMTA42 or PMBTA42

author: leeatljs
author_rank: Contributor
timestamp: October 11, 2016, 07:56:40 am
content: I used BSS131 in a nixie clock, works great.

author: 97hilfel
author_rank: Regular Contributor
timestamp: October 11, 2016, 06:56:45 pm
content: Tank you guys!Im gonna use the BSS131
Mosfet selection for motor PWM - Page 1
Forum section: electronics / beginners

author: ZeroResistance
author_rank: Frequent Contributor
timestamp: December 26, 2018, 08:30:02 am
content: So I have a task to control the speed of a 12V DC Brushed Motor by PWM.The PWM frequency I am thinking of is 25Khz.There are a variety of mosfets available with different "Total gate charge" values.But then I also see a parameter called "Input Capacitance". Are both of these related?From a PWM perspective would both have an impact on the switching speed of a mosfet?Also how does one lock down on the turn on speed of the mosfet. Is 1uS considered a good place to start with?I mean lets take a mosfet with "total gate charge" = 200nC that and a time to charge of 1uS so that would take a gate current of 0.2AAnd my motor is rated at 5A, I'm planning to use a simple low side mosfet for the PWM ( no forward / reverse is involved here).So considering the above aspects how does one calculate the switichng losses in the Mosfet @ 25Khz which is 40uS time period?I guess he mosfet will be in the linear region for 2us out of 40us so that is 5% of the time.

author: Zero999
author_rank: Super Contributor
timestamp: December 26, 2018, 09:51:20 am
content: The input capacitance is is measured between the the gate and source and drain shorted together.The total gate charge is the amount of charge which needs to flow into the gate to turn the MOSFET on. It's greater than what one would calculate using the input capacitance, because the gate to drain capacitance is increased due to the Miller effect, when the MOSFET starts to turn on.See page 8 of the poper linked below:https://www.infineon.com/dgdl/mosfet.pdf?fileId=5546d462533600a4015357444e913f4fWhat are you using to drive the MOSFET?The switching losses can be minimised by choosing a device with as lower gate charge as possible, whilst still having a high enough voltage rating an low enough on resistance to minimise the on loss. This isn't too difficult, just don't oversize the MOSFET too much and it will be fine.

author: ZeroResistance
author_rank: Frequent Contributor
timestamp: December 26, 2018, 11:26:47 am
content: Quote from: Zero999 on December 26, 2018, 09:51:20 amI'm planning to use a gate driver like MIC4422.My question also was what value off turn on / off time is acceptable is 1us considered good enough then the driver needs to put in just 0.2A to charge the mosfet.

author: Zero999
author_rank: Super Contributor
timestamp: December 26, 2018, 11:50:56 am
content: The MOSFET is in its linear region when it's turning on and off, with the peak power dissipated when the MOSFET has half the power supply voltage across it.Your MOSFET driver is overkill and there's no need to worry about it.There are plenty of MOSFETs which will do this and have a much lower gate charge than 200nC. See some example data sheets linked below.https://www.pololu.com/file/0J165/FDS5672.pdfhttps://www.onsemi.com/pub/Collateral/NDPL070N10B-D.PDFhttps://media.digikey.com/pdf/Data%20Sheets/ST%20Microelectronics%20PDFS/STD25NF10LT4.pdf
Mosfet senoidal driver, Metal film vs Carbon gate resistor, Ferrites needed? - Page 1
Forum section: electronics / beginners

author: guipoletto
author_rank: Contributor
timestamp: March 14, 2014, 05:31:25 pm
content: I'm in the process of repairing a full H-bridge senoidal driver, composed of 8 IRFP2907's.Two pairs experienced a non-passive failure (The KABOOM kind), possibly due to a shoot-trough.One of the gate resistors got smashed during the disassembly, and unfortunatelly i just have metal-film substitutes.Can i mix them together, or the change in inductance will be bad for business? (metal film vs carbon film)?I have some ferrite beads suitable to the leads of the Mosfets, but i'm not quite sure if the beads will prevent ringing, or cause it. those fets drive a quite thick(8mm²) low voltage high current primary in a transformer.I believe that beads in the supply side of the fet's would make the bus quieter from the switching harmonics, but since the currents are high, it could be that the beads would shoot back on the turn-off cycle, and act as little car-ignition coils, blowing the whole thing again.Electronics wizards, share some light? ^^

author: Holograph
author_rank: Regular Contributor
timestamp: March 14, 2014, 06:53:42 pm
content: My understanding is that it's considered good practice to replace all the gate resistors with the transistors and that they should all be the same. Whether it matters if they are carbon or metal oxide I don't know, but probably not, as long as they are the same.

author: guipoletto
author_rank: Contributor
timestamp: March 14, 2014, 08:02:25 pm
content: http://www.google.com.br/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CEgQFjAC&url=http%3A%2F%2Fwww.microsemi.com%2Fdocument-portal%2Fdoc_download%2F14693-eliminating-parasitic-oscillation-between-parallel-mosfets&ei=VV4jU4S8OqfV0QHDq4AI&usg=AFQjCNFx4nIFZLZHdXErKAATadkeupfzdg&sig2=gEoHPn6rEhe4hqUWm1V7lQ&bvm=bv.62922401,d.dmQ&cad=rjaThinking that this will be my sollution ^^
MOSFET sources - Page 1
Forum section: electronics / beginners

author: microbug
author_rank: Frequent Contributor
timestamp: August 10, 2013, 08:06:40 pm
content: I want to make an arduino-controlled battery tester and will need a FET. Rather than buying them individually, is there a way I can get a selection of FETs as a kit (like you can with LEDs or resistors)? I looked on eBay with no avail...

author: Legit-Design
author_rank: Frequent Contributor
timestamp: August 10, 2013, 10:26:02 pm
content: I didn't see any good premade kits of mosfets from the usual sources either. Assuming you meant MOSFET. Most assortments seem to have mostly normal transistors.Your local electronics store? Get few different kinds, first specify how much current you need and so on, you probably want a logic level fet if you want to control it straight with arduino pin. (with resistor between to reduce ringing) If you just want to whack something in there, then disassembling few products might be an option. Old computer power supplies might be a good bet for some beefy mosfets. Last psu I took apart had two irfb4110, I could have used more for free. The psu had most of it's low voltage electrolytics fail. Your typical psu also has it's mosfets already on a heatsink, properly mounted, thats a whoppy saving right there which even the chinese cannot beat easily.
Mosfet switching - Page 1
Forum section: electronics / beginners

author: mp90
author_rank: Newbie
timestamp: November 20, 2017, 07:58:37 am
content: Goodmorning,I'm trying to light up a led with an old light barrier I still have around. I want the led to light up when someone passed the barrier. Unfortunately I have a 24v signal when the barrier is safe and when someone walks through it, the voltage drops to 0.I still have some mosfets around but I’m not sure how to tackle this problem. I know I could use relay’s but I do not really have space for one. I have some mosfets and resistors so that shouldn’t be much of a problem.Long story short: I’d like to make a 24v circuit with mosfets. When there is no signal my led should light up.Is there a simple way to do it?

author: sanwal209
author_rank: Regular Contributor
timestamp: November 20, 2017, 08:47:37 am
content: If you have a mosfet with VGS above 24V you can apply that signal to its gate via series resistor and turn on LED.Check the attached Image which shows the basic configuration of Mosfet switch

author: alsetalokin4017
author_rank: Super Contributor
timestamp: November 20, 2017, 09:29:19 am
content: But the requirement is that the LED light up when there is NO signal, that is, the voltage level from the barrier strip is zero. And I think we are to assume that no microprocessor is used or desired.What then will power the LED? There has to be a power source for the LED that is separate from the barrier strip signal, that is, stays ON when the barrier strip signal goes low. Then a P-channel mosfet in a highside switch arrangement can be used.

author: danadak
author_rank: Super Contributor
timestamp: November 20, 2017, 10:36:43 am
content: Simple method, attached.Vz must be chosen based on Vth of MOSFET and system tolerances.If you don't like fact when LED is off power is being used, add anotherMOSFET or bipolar to invert signal and place LED in drain lead.Regards, Dana.

author: radiogeek381
author_rank: Regular Contributor
timestamp: November 20, 2017, 01:21:12 pm
content: Assuming you want to turn on an LED when the output from your sensor is low,and that you only have a 24V supply, Assume further that the sensor outputcan sink 10mA or so:What you need is not a MOSFET, You need a resistor.If the diode drops 2V then you need to take care of the remaining 24V.Most LEDs are happy to shine with about 10mA of current. So, we need10mA to cause a 22V drop:R = E/I = 22 / 0.01 = 2200 ohms.do this:24V supply --- 2200 ohm resistor -- LED -- > output of sensor.
Mosfet terminology - Page 1
Forum section: electronics / beginners

author: Faranight
author_rank: Unknown
timestamp: August 28, 2022, 11:07:09 am
content: So I've been browsing some electronic catalogs from online distributors like Mouser, Digikey, etc.When browsing for FETS I noticed there is usually a field in the selection filters where certain mosfet-related keywords appear.Keywords like:CoolMOSDirectFETHEXFETHyperFETIntelliFETNexFETOptiMOSPerFETPowerMOSSuperFETTrenchFETUltraFETUniFETCould someone please explain to me what these keywords mean?

author: Whales
author_rank: Super Contributor
timestamp: August 28, 2022, 11:13:50 am
content: Completely marketing.Some may refer to a specific series of mosfets made by a specific company that has some particular features (eg low Vthreshold, better linear power handling, etc) but sometimes they keep re-using the same name in later years for unrelated parts anyway (or have used the name for so long that the goalposts have shifted).If you select by those name then you will probably get very few matching results.

author: Circlotron
author_rank: Super Contributor
timestamp: August 28, 2022, 11:21:34 am
content: CoolMOS was a pretty big deal in the late 90s.https://www.researchgate.net/publication/3797528_CoolMOS_-_a_new_milestone_in_high_voltage_power_MOS

author: Terry Bites
author_rank: Super Contributor
timestamp: August 31, 2022, 04:16:50 pm
content: Mostly the same thing but with some internal structural variations and SOA protections eg the intellifet.Specmanship, bullshit and other parameters may apply.

author: Vovk_Z
author_rank: Super Contributor
timestamp: September 01, 2022, 08:09:55 am
content: Quote from: Faranight on August 28, 2022, 11:07:09 amYou may sell usual good FETS and you may sell 'HyperFET' or 'CoolMOS' or 'SuperFET'. What do you choose to sell? What do you think will be sold better?
mosfet testing - Page 1
Forum section: electronics / beginners

author: Flump
author_rank: Frequent Contributor
timestamp: September 18, 2014, 07:28:16 am
content: hi alli'm trying to test an N channel mosfetcould you tell me if these are the right procedures for digital and analog meters ?digital metergate drain sourceblack lead right pinred lead center pinshould have open circuittouch red lead to left pin for 2 secondsput red lead back on center pinshould get 0.000 or closetouch finger on middle and left it should go open circuit**********************************************analog metergate drain source1.) Set to times 10K ohm range to check it.2.) Put the Black Probe to the center pin.3.) Touch the left pin with the Red Probe to discharge any internal capacitance in the MOSFET.4.) Now move the Red Probe to right pin while the Black Probe still touching the center pin.5.) Use your finger to touch the left and center pin together.You will notice the Analogue Multimeter pointer will move forward of the meter's scale.

author: abaxas
author_rank: Regular Contributor
timestamp: September 18, 2014, 07:37:08 am
content: Buy one of these...https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/Put device in tester. Press button.Don't even think about it, just buy one. I paid ~£13 for one and when/if it breaks, I'll just buy another. They are amazing bits of kit.

author: Flump
author_rank: Frequent Contributor
timestamp: September 18, 2014, 07:42:38 am
content: I have one already but I am trying to help a friend out on the telephone and he doesn't have oneso were trying to use his multimeters to test it with

author: fubar.gr
author_rank: Unknown
timestamp: September 18, 2014, 09:20:17 am
content: Quote from: Flump on September 18, 2014, 07:28:16 amThis is pretty much the correct procedure. However, it might depend on the particular multimeter used.For example, my Uni T UT61E doesn't have enough juice to charge the gate while in resistance mode. So to do the test I have to switch to diode mode, touch the gate with the red probe and then switch back to resistance mode and measure the resistance between Drain and Source.

author: Flump
author_rank: Frequent Contributor
timestamp: September 18, 2014, 06:31:16 pm
content: thank you fubar
MOSFET to power a 24V load and SOA - Page 1
Forum section: electronics / beginners

author: Tantalum
author_rank: Regular Contributor
timestamp: July 10, 2022, 05:53:45 pm
content: HiLet's say I will use a LTC7000A gate driver to power a load with 24VDC.How should I select my MOSFET for a 16A max load???Should I take care about the SOA???I never really understood that diagram, because I don't know if Vds is 24V or less in full on/off mode.Let's say I'll take a SUG80050E MOSFET.Should I consider the blue line (Vds 24V) or the red dot (Vds ~0.1V)Thanks

author: langwadt
author_rank: Super Contributor
timestamp: July 10, 2022, 06:30:41 pm
content: Quote from: Tantalum on July 10, 2022, 05:53:45 pmthe red dot is where you are at when the mosfet is on

author: Tantalum
author_rank: Regular Contributor
timestamp: July 10, 2022, 06:34:44 pm
content: Thank you!
MOSFET VDSO/VGSO - Page 1
Forum section: electronics / beginners

author: fourierpwn
author_rank: Regular Contributor
timestamp: August 23, 2018, 11:45:05 am
content: Hi all,This may be a simple question, but is there a way to determine VGSO (gate-source voltage open drain) and VDSO (drain-source voltage open gate) from I-V curves? If not, is there any way to determine this voltage without measuring the device with open drain/gate?Thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 23, 2018, 12:24:23 pm
content: That's an absolute maximum, design, rating. Exceeding it has some electrical effects (increased gate leakage current, and after extended exposure, drift in Vgs(th)), but the most important one is causing abrupt and permanent failure of the device.Tim

author: fourierpwn
author_rank: Regular Contributor
timestamp: August 23, 2018, 12:39:42 pm
content: Thanks for the response.Sorry if I wasn't clear. I was not asking what is meant by VDSO/VGSO, I am aware of this. I was asking about ways to find out this value if all you have is DCIV measurement data (no datasheet etc).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 23, 2018, 11:52:15 pm
content: Well, yeah, I gave two properties, one possibly non-destructive, one destructive, that could be used to find that out. Obviously, the destructive test only helps if you have spares to sacrifice.Apparently, failure isn't a good indicator anyway, as a 20V gate might pop at 30V to 80V.Probably safer and more reliable is to just assume what voltage it is. Low Vdss transistors usually have low Vgso ratings. I don't think I've seen anything over 30V that wasn't rated for +/-20V gate.Tim
Mosfet wanted  - Page 1
Forum section: electronics / beginners

author: 10101
author_rank: Contributor
timestamp: June 03, 2015, 12:21:20 am
content: I've searched the internet already but there are so many mosfets that i can't find the right one.So my question is, is there any logic level (5v) cheap comon mosfet that can handle atleast 1 amp when fully on in the market ? (to-92 case prefered).PS: they will be used to make 3 h bridges controled by an atmega328p.Thanks in advance

author: edavid
author_rank: Super Contributor
timestamp: June 03, 2015, 01:19:21 am
content: NTD3055L in IPAK?

author: LabSpokane
author_rank: Super Contributor
timestamp: June 03, 2015, 04:32:44 am
content: Quote from: edavid on June 03, 2015, 01:19:21 amIn my searches, the 3055 seems to trickle to the top in bang for the buck.

author: agehall
author_rank: Frequent Contributor
timestamp: June 03, 2015, 05:52:32 am
content: If you are looking to create H-bridges, why not have a look at the BTN7971B and newer models. They might be overkill for your application but they form half H-bridges all in one piece and I'm sure there are even more suitable ones (i.e. full H-bridge ones) if you look for them. Just giving you a starting point here...

author: 10101
author_rank: Contributor
timestamp: June 03, 2015, 04:12:41 pm
content: The NTD3055L seems to be a good option !!! just need to check the price with a local distribuitorI think that an h bridge ic maybe it's a bit overkill since i want to make it as simple as possible.Thanks to all that tried to help

author: LabSpokane
author_rank: Super Contributor
timestamp: June 03, 2015, 05:35:52 pm
content: Quote from: 10101 on June 03, 2015, 04:12:41 pmWithout a doubt it is overkill, but one generally must buy 10 ore more for a decent price, so it's nice to have a very flexible, inexpensive MOSFET on the shelf.
MOSFETs and different voltages for load/pin - Page 1
Forum section: electronics / beginners

author: analogo
author_rank: Regular Contributor
timestamp: May 09, 2017, 07:10:31 am
content: Hello forum.I have a load that require 12v/500mA to operate and I would like to switch it on and off using and Arduino (5v on the pins). The whole project will be powered by a 12v transformer and a step down converter will be used to turn 12v into 5v for the Arduino. Can I use a MOSFET to switch the load on and off?I simulated a circuit where both the load and the Arduino are powered by the same 5v supply and everything work. What I do not understand is if the 12v of the load will create a problem.I understand that MOSFETs can be used only when the driver and the load share the same ground, otherwise a relay is needed. In my case are the two grounds different grounds or the same ground?

author: danadak
author_rank: Super Contributor
timestamp: May 09, 2017, 11:07:18 am
content: 12V not an issue for switch, just choose one that meets this as a breakdown property+ some margin.Load can be switched high or low side, low side simplest, high side more involved in orderto get adequate gate drive to achieve low Rdson.http://www.onsemi.com/pub/Collateral/AND9093-D.PDFhttp://www.infineon.com/dgdl/Infineon+-+Application+Note+-+Power+MOSFETs+-+OptiMOS+P-channel.pdf?fileId=db3a304341e0aed001420380cc13101bhttp://www.vishay.com/docs/91421/appnote9.pdfIf you are switching L loads make sure you use protection diodes and snubbers to clampany transients fed back to processor drive pins.https://www.circuitlab.com/circuit/t67g8z/mosfet-switching-inductive-loads/http://www.nxp.com/video/driving-inductive-loads-with-mosfets-nxp-quick-learning-44-part-1:MOSFETS-INDUCTIVE-LOADS-1Regards, Dana.

author: analogo
author_rank: Regular Contributor
timestamp: May 09, 2017, 02:14:59 pm
content: Thanks you Dana for all these links!One thing is not clear to me. Can I just always merge grounds? are there cases where it is better not to or plain dangerous to merge grounds from different power sources?

author: Zero999
author_rank: Super Contributor
timestamp: May 09, 2017, 04:57:27 pm
content: I'd just use BJTs for 500mA.Note, this circuit was originally designed for a much lower current, soR1 will need to be changed to 100R for operation at 500mA.The 5V and 12V grounds must be shared for this to work. If you want the 12V supply and 5V supply to be completely isolated from one another, then you can use a relay, such as the old electromechanical type or solid state, whether as a module or a combination of an opto-isolator and MOSFET.
MOSFETS for H-Bridge - Page 1
Forum section: electronics / beginners

author: francisjoe45
author_rank: Newbie
timestamp: May 04, 2011, 04:30:03 pm
content: Hi, it is my first time to design a motor controller for a BLDC motor and I am confused on what kind of MOSFETS to use. I would like to drive the MOSFETs using a PIC microcontroller, (dsPIC33F).Let's say an H-bridge for example, where there is High-side and Low-Side driving, should I use a pair of P-Channel and N-Channel MOSFETs for the half bridges or can I use 4 N-Channel MOSFETs instead? I am very confused since the gate of P-Channel MOSFETs, as I understand, needs to be supplied with a negative voltage for the FET to turn on.

author: sacherjj
author_rank: Frequent Contributor
timestamp: May 04, 2011, 04:59:32 pm
content: Here is a decent article that might help.http://www.modularcircuits.com/h-bridge_secrets1.htmN Channel just generally perform better, but are a little harder to use on the high side. That article discussed some of the challenges.

author: Neilm
author_rank: Super Contributor
timestamp: May 04, 2011, 06:49:59 pm
content: Quote from: sacherjj on May 04, 2011, 04:59:32 pmThere are chips available that will take the the work out of driving either half or full H-bridges (for instance NCP5304 first one I found). All the user has to do is provide the drive signals. Some of the chips available will also provide shoot through protection.Neil

author: mkissin
author_rank: Regular Contributor
timestamp: May 05, 2011, 08:16:59 am
content: Yeah, I'd definately go with four N-channel FETs.How easy or hard they are to drive will depend on your DC bus voltage. Up to about 600V, things are pretty easy, as you can get heaps of half-bridge driver chips with inbuilt bootstrap power supplies to drive the high side FETs. Personally, I usually use the ones from International Rectifier (like the IR2104), but there are plenty of others.The half-bridge drivers generaly have built-in dead time to avoid shoot-through faults (although they often don't have shoot-through detection. That's another issue), and the bootstrap supply is simply a diode and a capacitor.Above 600V things are trickier, but unless you into really high power stuff that's not such an issue.

author: Zero999
author_rank: Super Contributor
timestamp: May 05, 2011, 04:44:10 pm
content: For higher voltages (above around 400V) IBGTs start to become more efficient than MOSFETs.
Mosfets - Page 1
Forum section: electronics / beginners

author: Rats
author_rank: Newbie
timestamp: March 30, 2016, 11:03:15 pm
content: Ok so im a bit stuck with finding a faulty mosfet replacement for a power amp im repairing.The faulty one states the following on the front: "IRFP250N 811P E1 (over pin 1) B5 (over pin 3)"I can find a lot of mosfets with "IRSP250N". However, I am wondering if the "811p" and the "E1 & B5" have any significant meaning? as I cant seem to find anything onlineAny help would be great.Thanks a lot.

author: Andy Watson
author_rank: Super Contributor
timestamp: March 30, 2016, 11:27:01 pm
content: IRFP250N the rest is just date code and assembly location.http://uk.farnell.com/international-rectifier/irfp250npbf/mosfet-n-200v-30a-to-247ac/dp/8649260

author: Rats
author_rank: Newbie
timestamp: March 30, 2016, 11:33:27 pm
content: Thanks a lot mate! Much appreciated!
MOSFT capacitance  - Page 1
Forum section: electronics / beginners

author: stafil
author_rank: Regular Contributor
timestamp: March 31, 2020, 08:22:09 pm
content: Hi!In the circuit below I understand that the undershoot/overshoot and slow rise time I see is because of the MOSFET capacitance, but I have a couple of questions.1. Which capacitance specifically is it? Is it the Drain-Gate capacitance that causes this?2. Any way to fix all of the above, rise time and understhoot/overshoot, assuming I don't have any control over the R1(20k) Resistor and and V2(5V) voltage source?(The greenish line is the voltage at the drain, and the blueish(turquoise) the voltage at the gate)Thanks,Stavros

author: Manul
author_rank: Super Contributor
timestamp: March 31, 2020, 09:10:56 pm
content: I will try to put it simple.Slow rise is because:1. When gate voltage goes down, drain is at almost 0 volts2. There is capacitance between drain and source Cds3. Cds charges up from V2 through R14. Rise time is determined by Cds and R1 time constantYou cannot do much about it without changing R1, or Cds (mosfet used).Undershoot and overshoot is because:1. There is capacitance between gate and drain Cgd2. Extremely fast gate voltage rise and fall times means that it includes very high frequencies3. For these high frequencies Cgd has low impedance and becomes significant path4. So it pulls down and up drain voltage, while Cgd charges/dischargesTo solve undershoot/overshoot you need to slow down gate rise and fall times by adding current limiting gate resistor. Together with gate source capacitance it creates low pass filter. It also helps to stop gate ringing. Almost a must in all practical circuits.

author: stafil
author_rank: Regular Contributor
timestamp: March 31, 2020, 09:19:22 pm
content: Quote from: Manul on March 31, 2020, 09:10:56 pmThanks. I wish all the answers to all the questions I ever had were so precise and well explained!

author: Manul
author_rank: Super Contributor
timestamp: March 31, 2020, 10:12:17 pm
content: As a side note - in practice you have gate resistor even if there is none. By that I mean, that the gate driving source has some internal resistance. For example - arduino output pin can have 30-50 ohms of internal resistance. Also mosfet gate itself has some little resistance. In a simulation it is different story. It may simulate gate resistance, but signal source is by default 0 ohms.Also real circuits have inductances everywhere. Then it really starts to get messy.

author: Zero999
author_rank: Super Contributor
timestamp: April 01, 2020, 10:31:13 am
content: Power MOSFETs aren't designed to be used in this manner. It's possible to get MOSFETs with a smaller drain-source capacitance such as the FDV301N.https://www.onsemi.com/pub/Collateral/FDV301N-D.PDFAnother option is to use a logic gate with an open grain output, such as the 74LVC1G06.http://www.ti.com/lit/ds/symlink/sn74lvc1g06.pdf
Most complicated chip or specialized part in TEKTRONIX 2213A 60MHz scope ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 15, 2017, 10:53:58 pm
content: Looking for analog scope, so I can fix it if I break it. And if I want to risk buying it broken.What are some good ones with simple parts ? Have'nt had time to check the 2213A manual get, anyone know ?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 15, 2017, 11:59:18 pm
content: Are you focusing on Tektronix only? There are those philips scopes that are all made out of transistors. Like for example the PM3226.

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 16, 2017, 02:06:17 am
content: no just looking around, but as of today I barely know any other brands/modelsI'd love an all transistor and all tube scope. I will get both someday for fun. I guess a big woory with older and older scopes tho is finding CRT replacements

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 16, 2017, 03:00:50 am
content: Some other brands of old CRO's to look for other than Tek and HP are:Hitachi, Iwatsu, Philips, BK Precision, Leader, Kikusui, Gold Star, GW Instek, and the classic Hung Chang (you know..they're ok)

author: David Hess
author_rank: Super Contributor
timestamp: September 16, 2017, 01:35:19 pm
content: The only Tektronix custom IC in the 2213A/2215A is the horizontal amplifier IC but they very rarely fail; I am not sure I have every heard of one failing. Unlike the higher bandwidth members of this oscilloscope family, the 60 MHz 2213A/2215A use standard parts although that includes standard transistor arrays.

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 17, 2017, 08:01:48 am
content: Ok thanksI ordered a Tek 2215 so far, but it is broken. Time to start reading up on them.

author: David Hess
author_rank: Super Contributor
timestamp: September 17, 2017, 12:35:25 pm
content: Be warned that the 2213/2215 is *not* the same oscilloscope as the 2213A/2215A. They share very little in common.The 2213/2215 do not have the custom horizontal amplifier IC found in the 2213A/2215A but they do have a pair of custom vertical amplifier ICs which again, are unlikely to be bad.The most common problems with the 2213/2215 are with the power supply, the resistor loads in the vertical CRT amplifier, and focus resistor chain simply because of age.
Most "professional" way to provide constant voltage from a battery pack - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 21, 2022, 01:28:22 am
content: Hi,So say I have a 24V battery pack, I want to be able to use this pack to power a number of lower voltages, at least 12V, 16V & 19V, one voltage at a time.The 24V pack is 11S LTO 2.3V, so it's actually 25.3V nominal, it charges up to about 29V and discharges to around 22V.I see talk of SEPIC and lots of cheap buck boost converters but I don't really see anything that would provide up to 100W of reliable constant voltage that I can select?Thanks.Richard

author: IanB
author_rank: Super Contributor
timestamp: April 21, 2022, 01:44:14 am
content: If you search around the usual sources there are many variations on this kind of module with varying voltage and current ranges:https://www.amazon.com/UCTRONICS-Numerical-Stabilized-Converter-Adjustable/dp/B01LWXAC5EIs this the sort of thing you are looking for?

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 21, 2022, 02:00:25 am
content: Quote from: IanB on April 21, 2022, 01:44:14 amThanks IanB, I actually have one very similar to this, are they any good?

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 21, 2022, 02:11:05 am
content: Thanks evb149!Maybe the best way to do it is just have three seperate buck boards, one for each target voltage, high efficiency would be great also!Any suggestions for something like that, over 90% efficiency buck circuit with selectable output voltage?

author: bdunham7
author_rank: Super Contributor
timestamp: April 21, 2022, 02:23:42 am
content: Get and examine one of these. See if it works well enough regarding efficiency and noise, then either use it or improve on it. You can take this approach--an MCU-controlled variable buck, or you can just have a hardwired 3-voltage buck. I wouldn't think you'd need to use 3 different boards to get good efficiency.

author: John B
author_rank: Frequent Contributor
timestamp: April 21, 2022, 04:26:59 am
content: Quote from: rthorntn on April 21, 2022, 02:11:05 amI think you'd be wasting money on 3 separate buck modules. I would expect the FETs and inductors to cost a bit and so I wouldn't buy them 3 times over and have 2 lots sitting idle. I would use a synchronous buck controller with external FETs. Also, the controller might cost a bit, too. TI has some nice stuff but I have no idea about availability at the moment.
Motherboard component identification - Page 1
Forum section: electronics / beginners

author: Roverfan
author_rank: Contributor
timestamp: September 28, 2023, 06:51:44 pm
content: Hi guys anybody know what this component is? The phone motherboard seems to have lots of them but I have been unable to find any wiring diagrams or schematic for any phone.

author: ataradov
author_rank: Super Contributor
timestamp: September 28, 2023, 06:57:05 pm
content: They are u.fl connectors.Although if this is a phone, they may be some smaller version, but the idea is the same - RF connectors.

author: Roverfan
author_rank: Contributor
timestamp: September 28, 2023, 07:44:48 pm
content: Thank you ataradov, although I'm totally clueless I didn't think they are rf connectors, the tops do look like the same basic shape as connectors but seeing them in person they don't have any clip on mechanism. Also there is atleast 4 in that picture alone, so I don't think any phone manufacturer would put so many unpopulated connectors on a tight motherboardCould they be some kind of antennas?

author: ataradov
author_rank: Super Contributor
timestamp: September 28, 2023, 08:32:31 pm
content: There are also similar style RF test points too. They allow connection of the test equipment. They may be used for manufacturing. They act as switches, redirecting the signal from the real antenna into the test port. Given their proximity to the real antenna connectors, this is like it.They are not antennas, for sure. If you can get a better picture, it may be easier to recognize them.

author: Roverfan
author_rank: Contributor
timestamp: September 28, 2023, 08:45:18 pm
content: Thank you ataradov. I couldn't find any more info other then the video I got the picture fromShows component 3.40mins onwards

author: ataradov
author_rank: Super Contributor
timestamp: September 28, 2023, 08:57:33 pm
content: Yeah, those are test switches. Something similar to thishttps://www.mouser.com/new/murata/murata-swg-rf-test-probes/

author: Roverfan
author_rank: Contributor
timestamp: September 28, 2023, 09:23:40 pm
content: Thank you so much ataradov for your help, awesome
Motherboard overvoltge protection? - Page 1
Forum section: electronics / beginners

author: carlhoward
author_rank: Newbie
timestamp: January 13, 2018, 08:09:28 pm
content: Is it common for netbook or laptop motherboards to have overvoltge protection built in?My friend's son tried to help charge a netbook (Gateway LT3120u, 19v) with my POE power injector (48v). :-(Now shows no signs of life.Just wondering if there's any hope.Thanks

author: Cliff Matthews
author_rank: Unknown
timestamp: January 13, 2018, 08:25:34 pm
content: Small currents from PoE injectors somehow give doubt the laptop wasn't pooched prior (my sons are sometimes reckless). Also, the 19v never reaches the logic on the mobo. It must pass through battery/charge chips and DC/DC convertors before that. If the 48v did anything, it may have hurt a mosfet or some TVS diode.

author: wraper
author_rank: Unknown
timestamp: January 13, 2018, 08:31:00 pm
content: Often there is a TVS diode in parallel with charging input. In case of overvoltage or incorrect polarity it usually gets fried first. In such cases often it may be a relatively easy fix. But's it's still a component level motherboard repair.

author: xavier60
author_rank: Super Contributor
timestamp: January 14, 2018, 06:41:33 am
content: On the adapter input there is usually one or two MOSFETs for reverse polarity and under/over voltage protection. One might have a spiked Gate.
Motherboard power issue - Page 1
Forum section: electronics / beginners

author: Mandarin47
author_rank: Contributor
timestamp: July 14, 2015, 08:01:47 pm
content: Hi everyone. I would appreciate any help in helping me solve my problem. I have an ASUS x99-delux motherboard that suddenly stopped working. There has been no physical damage, ie liquid damage. It was working fine and then shut down and now won't restart. The q-code is 00 which according to the manual is not a used code.I have checked all cables are fitted correctly. The psu is also good (checked on another pc). I have also tried to reset the bios and cmos and still nothing.Online forums are suggesting it is a dead motherboard.I disassembled everything and only connected the 24 pin connector. The psu starts but I still get the 00 code. However when I connect the cpu cable and restart the psu, the psu stops working, as if it shorts. No fans turn at any point.I understand that this is probably a very complicated repair where specialised equipment is needed but on the off chance it might be a simple component fail it will save a lot of money if I can repair it myself.Hope someone can help me

author: madires
author_rank: Super Contributor
timestamp: July 14, 2015, 08:40:42 pm
content: The POST code is 00 because the CPU isn't running. And the PSU stops because the DC-DC converter for the CPU is broken (short circuit). I'd buy a new mainboard.

author: cpt.charlie
author_rank: Contributor
timestamp: July 14, 2015, 09:50:36 pm
content: If the PSU doesn't start with the 12v P4 connector plugged in, it means that you have a short in the VRM of the CPU, remove the processor and check the resistance to ground in the VRM mosfets.
motion activated message with flashing lights - Page 1
Forum section: electronics / beginners

author: muddy
author_rank: Newbie
timestamp: August 25, 2016, 01:01:39 pm
content: Hello AllI am retired and a complete beginner when it comes to electronics. I will need to be spoon fed information if I am to be successful with my project. I hope there is enough people on the forum with patience and understanding to help me.I have a display in the shape of a pyramid, it is hollow. I take it to shows, fetes, etc., but I wanted to draw peoples attention to my display and therefore our stand.I wanted my display to have a motion activated sensor, so when people were walking by it would activate a prerecorded 10 second message and five small L.E.D. lights at the same time, just for a short period to draw peoples attention.I am hoping the circuitry will be small enough to be concealed in the hollow of the pyramid display, which could also act as the box for a small speaker.I have tried to search the internet for any pre-made items that fit my description, but without success. I did find a motion activated speaker that would give a 10 second message (speaker likely to large to conceal), but nothing with flashing L.E.D. lights.Therefore I thought the only option was to make it myself as getting someone to make it for me would be too expensive.If I knew what components I needed, where to source them and guidance on putting the circuitry and bits together, I could achieve a successful and affordable outcome.Here's hoping someone can help. Thanks.

author: MosherIV
author_rank: Super Contributor
timestamp: August 25, 2016, 01:56:19 pm
content: QuoteWhat you want is something called a passive infrared sensor (PIR sensor)Here is one :http://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=302_303&products_id=2076If you supply it with 5V, when triggered the output will go high (5V).Next you will need a sound play back device :https://www.sparkfun.com/products/11125You will have to figure out the amplifier and speakers yourselfYou can figure out the flashing lights yourself.
Motion sensing for Midi project question - Page 1
Forum section: electronics / beginners

author: ChrisW
author_rank: Contributor
timestamp: April 23, 2013, 06:56:17 am
content: Hey guys,I am contemplating a diy midi keyboard project but am not sure how to sense and measure the timing of the movement of the individual keys in an accurate manner.Would hall effect sensors work or would I have to design some light based solution like an led and photo-diode?Any pointers would be greatly appreciated!-Chris

author: Memphis
author_rank: Contributor
timestamp: April 23, 2013, 01:04:18 pm
content: Hall-efect sensor is reasonable but much better would be an accelerometer for each key. Todays accelerometers can be chained with one bus I2C or SPI and thus you can easily process it with for example ATmega168.I was playing with midi on University and this was a result:Industrial orchestra

author: Hideki
author_rank: Frequent Contributor
timestamp: April 23, 2013, 04:46:36 pm
content: I think you will find it very hard to get any sensible data out of an accelerometer without a lot of processing. It will also require running wires to every key, unless the intention is that the key actually hits the accelerometer at the end of its travel. It might be fine for a more percussive type of instrument. Determining if the key is actually up or down also gets a bit tricky.The usual way to do it is to have a pcb with two contacts per key. A silicone membrane strip sits above it with two carbon pill contacts per key. One is a bit higher than the other, so as you press the key down, one switch closes before the other. You measure the time between them to determine the key velocity.It's used by nearly all midi keyboards on the market, but I guess it's very hard to DIY that at home.There are optical methods, like pnoscan.http://www.midi9.com/products.htmbased on reflective optical sensors likehttp://www.digikey.com/product-detail/en/QRE1113GR/QRE1113GRCT-ND/965713Hall effect should work fine too, but then you need to put a little magnet in every key.

author: jmole
author_rank: Regular Contributor
timestamp: April 23, 2013, 06:08:05 pm
content: My advice:Forget about a DIY keyboard unless you're trying to do something totally new, like theContinuum, orROLI.Pick one up at your local pawn shop, it will save you lots of money. Then, hack on whatever other functionality you want by hacking on the MIDI stream.But, if you're still considering it, check out a related project I did a while back:http://portfolio.moeller.io/happy-feet.htmlI'm sure you can adapt the pressure sensing technique to whatever you're looking to create.
Motor Circuit - Large 1ohm 10w resistor - Why? - Page 1
Forum section: electronics / beginners

author: Szewczykm
author_rank: Regular Contributor
timestamp: January 09, 2015, 09:48:18 pm
content: Hi,There is a circuit that goes into pinball machines for those equipped with a "shaker motor". I understand most of the circuit but I'm curious about a big resistor that's in there.Here is the Schematichttp://www.ki4swy.org/images/pinball/lah/lah-shaker-board.pngHere is a picture of the boardhttps://ksarcade.net/media/catalog/product/cache/1/image/a449636a7e0327a12453e7ee4d97c439/5/0/502-5027-00.jpgBasically A/C is coming off a transformer, there are a couple of Diodes that I'm assuming are acting as a rectifier (half wave I think), a couple of fuses and a big 10w 1ohm resistor. The motor is being driven on a different board, and that part of the circuit is on the schematic.I'm wondering if anyone knows what the purpose of the big resistor is? I spoke to one of the electrical engineers at the iron foundry I work at (we use a lot of electricity melting iron!) what his guess was and he said he thought that maybe it was a kind of protection against the motor seizing up. He said that if the motor were to get jammed, stuck, seized, whatever, and it started to draw a lot of current then rather than burning up the circuit or motor, that resistor would just dissipate the draw as heat.This seemed reasonable, but I wondered, wouldn't a fuse just blow? Maybe there are instances where the fuse wouldn't blow but the motor would get hot if something jammed it, but the resistor helps dissipate some of that. But really it's a guess. I'm trying to get into the designer's head. Any ideas?Thanks!Mike

author: dannyf
author_rank: Super Contributor
timestamp: January 09, 2015, 09:55:31 pm
content: To limit the start-up current.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2015, 06:10:58 am
content: It limits the start up current and also reduces the speed of the motor slightly so that it does not vibrate so vigorously. As the motor draws more current during lifting the shake mass the resistor lowers the voltage applied to the motor ( it is 100/120Hz full wave rectified DC, the lower link on the diagram shorting the one diode and fuse is incorrect) so it does not shake itself to bits.
Motor control boards - Page 1
Forum section: electronics / beginners

author: Explodey
author_rank: Contributor
timestamp: June 26, 2019, 04:14:05 am
content: Hi everyone! I have this big ol' motor (picture attached) that someone gave me years ago, and I've just been sitting on it, figuring that eventually I'll have a need a powerful motor. So I think I finally might have such a need -- to power a pinch roller assembly. But I've never worked with an AC motor like this one, so before I try to give it some juice, I thought I'd take advantage of all the big brains here at EEV. From the specs printed on the motor, it looks like I could just connect an AC signal directly from the wall. But I actually need to be able to adjust the speed and reverse the direction. When I've worked with DC motors in the past, I've had good luck by using a motor speed control board like this one,https://ebay.us/BYh5bTalong with a polarity-reversing rocker switch. But I'm not sure if there would be an analogous board for an AC motor, and I definitely don't know how you would reverse the direction when you're working with AC.Anyway, would it be simpler for me to just get a different motor? I guess I'm just hoping to find a way to rationalize hanging on to this big paperweight for all this time!Thanks!

author: MosherIV
author_rank: Super Contributor
timestamp: June 26, 2019, 06:16:11 am
content: Hi.Yes, looks like you just connect it to 110V mains. Make sure you use a fuse.I do not think you can control speed or direction.Yes, you can get controllers for AC motors, they are called Inverters (at least in UK). As far as I know they are only for 3 phase motors.The motor you have is for single phase. The device on the side of the motor is a capacitor, it is there to create a phase difference and that 'alternate phase' is used for another winding on the motor. AC motors need either a phase difference or a rotating phase to start.

author: Explodey
author_rank: Contributor
timestamp: June 26, 2019, 05:34:36 pm
content: Alrighty, well thanks for your reply. I think I'll just buy a DC motor then. Cheers!