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  • Опубліковано 28 лис 2024

КОМЕНТАРІ • 61

  • @Hellhound604
    @Hellhound604 9 місяців тому +22

    And the NTC is the reason why you should wait some time after unplugging a PSU before you plug it in again. Gives some time for the NTC to cool down, so that it can do its job preventing the high inrush current.

    • @1kreature
      @1kreature 9 місяців тому +4

      Yep, and it's why shorter interruptions in power can blow the built in fuse rendering your brand new psu useless after just first short supply interruption.
      I've had this happen on a UPS of all things. Needless to say, a UPS that blows it's input fuse first time there's a supply disturbance went right back to the store!

    • @snakezdewiggle6084
      @snakezdewiggle6084 9 місяців тому

      Why does it have to be a "brand new" psu.?

    • @1kreature
      @1kreature 9 місяців тому +2

      @@snakezdewiggle6084 I was "painting a picture" of your future experience... Call it a foreshadowing.

    • @snakezdewiggle6084
      @snakezdewiggle6084 9 місяців тому

      @1kreature.
      Oh, well thank you. Good luck with it. 😉

    • @dedskin1
      @dedskin1 2 місяці тому

      Not really , the Caps are full , so if you plug it out , and plug it back in , caps are still full . And things dont work like you think they work You would think 1.5V battery is discharged when it goes down to 0V , well no , its empty at 1.4V , so the amount of energy , current is not the same as Voltage . So even if built in Caps drop from 200V down to 20V being drained somehow , you would think that will take 9/10 of inrush current when turned on again . NO , why because voltage is not the same as current . One would need to investigate this to find what happens , i dont know , but i know its not 9/10 of inrush current , its strange but just like when you take a 200V cap , and discharge it , boom . You would expect it to be at 0V or close , and it is , and then you observe it rises in voltage and its not even turned on , raised to 40V. Why , leftover current . So once you energize a Cap , turning it off and on Again , wont do much .

  • @captainmother1268
    @captainmother1268 9 місяців тому +13

    The downside of these devices is when the power drops for just a moment and then comes back - they won't be an in-rush current limiter anymore since they haven't cooled down. Can be a problem if you don't plan for that.

  • @bobdoritique7347
    @bobdoritique7347 9 місяців тому +11

    I wanted to thank you for all the videos you make, they are very appreciated. A big THANK YOU for everything, I imagine it's a lot of work...

    • @gorak9000
      @gorak9000 9 місяців тому +2

      I'm very impressed that there's a new video EVERY day, and never a bad one!

  • @ericksonengineering7011
    @ericksonengineering7011 9 місяців тому +3

    Great video, thanks!
    Those things saved my butt on a medical system. We used a medical-grade toroidal AC isolation transformer to feed various equipment, about 300W total. The transformer blew 5A slow-blow fuses, but only when the system was plugged in near an electrical panel. Even 50' of 12-2 AC building wire was enough added resistance to prevent fuses from blowing. Adding an AC extension cord also prevented fuse blowing. I measured over 100A inrush current on power-up of the transformer. Two 4 ohm NTCs later (one in series with each 120V primary winding), and problem permanently solved. This same problem can be found on many AC transformers, especially large ones.

    • @sstorholm
      @sstorholm 9 місяців тому

      There’s also a phenomenon that I can’t remember the name of, but essentially a transformer core “remembers” in what phase of the AC cycle it was disconnected, and if you happen to reconnect it 180 degrees out of phase you’ll see really large inrush currents. Small transformers are the worst, it can be 100 times the rating of the transformer, bigger power transformers designed for 100+ MW are a bit more tame, around 4 times the nameplate power, but still a big issue. On transformers over 25MW they use a synchronized phase breaker, so that each phase core is disconnected and reconnected at the zero crossing of the wave form to avoid this problem.

    • @thomass7877
      @thomass7877 9 місяців тому

      It happened that I got a large isolation transformer for small money. 1500W, 6A. I turn it on via a 500W halogen bulb in series. Of course, I have a voltage drop that I compensate with a variac. Which NTC would you recommend, or a combination instead of my method? Thx.

    • @sstorholm
      @sstorholm 9 місяців тому +1

      @@thomass7877 on my isolation transformer I use an NTC and a time delay circuit that bypasses the NTC with a relay after a while, 6-7 components is all it takes.

    • @thomass7877
      @thomass7877 9 місяців тому

      @@sstorholm thank you...

    • @analoghardwaretops3976
      @analoghardwaretops3976 9 місяців тому

      ​@@sstorholm..transformer ferromagnetic core magnetization &
      de magnetization , depend according to their B- H curve..which is also known as Hysteresis curve...and is a function of the frequency of the alternating current that produces its magnetic field ( flux )..
      In each half ac cycle this flux polarity reverses....
      Loaded or unloaded transformers (& inductors too)
      must have " equal Volt.-Sec. ..so also Amp.- Sec. "
      product in each half cycle..( or during " t-on & t-off in pwm) to cancel out, for net Zero Residual flux after one complete cycle.
      If this does not happen , there is a gradual flux buildup of one polarity.....
      Therefore even if the current is within limits...,that gradual flux build up over some time, causes the core to reach its peak saturation point....Thereafter even the smallest amount of current in the next (t-on)/half cycle , it crosses its saturation point.leading to mosfet/bjt blowing or circuit breaker tripping. as the case may be.

  • @pault6533
    @pault6533 9 місяців тому +10

    I have a bunch of take-off parts from power supplies and noise filters. You have covered the shiny yellow ones and dull green ones. Now I have shiny red ones and shiny blue ones too. Can’t wait for the next installments to understand what they are too😊

    • @Edisson.
      @Edisson. 9 місяців тому +2

      The color is not decisive, you always need to be oriented according to the marking - yellow can be, for example, Polyfuse - self-resetting fuse, or Varistor. The varistor can be blue, the X1 type capacitor can also be blue. NTC thermistor does not have to be green, for example they are black etc.
      Nice day 🙂 Tom

    • @pault6533
      @pault6533 9 місяців тому

      @@Edisson.thanks Tom, I looked up some of them and found out these other colors are also MOV’s and other safety caps. I’d like to know the reason for the different colors- if there is any.

    • @Edisson.
      @Edisson. 9 місяців тому +3

      @@pault6533 If the color is not part of the coded color marking, then I would say that the change in the color of the case is just a manufacturer's difference, this also applies to other components.
      For example: I have X2 capacitors in yellow, red or gray design, and not only the color is different, but also the marking for the maximum voltage, some manufacturers give the value in AC, another in DC - again, you always have to check the marking - but it is still a capacitor with a functional properties of X2

  • @Oldclunker-ge5zp
    @Oldclunker-ge5zp 9 місяців тому +6

    I use a relay to short out the NTC when the voltage at the car headlight halogen bulbs has reached approximately 75% of final value. It improves the lifetime of the bulbs while not losing any brightness. The NTC cools down within seconds after the relay has engaged. It's ready for the next start and avoids heating up the dashboard and cable harness.

    • @MrHerhor67
      @MrHerhor67 9 місяців тому

      How did you detect the 75%? Coil connected parallel with bulb?

    • @Oldclunker-ge5zp
      @Oldclunker-ge5zp 9 місяців тому

      Yes, coil in parallel to bulbs. Very simple but effective.

  • @WestCoastMole
    @WestCoastMole 9 місяців тому

    Hi Mark Thanks for introducing the NTC to your audience. There are numerous applications for them including Soft Start Circuits. Hams use them in Vacuum Tube Power Amps that use tubes with Thoriated Tungsten Filaments. That type of tube filament generates svery high inrush current for an instant at power-on. It also generates a very intense magnetic firld which can also damage the filament, thus the requirement for a Soft-Start Circuit.
    Even in a Steady State On condition after everything has settles down there is still a residual power dissiption that can heat the NTC which necessitates providing airflow to keep the device coolER. In the Inrush Application it is a simple matter to tie the normally open contacts of a relay across the NTC and install half second delay in the coil line of the relay. That makes for s subdtantial increase in the life of the device.
    The failure mode of the NTC is a short circuit. That is in contrast to the MOV Device which you covered in a separate video yesterday. MOVs can only be "rapped" a finite number of times before they go kapput. Their failure mode is an open circuit.
    Why can't life be simple ?

  • @flapjack9495
    @flapjack9495 9 місяців тому

    Thanks for covering this! I built three different iterations of a linear power supply once (to power a shortwave receiver and a couple of Raspberry Pis without acting as a localized jammer). The third iteration included an NTC thermistor to limit the inrush current to the big smoothing cap I was using. It also had what can best be described as an absurdly oversized heat sink. I wasn't taking any chances after my first two attempts failed over time. The latest version has been running 24/7 for many months and hasn't given me any trouble at all!

  • @Mr_Meowingtons
    @Mr_Meowingtons 9 місяців тому +4

    Nice I used PTC Thermistors on crystals in CB radios that I had in a car when it was winter it helped heat up the crystal so when on SSB it would stabilize way faster.
    i took the crystal off the board and made a little insolated can attached the PTC with conductive glue to the crystal.

  • @MyProjectBoxChannel
    @MyProjectBoxChannel 9 місяців тому

    I have seen them being used in self heating mode, as a "proof of airflow" sensor. Some amount of current is used to trigger it, and if the airflow is significant, it will cool it back down, and the current draw will increase.

  • @englishrupe01
    @englishrupe01 9 місяців тому

    Don't forget that there are better thermal temperature guns, if you need them. Mine goes up to 1800F. Great video.....many thanks.

  • @1kreature
    @1kreature 9 місяців тому +2

    Btw: I've seen plenty of PSU's having the hot inrush limiter next to a capacitor degrading it's life significantly.

  • @robertmeyer4744
    @robertmeyer4744 9 місяців тому +1

    that a great park. love the testing on new antenna . I bet it works great with 100 watt radio. has anyone done digital yet on it. like JS8 call of FT8 ? wondering about ferrite heating . nice coax feed line. I put chokes on my Pota flex 7 reel kit coax. love the bright yellow . 73's

  • @BJcanal270
    @BJcanal270 3 місяці тому

    Thanks for sharing your knowledge

  • @mikefinn2101
    @mikefinn2101 9 місяців тому

    Very nice explanation and learned something new very thankful for this video.

  • @aduedc
    @aduedc 9 місяців тому

    Problem I anticipate with NTC: Lets say we use it to limit the inrush current of a Drill motor. At first, when you turn on your drill it works fine and limits the current. Now you turn the drill off and turn it on again in a short time. Your NTC is still warm and does not limit the current, now you burn your fuse.
    I have seen active circuits that limits inrush current and force the device to soft start without having this problem.

  • @onecircuit-as
    @onecircuit-as 9 місяців тому +1

    Oh snap! I've just made a soft start circuit for fume extracting fans based on the LM317 and a PNP. Thank you for the video! 👍😀

    • @mikebond6328
      @mikebond6328 9 місяців тому +1

      Schematic or it didn’t happen.

    • @onecircuit-as
      @onecircuit-as 9 місяців тому

      @@mikebond6328 on my channel. 👍😀

  • @paultomlinson528
    @paultomlinson528 9 місяців тому +1

    Fantastic explanation and love the HP calculator!! Looks retro TI

  • @Forensic1Man
    @Forensic1Man 9 місяців тому

    Hi! Again, you have presented a really nice video. Could one use these NTCs to switch on a relay in a very hot attic so as to turn on a fan? If the NTC has less resistance with heat, a circuit could be built that allows a relay to close when the temperature is hot and thus switch on the fan motor.

    • @IMSAIGuy
      @IMSAIGuy  9 місяців тому

      no, I would use a thermal switch, like the one I showed attached to the heatsink.

  • @RensePosthumus
    @RensePosthumus 9 місяців тому

    What a coincidence, while your video appeared I was looking into a non working power strip.The circuit had two MOV's (20D168K and 20D_V3.0) that sandwich a T115 Setfuse (the trio was enclosed by black tape) no I have a legal excuse for some further tinkering ;-).

  • @RedDeckRedemption
    @RedDeckRedemption 9 місяців тому

    Huh, and i thought those were capacitors.
    Does anyone know what the thermister things of that style are made of?

  • @Duckariffic
    @Duckariffic 9 місяців тому

    AWESOME!! TY!!

  • @dimBulb5
    @dimBulb5 9 місяців тому

    Very helpful! Thanks 😀

  • @thevoidedwarranty
    @thevoidedwarranty 9 місяців тому +1

    I've seen black ones too

  • @TheDigitalAura
    @TheDigitalAura 9 місяців тому

    How do these and MOVs fail? Is there a way they can be tested using a multimeter, or other common lab equipment? I, like so many people don't have a curve tracer.

    • @loukashareangas4420
      @loukashareangas4420 9 місяців тому +1

      Both usually blow up or break apart when they fail, so they should be easy to spot.
      NTCs can be measured with a multimeter, as they are resistors basically, and check against the value they have printed on them.
      MOVs should appear open circuit when tested with a multimeter (not sure if you'll see anything on the larger resistor scales). If they are low resistance, they are faulty, but at that point they will probably have blown up on their own.

    • @TheDigitalAura
      @TheDigitalAura 9 місяців тому

      @@loukashareangas4420 Thank you.

  • @clems6989
    @clems6989 4 місяці тому

    Should do same test with a PTC. to show the opposite operation...

    • @IMSAIGuy
      @IMSAIGuy  4 місяці тому +1

      PTC ua-cam.com/video/eeaqyD3ZYjI/v-deo.htmlsi=LM7zedQewvxdX2ug

    • @clems6989
      @clems6989 4 місяці тому

      @@IMSAIGuy AWESOME SAUCE !!

  • @snakezdewiggle6084
    @snakezdewiggle6084 9 місяців тому

    But why does it do that. How does it work. Why not SCR, or Zener.

  • @byronwatkins2565
    @byronwatkins2565 9 місяців тому +1

    They are often black.

  • @guy4698
    @guy4698 9 місяців тому

    thxs for this info

  • @tfrerich
    @tfrerich 9 місяців тому

    Now that you've done NTCs you'll have to do PTCs next. To be honest, about the only place I've seen them used is in old color TV (CRT) automatic de-gaussing coils. I suppose you could use them as temperature sensors or self-limiting heaters, but I'm sure you have an old color CRT someplace in that garage. That'd be more fun to watch. - grin

    • @rfburns5601
      @rfburns5601 9 місяців тому +1

      PTC's are in most every refrigerator. I got an education on these last year when the PTC motor starter fried and opened up. Ruined a few hundred bucks worth of food. The PTC starts out at 5 ohms giving current into the compressor start winding. After a few seconds, it'll go up to several hundred ohms so the start winding doesn't burn up. The PTC and overload (thermal circuit breaker) was $8 from amazon. In the olden days, they used the klixon starter relays that would drop the start winding when current in main winding dropped as the motor came up to speed. PTCs allowed for cheaper cost, as a quality relay with reliable contacts is more expensive than a chunk of semiconductor material.

    • @Edisson.
      @Edisson. 9 місяців тому

      Yes - a three-pin Pozistor for coil control, I still have one original Grundig in the drawer 🙂

    • @englishrupe01
      @englishrupe01 9 місяців тому

      You will also find PTC's in any good quality multimeter, for protection.

  • @dilbertnewton6864
    @dilbertnewton6864 9 місяців тому +2

    For a long time people have been using a light bulb in series with the power line while troubleshooting equipment. Can i assume this is a PTC?

  • @paulgraf4140
    @paulgraf4140 9 місяців тому

    👍👍👍

  • @aaax9410
    @aaax9410 9 місяців тому

    👍

  • @wiwingmargahayu6831
    @wiwingmargahayu6831 9 місяців тому

    knowledge is from youtuber like you sir who have a lot of subscriber and nice instrument collection

  • @dedskin1
    @dedskin1 2 місяці тому

    I have a problem , and its not a capacitor . ITs a motor , a coil , coils are worse then caps , they store energy faster , Caps are mechanical or chemical , coils are well our science doesnt know what it is , makes magnetic field , what is it , well i say eater flow , what is eater its what we call space , cant see it so we are not used to it moving , but it does move and make shapes , you just cant see it , it has 0 resentence , So once flowing it just flows , like super cooled gasses , they start behaving strange , this is something like that but like 100x stranger , temperature is absolute 0 , not close to it , absolute 0 , no temperature , everything is frozen there is no elasticity , so a rod of eater that is 200 light years long , if you push it , instant response on the other side ,strange thing , also no time in it , time does not flow there , forget the speed of light , eater can flow around the galaxy in a second and it does even faster . That is why things work in space , gravity is too slow , limited to speed of light on a galactic scale or even Solar system scale that is 10minutes delay , system cant work like that . And it doesn't .
    But enough of that , i was on a tangent . I fixed a freezer , the board got in to water we had a flood , and stupid thing was in casing under it on the floor , filled up real good , and stayed there for like 2 weeks until evaporated , corroded the hell out of control board and i get 50V on the built in Vent on the evaporator now instead of 220V , . So since i have no special tools , Board is roasted , i did not want to play with it troubleshoot it , strange word , shooting troubles , pulling triggers on purchases and stuff . Sorry tangent agent . I hooked it up directly on 220V AC , works like a charm , problem being , soon as i plug it in , my fuse blows . Such a small motor maybe 50W i don't know its small . Yet it blows a fuse . So what did i do , i put a 50W light bulb on it in series . since that has some resistance limits the current and it works . But i dont want to keep my light bulb there it can brake kill a kid or what not . I was thinking of using NTC , would that be good solution, NTC in series on 220V line , hot probably . Would that be better .