I've been thinking that for years. I wanted to understand and know how to do many things while in my youth but had no available quick easy answers like now. This guy basically covered a 50 page chapter in 20 min without going to the library first. This information would have taken most of a day to learn, if I found the right book. Having someone explain and show examples is so much better than reading about it. Kids these days have no idea how much easier it is to acquire information today compared to 25+ years ago.

Humble boomer brag

Yeah, but now they use it just to watch non educational stuff !!!

C'mon now! Radio Shack had a "101 Electronic Circuits You Can Build " book you could buy...Healthkit offered radio controlling stuff (RC airplanes) and amplifiers...remember the ol' crystal radio? - I built one using thin lacquer coated copper wire, a simple crystal, a empty toilet paper cardboard tube, cheap low power earplug type headphones and a long piece of wire for antenna...it actually worked too..1965! (Crystal radio plans probably somewhere found on YT.) Aah yes..the good ol' days! Truth be - it's much better these days....so all you kids out there...you're spoiled rotten! Ha ha ha! 😉

Yead for my essays had to rely on library, when i go to library the book i want is already has been borrowed😏

PNP transistors especially, or transistor power that is used a little to warm up the transistor, so using Ohm Law is not 100% accurate :P.

your comment makes no sense....wanna take another run at it?

lol......great video mate, very well explained.

"Power used to 'warm-up' the transistor" ?? The .7V loss through the Base/Emitter calculation, is a bit more complex than, but 'like' the typical .6V loss through a forward-biased diode. At such 'PN' junctions, the 'P'-type having a deficiency of Electrons, and so having 'Free-Holes'. The 'N'-type has an excess of Electrons ! (I'm keeping it simple here...). Now where they are physically touching, (and no voltage applied), for so many atoms thick in the lattice some of the excess flows into the deficiency, creating an Insulating barrier at the physical junction ! As a result, even when 'Forward-Biased' from a voltage source, a Diode needs at least about .6V just to break down this barrier, before it starts to conduct, so you will always loose this! A similar effect(s) are going on inside most typical Transistors. (Hence his '.7V' loss in his calcs). (1) For a Diode, this voltage loss is NOT dependent on the LOAD after the Diode! So for example, you could connect 5 diodes in series, for a precise 3V drop, or 10 in series for a 6V drop, irrespective of the load !! (2) This 'Insulating' barrier at the PN junction, can be considered the 'Dielectric' of a capacitor, so our Diode is ALSO a Capacitor, with the 'plates' being the P/N materials area themselves. NOW it get's interesting though!! as the higher the 'REVERSE-Bias' voltage across the Diode, this FORCES an even LARGER non-conducting 'neutralized' gap/barrier. 2 main things control capacitance.... The area of the 'plates', and the 'space' (dielectric) between them. So what do we have now??? A solid-state Voltage-Dependant Variable-Capacitor !!! Yep... and it is utilized a lot these days..... although now 'Special' Diodes are made to take advantage of this effect, called 'VariCap-Diodes'. Sorry about all that... :-) I just get 'excited' playing with software like 'Circuit Wizard', that allows you to design on screen virtually any electronic circuit including virtually all elect/electronic components & IC's, see it all run in REAL time, monitor ALL voltages & currents from ANYWHERE in the circuit simply by mouse movements. Not to mention auto creation of your PCB & all artwork when you are ready, with auto track routing. ALL before you touch your soldering (not the American 'soddering' :-) ) Iron. Have fun !!!

There are several components to learning electronics. One place I found that succeeds in merging these is the Gregs Electro Blog (check it out on google) without a doubt the no.1 course that I've heard of. Check out this amazing site.

JonathanAnon because those courses are made for engineers . For hobbyists this is probably enough. For an engineer this is not enough.

Even engineers would benefit of easier introduction to the matter.

@@EdwinFairchild But the introduction at microscopic level kinda kills the interest in my opinion. I like to develop interest in something before getting started.

@@curiosity551 thats what i mean, if interest is the issue which implies a hobbyist, then ignoring the physics part of it is just fine. For an engineering perspective you dont have the luxury of interest, you NEED to know the intricacies whether they interest you or not.

@@EdwinFairchild if you know it all, why are you here?

Applied Science that part was curious, I was wondering why the diode feeds it back, wikipedia said it feeds the back emf back into the solenoid to lessen the change in current it experiences when turned off, love it.

With the capacitor it make sence. But in all my life I never saw that capacitor to ground in Relay circuit. i red the use fast diode or low threshold voltage diode (Shotky?)

schottky diode will just fine.

Your 5 volt input may have been solid between ground and +5v. I always put a 47K from base to emitter to deal with any leakage currents if the input is inadvertently left open, either by design, or by a failure mode.

amazing video mate! but, could you tell us what diode should we use for this clamp?

Don't damage the circuit with your hard head.....lol

See my vedio on transistor ckt design

1N4007 has higher forward voltage than 1N4001. 1N4007 waste more energy to operate... Same thing happens to higher voltage transister. So not a good idea to choose higher rating voltage than it needs to be. PS.....Also I have heard word "free wheel diode"

ຮຸ່ງ ພຸ່ງແຣງ So what would be the best way to protect the transistors if picking a higher value diode is not efficient?

@@Asyss_Complex The Fairchild (On Semi) 2014 datasheet for the 1N4001-1N4007 series specifies the same forward voltage of 1.1V at 1.0A for the entire range. In addition, the energy dissipated in the diode is not a consideration in these sort of applications unless you're trying to switch the solenoid at kilohertz frequencies (!), so it doesn't really matter which diode you use.

cos è sta supercazzola? ...hai il dono della sintesi? me la riassumi? :)

La cultura non è per tutti!! 😜

a hahaha....preparati per la stagione venatoria che siamo a brucio vah!!!

Perfectly done

Just a curious question. Why is your current flow in reverse? Current flows from negative to positive

fernando velasco mathematically it makes no difference which way current flows. Most people use conventional current flow over electron flow

Yes it does but he is talking about CONVENTIONAL CURRENT FLOW where it is imagined that current flows from + to -

I ve deep interest in electronics i want to learn more...

Same here :)

Livin' the voltage life.

Absolutely. Although MOSFETs have to be driven hard(er) for higher voltages - and even in this case, they would require a pull down resistor at least (5V is high enough gate voltage for most cases to driver 12V). It's harder to explain.

A BJT is a perfectly reasonable choice for currents up to 100mA as the voltage drop and power wasted is then negligible. Above that, a logic-level power mosfet is a good choice, and essential if you have a 3.3V microcontroller. Remember that the mosfet will normally cost three times the price of a small-signal BJT.

Try to watch Razavi lectures you won't need hacks to remember that

I learned the difference by just never using PNP *dabs*

''Points the arrow to the B - it's PNP'' is another way

@@ajayrajan8882 mnemonics is not a bad method to reliably revert stuff though

It's still the best way to remember it.

Andrei Stefanescu, since the logic input signal varies between 0-5V and the emitter is at +12V, the base current can never reach zero. Thus the PNP device is a poor choice here. On the other hand, if the logic -input- output varied 0-12V it would be acceptable.

@andrei, think opposite. in an npn a + voltage at the base turns it on. in a pnp a + voltage at the base turns it OFF. 12-5=7VDC across the emitter/base juction, because you have + 12vdc at the emitter.

@@avid0g so you would use that if you needed a 12V signal to control a 5V device?

@@renakunisaki My point was that an open collector logic device with a resistor pulling up to +12 volt would have the correct output. The logic device needs to be rated to handle the +12V. An NPN would also translate, but with inverted logic. One downside to resistor pull-up is the RC time constant rise waveform.

What about the power loss that occurs between base emitter junction due to low resistance? Cant ignore that either.

right what I was going to say

10, not 100. As a switch, base current should be 1/10th of collector current. Read the datasheet.

@@AlienRelics Can't help think that Ben has been scarred by destroying many transistors when he started out that he errs on the side of minimizing base current. 1K would do the trick.

@@kissingfrogs Perhaps. But beta varies from batch to batch, device to device, temperature, and time. I'd accept 15 or even 20, but 100? That is the rated beta in the active region. You'll destroy more transistors with excess Vce drop at higher current.

"A little more expensive" can add up to a lot more expensive if one is building hundreds of thousands or even millions of widgets, with each widget possibly having many transistors. I would guess most companies simply go with the least expensive option that meets the requirements.

Yeah but the very high efficiency translates in to a more quality product when it comes to power consumption and simplicity anyway mosfets get cheaper and cheaper over time.

True. It would then depend on what the requirements were, and if reaching higher efficiency is more important than reducing costs. In some cases it would be worth it, in other cases, not so much. But either way, you've made me think about it and I will do some more learning about BJTs and MOSFETs so I actually have a clue what I'm talking about lol.

Yeah that would be great!

Michael bjt transistors aren't inferior because they're older they happened to be discovered 1st. Fets are a cousin to tubes which came before that. Tubes still have their place. darpa is still pouring money into tubes. a plain old 3904 bipolar isn't going on the scrap heap any time soon.

I tried that once, but the wires kept getting caught in my teeth.

Beboba This tutorial discusses bipolar transistors, which do not have floating bases, and do not need such a resistor. An insulated-gate transistor such as a MOSFET or IGBT have high impedance gates that may need a resistor to tie the gate high or low.

Applied Science Interference from nearest components can easily turn the bipolar transistor on. E.g. if you have high voltage generator.

+Applied Science Can you explain what a floating base, or floating anything is? I see this mentioned a lot when reading about electronics.

+Akfloatable Leaving a pin of an electrical component not connected to anything is considered "floating". This means that the voltage at that pin can change very rapidly if there is nothing to sink or source current. Turn on a digital multimeter to its voltage range, and leave the test leads disconnected. You'll see the voltage floats around. For some components like bipolar junction transistors (BJT), leaving an input floating is not particularly bad because the device requires a fair bit of current to operate, so the pin will remain fairly stready by itself. A MOS component requires almost no current to operate so the slightest bit of charge will cause the pin voltage to change, and turn the MOS on and off very rapidly or partially, which is not good.

+Beboba BJTs are current activated devices (current from base to emitter establishes the current from the collector to emitter.) If the base is floating, there is nothing to induce a contiuous current from the base to the emitter, an electrostatic charge, while a very high voltage, doesn't have enough charge to induce a large enough current to turn a small signal BJT on. FETs have the issue you discuss where they are voltage activated devices (voltage between the gate and source establishes the current from source to drain) and can easily be turned on by stray voltages. All that said, very high gain BJTs (especially darlingtons) can be briefly turned on by small electrostatic charges.

electronics.stackexchange.com/questions/110574/how-to-choose-a-flyback-diode-for-a-relay