eapbg #47 Introduction to TRIAC

[@elibarton2274]

This is the fourth video I watched today on triacs. the first three were basically useless. This one was great.

[@eapbg]

Glad you like.

[@chinmaykulkarni237]

agree

[@Typical.Anomaly]

@@eapbg Upvoted and subbed. Excellent explanation. For the application I'm working on I'm considering using a 555 timer and CMOS (4024 binary counter most likely) to make several clamp-on work lights with 9W LED bulbs turn on and off (I'm in the US so 115V 60 Hz). A crazy kind of strobe light, if you will. My experience is mostly low-voltage analog experimentation for building guitar pedals and ambient (usually; it can get pretty gnarly at times lol) noise production. Started learning about TTL when I was about 4 years old (1982) so I'm very comfortable with that aspect. Just trying to absorb as much information as possible before experimenting with 115VAC because I really don't like being shocked and really really don't want to set the house on fire. I'd like to ask you a few questions if you don't mind- I currently have some MAC97A6 (TO-92 package; rated max 400VAC) triacs and some optocouplers (PC817). Only kind of either that I have in my possession at the moment. I'm guessing that they'd suffice but my anxiety is holding me back a little bit. One bulb should only take 0.09ish amps so I'm pretty sure it's okay but any kind of feedback would be very appreciated! Thank you!

[@eapbg]

@@Typical.Anomaly The triac looks ok if the current is kept under 600mA. The opto is of the bipolar variety and won't work. You need a triac opto.

[@hansvdwesthuizen1694]

Well done, I retired out of the electronics industry 20 years ago and this video refreshed the mind again. keep up the good work. I have subscribed and will follow your videos.

[@nsknyc]

This is a great explanation of triac phase cycle control. Anyone can shrug off triac as a switch, but your perfectly explain the how! Thanks for the video!

[@ljvanstaden6847]

You have an excellent understanding of this topic, I thank you for sharing your knowledge!

[@kabandajamir9844]

The world's best teacher

[@andredeschamps1587]

You really helped me to understand the concept of the triac in a chopper application. It totally makes sense now. Thank you!!!!!!

[@laserdad]

As always, your presentations explain things in an easy to understand format. Great job!

[@UNKNOWNHINSON666]

I will show in my class tonight. Nice job

[@jorgea380]

After watching many videos this is the first one that i actually understood, thank you so much!

[@peterldelong]

I’ve been repairing some old control boards that use the old Motorola 68705 MC. The outputs of the MC that trigger several triac circuits to control water pumps go through darlington transistor pairs before the optocoupler inputs that then fire the triac gate. The MC outputs couldn’t sink enough current to fire the LED in the optocoupler. Darlington transistors can be your friend in these types of circuits. Great video.

[@jeffmarlowe2727]

I was a navy et and this was a great explaination.

[@will_doherty]

Great description of the triac - very easy to understand, thanks. One minor point: @1:19 you suggest that the gate is the output, which I don't think is what you meant to convey...

[@dannylivshitz6846]

Great explanation, we building a circuit to be contol by microprocessor, so this helps!

[@flashingsword]

Awesome! Great job! You made it extremely clear and relevant to real world circuit engineering!

[@eapbg]

Theory is great and all, but whats theory if you can't apply it. I will always try to do something practical if i'm talking about theory.

[@joeyleckie2270]

you legend, this video should have more views/exposure.

[@mark8664]

I love that you can speak and speak in English even without any kind of an accent!

[@eapbg]

My accent is slight, some people can't hear it.

[@mark8664]

@@eapbg I can't hear it but just guessing I'd say you were from Hollywood, CA.

[@micdal22]

Thanks for a great intro to diacs and triacs. I have a stack of BT141D triacs (6amp, 800V), that I purchased 30 yrs ago but have hardly used. I think I'll make a few motor speed controllers with them just to get my hands dirty.

[@eapbg]

Sounds fun, just be careful because a triac will only speed control some motors. A universally wound one and a plain DC one if you use a bridge rectifier. Also with motors, you will need a snubber.

[@abegafouda9136]

Thanks for this great video. It just bypassed anything I have seen before on the subject. But I have a question. How do I use a triac in a clap-switch with two transistors (no IC) to turn on lights that will go off same time with my LED after half a minute ?

[@eapbg]

I would use the Opto as the interface. You could tap power from the mentioned LED to light the LED inside the Opto. Don't forget the current limiting resistor.

[@abegafouda9136]

@@eapbg Aaah! Sooo simple! You are the one... Just saved my life! (Smile). And thank you for answering so fast. Blessings.

[@abegafouda9136]

@@eapbg An opto-triac will surely work fine by itself. Can I use an OPTO-MOS or simple opto-diode/transistor to trigger a regular triac as I have lots of them? And what else should I add? Your first answer rejuvenated me from 73 (sic) to 60. Guess what will do the next...

[@eapbg]

@@abegafouda9136 To trigger the triac properly the pass element needs to be bidirectional. A MOS or a simple transistor are not bidirectional. Also, make sure that the pass element will handle the voltage. In the OFF state, the element will see nearly full AC voltage. The only thing I forgot in the video is a resistor to the N line. Similar to how I have it with the basic switch.

[@abegafouda9136]

@@eapbg Thanks once again.

[@adamschlaegel9946]

Thank you for a very informative video - I am here looking to understand triacs and this answered all my questions and then some (especially the quadrants portion). I was wondering - I have a hobby project that I am wanting to get feedback on - is there a place that is better than others for a total noob like myself to share my idea/what I want to do and get good feedback on it ?

[@UberWagen]

Might be a dumb question...do commercially available TRIACs (Semikron SKKT 92 for example) have a built in snubber, or is that something you have to provide when designing? What I'm after, is that, if I stop driving the gate of the TRIAC, do most commercial TRIACs have built in circuitry to shut off on the zero crossing?

[@eapbg]

No triacs don't typically have built-in snubbers. A triac shuts down at the zero crossing inherently. This only happens when the current and voltage wave forms line up. If they are missaligned, such as when driving an inductive load, there is a chance that the triac will not shut down. This is what the snubber is there to do. Make sure that the triac shuts down. There are "snubberless" triacs, but your milage may vary. I would try one out in your application first as a prototype and not depend on that it will work.

[@prashkd7684]

Great explaination on TRIAC. In regards to the snubber circuit, is its function just to discharge "out of phase" current or is the capacitor also compensating for inductance in the circuit? I've seen these circuits used extensively in motor control but if you ask 10 different engineering about them, they'll give 10 different functions of this circuit.

[@eapbg]

I guess here are my 2 cents. I look at a snubber circuit kind of like a condenser (they used to call a capacitor that) in points and breaker ignitions. The points were a set of contacts that would close causing current to flow. To fire the ignition the points had to open. As they began to open the current wanted to flow and a high difference of potential resulted across the barely open points. This would cause an arc. Constant arking would burn the points. To fix this a capacitor would be installed in parallel across the points. When the points were closed there would be zero difference of potential across the capacitor. As the points would open the resultant difference of potential would charge the capacitor instead of arking. The size of the capacitor would be such that when it became fully charged and the current came to a stop the points would be far enough apart that they wouldn't ark. All that being said, I think that the snubber works like the capacitor in the pints and breaker. When the triac wants to shut off it starts increasing its resistance. The lagging current then forces the triac open again. When a snubber is installed, when the resistance of the triac exceeds the resitance of the series resistor the current stars flowing through the capacitor. This allows the triac some finite amount off time to fully shut off. When the triac is on the difference of potential across the capacitor is small and dose not contribute to any power factor correction.

[@CopperMasud]

sir, Thank you so much for this great video .

[@maxgrind28]

Thank you for exlanation, but are you sure that the quadratns are the 4 parts of the periods? The I and III quadrands are matching what you were explanied, but the 2 quadrand is charachterized by positive MT2 and negative G against MT1 (MT2+ G-) - this doesn't match to what you were talking about: in your expanation the 2 quadrant is charachterized by positive MT2 and also positive (but decreasing) G, not the negative G. The same thing is for the 4th quadrant. I am taking into account the case when the G is powered from the MT2, exaclty like in your drawings. As I understand, to implement the II and IV quadrant we need to power G not form the MT2, but from some other source to make create G polarity other than MT2.

[@eapbg]

You are correct, I totally missed the mark on the quadrant explanation. I primarily dealt with triacs driving inductive loads such as motors. My description is how a triac behaves driving an inductive load.

[@josephjerardmichael6263]

Excellent. Thank you. God bless you.

[@itsmeatiq]

Great explanation!

[@OliverHorn-u8o]

I have tried using a triac to control output of a transformer. The cct controls fine but after a while the triac is destroyed . Have tried putting a snubber composed of 100ohm resistor and 100nano capacitor across the triac but still destroys the triac. Can you tell me where i am going wrong please? Transformer output is 12v and need 4v at around 60amp

[@eapbg]

Are you running in the 1st and 3rd quadrant or in the 2nd and 4th? If it's the latter then can your triac handle that? What about current and heat sinking. Is the triac properly rated for the current? The triac should be rated large enough to supply full current at 100% duty cycle. It should also have a large enough heat sink to handle that.

[@hellomilan03]

I am trying to use an optoisolator to control a triac. I'm simply trying to turn a light on and off. My next step is to figure the resistor values I need in my circuit to fire the triac. Any help would be appreciated.

[@mussib6855]

This is so helpful ..Thank you

[@qadoosi09]

I want to design a soft starter for induction motor using triacs but i have a difficulty in managing fire angle of triacs by using microcontroller that how would i use a microcontroller to achieve smoth start to avoid surge current and jerks of induction motor.Basically i want to know that how i ramp up and ramp down triacs voltages to acomplish soft start. I would be very pleased if u help me in this problem.thanks

[@eapbg]

Are you using zero crossing detection? Are you using snubbers on the triacs?

[@christiankulmann3325]

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[@AlexsandroRNeto]

Best explanation..

[@jaythompson5102]

Killer video! I just subbed.

[@waynegram8907]

EAPBG, How do you change the triac holding current and passing current? when increasing or deceasing the load on the triac will alter the triacs holding current and passing current, any reasons why?

[@chrisrix7645]

Is the gate trigger voltage always ac or can a dc current be used to control the gate?

[@eapbg]

Theoretically yes, with two caveats. The DC reference would need attached at the correct spot. The DC would only be able to trigger the triac every other half cycle.

[@DEO777]

How likely is it for a TRIAC to fail and stay stuck in the closed position every time an appliance (ie. water heater) is used? Or is it more likely that there is a problem with another component that sends the signal to the TRIAC? There's an opto-isolator in the circuit.

[@igorzherebiatev5751]

Hi! Will it work without a dinistor? Why do I need to loose 10% of the wave?

[@eapbg]

I'm guessing you mean diac. It will work as an on/off switch. If you want phase angle control you need the diac. Also the first 10% of the wave is only 2.5% of the energy delivered.

[@igorzherebiatev5751]

@eapbg yep, sorry. In my country, the name "diac" is barely in use. Many years ago, I built a triac (simistor here) based AC dimmer. Late 90s. No diacs on sight. It worked somehow. Still don't understand how. Potentiometer, resistor, and an electrolyte capacitor. Based on simple power regulator for soldering iron. Thyristor and diode. But I totally forgot what changes I made. And the device is long gone.

[@billwilliams6338]

Thanks, but how do you turn off a SCR and a Triac without turning off the power supply to the circuit to "reset" the SCR and Triac? any ways of "resetting" an SCR and Triac device?

[@eapbg]

This is why TRIACs and SCRs are often used with AC. AC always crosses zero volts and zero amps that allows them to shut off. The catch is that those two don't always happen at the same time and that's when you use a snubber.

[@gelber9543]

Thanks..., it would be great if you made a video about how to design a snubber circuit...

[@billwilliams6338]

Can you give some examples of when TRIAC and SCR devices are in automotic car circuits?

[@eapbg]

TRIACs and SCRs are not used in cars. They are used almost exclusively with AC and cars are DC.

[@FooBar89]

thank you very much, your explanation is really great!

[@TheTazzamal]

Can we acquire variable capacitance with the help of triac? I shall be very greatful if you suggest circuit diagram or any helping material regarding that.

[@jarredhendersonmusic6905]

How do you calculate the correct rating for the resistor wired in series between the baby triac and the big one?

[@eapbg]

There are three things to consider. The most important is the current rating of the baby TRIAC. The resistor needs to keep the current below the max to keep the baby TRIAC from burning out. The second is the wattage of the resistor. The chosen resistance will dissipate some amount of heat that depends on the value and resultant current. The third is the voltage rating of the resistor. Since you'll probably be working with 120 or 240 volts rms it is important that the space between the pads or "clearance" is wide enough that the voltage can't jump over.

[@gordongecko9405]

@@eapbg I think the most important reason is the switch on current of 2'nd triac. The rest is derivative the above reason.

[@kalpeshparmar165]

Superb explanation. I am making a vibrator feeder controller, but not getting succes. Would you help me to make it with basic electronics components like TRIAC, diac, resistors, capacitors, potentiometer, diode,etc. Thank you, that was helpful.

[@eapbg]

Look at the datasheet for a triac for a reference design. Use that.

[@kalpeshparmar165]

@@eapbg as, I check the output voltage ni multimeter, it doesn't show any change in output voltage, bus as I connect a 100w load and parallel check it's voltage, i can see change in output voltage, as it vary as we vary potentiometer. Can you explain me the reason behind it.

[@gamerstudio4990]

can we trigger a tric just by applying a square wave voltage of amplitude (equal to that of its threshold)

[@eapbg]

Theoretically yes as long as the square wave is referenced to MT1. In reality, don't do this for a few reasons. First, a general square wave won't be synced to the mains. More importantly, whatever is generating that square wave won't be isolated. Without isolation from mains, you run the risk of burning up whatever you connect. Worse, you can receive a shock.

[@vamsikrishna5391]

Sir other than opto coupler triggering in normal triggering of triac using diac y can't we directly connect our capacitor directly between gate y we r unnecessary ly inroducing diac what advantage does this offer

[@eapbg]

A diac makes sure that there is a clean on. A diac breaks down at a specific voltage. Once the current flow through the diac drops below a threshold the diac closes and need the break down voltage to turn back on. Without the diac the gate of the triac will see voltage all the time. This can cause false triggering and possibly a partial on type situation.

[@vamsikrishna5391]

Thank u i understood the basic thing which u wanted to convey.But suppose say for alpha=30 degrees i want to trigger the triac,diac also ons at this voltage across capacitor n if a diac breaksdown at voltage corresponding to 30 degrees it would obviously be on 30-150.our main intention is to stop the gate pulse once the triac switches on.but here diac will be on continously for 120 deg.

[@eapbg]

@@vamsikrishna5391 There is no need to stop the gate pulse once the triac switches on. The gate pulse only has to be removed before the tiac switches off, that is all. If the diac switches off at 150 degrees the triac will continue to fire until 180. At 180 degrees the triac will shut off (a snubber may be required to do this) and won't fire again until 210 degrees.

[@felixcat4346]

Very nice description. Thanks. I will subscribe.

[@MechanicForGMCCars]

I have small problem how is phase shifting done to inductive pick ups,sensors or singel phase pulse generators if narow phase angel is requared? I try figuring out how I can retard me ignition timing on me hei 4pin ignition module just during engine start up wia toggel switch. I come across lot problems with wire resistance and useing only 500k potenciometer the engine did cinde of work even tought sloppy and insted compresion ignition I ended up at exaust ignition insted. So thats why Im confused many peopel use different things like transistors ,triacs,scr's but cant realy finde any calculation methode for me particular aplicalition . So any advice on this topic? Does there exist remote controled resistors mostly what I have problems are wire resistance and finde correct components for controling varianel frequency ranges below 60hz . Me ignition module works at osulating frequency at 33 up to 333 hz I seriusly dont know at what voltage or frequency me pick up coil is operating at . So some how this is mostly related to guitar pick ups volume and tune control I ques. Did ever some one try to control sensors with simpel circuet from a distance away remote controled?

[@eapbg]

TLDR; get an ignition computer and program it to do what you want. Getting a phase delay in the analog world is hard. Look at delay lines. It is even harder to make it switchable.

[@perceptrongaming4290]

excellent explaination

[@eapbg]

Thanks

[@acqurius-gx8lr]

what is the best device that can be used to control the direction of motor

[@eapbg]

It depends on the type of motor. Three-phase AC motors both induction and Magnetic (MAG) work with a variable frequency drive (VFD). Single or dual phase AC is tricky. Many of these motors are not reversible because they use a start/run capacitor. Often this type of motor needs to be wound in a special way to include extra windings for reversing direction. I have seen single phase VFDs but I've never used one. Brushless DC motors (BLDC) is just a small MAG motor and similarly need a VFD or a specialized drive. DC motors work with a full bridge motor controller.

[@billwilliams6338]

A snubber circuit puts the voltage and current In phase and aligns the voltage and current together to be in sync?

[@eapbg]

If you want to think of it that way you can. In reality that is not what they do. The shunt current around the device allowing it to shut off. When the voltage hits zero the device wants to shut off but the misaligned current keeps it on. As the device wants to shut off it starts to resist the current and the current finds it easier to flow through the snubber. As this happens the device will fully shut off. This is similar to how a condenser works in points and breaker ignitions. Snubber theory is its own whole field. I only know the very basics.

[@billwilliams6338]

@@eapbg you're saying that a snubber circuit is a drain bleeding off circuit to bleed off or drain off the voltage and current when the Triac or IGBT is turned Off?

[@eapbg]

Kind of, I would do your own research on them. My knowledge of snubbers is very limited.

[@billwilliams6338]

@@eapbg Thank you

[@kabandajamir9844]

Can we use triac in mobile phone charger circuit

[@eapbg]

Depends on what you want to do with that circuit.

[@funoutdoor6253]

Thank you. Great explanation!

[@eapbg]

Thanks

[@brainstorm9577]

this is the best explanation there is on youtube .If u dont mind sir ,could u tell me what would happen if the hot and neutral are reversed in this situation .Thank u

[@brainstorm9577]

and what would be the right value of resistance and capacitance to adjust for an inductive load . would this work for a ceiling fan.

[@eapbg]

If neutral and reverse are switched the TRIAC would not trigger properly. This is because the gate can no longer go positive and negative compared to MT1.

[@eapbg]

@@brainstorm9577 this would not work for a ceiling fan. A ceiling fan requires a special speed controller. The values of capacitor and resistor will be found in the application section of the data sheet.

[@brainstorm9577]

@@eapbg thanks for replying ...what if i just want to on and of the fan ..will that work

[@eapbg]

@@brainstorm9577 At that point simply use a switch.

[@ShopperPlug]

Can you make a tutorial how a triac can control AC dimming by using an Arduino?

[@eapbg]

Why specifically an Arduino? The Arduino environment has too much overhead to do this. The ATMEGA 328p is capable enough if you use interrupts. The Arduino environment does handle interrupt on change but it does not handle timer interrupts. That all has to be coded from the raw datasheet.

[@ShopperPlug]

@@eapbg This is exactly what I am talking about, think you can make a video in implementing it? Seems like assembly is needed.

[@eapbg]

@@ShopperPlug Assembly is not needed. You need a zero-crossing detector fed into a pin change interrupt. This will prime a timer. Then you need a timer interrupt to do the timing of turning the tiac on and off. If you want to be fancy you can detect if you have 50/60Hz and work accordingly. I could do a video but it would take me a long time to actually get it out.

[@ShopperPlug]

@@eapbg Extremely interesting. I know it will make life much simplistic if using commercial bought optocouplers which has built in extra stuff like Diac and Zero Cross Detection. But would really like to learn how to drive the Triac using raw components and a microcontroller. I know an optocoupler is needed to isolate the circuit from the microcontroller, can build an effective optocoupler from infrared and phototransistor LEDs, I can also build a Zero Cross Detection circuit from a full bridge rectifier, but what really confuses me the most is how to implement the Diac to the Triac and optocoupler properly. I have a bunch of 2A 32V DB3 Diacs. Do you know any articles or have any schematics on how to build a Triac driver circuitry from scratch?

[@eapbg]

@@ShopperPlug Considering how dangerous mains power is, from a beginning level just use all the prebuilt stuff. Everything is rated and tested for safety.

[@dhrumilen]

Why does motor make winning sound when using triac for speed control.

[@eapbg]

That is going to depend on the kind of motor and how deeply the waveform is cut up. Not all motors can be speed controlled with a triac.

[@w1zzard418]

Very well explained!

[@saqibalim1545]

great sir , i want to add LDR for automatic on and off of load with sunlight, connected with the triac how to do that

[@eapbg]

Not a simple answer. I would start with an opto isolation triac to control the main triac. Then all you need to do is turn the opto led on and off. That's where things get a bit more complicated. For best results, I would suggest some hysteresis, preferably adjustable so that you can tune it to you lighting conditions.

[@charleslyell3748]

Like eapbg said, try a 555 ic working as a Schmitt trigger for hysteresis.

[@monajitsaha9652]

Hi sir , can you tell me about the heating issue in triac if we don't use heat sink for example bt136 how much Ampere we can pass through this.

[@eapbg]

at 25C free air ambient it's a little over one amp (it will still be very hot so be careful). This is a complicated topic and will require an in-depth video to explain.

[@monajitsaha9652]

Thank you sir

[@hbelectric6072]

4amp

[@mexbob52]

Excellent !!! Thanks

[@mauramvar845]

What happen with the baby Triac once the Main Triac start conduncting current?

[@eapbg]

The baby triac continues to conduct just like the big triac. Once the LED is turned off and the current reaches zero the baby triac shuts off.

[@gordongecko9405]

@@eapbg Sorry, you made big mistake. 1'st triac switch off immediatly becouse the voltage on 2'nd triac terminals is olmoust zero

[@eapbg]

@@gordongecko9405 Could you elaborate?

[@mark8664]

I am going to use the triac to lower the rectified dc voltage so I don't have to use a transformer. Everyone says not to do it.

[@eapbg]

That is a great way to get killed. Power supplies should always be isolated.

[@mark8664]

@@eapbg Isolation is simply allowing people to touch high voltage and not get shocked but I say just don't touch high voltage in the first place and you won't get shocked.

[@eapbg]

@@mark8664 depends on the kind if power supply you are building. The implication in your post is that this will be a bench top lab supply. That is a great way to let killed. If this is a supply that is non adjustable and sealed in a box along with what it is powering, then have fun.

[@billwilliams6338]

Power supply protection circuits use SCR for crowbar protection, which is DC i thought? why are they using an SCR device in a DC circuit

[@eapbg]

An SCR is a latching device. That is probably why they are using it. I did say it was almost exclusive. There are other applications.

[@charleslyell3748]

Probably to blow the fuse for safety reasons.

[@FooBar89]

excellent video

[@kabandajamir9844]

So nice

[@abrahamadam8357]

tthank you so much for your help

[@acqurius-gx8lr]

how to control the direction of motor using triac

[@eapbg]

You can't. A triac is only a throttling device.

[@dobosattila3855]

U can not trigger the SCR with a negative pulse so the analogy is wrong.

[@reverbva]

Thank you!

[@billwilliams6338]

A TRIAC and DIAC are latching devices? A SCR is a latching device which you have to turn off the power to reset the SCR device to unlatch it.

[@eapbg]

A TRIAC is two SCRs stuck together. A DIAC is like a zener diode except for the voltage collapses after breakdown.

[@kieranj67]

Thank You

[@eapbg]

Kieran Jefferies I'm glad you like

[@AntiCoruptionCentral]

Excellente'!

[@mark8664]

I can build a 500 Watt power supply with some N Channel Mosfets and this circuit.

[@robertpertuit9530]

Very good work, but you need a script. You mention a processor needs a zero crossing detector, but don't show one.

[@eapbg]

A script has never really been my thing. A zero-crossing detector is a video in an of itself. It would be too much to fit it in with the triac.

[@peki1701]

Why doesn't the current just pass through the snubber while the triac is off?

[@eapbg]

A small amount does.

[@peki1701]

@@eapbg Ok, so if I understand correctly, the small amount of current that passes trough the snubber while the triac is off doesn't provide enough power to run the load?

[@eapbg]

@@peki1701 correct, this is a leakage current.