triac environment

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#1
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Hi everybody!

I'm not very good in this analog stuff and it's my first try with a triac!
What do you think of my safety considerations?

Any suggestions?

Could this work?
(It works without the inductor)
I haven't found the time to try 'til now!

best regarsds

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Hi,

Good to see people doing electrical projects.
Well I had Power Electronics as a subject in my Masters.
I can help you with this provided you give me all values of the above circuit correctly.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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R15 and C2 would normally be the "snubber" network, making R16 and C3 redundant.
I would move L1 "off to the right" to be directly in series with the load/line so that
R15 and C2 can best perform their snubbing task. If this is going to be used on
240 volts, I might be inclined to use 600 volt devices rather than 400 for a little bit
better reliability margin, but otherwise, looks fine to me. Were you thinking
maybe 100 ohms for R14 and R15 and .1 mfd for C2?

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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@boseji: I would be very pleased, if you would help and you are
an expert at this topic! Because I'm really a newbie in that stuff!

@tpappano: You're right, R16 and C3 is redundant then!
Yesterday evening I built one circuit from 2 and that's the result! I was
already a bit sleepy, I guess! :lol:

I just found out, that there is some missing information:

The line above is the 240V AC line and the other one below is the
neutral!

JP2 is the load!

I just had a look at the MOC3020 data sheet
http://www.fairchildsemi.com/ds/...
and this circuit can be found there EXCEPT the inductor!
But for a dimmer you must use an inductor, don't you?

The values are:
R14 360
R15 470
C2 0.05
C3 0.01
R16 39

So you would shift the inductor next to the load? Outside of this "snubber"
network? But this RC chain should also minimize spikes, shouldn't they?

best regards

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tpappano wrote:
R15 and C2 would normally be the "snubber" network, making R16 and C3 redundant.
I would move L1 "off to the right" to be directly in series with the load/line so that
R15 and C2 can best perform their snubbing task. If this is going to be used on
240 volts, I might be inclined to use 600 volt devices rather than 400 for a little bit
better reliability margin, but otherwise, looks fine to me. Were you thinking
maybe 100 ohms for R14 and R15 and .1 mfd for C2?

Tom Pappano
Tulsa, Oklahoma

But I think that the R16 and C3 are still required because it will be an independent Snubber network. The use of R14, R15 and C2 is to generate the time and phase synchronized GATE pulses to the Triac and not as a snubber. They help to keep the Circuit being triggered by the Opto when its on . By activiating the OPTO it mearly open the gate drive and de activating it will stop the device.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Would you think, that this is a good circuit as it is? Or is there some
potial to improve this ciruitry?

I'd like to control an AC motor up to 1.5A @ 230V AC! And I'd like
to have it as best as possible, without hearing it in my radio, when the
motor is on! :roll:

A second thing is for inductive load, how can I get the zero cross point?
Or which zero cross point is needed? voltage or current?
If voltage is needed, a voltage divider with a diode must be enough?!?

regards

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Wulfinator83 wrote:
Would you think, that this is a good circuit as it is? Or is there some
potial to improve this ciruitry?

I'd like to control an AC motor up to 1.5A @ 230V AC! And I'd like
to have it as best as possible, without hearing it in my radio, when the
motor is on! :roll:

A second thing is for inductive load, how can I get the zero cross point?
Or which zero cross point is needed? voltage or current?
If voltage is needed, a voltage divider with a diode must be enough?!?

regards


Well Yes I feel your circuit is fine for all types of loading only ensure that before the line is connected to the AC motor there you must have fast acting fuses or Varistors across the incomming supply to the circuit.
Do not try any type of DC manupulation like putting DIODES it will only increase the danger. Your Triac can handle up to 10A minimum at 400v.
Also that the inductor contacts are proper otherwise you can also use a High Voltage AC capacitor for the regulation you require at the input stage.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Honestly said, I can't follow you!

You mean, I should put a varistor of the motors pin (to reduce spikes?)
But I can only put it on my board! I have no access to the motor itself! I have only three wires!

How big should the inductor be? 1mH?

I just saw a possibility to trigger the triac direct by a microcontroller!
Ground was connected to the neutral like the triac mt1 pin and the other
side goes to the load and then to the hot wire.
Is that also a possibilty? R14, R15 and C2 aren't needed then...
link: http://www.velleman.be/Downloads...

regards

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may be you need optically coupled switch light activated zero voltage crossing triac to minimize spikes?

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zauberer wrote:
may be you need optically coupled switch light activated zero voltage crossing triac to minimize spikes?

:?: :roll: :?:

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Quote:
Would you think, that this is a good circuit as it is? Or is there some
potial to improve this ciruitry?

I'd like to control an AC motor up to 1.5A @ 230V AC! And I'd like
to have it as best as possible, without hearing it in my radio, when the
motor is on! Rolling Eyes

A second thing is for inductive load, how can I get the zero cross point?
Or which zero cross point is needed? voltage or current?
If voltage is needed, a voltage divider with a diode must be enough?!?

regards

Yes, I would put the inductor simply in series with the load, if I was going to use
an inductor at all. The inductors I have actually seen used in commercial lamp
dimmers have only been about 30 uh, which seems a pretty small inductance
to have much noise supression effect. I would not even bother with it, especially
since you are wanting to control a motor which is an inductor anyway, An
important question, are you simply wanting to turn the motor on and off, or are
you wanting to use phase control to vary the voltage to the motor for speed
control? For just doing on/off control, the circuit (as improved) should work
fine as is. Trying to turn on at the "zero cross" won't gain you anything with
an inductive load. If doing phase control, pick up the "zero crossing" sync
signal from an opto isolator whose led input is being driven through through
a resistor, by the voltage directly across the two main terminals of the triac,
rather than directly from the line voltage. This is important because the
motor inductance causes the voltage "seen" by the triac to be out of phase
with the line voltage, so monitoring the voltage actually across the triac makes
for much simpler operation. You will be doing your firing delay timing based
on the voltage zero cross that the triac "sees", but the triac actually will be
switching off when the *current* through it drops to zero each cycle. Looks
cool on a scope. Now, because the triac switches off actually at the zero
current point, that means because of the inductive load the voltage will *not*
be zero. The voltage across the triac takes a sudden jump. This fast voltage
change can be enough to re-trigger a triac by itself (dv/dt firing), and this is
precisely what the snubber network is for- to limit the rate of voltage change
that the triac is exposed to so that ugly dv/dt firing is prevented. Just as
a guess, I would try about .05 mf cap and a 100 ohm resistor for the snubber.
It is not real critical, but the rc time constant needs to be slow enough to limit
the rate of voltage change at turnoff. You will know it if you get dv/dt firing
because the motor will make all kinds of strange noises, and will not run
smoothly at all, even displaying a sudden "braking" effect 8-) The amount of
practical motor speed control you get doing this is somewhat limited because
motor torque drops quickly as you reduce the motor voltage, and the motor can
stall at some point. If you want precise speed control, you may want to add a
tach pickup arrangement and control the motor closed-loop.

Be cautious working with high voltage, and wear safety glasses! Experimenting with
thyristors sometimes results in sudden unexpected device destruction with
attendant launching of high velocity bits of hot plastic and metal. As the saying
goes, don't ask me how I know this 8-)

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Quote:

Be cautious working with high voltage, and wear safety glasses! Experimenting with
thyristors sometimes results in sudden unexpected device destruction with
attendant launching of high velocity bits of hot plastic and metal. As the saying
goes, don't ask me how I know this 8-)

Yes, I already know about this deep flying and unrelaxed transistors, triacs and caps! :wink:

I'd like to do phase control with normal lamps OR switch ON/OFF a motor!
First I planned to make a "soft start", but I've already heared about this strange motor torque effect! So I'm really not sure if it's possible in an easy way!

I modified the circuitry and attached it again!
Is this applicable for phase control and motor switch on/off?

ad zero cross detection: how can it be possible to take it from the triac? If it's switched on for example, you don't really have a voltage, don't you?

best regards

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I liked your original diagram better, except replace the inductor with a direct connection
instead, and delete R16 and C3. Use 100 ohms for R14 and R15 and make C2 0.047
mfd.

You can use this same circuit to drive the triac for on-off and phase control both.
For zero cross detection, use a H11AA1 opto isolator, which has 2 leds inside
so that voltage of either polarity can be sensed. Connect the opto's led through
a resistor to the two main terminals of the triac. Now, if the triac is seeing zero
voltage, the opto's output will be off. The opto's output will also be off when the triac
is conducting, but that does not really matter. If voltage of either polarity is present
across the triac, the opto's output will be on. To "dim" a lamp, you want to watch
the opto's output for the zero crossing which would be the hi to lo transition of the
opto's output. To deliver half-power to the load for example, at a line frequency of
60 hz, you would now start a timer and wait 4.16 ms, then *pulse* the moc3020. This
turns the triac on and it will now conduct for the remainder of the half-cycle. While
this is happening, you go back and watch the opto's output again for the next
zero crossing, then repeat. To go from max down to min power, you would use
a delay from zero to 8.3 ms. For simple on-off control of the motor, you do not need
to care about the zero crossing, just turn the moc3020 on continuously to run
the motor, and off to stop it. Or, go ahead and do the soft-start by using the
full phase control method. You can use various interrupt and polling schemes to do
these functions in the foreground or the background as you see fit.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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I found this once when i was "Surfing"

http://www.hoelscher-hi.de/hendr...

There are some other modules there

Can anyone see if they are "safe"

/Bingo

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Quote:
Can anyone see if they are "safe"
I see no unusual hazards in the circuits. If you distribute power through the tab of the triac, it's easy to do it unsafely, but use common sense here.

All resistors shoud be flame resistant. The spacing on all of the AC terminals (both on the load and on the ZC detectors) is not adequate. I use 3 mm of open space between all traces carrying 240V. This requires bending the center pin of the TRIAC and routing other traces accordingly. (I once had to fix a colleague's designs to satisfy UL, CSA, and VDE). This also means choosing different connectors, as it appears that the ones used are on 2,5 mm (0.1") centers. You need at least 0.156" for US and 0.2" (5 mm) for 240V.

Other than these common amateur mistakes, the circuits look pretty good.

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Wulfinator83 wrote:

I just saw a possibility to trigger the triac direct by a microcontroller!
Ground was connected to the neutral like the triac mt1 pin and the other
side goes to the load and then to the hot wire.
Is that also a possibilty? R14, R15 and C2 aren't needed then...
link: http://www.velleman.be/Downloads...

All the circuit that you have is a correct one I was only making you aware of the extra safty mesures you can employ.
But dont connect the Gate Drive directly from the controller . The kick back of the gate drive may cause damage beyond repair. Also then you will reqire to externally synchronize the pulses to match the Current and voltage Phases.
So you can go ahead with the current circuit . Just test it first with a bulb as the load.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Obviously, too, when making direct connections between the mcu and the triac,
your whole circuit/system becomes "hot" with line voltage. This is fine if making
a simple circuit like a plain lamp dimmer that can be completely insulated, and
needs no other direct connections to other equipment. For anything more complicated
at all, I recommend complete isolation between the triac circuitry, and the
microcontroller/user interface circuitry. Boseji is correct about driving the
gate, as it becomes a voltage source of alternating polarity as the device
goes into conduction on each half cycle. Another important thing about
driving triac gates directly is that they have their best trigger sensitivity
when the gate is driven negative with respect to the lower main terminal,
rather than positive. Some triacs are not even being specified for positive
gate drive because of the large difference in gate gurrent needed to trigger.
A transistor is a good thing to use because gate currents often need
to be 75 ma or more (however, only briefly).

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Another think is that if we use a Pulse transformer it might be that we can reverse the terminals and generate a negative gate drive with external Phase synchronization using some opto such as PC817 to sence the begining and end of the hakf cycles in the line.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Quote:
Another think is that if we use a Pulse transformer it might be that we can reverse the terminals and generate a negative gate drive with external Phase synchronization using some opto such as PC817 to sence the begining and end of the hakf cycles in the line.

On some direct gate drive devices I build, I connect the triac main terminal to the "Vcc" rail,
then the mcu can give the gate a negative pulse by pulling it to the "Gnd" rail. Pulse
transformers work fine too, but their price is a little hard to take. I think I paid over $15 US
each for a few to test in a new design. I stayed with the optos 8-)

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Well Ya thats on thing you can say the disadvantages of pulse transformers. Thats why optos are preffered.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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:shock:

mneary wrote:
Quote:
Can anyone see if they are "safe"
I see no unusual hazards in the circuits. If you distribute power through the tab of the triac, it's easy to do it unsafely, but use common sense here.

All resistors shoud be flame resistant. The spacing on all of the AC terminals (both on the load and on the ZC detectors) is not adequate. I use 3 mm of open space between all traces carrying 240V. This requires bending the center pin of the TRIAC and routing other traces accordingly. (I once had to fix a colleague's designs to satisfy UL, CSA, and VDE). This also means choosing different connectors, as it appears that the ones used are on 2,5 mm (0.1") centers. You need at least 0.156" for US and 0.2" (5 mm) for 240V.

Other than these common amateur mistakes, the circuits look pretty good.

What exactly do you mean with this 3mm? It's not really possible to
assemble the TO220 with a 3mm spacing!
For VDE you need different connectors? For what? To foreclose a
wrong connection?

Ok, @ direct connection:

In my feeling, you don't really say that it's bad, but you advise me to
don't use it...

I will take the first circuitry (if you say, that it's better and SAFER) and remove the RC stuff on the right side)
Should I add an inductor just to make sure... ?!?

The next thing, you mentioned that you would advise me to isolate the TRIAC from the microcontroller! BUT i have only a "RC link" (is it called in that way in english? I don't know...) for power supply! With 1 diode and zener diode and a 7805! So doing it in that way would mean that the neutral is my ground. So the uC is "hot" again! Isn't it?

best regards and thank you all guys for helping!
I appreciate it...

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There is a good paper on this at:
http://www.littelfuse.com/data/A...

Randy Ott

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Quote:
What exactly do you mean with this 3mm? It's not really possible to assemble the TO220 with a 3mm spacing!
For VDE you need different connectors? For what? To foreclose a wrong connection?

For a TO-220 to respect 3 mm spacing, you bend the center lead away from the line of the other two. Create a triangular pattern with at least 3 mm spacing between pad edges. For some reason, the regulations forgave the fact that the device itself didn't meet the spacing.

There wasn't a substantial difference between the VDE and UL/CSA requirements that I had to follow. It's just that my UL/CSA requirements were at 125V only. So, I could use 0.156" connector spacing for 125V but it was easier to design for 220V if my connectors were 0.20".

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Ya the above method suggested by mneary is correct. And one more precaustion you may take is that before the load you must connect some type of low current fuse.

Connecting the Digitial ground of your microcontroller to the Neutral is not a good Idea becuse the spikes in the neutral when your device is powered on will cause the controller to work irratically.

Also dont remove the RC circuits because they are for phase synchronization.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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*arrgh*

It can be seen, that I'm really just getting started with this analog 230V stuff. :?

Yesterday evening I was searching for a capacitor with 0.68uF for my 230V AC (as voltage divider with a resistor). It'a an application note, I have.

There they are talking about 600V! I don't know why, but ok! I took my
digikey catalogue, had a look through the capacitor sites and I stopped at the ceramic ones.

They are usable for AC, aren't they? So why is there a VDC given? I saw, that when VDC was given, it was most of the time really low (50V, 100V, max 200V), BUT when there was VAC given, it was quite high (few hundred volts)

Is there a direct relationship between? For 230V AC, do I need a capacitor with at least 230V * sqrt(2) VDC?

How is the relationship between VAC and VDC here (at a capacitor without polarity)?

thanks

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If you are wanting to use a capacitor as a series "ballast" to power a circuit
directly from the ac line, use a "metallized polypropylene film" type. They will
be smaller physically, and provide the durability and safety such an application
requires. You will find that in most cases, it takes a 630 vdc part to operate
on 250 vac, and some caps of this type actually carry an ac voltage rating.
I'm not sure how manufacturers establish the ac rating, I have seen some
400 vdc parts that carried a 250 vac rating, but not many. Metallized film
capacitors have a property known as "self healing". If the dielectric breaks
down during a high voltage application, they will not fail. A conventional foil
capacitor can fail "shorted" after a breakdown, and you can imagine what
happens next in an ac power application! 8-)

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Yes, I guess! :D

tpappano wrote:
If you are wanting to use a capacitor as a series capacitor can fail "shorted" after a breakdown, and you can imagine what
happens next in an ac power application! 8-)

But, if there is only the VDC voltage given, how can I know for which AC it can be used? Peak Value?

If a capacitor has a VAC 275V, can i take it for 230V AC? Or do I have to double this value for sure?

regards

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I think the original triac drive circuit is the go. This was normally recommended in the Motorola triac data book which has the equations for working out the component values. C3 + R16 are redundant in this instance. The usual values were 330R for R14 + 15 and 100nF X2 for C15. For dimming lights you will need an inductor in series - not like in the second circuit! Like - active - load - inductor - triac circuit. How much inductance? The more the merrier! Depends on the load. If you ignore it, the circuit will generate a heap of RF noise. As for zero crossing detection - for light dimming use the voltage zero crossing. I normally grab the ac signal from the low voltage side of a transformer, add a little bit of low pass filtering and into schmitt trigger then into the micro timer capture input. My code checks the time between captures and rejects any the are out of range. It then uses the value to correct an internal timer value which is used for the timer compare for firing the triac. If you use the zero crossing value without any filtering, spikes and noise will cause the light to flicker. As for controlling AC motors - depends on the type of motor. Synchronous motors wont appreciate being fed a chopped waveform if the motor is under load although if you increase the phase control value fast enough, you get a soft start feature. AC/DC motors like in power drills can be speed controlled using phase control successfully.

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Quote:
As for controlling AC motors - depends on the type of motor. Synchronous motors wont appreciate being fed a chopped waveform if the motor is under load although if you increase the phase control value fast enough, you get a soft start feature. AC/DC motors like in power drills can be speed controlled using phase control successfully.

True "synchronous" motors, like hysteresis-synchronous types, are designed to run at a precise speed
and would indeed quickly stall under load if an attempt was made to reduce their speed by reducing
the operating voltage. These motors are usually found in clocks and other mechanical timing applications,
used as capstan motors in tape decks, high-end phonograph turntables, some 8" floppy drives, etc.
Normally you would never want to vary the speed of one of these, because their main virtue is
running at an exact speed. Almost all other types of AC induction motors, split phase, split phase
capacitor start, split phase permanent capacitor, shaded pole, three phase, etc. *can* be driven
with phase controls, provided one understands, for example, that available torque is reduced
as voltage is reduced, and that the motor may need to be initially started at full voltage.
This would be a poor way to vary the speed of something like a conveyor which is a constant
torque application, but a fine way to vary the speed of a fan or blower. Without some sort of tach
feedback, it is difficult to get predictable results, and the practical speed range will be small.
I use closed-loop control on a 460 volt PSC blower, and I get very tight control from 60 rpm
all the way to 3200. Phase control can also be used for power factor correction of induction motors.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Quote:

I use closed-loop control on a 460 volt PSC blower, and I get very tight control from 60 rpm
all the way to 3200. Phase control can also be used for power factor correction of induction motors.

How does your close loop look like? With rpm measurement?

What do you think about my new circuitry?

regards

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Quote:
What do you think about my new circuitry?

It looks great, just need resistance added in series with the leds of
the H11AA1. For 240 volt operation, I would use a 47 k, 2 watt
metal oxide film (MOX) resistor. Give it a little room for air circulation
because worst case power dissipation will be about 1.25 watts on 240 volts.
This is just a necessary evil for picking up the sync signal in a way that will
be compatible with an inductive load.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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The above shown circuitry is perfectly fine but the H11AA1 is some what troubling. Because all the base of this opto is to adjust the trigger voltage of the transistor. The outpust should be taken from the collector of the output transistor.!!
Pls Check that..

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Ooops, yes I missed that! The output should come off of pin 5, with pin 6 left unconnected.
Good catch Boseji!

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Ups! While uploading yesterday, I saw and changed this base-collector stuff, but I forgot to upload the new one.

Should I add a small inductor? Just for sure? I also want to drive lamps with that, not only a motor! (multiple application areas)

Must this resistor really have 2W? Why can I not take a higher resistor in a smaller package?

regards

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Ya the Inductor can be a good solution for multiple applications but there is sight problem. If the load being connected is more inductive such as the normal Induction motors or Phase synchronous motors then the power fator may get affected widely. This will show more consuption on the watt meter even though the device is rated for less power as "RealPower". This is because the total power is the sum of the "Real Power" and the "Apperent Power". Its better to use some type of equivalent Capacitive reactance to rectify the power factor to unity. Also the reverse will occour when the u have a capacitive load. Thus what I will suggest here is that we must do a trade off between the power consuption to realize your application.

The 2W resistor value is nessary because the current drawn will cause the destruction of the resistance if its rating is not high.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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You can drive incandescent lamps or motors with this circuit. You can try a larger value resistor,
and see if it works ok. What will happen as you keep increasing the resistance, the turnon
and turnoff of the opto will start to get slower as the led current gets weaker. This will cause
a bit of a time shift in the opto's response to the zero crossing. At some point the zero cross
detection may get too "sloppy". 100 k may work fine, I just have not tried driving a H11AA1
myself at that current level. You could stick an inductor in series with the load as a rf noise
supressor, but I bet you will not need it. If you do use an inductor, it will have to be able to tolerate
the peak load current without saturating, or it will have little effect.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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The power factor when used in a motor circuit isn't an issue if the added inductor is reasonable. You need an inductor in an incandescent circuit to keep the electrical interference to a minimum.

What's the maximum inductor you should use? I use one which would drop less than 5V at the mains frequency, given the maximum design load.

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HI
tpappano have a look at the Capacitive switch Triac Dimmer project ID: 219 in the ACADEMY section.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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what's up with that?

regards

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Have a look at the Capacitive switch Triac Dimmer project ID: 219 in the ACADEMY section.

I think its the right circuits you are looking for..

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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boseji wrote:
Have a look at the Capacitive switch Triac Dimmer project ID: 219 in the ACADEMY section.

I think its the right circuits you are looking for..

Now I'm completely confused! It's totally different from my one! Why do you think, that this is the circuit I need?

regards

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Well I am sorry its not exactly but it deals with the basic Triac control. So that you can use it as a reference sake. Then you might be able to understand all the concept of Triac triggering.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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boseji wrote:
Well I am sorry its not exactly but it deals with the basic Triac control. So that you can use it as a reference sake. Then you might be able to understand all the concept of Triac triggering.

I just had a look at the circuitry and I have exactly no clue how the triggering with BC547 should work! :?

BUT, I had only a short view! :lol:

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You only have to replace this BC547 by your Opto. Thats all . The rest of the phase synchronization can be established by the parallel RC circuit like yours.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Quote:
I just had a look at the circuitry and I have exactly no clue how the triggering with BC547 should work! Confused

That is an example of directly driving the triac gate. In this case the transistor is an
emitter follower, so a "hi" pulse from the port pin delivers a positive pulse to the gate.
(this is not the best way to do it, but it is one way) Please note that triacs are happier
being triggered with a negative pulse on the gate, generally having the same sensitivity
for both polarities of the load voltage.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Hi everybody!

Yesterday I got my PCB's, when I realized that I still don't have all parts!
I just used 1206 for C2 and C4 what was definitely a mistake!

Can anybody tell me a capacitor to use for that?

best regards

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Well I tink the SMD caps wont work out. You can use the normal tiny Ceramin Caps instead. Also there are very high voltage ceramic caps available. Checkout mouser or digikey. These caps look more or less like the normal cereamic caps but Have voltage tolerances of up to 1KV. So using them will surely make ur circuit safe.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Metallized polypropylene or polyester film would be a good choice while being fairly compact.
They have the advantage that they will not fail catastrophically, like ceramic or foil types.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Ya I surely agree with "Tom". But you see wont they be a bit costly for this application. Its only feasable if you have 10 or 20 of them and you cant aford a risk on life!

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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Hi everybody!

I've already me pcb and it works fine!

I just have one problem: when taking the optocoupler parallel to one triac for zero cross detection, I'm loosing the zero cross info, when this triac has been switched! And because I have a second output, I'm not able to dim it!

So, my question: Is it possible to connect the opto direct to L and N? Or is there any problem in cause a "phase moving!" (I'm not sure about the term, but when you have an inductive or capacitive load, then there is a movement between the phases!

best regards

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You can only do that if you have provided a Isolation transformer in the input with a minimum of 30% Isolation.
One way is by using a optically triggerred TRIAC some thing as MC3011 or so. Just check the datasheet of this.

AVR Rulez...;-)

Warm Regards,
Boseji
http://m8051.blogspot.com/

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