Hi All,
I am interested in making an AC light dimmer that can be controlled by my Arduino. I was planning on using a circuit similar to the one posted here: http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/
I believe this is a fairly common approach, and other people have had success in reproducing it. I have purchased all of the parts, and am presently assembling them onto my breadboard. However, I have run into a few questions regarding how this circuit is connected.
I have saved the circuit diagram, and my 5 questions in an attached ppt. file.
I would really appreciate any guidance/answers to my questions.
Thank you in advance,
Dustin
AC Dimmer Questions.pptx (100 KB)
1)yes.
2)huh???
3) yes, at a glance it would appear that no bridge is needed.read the datasheet to make sure
4) nowhere... actually.
5) no. Pins are not interchangeable.
Find a better schematic; that one is terrible. Do more research. Googling "h11aa1" returns better examples than that one. Or try "triac circuit design". What are trying to dim?
Hi Seanz2003,
Thanks for your answers. Regarding question 5), are you saying that the TRIAC pins 2 and 3 are also not interchangeable? The data sheet shows pin 1 and 2 as "main terminal 1" and "main terminal 2". Thus, are they not interchangeable since "main terminal 1"/"main terminal 2" is not very specific.
I'm sorry that you found my "question 2" to be confusing. This question was about trying to understand where the "load" and "220 V" connections are going in the circuit diagram. If anyone has any insights, I would really appreciate the help.
I am trying to dim a 60 W light bulb. I have already searched for h11aa1 circuits, and triac circuits. The reason I chose the specific example (that I provided a link to in my original post) was that it had the most detailed description of the theory and the code required to make the circuit work. Unfortunately, as you have said, the circuit diagram is not very clear. Thus, I was hoping that someone with more experience with these circuits could help me understand a few of the unclear aspects.
I have looked over the data sheets for all of the components in the circuit. Unfortunately, unlike some of the other components I have used for previous projects, none of the data sheets for these components have "example circuits" that I can look through.
Again, I would really appreciate any help that anyone could provide.
Thank you,
Dustin
On question 2 the answer is this:
The lamp and the triac are connected in series so which wire is live and which is neutral does not matter. But the zero crossing detector must have the full line voltage across it.
Question 5
Pin 1 and 2 on the H11AA1 are interchangeable. Terminals mt1 and mt2 on a triac are normally NOT interchangable because triggering is relative to mt1
Yea I confess, I responded without reading through the instructable, which does do a pretty good job discussing the theory and code. Unfortunately, schematic isn't clear and has unnecessary wires and crossed lines.
Another way of accomplishing the zero crossing detection would be to use a small transformer, which is needed anyway to power the arduino, and detect the zero crossings on the secondary. This can be done by just adding an extra diode between the rectifier and the reservoir cap and feeding the unfiltered but rectified voltage to an analog pin through a voltage divider
Please post as a JPG, GIF, or PNG, not a Powerpoint file. Not everyone has Microsoft Office.
On question 2 the answer is this:
The lamp and the triac are connected in series so which wire is live and which is neutral does not matter. But the zero crossing detector must have the full line voltage across it.
While this statement is true in Sweden where they run 220V it is NOT true in the United States. Here, our lights are at 115V and one side of the line is NEUTRAL. Same potential as Ground. Neutral is always the white wire. Therefore your triac needs to be in series with the black wire. We do not want to switch the Neutral.
rmetzner49:
On question 2 the answer is this:
The lamp and the triac are connected in series so which wire is live and which is neutral does not matter. But the zero crossing detector must have the full line voltage across it.
While this statement is true in Sweden where they run 220V it is NOT true in the United States. Here, our lights are at 115V and one side of the line is NEUTRAL. Same potential as Ground. Neutral is always the white wire. Therefore your triac needs to be in series with the black wire. We do not want to switch the Neutral.
And what happens if you turn the plug 180 degrees??
And what happens if you turn the plug 180 degrees?
Most of our (decent quality) plugs are polarized as in they only fit one way. Cheap stuff from china is a different story.
seanz2003:
And what happens if you turn the plug 180 degrees?
Most of our (decent quality) plugs are polarized as in they only fit one way. Cheap stuff from china is a different story.
My point was that the circuit still works no matter which way you turn the plug. And the safety issues are not relevant when it comes to a solid state switch (which a triac is) The circuit will be unsafe no matter if you break on the live or the neutral side. So safety has to be dealt with separately by using appropriate IP enclosure and connecting touchable metal parts to protective earth
As far as turning the plug 180 degrees - dimmers are typically wired in, and are wired in on the Hot side (black wire) so that the light bulb socket is not wired directly to the Hot side.
For plugs, two wire plugs in the USA are polarized and all three wire sockets are polarized. And of course if it is a three wire plug, you can't reverse it.
My point was that the circuit still works no matter which way you turn the plug.
Did I say it wouldn't work? Obviously it works since it's a series circuit and you can intercept it anywhere. I was attempting to instill US convention which is of course lost on you.
I still don't get the point. This so called convention does not affect functionality nor does it affect safety. So what other reason could there be?
Yes it does affect safety because neutral is connected to earth ground, and switching hot side is safer than switching neutral because the load is at ground potential and not 120v.
As i stated before a circuit containg a semiconductor is inherently unsafe, especially when using phase angle control. So is just as unsafe if the switching is made on on the live side than on the neutral side.
Makes no difference if the load is "on" 24/7/365. But if the load is off any significant amount it is safer to switch high side so it's not at voltage waiting to zap you if something goes wrong
it is safer to switch high side so it's not at voltage waiting to zap you if something goes wrong
Not just that, but in the US there is a CONVENTION that should be followed. For the same reason Neutral is WHITE and Line is BLACK. If you were to apply for a UL listing and you were switching the NEUTRAL, your testing phase would end as soon as the unconventional wiring is discovered.
polymorph:
Please post as a JPG, GIF, or PNG, not a Powerpoint file. Not everyone has Microsoft Office.
Hello Polymorph,
Thanks for this suggestion. I have attached a PNG version of this file.
Dustin
rmetzner49:
it is safer to switch high side so it's not at voltage waiting to zap you if something goes wrong
Not just that, but in the US there is a CONVENTION that should be followed. For the same reason Neutral is WHITE and Line is BLACK. If you were to apply for a UL listing and you were switching the NEUTRAL, your testing phase would end as soon as the unconventional wiring is discovered.
That is true ONLY for electromechanical switches. Not for solid state ones. There is NO way whatsoever that a solid state switching device can be considered to safe. But thinking that you can achieve any kind of increased safety by connecting it one way or another is much more dangerous than actually connecting it the wrong way. A circuit like this should always be considered unsafe and have all applicable safety measures.
