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Hi Kiss,
Good to hear from you,
After reading through the posts I remember I was up to the stage of trying to control the inductive load which I will continue with now.
For me this is the first step, if I can't do that then I have no chance of proceeding with things. The resistive load was ok & I was controlling the Lamp temperature.
I think I will try to control a very small transformer to start with as I can do that on my work table.
Yes, health is the most important thing for sure, exercising the mind is a way to good health though.
I was having trouble creating the pulse train to the Triac Gate, so this is my first problem to overcome.
Can you suggest a suitable load to control with the small Transformer?
I really think this is the first step for me to take.
I am glad to hear that you survived instead of kicking the bucket. Me too.
almost 7 years ago I had a sudden massive heart attack and I was minutes from death, then they fixed me while I watched them put 2 stents in my heart arteries. No damage since I was fixed quickly. I am young again.
Then I went blind with cataracts and they fixed me again and I don't need glasses anymore.
Then I ran out of excuses why I can't hear when everybody mumbles so my new hearing aids let me hear everything properly again.
Hi Audioguru,
Thanks for the comment,
Yes, I guess we all require running repairs at certain times in our lives, the permanent irreparable issues are the ones I don't like.
Like most of my electronics experiments, they are just not fixable?
I think the best part about being ill is how much you appreciate all the little things in life that you totally ignored before, like waking up in the mornings etc!
Otherwise 1 uF's Metalized polyester are common at say 50 to 100 V. Whatever low voltage you have and somewhere between 100 and 1000 ohms.
Look at the voltage either across the cap or resistor with an AC voltmeter.
I would suppose that if stuff worked and you looked at the voltage across the resistor or cap, there would be no discontinuities.
This really doesn't give you something to control, except 0-100% should not give discontinuities.
With an C circuit, you should be able to monitor the voltage across the cap and the voltage across the resistor (current) and see the phase angle.
==
so, see where your "junk box" leads.
Some low voltage transformer
Some R
Some C that likes AC
Monitor V across Cap and I (Voltage across resistor) with scope, It will be isolated at that point.
Adjust R and C until you can see a phase difference.
==
You won;t be controlling anything, just outputting a "% power" %(V^2) (if you use your table) and watching the waveform/
Meanwhile, try to find a universal motor for a final test. These are found in drills and will operate on AC and DC. Just don't use it in the beginning.
Thanks Kiss,
Ok, I see what your saying, I have quite a few Caps etc that should be suitable, I will see what I have & get into it.
I also have plenty of Transformers.
Yes, I have a few universal motors as well that I used to test & adjust Ignitions with but I didn't want to start there as you suggested as well.
Thanks for the quick reply.
I'll see how I go!
Oh yeah, sorry to hear you have complications now!
Cheers
Very basic question here but I just want to make sure of something that I am unsure about?
I have setup the transformer & have a 12V output low side which I have a 6Ω 50W resistor in series with a 100uF 50V BP Capacitor then connected back to 0V on the Transformer for the load.
I have never checked the voltage across a resistor before with a scope only a DMM.
The problem I see is there is no Ground to connect the Oscilloscope ground clip to?
On the Zero Cross circuit there is a ground but this is to the Arduino & a separate circuit which is not suitable.
The mains input to the circuit has only an Active & Neutral--no Ground connection.
Where do I connect the Ground Clip on the Oscillscope Probe, I can't connect it directly across the resistor!
The xformer provides isolation therefore pick between the cap and resistor. Then one probe on the opposite side of the resistor and another to the cap. Invert one of the channels.
Sorry for the double post but after thinking maybe wrongly about this.
If I connect the Ground Clip of the oscilloscope probe between the cap & the resistor isn't that still a hot connection as it still has voltage?
With the Oscilloscope Grounded won't this cause a short.
I'm having a couple of issues & require some advice?
The AC control circuit works perfectly with the LAMP- Resistive Load.
When connected to the Transformer-Inductive Load there are a few issues.
The circuit applies power smoothly to full output voltage from the Transformer secondary winding when increasing the Pot but will only decrease to around 6V AC minimum as if the Triac will not turn off correctly.
When decreasing the input voltage from the Pot into the Arduino you get to around 100mV input to the Arduino which is still around 6V Transformer Secondary output, which should be near Zero Voltage?
The second issue is:
As soon as you go below the 100mV input to the Arduino the voltage at the Triac output & the Secondary on the Transformer goes into over voltage, output at 275V from the Triac into the transformer & little over 15V output from the 12V Secondary winding with Zero Volts into the Arduino from the pot?.
I have an RC snubber across the Triac a 39Ω resistor with a .01uF Capacitor, I am thinking that it is a Snubber issue & need some advice please.
The Triac doesn't appear to be turning off correctly, maybe it is something else?
I'm having trouble understanding your post. Nothing new.
Remember that the triac turns off at zero voltage and zero current, so now you have TWO places where it turns off.
There may be a much simpler way to "skin the cat", so to speak. Create a pulse generator in which you "gate". There was that PDF sometime ago that had a minimum pulse width.
I think your effectively "gating" now, but stuff will turn off 2x because of the phase shift. The 2x, really isn't 2x ut it's really two soon.
So, you have to generate, the turn on as a series of pulses. You can do that in one of two ways:
1) The Arduino
Basically an ISR that enabled your turn on signal.
If you find out that two ISR's together are a bit much to handle in programming, make it one and use a monostable
2) Externally by gating a pulse generator.
The "other" problem that you had, if I remember, was that the zero cross detector was a little crude.
Hi Kiss,
Yeah, look I am sorry, I don't have the vocabulary necessary to explain things in a technical manner being uneducated.
No excuses but I only learnt how to read & write not that many years ago I do struggle quite a bit?
Anyway that aside.
Yes, I have a Pulse Train to the gate of the Triac, I worked it out with the Arduino & I made sure I had this correct before testing the Inductive Load out.
I can adjust the number of pulses & the on time which I have played with quite a bit up to around 5mS on time, I found if the on time is to long it has an adverse effect at full power settings.
Around 3 to 4mS appears to be the limit. I can have 1 to 50 pulses in that time-adjustable.
Yes, I now remember you mentioned about the zero cross circuit before.
Before, I could get a TRUE ZERO, when the Pot was totally off I had zero output from the triac but now with the inductive load I can not get below about 120V at the triac output or 6V at the output of the secondary transformer winding.
This is with the Pot not totally off but with 100mV still going into the Arduino, if I adjust the pot any further down lower than the 100mV I get the over voltage scenario with around 275V at the Triac output.
The other thing I have noticed this morning is that when looking at the Zero Cross pulse & the Triac Gate pulses on the scope together you see the pulse train gate signal sits just to the left of the zero cross pulse signal as expected. But when you turn the Pot to the Arduino totally off the pulse train signal becomes unstable & jitters to the left & right of the zero cross signal.
This may be what is causing some problems as the voltage from the Triac becomes unstable as this is happening?
Hope I explained it in a coherent manner this time
Hi Kiss,
I will try to force the Triac off as you mention, I will do that now actually, maybe my turn off approach is a bit soft now that you mention it.
I will have to order some other parts for a different Zero Cross circuit, until I receive them will have to continue with this one.
Obviously if you have the time I would be very interested learning how to sort this issue with any calculations or whatever it takes.
If you require any Inductance or Resistance values for the transformer or anything else please let me know.
It's all very interesting!
If you require any measurements to be taken let me know what you need & how best I do things & I will certainly go for it.
You can estimate the phase shift with your scope. Withe the suggested connections I and V with one inverted, you can determine lead or lag. The time between the zero crossings of V(t) and I(t) can be converted into degrees.
so, you can estimate x degrees leading or lagging. I think V is the reference.
Many times the Invert is part of the uncal knob. some of the Tek scopes have a red knob and a grey knob on concentric shafts. Then there is usually a light nearby that reminds you that the gain is uncalibrated. Usually you can pull out that knob to invert so it's usually not obvious. It's also usually channel B.
The reason for the invert signal is for doing "Differential" measurements. "Differential" in this case means "pseudo-differential" . Pseudo-differential requires a ground connection somewhere. So its really (A-Gnd) + -(B-Gnd) giving you A-B.
One reason for variable gain is for Lissajous patterns.
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