a little help with capacitive power supply values

[Dennis]

Steve :-) ....
OK .. I actually un-voluntarily spat the sip of coffee out trying to suppress the laughter :-) and am still having a good chuckle ... laughing with you not at you!
I had a similar incident on an old Zenith CGA and EGA monitors whose chasis' was live/hot.
In order to get the colours and sync right one had to use a very long trim-pot tool , sometimes we had to improvise and use a long screw-driver because all of the trim-pot tools were out of the workshop in the field with other technicians to make matter worse we would place the monitor on a metal trolley with wheels.

With the right (wrong!) combination of screw-driver and hand grips and a kinda left-hand suzuki method I very quickly was sent hurtling with an ear-piercing yell across the workshop into the bench behind me knocking my mentor straight off his feet !

Well needless to say after the initial shock was over and it was established that I was OK, the entire workshop spent the rest of the day laughing to crack their sides. And I definitely feel quite wound up after that.

There's that statement in the Star Trek intro "to boldy go where no man (or woman) has gone before"
There are some options of course
"to boldly go where no man (or woman) has come back from before"
or
"to boldly go where men (and women) have come back from before"
or
"to boldly go"
finally ..."just don't go !"

Thanks for the offer .. would you like to try the circuits a few posts ago or would you like something more finished ?

Awaiting an episode of the unexplained now I think !


By the way this was an interesting find of yours..! Definitely puts and angle on things !
I was wondering all through the article where the bleed resistors where ... and then saw them and mention of them in the last few pages !

A Capacitor-Fed, Voltage-Step-Down, Single-Phase, Non-Isolated ...
http://www.grix.it/UserFiles/Powermo...L_acfvsdsp.pdf

Kind regards
Dennis

[Dennis]

Gee suddenly this thread has quietened down :-(

There were no explosions, no loud bangs , nothing that went bump in the night...
No loud bangs, nothing burned out ...!

I decided to go ahead and build the circuit for testing ... nothing worked initially :-( the LED which I had enabled to go high every 15 seconds didn't even come on :-(
I went over it again with a fine-toothed comb..and found my 100uF and 100nF cap were in the wrong places.

I had programmed my PIC outside the board of course (no ICSP implemented yet !!) the program simply blinks an LED(GPIO.5) this would tell me the PIC has voltage and there would be no need for voltage measurements and also sets the TRIAC gate (GPIO.0) to go high for 15 seconds and the low for 15 seconds.The TRIAC in turn turns on the light buld for the same amount of time.

After correcting the capacitor issue,I put my welding glasses on and a pair of earmuffs and I used a broom stick to flip the AC wall switch :-)
Well the LED came on ..YAY :-) but the connected light bulb sadly did not !
SIGH !
The I looked back at the the circuit schematic and the calculations and it dawned on me that the TRIAC gate current may not be enough.Initially I had just popped in a 1K 1/4 Watt resistor just as a placeholder in my schematic with the idea that it may or may not work.
I quickly flipped the wall switch off, unplugged the extension cord (yes that too !) and unplugged the circuit board (strip-board for now), I made sure not to touch the large caps while unsoldering the gate resistor (R3) and replaced it with a 390R one!

Again repeating the same steps, earmuffs etc,I once again powered on the circuit .....
And to my absolute surprise the light bulb came on then 15 seconds later it switched off and the LED came on ! So when the LED is ON the LIGHT is OFF and vice-versa !
WHY ?
How could both be set to come on at the same time ?
But YAY it works :-)
There is a slight flicker when the light buld is on and I'm thinking it may be the TRIAC resistor or ??? the mind wonders...!

So now I need to test more.
The questions now are :
1.Is it the TRIAC gate resistor causing the flicker ?
2. Are there any suggestions for the the value for R3 ? (Check earlier posts for BT-139 gate current values and specs.
3.Cap C1 value is 275V and I'm thinking rather to use a 400V rated X2 instead, any thoughts on this ?
4. What's a concern is in times of NO LOAD , what will life be like for the PIC control PIN and the TRIAC gate ?
5.Other options include using an opto-isolator (possibly a MOC3023 or 30XX) in conjunction with or stand-alone ..any thoughts ?

On a final note... Please note that the attached circuit design is merely for testing and discussion purposes and has NOT been completed nor cleared for safe use of any kind and is missing several safety elements like a FUSE, MOV and a parallel bleeder resistor across C1.
Also note that this is a HIGH VOLTAGE circuit and neither I nor anyone else posting on this thread assumes any liability which may arise from any aspect of the circuit and or its development and/or use.
Working with circuits like this one are HAZARDOUS and UNSAFE and could result in serious injury and/or death !
DO NOT build this circuit unless you have HIGH voltage experience, rather use a transformer based circuit which is isolated from the LIVE AC supply.
You have been warned!

Steve ... are you ready to measure ? ;-)

Any thoughts would be appreciated

Oh .. and last but not least a popquiz question... Am I using a COMMON LIVE design or a COMMON NEUTRAL design ...and why ?

Kind regards

Dennis

[Byte_Butcher]

Gee suddenly this thread has quietened down :-(

There were no explosions, no loud bangs , nothing that went bump in the night...

Gee, that's kind of anticlimactic after all the DANGER warnings, now isn't it?
No conflagrations = Congratulations.

The questions now are :
1.Is it the TRIAC gate resistor causing the flicker ?

Maybe. Honestly, I think I'd use an opto-isolator to drive the triac. But that's just the way I am...

2. Are there any suggestions for the the value for R3 ? (Check earlier posts for BT-139 gate current values and specs.

Refer to answer #1...

3.Cap C1 value is 275V and I'm thinking rather to use a 400V rated X2 instead, any thoughts on this ?

If your mains is 220V, then I 'd use a 400V rated cap. No way, on the 275V.

4. What's a concern is in times of NO LOAD , what will life be like for the PIC control PIN and the TRIAC gate ?

Not quite sure of the question here, but I think it goes back to answer #1

5.Other options include using an opto-isolator (possibly a MOC3023 or 30XX) in conjunction with or stand-alone ..any thoughts ?

Hmmm. Yeah, I think an opto-isolator would be good.

Steve ... are you ready to measure ? ;-)

Rat's, and I just sent my nomex suit to the cleaners and loaned my 10' insulated pole to my neighbor.


Say, don't you think it might be a good idea to put a small 5 volt zener from pin 5 to ground? I know that 1M is a pretty high value resistor and the PIC pins have some protection against over-voltage, but there's something kind of creepy about just connecting a PIC port pin to that high of a voltage, even through a big resistor. Probably no big deal, but it makes me nervous connecting that pin to 220v with just a resistor.


steve

[Dennis]

Hi all

OK 8 hours of flashing a 60W light bulb and no issues yet , Im feeling a little 'strobed-out' though :-), battling to decide to watch the light or the LED :-)

I'm also more keen on the OPTO , just wondering how it will survive the capacitive 5V floating circuit on the PIC side of things ... will explain more a little later.

Regarding the PIC for zero-crossing sensor , have you read the Microchip appnote 236a ? It should make you feel a little more confident , but I can try a diode if you like ?

Now about those screen caps and measurements :-) haul out that isolation transformer and scope and let's get some more info :-)
If you are curious and have the time of course ..

Kind regards

Dennis

[Byte_Butcher]

Regarding the PIC for zero-crossing sensor , have you read the Microchip appnote 236a ? It should make you feel a little more confident , but I can try a diode if you like ?

Nope, haven't read it. But I will in the morning.
But if it's OK with the folks at Microchip, then I guess it's OK with me.

I will read the appnote tomorrow... zero crossing detector is one of those things that will come in handy for me someday.

steve

[Dennis]

Hi all

Steve ...
Also check out the posts by Dave Houston regarding the x10 info ... they have indeed been using an MCU's for many years and I recall seeing a post or two by Dave referencing certain models in particular even a PIC 12XXXX if I'm not mistaken.

You could also always conduct AC testing on low-voltage 'downlights' (not sure what you call them in the US or Europe ... ?

Keep those posts coming , this is a very interesting thread so far :-)
Oh and see post 66 (clickety clicks :-) )

Oh .. and last but not least a popquiz question... Am I using a COMMON LIVE design or a COMMON NEUTRAL design ...and why ?

Kind regards
Dennis

[keithdoxey]

Oh .. and last but not least a popquiz question... Am I using a COMMON LIVE design or a COMMON NEUTRAL design ...and why ?

Common Live so that the triac is switching the live supply to the load.

If the circuitry was common neutral then the triac would also be switching neutral with the result that the entire load would be live when the circuit appeared to be OFF.

[Pic_User]

I had programmed my PIC outside the board of course (no ICSP implemented yet !!)

Hi Dennis,

Great work so far. Let us know how things are going.
Especially how the ICSP works out, on the non-isolated circuit board.
This has turned into an interesting thread. A mix of past and future adventures in electricity land.
I really like the guys telling (on themselves) about the mishaps that have befallen the adventurous types. That is how we learn. Sometimes just being told carries little weight.

Oh .. and last but not least a popquiz question... Am I using a COMMON LIVE design or a COMMON NEUTRAL design ...and why ?

Good question!
I would guess the answer is: It is either a “COMMON LIVE” design OR a “COMMON NEUTRAL” design depending upon whichever way you happen to insert the plug. Why? Because “Sometimes just being told carries little weight.”

Keep us up to speed on this “excellent adventure”. Your posts are a great mix of adventure, work, learning, teaching, doing, telling, asking and just plain fun. –Adam-

[Dennis]

Hi guys
With reference to post #66 and the rest that follow and everything else prior to it.

Interesting indeed !

Keith ..AWESOME reply!

I agree with you here

triac is switching the live supply to the load.

Ok now for the beginning of the mystery and to add to this threads confusion you added this in :-)

If the circuitry was common neutral then the triac would also be switching neutral with the result that the entire load would be live when the circuit appeared to be OFF.

So from that statement we should assume COMMON LIVE is the supply of choice (in terms of being a little safer) not COMMON NEUTRAL ? Assuming of course that this circuit is indeed a COMMON LIVE circuit ?

Any comments on the above statements ?

Steve ....

Nice...! You threw in another side-winder, in fact, you mentioned something very real !
A two prong(pin) plug in most countries (correct me if I'm wrong ?) is easily reversed , in other words pluged in the other way around .. both sides same sides kind of thing so if I decide to design my PSU with the left prong as LIVE and the right prong as NEUTRAL .. all fine and dandy but then I unplug the device, put the pulg into the wall socket the other way around and suddenly everything is changed around :-)
Does this mean I should re-design my whole circuit ?
UH OH !

Well I encountered this dilemma a few nights back ... just before I got the broomstick, earmuffs and rubber gloves out and got all kitted up, I thought "Gee on this two-prong plug what happens when everything turns around ?"
"Will the circuit blow? What will the effect be? Will I need to change everything?"

So it works , turned either way around ! ( AC @ 50 Hz hmmm? )

And ..on the safety side is this circuit any less dangerous than a lamp that takes a bayonet or screw in light bulb ? Let's face it there is 110/120VAC or 220/230/240VAC right at the contacts where you screw the light in , not so ?

What about the computer AT form not so long ago which had mains voltage right at the front panel pretty much like may household appliances,TV's and radios before soft-power switches became the flavour of the day.

OK my next mission would be to alter the circuit so that the 'circuit ground' is the LIVE line in the schematic but .. do I really need to ?

Awaiting more comments and thoughts :-)

Oh and the question still remains ... is the circuit in post # common live or common neutral ? and why ?

Kind regards

Dennis

[keithdoxey]

Keith ..AWESOME reply!

So from that statement we should assume COMMON LIVE is the supply of choice (in terms of being a little safer) not COMMON NEUTRAL ? Assuming of course that this circuit is indeed a COMMON LIVE circuit ?

Living in a country where every mains outlet is a 3 pin socket so polarity reversal is impossible unless the actual outlet is incorrectly wired I would say that common live *should* be the supply of choice particularly if the load it was controlling was external to this box of tricks so that it would be recieving a correctly switched supply.

Irrespective of supply polarity, becuase this circuit is tied directly to one leg of the mains supply it should be totally enclosed and should never be worked on except via an isolation transformer.

All "basic" light dimmers have a common live supply as they are only connected to the live and load.

[Dennis]

Hi again

Nice one keith ...safety and isolation for sure! Have you read the earlier posts ?

Living in a country where every mains outlet is a 3 pin socket so polarity reversal is impossible unless the actual outlet is incorrectly wired I would say that common live *should* be the supply of choice particularly if the load it was controlling was external to this box of tricks so that it would be recieving a correctly switched supply.

And those plugs quite often contain fuses (probably on the LIVE) not so ?
And the looking at the APPNOTE that I referred to in post #1 under the designing for safety heading you would see the fuse placed on one of the lines as well as a fuse and a bleeder/'safety' resistor sitting parallel with C1.

Now let's chat about the 2 prong device that need to be plugged in the countries you're referring to.
We need some sort of adapter to plug the 2 prong device into the 3 prong plug right ? Does th adapter contain a fuse as per country electrical regulations (if any ) ?
So again plugging a PSu like this one into the adapter, one can plug in either way ... and yet again NEUTRAL and LIVE are switched around (in the circuit of course)!

If this indeed is the case then we are right back at the million dollar question
"Is this circuit Common LIVE or COMMON NEUTRAL ? And why ?"

And then we must look at the designing for safety aspects where we discussed fuses.
One of the original draughts had two fuses , one on each line, and a point or two were raised about one of the fuses (the one on the neutral line) would be pointless. Yes indeed it probably would be useless as well as unsafe ...IF this circuit contained an earth(real ground) !
But alas, the circuit has no earth point or connection at all !

SO it seems this circuit will always 'FLOAT' either at 5volts(or whatever you designed it for) below live or 5Volts above neutral.
In earlier posts I showed circuit diagrams of common live and common neutral from various references.Circuits with components changed around, in different places forcing flow in different directions.
Are these circuits incorrect ?

Sadly I don't have an oscilloscope or an isolation transformer at my disposal anymore but I certainly will check/test/build blow-up each circuit depicted and feedback so we can continue this discussion.

Anyone feel like building a calculator to calcualate the APPNOTE referred to in post #1 and/or the circuit in #66 ?

Regarding the 'BOX OF TRICKS' you mention ...

If all of you that are following this post have some time , go and google for 'Ben Franklin flyng a kite in the rain with a key tied to the string' to attract lightening strikes.

And then along the lines of safety and climate change try google H.A.A.R.P.

Sure... why not try heat the ionosphere at it's thinnest points at the poles to blow a hole in it just to see what happens .. now that's safety for all mankind not so ?

All thanks to folks like Tesla, Franklin and ...aaargh let's not go there!

And is the H.A.A.R.P experiment over ... well apparently (will we ever really know?), but google earth and satellite pics show the facility plain as day !

Oh well at least we can get answers about the PSU circuit :-)

Kind regards
Dennis