an UPDATE ***
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
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