The meaning of HIGH (in reference to a pin) is somewhat different depending on whether a pin is set to an INPUT or OUTPUT. When a pin is configured as an INPUT with pinMode(), and read with digitalRead(), the Arduino (ATmega) will report HIGH if: a voltage greater than 3.0V is present at the pin (5V boards) a voltage greater than 2.0V volts is present at the pin (3.3V boards)
The links just take you to a span site that wants to download Cookes to you otherwise it will not let you see anything.If you read the how to use this forum sticky post it will tell you how to post images here.
But the signal is "low" when there is mains. If you use a capacitive dropper instead of resistors you can drive the opto harder without generating heat.
Hi All,I suggest the 1N4007 diode should be used as a half wave rectifierso that only one 120K resistor is required.Herb
Hi All,You do not need theintegrating capacitor(s). Just go with the square wave output.Herb
I tried it with IE (browser I never use) and show the images w/o any problem(!).
You probably let the site down load stuff to your computer, without it there is a dark filter over the image and while I can just about make out the waveform the other image was too dark to see.
What format is your picture you are trying to attach to a post?
the 240K isnt a dropper but a current limiter.
Capacitive dropper wont limit the current to the ir LED in case of high freq components such as when sw1 is turned on or heavy loads (A/C etc) are started / stopped and so I would not recommend that
Can you please shade some more light om this idea?
Regarding the caps: Assume the transistor is off: the cap is charging.This takes time because the resistor limits the current, so the capvoltage ramps up. When the transistor turns on, it quickly dischargesthe cap. So, without the cap, the waveform would be like a square wavebecause the transistor collector current can change quickly from +5Vto almost 0V.Herb
It's dropping the voltage isn't it? So yes, it's (also) a dropper
That's why in a normal capacitive dropper design you combine a capacitor with a inrush limiting resistor.