Hi, guys

I am building the following dimmer circuit however i am having alot of issues.
I built everything up to the optocoupler the 555 and zero crossing detector work great along with the npn transistor. I had the remove the coupling capacitor 0.001uF between zero crossing and 555 to get it to work.

http://www.onsemi.com/pub_link/Collateral/AND8011-D.PDF

The issues I am having are when trying to trigger the MOC3022. currently have an LED at the output however even without input output of MOC3022 is constantly shorted. When I attach my npn transistor with a pulsed waveform saturating at my top rail of 12V the voltage at the input of the MOC3022 drops to about 1.8V PWM.

Thanks in advance

 

Hello,

It looks like you have connected the led in the MOC the wrong way around.
12 Volts at the input of the MOC is not possible, as the led inside the MOC is most likely an IR led wich has a voltage drop of about 1.2 Volts.
By connecting the led the wrong way around, it is probably blown, as leds can not have more than about 5 Volts in reverse.

Bertus

 

The issues I am having are when trying to trigger the MOC3022. currently have an LED at the output however even without input output of MOC3022 is constantly shorted. When I attach my npn transistor with a pulsed waveform saturating at my top rail of 12V the voltage at the input of the MOC3022 drops to about 1.8V PWM.

I may just be dense, but not following..
What do you mean by MOC3022 constantly shorted? 1.8v indicates it's not "shorted"
You could test the npn/moc3022/triac portion by removing the 1k base resitor from 555 pin 3 and connect it first to gnd (load is on) then to +12v (load is off).

 

I had the remove the coupling capacitor 0.001uF between zero crossing and 555 to get it to work.

What? "I had the remove..."? does not make sense in English. Maybe you did remove the important capacitor but it is needed for the 555 to work properly.

The issues I am having are when trying to trigger the MOC3022. currently have an LED at the output however even without input output of MOC3022 is constantly shorted.

What? Are you trying to say that when there is no input then the MOC3022 is always turned on?
That is normal. The 555 must be triggered for its output to turn on the transistor which turns off the MOC3022.

When I attach my npn transistor with a pulsed waveform saturating at my top rail of 12V the voltage at the input of the MOC3022 drops to about 1.8V PWM.

What? The input of the MOC3022 is an IR LED with a typical forward voltage of about 1.15V. The 620 ohm resistor turns it on and the transistor turns it off.

 

I attached a file that shows the input into the MOC3022 (Red line is input to MOC3022, Blue line is input to NPN). When this input is coupled to pin 1 of the MOC3022 it drops to about 2V. I have many MOC3022 and all perform the same. The output is constantly open, even when no input is attached.

 

I had the remove the coupling capacitor 0.001uF between zero crossing and 555 to get it to work.

What? "I had the remove..."? does not make sense in English. Maybe you did remove the important capacitor but it is needed for the 555 to work properly.

The issues I am having are when trying to trigger the MOC3022. currently have an LED at the output however even without input output of MOC3022 is constantly shorted.

What? Are you trying to say that when there is no input then the MOC3022 is always turned on?
That is normal. The 555 must be triggered for its output to turn on the transistor which turns off the MOC3022.

When I attach my npn transistor with a pulsed waveform saturating at my top rail of 12V the voltage at the input of the MOC3022 drops to about 1.8V PWM.

What? The input of the MOC3022 is an IR LED with a typical forward voltage of about 1.15V. The 620 ohm resistor turns it on and the transistor turns it off.

 

Hello,

How did you connect pin 2 of the MOC?
It should be connected to the ground pin of the NE555 (pin 1) and the emittor of the transistor.

For more easy taking about the schematic, I have extracted it from the PDF:

Looking at the powersupply part of the schematic, the mentioned 12 VDC will be more like 15 Volts, as it is unregulated and smoothened with the 1000 uF capacitor.

Bertus

 

I attached a file that shows the input into the MOC3022 (Red line is input to MOC3022, Blue line is input to NPN). When this input is coupled to pin 1 of the MOC3022 it drops to about 2V. I have many MOC3022 and all perform the same. The output is constantly open, even when no input is attached.

What do you mean by coupling.
The MOC3022 does not have an "output". It has to be connected to a circuit like the one you posted.
To test it, build the circuit as posted and then test.
If you connect 12v thru a 620 ohm resistor to the opto per the schematic it will have about 2v from pin 1 to 2 because the internal LED has about a 2v drop.

 

Yup I attached as specified in the digital dimmer schematic. Reffering to an earlier question. I shorted the output of the zero crossing to the 555 timer. It would not work with the coupling capacitor dont know why. But its not important because everything up to that point works fine.

Still unsure at this point how to trigger the MOC3022 to simulate an output using an LED.

I have attached an image of the output of the 555 timer. Varying the pot changes the PWM and that portion of the circuit works correctly.

 

Still unsure at this point how to trigger the MOC3022 to simulate an output using an LED.

The MOC3022 is meant to trigger a triac, not an LED.
Build the dimmer circuit to test.

 

Hello,

Did you connect ALL the ground connections together?

Bertus

 

If you connect 12v thru a 620 ohm resistor to the opto per the schematic it will have about 2v from pin 1 to 2 because the internal LED has about a 2v drop.

No.
A red or yellow LED is 2V. The IR LED in the photo-coupler is typically only 1.15V.

 

Build the dimmer fully using a triac, but make sure you connect the Moc to MT2 and G

 

@IphoneDeveloper: I think the problem is you're using d.c. to test the ouput with the led, you should use pulsating d.c. to test the circuit (i.e. the one you're tying to the positive input of the lm339).

You see, a thyristor, as is the output of the moc3022, when used to switch d.c., once triggered stays on until the supply is cut off, that's why you see the output as "shorted".