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Cant get MOC3020 to work

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I am trying to make a digital dimmer circuit,But i was not successful so i was finding fault part by part Lets leave the ZCD and microcontroller thing apart for now.
I am using M0C3020 and bt138. I tried powering up Moc directly but that doesnt turn on triac.
So my connection is as follows

main 1.jpg

I powered moc using 5v with 470 ohm resistor.
I also tried swapping TRIAC pins.

When i short terminals 4 and 6 of MOC, i can turn the triac on.
I tried changing MOC

I really have no idea why it isn't working. When i power up moc it should right away activate triac right as long as their is voltage across pin 1 and 2 (ofcourse AC IN is ON)
 

According to datasheet, the maximum input current to trigger MOC3020 can be as high as 30 mA, typical trigger current is 15 mA. 470 ohm resistor with 5 V supply gives maximal 8 mA.
 

FvM said:
According to datasheet, the maximum input current to trigger MOC3020 can be as high as 30 mA, typical trigger current is 15 mA. 470 ohm resistor with 5 V supply gives maximal 8 mA.
Click to expand...



Swapped it with 150 Ohm , also replaced MOC again, still it doesnt get activated.
Is my connections wrong ?.
 

The connections are OK according to the schematic but I suspect you still have insufficient LED current.
Try this: disconnect pin 1 of the MOC3020 then link pin 1 directly to +5V. If that turns the triac on, your problem is lack of current from whatever drives the LED.
If your drive signal comes from an MCU, the logic high needed to provide enough current may not be reaching 5V.

If you have a voltmeter, tell us the voltage across pins 1 and 2 also the voltage from pin 2 to ground when it should be turned on.

Brian
 

Hi,

Please show a bit more of your schematic, so we can see where the signals come from ... and go to.

Klaus
 

Your schematic doesn't show the actual connection of driver side. Measure voltage drop at 150 ohm resistor to verify sufficient driver current.
 

betwixt said:
The connections are OK according to the schematic but I suspect you still have insufficient LED current.
Try this: disconnect pin 1 of the MOC3020 then link pin 1 directly to +5V. If that turns the triac on, your problem is lack of current from whatever drives the LED.
If your drive signal comes from an MCU, the logic high needed to provide enough current may not be reaching 5V.

If you have a voltmeter, tell us the voltage across pins 1 and 2 also the voltage from pin 2 to ground when it should be turned on.

Brian
Click to expand...

Voltage across pin 1 and 2 is 1.33
Voltage across pin2 and ground is zero,

i tried connecting moc directly to 5v, it still doesnt activate triac. Is my entire lot of moc faulty ? :)

By the way whats the minimum voltage that Moc should get

- - - Updated - - -

FvM said:
Your schematic doesn't show the actual connection of driver side. Measure voltage drop at 150 ohm resistor to verify sufficient driver current.
Click to expand...
Attaching my circuit,
Triac is bt 138
MOC IS MOC3020
CIRCUIT 3.jpg
 

Sounds like Pin 7 is sourcing a low µA current rather than the required LED current. You should still be able to measure it across R3 if you look sharp.

Anyway, PIC specification tells maximum rating for pin current is 25 mA, there are no indications that it can drive more than a few mA with the required low voltage drop.

You absolutely need a switch transistor to drive the MOC3020 safely.
 

Now iam trying to figure out if my MOC is working. I separated pic for now and i am directly powering MOC. But that doesnt activate TRIAC too.
How can i basically test if MOC is faulty
 

Hi,

i tried connecting moc directly to 5v
Click to expand...
you definitely need a current limiting resistor for this.
Connecting the MOC directely to 5V may immediately kill it.

And you didn´t write about a load. But you need a load to trigger the triac. To test use a low wattage incandescent light bulb.

Klaus
 

KlausST said:
Hi,


you definitely need a current limiting resistor for this.
Connecting the MOC directely to 5V may immediately kill it.

And you didn´t write about a load. But you need a load to trigger the triac. To test use a low wattage incandescent light bulb.

Klaus
Click to expand...

Directly in the sense.. I just removed pic

Now its vcc 150ohm moc
I even tried direct 5v..
I tried with different moc

Ioad is a 40 watt incandescrnt bulb
 

Hi,

Now its vcc 150ohm moc
Click to expand...
additionally you need GND.

If you connect 5v - 150 Ohms - MOC - GND
What is the voltage across the 150 Ohms?

Klaus
 

KlausST said:
Hi,


additionally you need GND.

If you connect 5v - 150 Ohms - MOC - GND
What is the voltage across the 150 Ohms?

Klaus
Click to expand...
1.33v . This is getting on my nerves now..lol
 

According to the VOH/IOH graphs in the data sheet, at 5V supply and 25C the 12F1840 should produce around 4.8V under 10mA load so the optimal series resistance should be (4.8 - 1.2)/ 0.01 = 360 Ohms.

Voltage across pin 1 and 2 is 1.33
Voltage across pin2 and ground is zero,
Click to expand...
Doesn't make sense, something is wired up wrongly. For there to be 1.33V across the MOC3020 it should be conducting and the current has to then flow through the resistor and drop a voltage across that also.

Conclusion: if it is a genuine MOC3020 it is either faulty or wired up wrongly.

Can you post a photograph of your construction please.

Brian.
 

Iam sorry.. i was away from forum for a few weeks.. i met with a serious car accident and was on bed for sometime.. :) Just recovering. So now iam back into this. With new circuit using moc3023.

Moc seems to work.. I can drive the moc from pic and blink led. Let me write a program to do dimming. will keep you guys posted..
 

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