MOC3020 & BT136 circuit problem.

bt136 circuit

Hi
In the given circuit, I am taking output from a microcontroller and load is a small electric bulb , 230 V , 50 Hz.
Please see the circuit diagram below and the test results and help me with the debugging

Circuit Diagram is
https://obrazki.elektroda.pl/21_1228334288.jpg


MOC3020 & BT136 crcuit testing
a) On giving 3 or 5 V input on the control side, still no output voltage observed on load side.
b) Resistance value on control side of MOC was shorted still voltage obtained in between doesn’t change.
c) 3 copies of this circuit was fabricated and bulb was put in all the three one at a time, still bulb didn’t glow ..i.e. there’s no problem with any device, there may be some logical problem.
d) Software is working fine. We checked it with LED and also by checking voltage at the control side of MOC3020.
e) When the connection between 1&2 or 2&3 of BT136 is shorted, bulb glows.
f) Blinking time was changed from 3 s to 5 s to 20 s. still it didn’t work.





h) Expected problem : MOC isn’t able to drive the load side.

moc3020 bt136

From your circuit, I don't understand the problem, apart from a possible damage of MOC3020 by an input current above maximum ratings, if connected directly to logic supply. You should verify, that the input current is above required minimum of 30 mA but not above 50 mA. Most microprocessors or logic circuits are not able to drive 30 mA without an external driver (e.g.ULN2803) or a transistor. You would need higher sensitive MOC302x variants to drive the coupler from logic directly.

bt136 + moc

Hello,
Connect the anode of moc3020 to vcc through 330 ohms resistor. Now drive the pin2 from microcontroller pin. When it is at Logic 0, then only it conducts. The idea is a processor can not source current, but can sink.

ok, from bangalore

bt136+test+circuit

Not a bad idea, but the current would be still to low for MOC3020. Also, newer processors have symmetric CMOS drivers rather than unsymmetric TTL. If no sensitive opto triac can be used, just accept, that an external transistor or driver is necessary with MOC3020.

connect load like this[/img]

Re: bt136 circuit

sharadbags said:

Hi
In the given circuit, I am taking output from a microcontroller and load is a small electric bulb , 230 V , 50 Hz. Expected problem : MOC isn't able to drive the load side.

Click to expand...

The said circuit work perfectly fine. I have used it practically in many of my designs. Ok...the MOC's Pin 1 may be 330E or 470E if the voltage is 5 volts. You may chnage it proportinally. Ok..Pin 4 of MOC connectes to the gate of BT136. The resistance between PIN 6 and MT2 may be 1K. (I have sued the same) Still if it didnt work, try shorting Pin 4 and 6 of MOC. If it still didint work, now there are just 2 possibilities. One is that the triac is blown off. Other the MT1 and MT2 pins are swapped. Try swapping them. As you have mentioned in the last line, the MOC is just triggering the gate of the triac and has nothing to do with the Load...Cheers