8051 Based Triac

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gauravkothari23

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Hi all.
I am trying to make a small circuit where i am just trying to just ON and OFF a small 5 RPM 220V AC motor.
I am using BT131 Triac to drive using 8051 microcontroller. What my problem is when i switch the 220V line, the Resistor R18 and controller both gets bursted.
i have connected Gate of Triac using series resistor to controller Port pin P06,

As it is stated in datasheet
Direct interfacing to logic level ICs
Direct interfacing to low power gate drive circuits and microcontrollers

Can anyone please explain where the problem is.
Circuit Diagram Attached.
 

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what is the rest of the circuit?
does the motor run correctly without the triac?

the voltage at the gate is referenced to another pin of the triac.
where is that connection?

how much current does the motor draw when on?
how long are you turning the triac on for?
do the resistor and the processor blow up immediatlry?

the current from the processor, pin P0.6, has to return to the processor - what is the path for that?
if it involves NEUT, you may be applying 220V to the rsisotr and processor.
 

rest of the circuit includes LED's and some buttons.
yes, the motor runs perfectly if applied 220V AC directly.

As you said
the voltage at the gate is referenced to another pin of the triac.
where is that connection?
what connection is required.

the motor draws hardly 100mA of current.
the resistor and the processor blows up immidiately and that too without load, the motor is not connected.
 


Suggest me a proper circuit diagram for BT131 to interface with 8051 controller.
I have tried but just bursting the controller again and again.
 

it's hard to know without the rest of the circuit

since the resistor and processor blow up without the motor,
it looks like you're applying 220 V to them

this may be a good start at understanding the triac

What is TRIAC: Switching Circuit and Applications

In this tutorial we will learn about the TRIAC, which is a bidirectional device meaning it can conduct in both the direction. Due to this property TRIAC is exclusively used where sinusoidal AC supply is involved.
circuitdigest.com

and this

Control Your AC Mains with a Microcontroller - Projects

Learn how to put together your own toaster oven controller with a handful of inexpensive, through-hole parts. The emphasis is on safety, low price, and minimal modification of the toaster oven.
www.allaboutcircuits.com
especially the section on
TRIAC Driver and Isolated Driver Circuit
replace oven with motor and triac-actived with P0.6

NOTE: you are working with lethal voltages - learn how to do that safely
 

Here i Have attached rest of the circuit.
In the circuit i have 2 AC Motors. Motor-1 and Motor-2.
For motor-1, i am using BT136 and MOC3021 and controlling using 8051 port pin P0.5, which works perfectly.

but the the problem arises with motor-2. where i am just using BT131 with gate pin directly connected to 8051 port pin P0.6.

I also have a non isolated 220V AC to 5V DC circuit.
 

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Power supply and non-isolated triac control don't fit. You must either flip the triac circuit, connect A1 to neutral, or the power supply, using line rather than neutral as common node.
 

Hi,

I wonder why you don't use the same MOC circuit as with the other motor.
...since MOC circuit is working and the other not..

Klaus
 

you have the solution you need
use the working circuit instead of blowing up more parts.
 

Actually I can't use the MOC part because of price factor.
The price of MOC is approx 0.25 us$ Each.
--- Updated ---

FvM said:
Power supply and non-isolated triac control don't fit. You must either flip the triac circuit, connect A1 to neutral, or the power supply, using line rather than neutral as common node.
Click to expand...
Sir, You Mean. Rather then Neutral connected to VCC after D13, i must connect Line after D13..??
--- Updated ---

Sir, One more question i had,
can i use PC817 optocoupler to isolate the controller and triac as per the circuit attached. the rest of the circuit will be the same.
 

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Last edited:

Hi,

I don't understand. If price is a problem, why can you use the MOC (one time).

On the other hand: If you don't need isolation why use the MOC at all?
If you don't need isolation, then even an optocoupler makes no sense.

Use the non isolated solution but with correct mains and triac connection.

Klaus
 

Two ways to assess your latest schematic:
- by the way of trial, burn an optooupler, resistor, triac
- calculate the maximum expectable voltage across the optocoupler, check with rating
 


Sir,
That's what i am confused. what is the correct circuit. to drive the BT131 Triac without using MOC.
Because the datasheet says, it can be directly interfaced with the controller. an NO recommened circuit is provided in datasheet.
 

Hi,

T1 is the reference for gate trigger (voltage and current).
Thus T1 needs to be the circuit GND as well as the common connection to mains (does not care whether Live or Neutral for operation. But for safety I recommend to use Neutral).

Klaus
 

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