BT136 TRIAC Overview
The BT136 is TRIAC with 4A maximum terminal current. The gate threshold voltage of the BT136 is also very less so can be driven by digital circuits.
Since TRIACs are bi-directional switching devices they are commonly used for switching AC applications. So if you looking to switch of control (dim, speed control) an AC load which consumes less than 6A with a digital device like microcontroller or microprocessor then BT136 might be the right for you.
 
How to use BT136
There are many different ways to use a TRIAC, since the device is bi-directional the TRIAC gate can be trigger with either positive voltage or negative voltage. So this allows the TIRAC to be operated in four different modes.
 
TRIAC Application Tips
Since TRIACS deal with AC voltages, the circuit involving them has to be designed properly to aboid problem some tips are shared below
All TRIAC circuits suffer from an effect called Rate Effect. This occurs when the TRIAC is switching frequently and a sudden high voltage occurs at either main terminal of the TRIAC and damages the TRIAC itself. It can be avoided by using a snubber circuit.
Similarly there is another effect called backlash effect. This occurs due to the capacitance that gets accumulated between the two terminals of the MT1 and MT2 of the TRIAC. Due to this the TRIAC will not turn on even if the gate voltage is applied. This problem can be solved by providing a resistance in series for the capacitance to discharge.
When controlling the output AC voltage for dimmer or speed control applications a Zero crossing method is always recommended to be used.
In switching circuits the TRIAC is easily subjected to harmonics and EMI interference hence should be isolated from other digital electronics.
There is chance of backward current when the TRIAC is switching inductive loads, so an alternate discharge path has to be provided for the load to drain the inrush current.
 
Applications
AC Light dimmers
Strode lights
AC motor speed control
Noise coupling circuits
Controlling AC loads using MCU/MPU
Ac/DC Power control