Pongsathorn Chumroenrattanakorn submitted their weekly report for their multidisciplinary workshop group Ferng. They were assigned to learn about triacs, specifically the BT136 series E triac. A triac is a bidirectional thyristor that can conduct current in either direction when triggered by a positive or negative gate signal. Unlike unidirectional SCRs, triacs allow for AC switching applications. Their engineering analysis found the BT136 triac appropriate and cheap for their application with no weaknesses identified. Their next steps are to purchase equipment and test the triac.

1. [INC 281 MULTIDISCIPLINARY WORKSHOP WEEKLY REPORT] March 28, 2012
Name-Surname Pongsathorn Chumroenrattanakorn (Arm)
Student ID. 53211820
Group Name Ferng (เฟื อง)
Engineering Team Fam, Sanook, Kwang, Opor, Will, Pieak, Nueng, Art
Members
Product Design P’ Mo P’ Nut P’ pin
Team Members P’ Mint P’ Pump
Weakly Progress
The last Thursday ago, my group are sheared the works. I receive work about triac. TRIAC (BT136
series E) , from Triode for Alternating Current, is a generalized for an electronic component that can
conduct current in either direction when it is triggered (turned on), and is formally called a bidirectional
triode thyristor or bilateral triode thyristor. TRIACs belong to the thyristor family and are closely related
to Silicon-controlled rectifiers (SCR). However, unlike SCRs, which are unidirectional devices (i.e. can
conduct current only in one direction), TRIACs are bidirectional and so current can flow through them in
either direction. Another difference from SCRs is that TRIACs can be triggered by either a positive or a
negative current applied to its gate electrode, whereas SCRs can be triggered only by currents going into the
gate. In order to create a triggering current, a positive or negative voltage has to be applied to the gate with
respect to the A1 terminal (otherwise known as MT1).Once triggered, the device continues to conduct until
the current drops below a certain threshold, called the holding current. The bidirectionality makes TRIACs
very convenient switches for AC circuits, also allowing them to control very large power flows with milli
ampere-scale gate currents. In addition, applying a trigger pulse at a controlled phase angle in an AC cycle
allows one to control the percentage of current that flows through the TRIAC to the load (phase control),
which is commonly used, for example, in controlling the speed of low-power induction motors, in dimming
lamps and in controlling AC heating resistors.
Figure 1.
TRIAC schematic
symbol
Figure 2. BT136 series E
Engineering Analysis
Strong Point
- BT136 is cheap and appropriate for the application.
Weak Point
- Not found.
Next Weak Job
- Begin to buy equipment and test it.
Department of Control System and Instrumentation Engineering
KING MONGKUT’s UNIVERSITY OF TECHNOLOGY THONBURI