Electronics & Software – Tips & Guide


How to use thyristors?

How to use thyristors

If you buy a thyristor, it must have given you the data sheet in which the voltage limit, the current limit, the performance charts, etc. have been given. from there, you can also know the connection mechanism.

What I get from this thyristor is the smaller cover that is used to connect the trigger circuit, and the others are anode and cathode respectively.

If you can not understand based on the data sheet, you probably do not know enough to work safely on a high voltage circuit. Know that in pursuing your project, you put yourself (and probably others) at a real risk of injury or death. For example, you could electrocute yourself or another person, or start a fire. Handling the mains can also lead to a power failure or damage to the equipment. Please keep in mind that I do not say this to be rude or mean, I say because the danger is very real, as such, I can not hold it responsible if you pursue this project against my opinion.

Based on your comments, I guess you are trying to identify the three terminals. the smallest eye is almost certainly the door; the other two terminals are the big eye and the screw. sometimes, the thyristors are designed for a particular purpose, so that you can not always know which end is the cathode by looking at it, but assuming it’s a general purpose, the cathode (what you call negative) is probably the end with the screw to be screwed to the ground), leaving the big eye as anode (positive terminal). but as I said, they could be reversed depending on the intended use of that particular device; the datasheet would say exactly what’s what, though. In addition, you will need to determine if the thyristor can even handle the use you are considering. So, unless you do not mind blowing something up, you really have to look for the data sheet first.

first: find the technical data sheet of your device. it will tell you what it really is.

in agreement with platt e jansson (2014) thyristor is a generic name for a class of semiconductors comprising at least four alternating layers of p-type and n-type silicon.

you have mainly three types of thyristors:


it is a bidirectional thyristor with self-triggering. the component has two conductors and it enters conduction mode when the voltage between its conductors reaches a determined value.


it is a semiconductor switch that can transmit high currents and voltages. it is triggered by the voltage applied to a door (this little wire). once you have triggered a current begins and will not stop until the voltage on scr goes to 0 volts. The stream of

scr is unidirectional.


works like scr but it supports bidirectional current flow.

main applications:

overload protection. if a level reaches its limit, a trip signal is applied to the gate to activate the protection circuit and / or the alarm.

phase control. it can moderate the speed of the motor or the heat generated by a resistive load.


platt, charles; Jansson, Fredrik. encyclopedia of electronic components volume 2: signal processing. leds, lcds, audio, thyristors, digital logic and amplification. 1005 Gravenstein Highway North, Sevastopol, CA 95472. USA: Maker Media, Inc., 2014. Isbn13: 978-1-4493-3418-5.

I recommend you read this book. he has several examples and is a reliable source of information.

I hope it helps

Recent Updates