Main Content

This is the solid state relay which is same as sugar cube relays available in market, These SSR based on electronics switching.

Relays are the most useful and stable AC power switching components. Relays provide complete isolation of DC operating voltage from AC mains. The regular size of relays is big because of mechanical moving actuator and a coil. The coil forms an electromagnet which then used to attract the metal actuator points and thus turn on the AC power. The most popular relay SPDT (single pole double throw) has 5 terminals, 2 for the coil and 3 for the mains connections. NO (Normally open), NC (Normally closed) and COM (common point).

The main problem is that the takes a lot of current and due to mechanical action of actuators there is sparks in between of both terminals. Which cause serious problems like tear down, terminal welding and damaging. But there is one solution to all of these problems known as SSR (solid state relays). They are the electronic based switches which can be used for fast switching of AC appliances or to control the power ratings.

These electronic AC switches are known as TRIAC. In last we will build our own SSR module using 4 TRIAC and compare the same with the existing mechanical relays. I am using JLCPCB SMT assembly service, JLCPCB is the China’s leading PCB manufacturing company working in this field for more than 15 years. You can explore the all services from here. Sign-up using this link to JLCPCB and get $54 new user coupons for the next order.

A TRIAC (triode for alternating current; also bidirectional triode thyristor is a three terminal electronic componentthat conducts currentin either direction when triggered.

TRIACs are a subset of thyristors(analogous to a relayin that a small voltage and current can control a much larger voltage and current) and are related to silicon controlled rectifiers(SCRs). TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction. Most TRIACs can be triggered by applying either a positive or negative voltage to the gate (an SCR requires a positive voltage). Once triggered, SCRs and TRIACs continue to conduct, even if the gate current ceases, until the main current drops below a certain level called the holding current.

The bidirectionality of TRIACs makes them convenient switches for alternating-current (AC). In addition, applying a trigger at a controlled phase angle of the AC in the main circuit allows control of the average current flowing into a load (phase control). This is commonly used for controlling the speed of a universal motor, dimming lamps, and controlling electric heaters. TRIACs are Bipolar devices.”

Link to article