TCA785

Description

This phase control IC is intended to control thyristors, triacs, and transistors. The trigger pulses can be shifted within a phase angle between 0° and 180 °. Typical applications include converter circuits, AC controllers and three-phase current controllers. This IC replaces the previous types TCA 780 and TCA 780 D.

Features

●  Reliable recognition of zero passage

●  Large application scope

●  May be used as zero point switch

●  LSL compatible

●  Three-phase operation possible (3 ICs)

●  Output current 250 mA

●  Large ramp current range

●  Wide temperature range

Light Dimmer Circuit using TCA785 and S202S02

You might have seen dimmable table lamps and wall lamps. This dimming feature add extra value to the lamp as we can choose or configure the intensity of the light as we need. But ready made dimmers or dimmable lamps may cost a lot. Today we are going to see how to build a dimmable lamp using TCA785 and S202S02 as main components.

What is TCA785?

TCA785 is a phase control ic designed for thyristors. We can set the phase firing angle using resistors and capacitors.  

Pinout of TCA785:

TCA785 phase angle control IC comes in a 16 pin DIP package. You can see the pinout of the TCA785 IC in below image.

Pinout of TCA785

Let’s see more details the pins of  TCA785 phase angle control IC

●  Pin 1 – GND – ground connection.

●  Pin 2 – Q2 – Output 2 pin (inverted signal).

●  Pin 3 – Q U – Output U pin.

●  Pin 4 – Q1 – Output 1 (inverted signal).

●  Pin 5 – VSYNC– Voltage for sync signal

●  Pin 6 – I – Inhibit

●  Pin 7 – QZ – Z output pin

●  Pin 8 – VREF – Stabilizing voltage

●  Pin 9 – R9 – Resistor for ramp adjustment

●  Pin 10 – C10 – Capacitor for ramp adjustment

●  Pin 11 – V11 – Control voltage

●  Pin 12 – C12 – Extended pulse output

●  Pin 13 – L – Long output pulse

●  Pin 14 – Q1 – Output pin 1

●  Pin 15 – Q2 – output pin 2

●  Pin 16 – Vs – input voltage pin for power supply

Features of TCA785:

Lets discuss the main features of the TCA785 IC.

●  Inbuilt ramp controlling.

●  250mA gate current

●  Can be used as a zero crossing detector

●  Can be configured for three phase operation

What is S202S02?

S202S02 is a traic SSR. triacs can be use to control AC voltages.  

S202S02 comes in a 4 pin package.

Pinout of S202S02:

As mentioned above S202S20 comes in 4 pin package lets check the pinout of the S202S02 traic.

Pinout of S202S02

Let’s see more details the pins of  TCA785 phase angle control IC

●  Pin 1 – VAA – Floating input positive supply

●  Pin 2 – GND – Floating input supply return.

●  Pin 3 – IN-  – Analog inverting input. This is the ground or negative connection of the audio input pin.

●  Pin 4 – COMP – Phase compensation input, comparator input

Features of S202S02:

Lets identify the key features of the S202S02 traic

●  Maximum output current of 8A

●  Inbuilt zero crossing functions

●  4kV isolation between input and output.

Basic Circuit Diagram:

Given below is the basic circuit diagram of the lamp dimming circuit.

Dimmer circuit diagram

Key Components :

We will need the fallowing complimentary components to build this circuit other than TC785 phase controlling IC and the S202S02 traic.

●  TCA785 phase control IC

●  S202S02 traic

●  BAY61 diode

●  15V Zener diode

●  4.7 kΩ resistor  

●  220 kΩ resistor  

●  22 kΩ resistor

●  150Ω resistor

●  2.2 kΩ resistor

●  10 kΩ Potentiometer  

●  100 kΩ potentiometer  

●  0.22uF 250V capacitor

●  470 uF 16V capacitor

●  1nF capacitor

●  2.2 uF capacitor

●  150pF capacitor

●  0.47uF capacitor

Tools Needed:

1. Soldering Iron

2. Iron Stand

3. Flux

4. Nose pliers

Step By Step Guide:

Step 1: Arrange the components.

Step 2: Connect the components as shown in the circuit diagram.

Step 3: This circuit involves mains voltage so do not touch it and always disconnect the circuit from the mains before troubleshoot.

Step 4: connect the circuit to the mains voltage

How It Works:

By adjusting the potentiometer, we can change firing angle of the S202S02 traic. 

By doing so circuit controls the portion of the sine wave which lamp is stays on. 

By doing so we can change the brightness of the lamp.

Conclusion:

This is a very useful circuit. We can use this to dim lamps and also control series wounded motors as well. Also be careful as we are working with high voltages here