This document discusses using a TRIAC and optoisolator to control 220V AC loads from an Arduino board. It explains that a TRIAC can be used to control AC power by turning on and off at different points of the sine wave. An optoisolator like the MOC3041 provides isolation between the Arduino and power circuit to prevent damage. It describes how the optoisolator works, using a LED to trigger the TRIAC at zero crossings. Sample circuit diagrams show how to connect the TRIAC, optoisolator, and load. Calculations for snubber resistors and capacitors to prevent false triggering are also covered.

1. Module for Static Control of 220V
AC Devices by Arduino/IR remote

2. Selection of Power switching Device
Isolation between Arduino and Power
circuit
Circuit & Load connection

3. Selection of Power switching Device
There are lots of Power
semiconductor switches
1. Diode(Uncontrolled Turn
ON/OFF)
2. Thyristors(Controlled turn ON
and Uncontrolled Turn OFF )
• SCR
• TRIAC
• GTO
3. Transistors(Controlled turn ON
and controlled Turn OFF )
• Power BJT
• Power MOSFET
• IGBT
Desired Characterstics
• Pulse Gate
• Controlled Turn ON
• Bipolar voltage
• Low cost (low
switching frequency)

4. Selection of Power switching
Device
TRIAC is Best suited
• Low Cost
• Bipolar voltage
• Isolator Driver is easily
available
• Zero crossing Detection can
be used to Turn ON
• Voltage control is possible for
Dimming of Bulb/Speed
control of Fan

5. Selection of Power switching Device
Basic
Operation of
TRIAC
TRIACs are like 2 antiparallel SCRs with a
common gate
They are thus able to switch both sides of an AC
sine wave
A TRIAC switch controls the current through
a load Because it can be controlled to trigger
at different voltage points on the sine wave it
can be used to effectively control the RMS
power delivered to the load rather just crude
on / off.

6. Selection of Power switching Device
Basic
Operation of
TRIAC
It's like a switch that can turn on and off at
different times on the sine wave.
Is this only
what we need
to do?
Of course not

7. Selection of Power switching Device
What we
want to do
with TRIAC
What is basically difference between last
waveform and this one?
We want to
Switch ON
and OFF AC
load
To Generate Vg we Use
MOC 3041 in our case

8. • These devices provide sufficient gate trigger
current for high current, high voltage
Triac, while providing a guaranteed 7.5 kV
dielectric withstand voltage between the
power line and the control circuitry
• An integrated, zero-crossing switch on the
detector chip eliminates current surges and
the resulting electromagnetic interference
(EMI) and reliability problems for many
applications.
Isolation between Arduino and Power
circuit
WHY??
The high transient immunity of 5000 V/μs, combined with the features of low
coupling capacitance, high isolation resistance and up to 800 volt specified V
DRM ratings qualify this Triac driver family as the ideal link between sensitive
control circuitry and the ac power system environment.
The zero-cross family of optically isolated Triac drivers is an
inexpensive, simple and effective solution for interface applications
between low current dc control circuits such as logic gates and
microprocessors and ac power loads

9. • OptoIsolators are Used in case of
TRIAC
• MOC 304_ series I.C. are used
Isolation between Arduino and Power
circuit
HOW??

10. Isolation between Arduino and Power
circuit
How does Zero crossing
optically isolated Triac driver
works?
Gates of the individual SCRs are
connected to high speed zero
crossing detection circuits. This
insures that with a continuous
forward current through the
LED, the detector will not switch
to the conducting state until the
applied ac voltage passes
through a point near zero
The detector chip is a complex
monolithic IC which contains two
infrared sensitive, inverse
parallel, high voltage SCRs
which function as a light sensitive
Triac .

11. • A forward current flow
through the LED
generates infrared
radiation which triggers the
detector.
• zero crossing detection
circuit insures that the
detector will not switch to
the conducting state until
the applied ac voltage
passes through a point
near zero
Isolation between Arduino and Power
circuit

12. Isolation between Arduino and Power
circuit
Electrical
Characteristics
The detector/Triac may be
triggered "on“ in following ways
• This LED trigger current (IFT)
• Exceeding the forward blocking
voltage between the two main
terminals (MT1 and MT2)
• Voltage ramps
(transients, noise, etc.) which are
common in ac power lines may
trigger the detector accidentally if
they exceed the static dV/dt rating
Accidental triggering of the main Triac is
a more likely occurrence thus a form of
suppression network commonly called a
"snubber" must be used to prevent false
"turn on" of the main Triac

13. Isolation between Arduino and Power
circuit
BASIC SWITCHING
CIRCUIT With TRIAC ,
TRIAC DRIVER &
LOAD
The gate resistor RG is only
necessary when the internal gate
impedance of the Triac or SCR is very
high .These devices display very poor
noise immunity and thermal stability
without RG
Resistor R (in combination with
R-C snubber networks) prevents
possible destruction of the Triac
driver in applications where the
load is highly inductive.
LIMITATION
Use of a gate resistor combined with the
current limiting resistor R can result in
an unintended delay or phase shift
between the zero-cross point and the
time the power Triac triggers.

14. BASIC SWITCHING
CIRCUIT With TRIAC
, TRIAC DRIVER &
LOAD
Load connection

15. Calculation of Rs and
Cs
If R, L and C are chosen to
resonate, the voltage waveform
on dV/dt due to damped quarter-
cycle of oscillation will look like.
Load connection

16. Calculation of Rs and
Cs
Load connection

17. Load connection

18. DEMO