Questions tagged [triac]

A TRIAC is a component often used to control high power currents, both as a switch and as a "dimmer"-like construction for controlling lamps or electric engines.

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Overvoltage protection circuitry choice

I need to design a input overvoltage protection for a 45 W DC-DC converter rated for a 9-24 V wall wart input (so, 45W/9V = 5 A input current at max). So far I've seen two approaches (schematics below)...
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Triac inductive load

I need to drive a inductive load with a triac dimmer. Circuit uses zero-voltage cross and delay for gate trigger. An additional circuit for detecting zero current cross has been added. So, what are ...
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Small single phase induction motor - triac control for startup and run

To repair a control board for a small single phase induction motor (35W 0.38A) I created this schematic to help me understand how it operates. The motor was overheating and not starting/running "...
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TRIAC driver circuit behavior when switching low current loads

I'm doing a project that involves switching different kinds of loads (edit: by that I mean loads that go from just a couple mA, up to 5A or so) using the usual TRIAC + opto-isolator combo (in my case, ...
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Connecting phototriac substrate to adjacent pins

For a regulatory exercise I am analyzing the result of a short fault between a phototriac's substrate (MOC3023) and its anodes (one at a time). The datasheet warns ...
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2 votes
2 answers
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Capacitor in parallel with relay coil backfires on contacts

I've got a smoothing capacitor(2,2uF) C1 in parallel with relay coils inside a fullwave diode bridge. When the circuit is closed through contacts in pre-relay RLY1 it first gives me, almost everytime ...
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Spurious microwave emissions perhaps coming from conducting TRIAC controlling AC power?

I have a TRIAC switch on an 240VAC single phase AC line. There is voltage on the gate as specified, there is a small dead band near zero. I.e. it is conducting as expected. However, I'm picking up ...
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2 votes
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74 views

Can't get my led bulb to turn on using triac and optocoupler

I have made the below circuit but my LED bulb won't turn on, although circuit works fine if replace the led bulb with a small led and ac supply with 5v dc supply. Can someone guide me in a right ...
2 votes
1 answer
1k views

Current zero cross detection circuit off of triac

I need help modifying the circuit below. The assumption in this circuit as it stands is that AC Hot would be common to GND and then MT2 of the triac would go through a light source to AC Neutral. ...
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Choose appropriate opto-isolator for 230 Vac zero-cross detection circuit

I struggle to understand the datasheet for opto-isolators. I am making a 230 Vac circuit with a full-bridge rectifier. What should I look for when choosing an appropriate opto-isolator? I've been ...
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Recommendation for optocoupler for SCR and TRIAC Gate driver

I want to use an SCR having gate current "Igt" = 50mA and a TRIAC with Igt = 50mA to 100mA. I am looking for an optocoupler IC to drive the SCR and TRIAC. I saw MOC3021 but it's "LED ...
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AC element control using TRIAC and optocoupler

I recently came across this circuit and I'm trying to understand it. This is designed to control an AC heater using a T435-600B-TR TRIAC and an MOC3063S optocoupler, connected to an Arduino Uno. From ...
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1 answer
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Triac driving motor with limit switch, needs protection?

I'm trying to drive a bunch of motorized ball valves from an ESP32. These valves have a 230V AC motor with one common wire, and two wires to set direction (open/close). When powered between common and ...
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Uneven Brightness Curve When Using Digital Triac Dimmer on Neon Transformer

I am working on an AC dimmer project using the following circuit: This circuit functions by detecting zero crossings in the AC power input via the LTV814 optocoupler connected to a pull-up input pin ...
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1 answer
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Using a BC3223 triac to drive a load directly

I am looking at the BC3223 which is quoted as a photoelectric thyristor(I assume this is actually a Triac=bidirectional?) and I was wondering if this could be used reliably to drive a resistive 230V ...
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121 views

Snubber circuit for TRIAC

I have built TRIAC circuit below which I got off the internet. Without the snubber circuit works good, but with snubber the TRIAC is always on. I'm using 9v ac just for testing purposes. Can someone ...
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TRIAC not triggering

I am attempting to make a circuit that would allow me to control a standard CFL 13W lamp with a microcontroller. As the lamp would run on AC power, I am making use of the following circuit using a ...
1 vote
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119 views

Using a triac plus an H-bridge to switch DC or AC

I've been working on a controller for inductive loads, and I want the system to be compatible with either DC or AC loads. I've got a 24V to 34V DC boost regulator powering an H-bridge, which is ...
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Does a hybrid DC relay suffer from contact erosion (albeit much less than normal), or is it effectively eliminated?

Given a hybrid DC relay, I've been wondering if contact erosion is occurring (albeit at a slower rate), or if the design eliminates this entirely. (Assume that there is no snubber or other contact ...
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Why is my replacement triac not working?

I have a Hakko FX-888D soldering station which stopped heating the iron. I found out that the triac (which is a BTA06-600b) went bad so I went ahead and replaced it with a BTA12-600bw. It didnt work. ...
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I want to handle the voltage and current spikes from inductive load of 220V AC ceiling fan

I am trying to regulate speed of 220V ceiling fan from Arduino but unable to handle the reverse voltage and current though I am applying the flyback diode across inductive load.
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Triac Driver Datasheet - LED Trigger Current

Looking at the datasheet for MOC30xx (here: http://www.farnell.com/datasheets/1806097.pdf) I see the following note on p4 under the table outlining the respective LED Trigger Currents of the various ...
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TRIAC broke (literally) – why?

I have built a circuit according to Dimming 230V AC with Arduino, with two output channels. The basic principle is: An ATtiny does zero detection via an optocoupler; when AC crosses 0 V, it triggers ...
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BTA16 triac snubber and operation quadrant

I am working on a dimming circuit to be operated by an ESP8266. I have read a lot on this over internet and got a working circuit as well. But myself I am not satisfied with my understanding of ...
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Pulse skip modulation vs Phase cutting for AC inductive loads?

What is preferred and safe mode for controlling power to an Inductive AC load when driven by a Triac? I am using a microcontroller with zero crossing optocoupler to drive the control signal and the ...
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1 vote
2 answers
918 views

Overvoltage protection for AC relay dilemma

I am currently designing a safety-related device that has to open a relay when a certain event occurs. During most of its life, this relay will be closed, and only open if the safety event occurs, ...
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Swap main terminals of zero-crossing triac

The question I have is maybe silly, but I cannot find strictly related info. When designing a mains switch with an optotriac driven triac (or discrete SSR for you), during layout I swapped the ...
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Zero Cross TRIAC circuit for regulator fails on voltage spike

I am using a ZC TRIAC circuit to switch and regulate an electric appliance e.g. a table fan, a electric drill etc. I must confirm that proper SNUBBER circuit is used and everything works fine. I ...
1 vote
1 answer
668 views

Refrigerator relay has a circuit board?

My fridge stopped cooling and kept hearing a click noise every 2-4 minutes. Researching led me to understand the start relay is nothing more than a PTC resistor that cuts the start winding once ...
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triac switch with two power suppllies

I'm building a furnace controller that should hook up in parallel to a home thermostat. The schematic of a thermostat-controlled furnace (omitting non-essential components) is below (Fig.1): I would ...
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249 views

Missing phase 3-quadrant TRIAC-based solid state relay for 3-phase engine

First of all, I'm a simple mechatronics technician student first time posting here, so please don't mind if I say something that seems completely stupid, since I consider myself to be a total newbie ...
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1 vote
1 answer
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BT138+MOC3063. How to calculate resistor power?

I want to use this schematic to control AC with maximum current of 10A The only thing I don't understand is how calculate power of resistors (marked red)? There are lots of such schematics on web, ...
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Firing a triac with PWM

I want to use an ESP32 microcontroller to power a 3600 W load with a triac. Using phase control requires accurate timing and that is nearly impossible with a lot of code already running in the ESP32. ...
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How to make a dimmer that doesn't depend on the load's resistance?

I have an angle grinder which has a maximum power of 950 W. My country provides 220 V as voltage source. It has only one speed, so I want to make a dimmer to control its speed. I used this circuit but ...
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DIAC/TRIAC heater control suddenly switches to max power after a short period

I am trying to build a heating mantle and I decided to use a DIAC/TRIAC pair to control the power, like this: simulate this circuit – Schematic created using CircuitLab I realize that there are ...
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41 views

potential free output signal with AC as input (no mechanical relay)

Here's what I'm trying to do: I have a a bunch of 24vac actuators running of a 24vac XFR. The actuators themselves are controlled by a thermostat. What I need is a isolated 0v signal when any of them ...
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AC Motor Control circuit not working in Proteus

I am new to 555 Timers, Triacs and Proteus and I need help to fix a circuit I have built. The intended function of the circuit is as follows. Two 555 Timers are used to produce variable duty cycle 0-...
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TRIAC protection for general domestic use

I am designing a smart switch for switching 220 - 240 VAC outlets for domestic use at a maximum of 16A. The load could be a washing machine, a toaster, a vacuum cleaner or any general home appliance (...
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63 views

Variable capacitive dropper power supply by means of capacitor switching with TRIAC?

Is it possible to increase the reactance and thus the current of a capacitive power supply by switching an additional capacitor in parallel using a TRIAC (e.g. zero-crossing SSR)? simulate this ...
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Can I use a single snubber circuit for multiple triacs?

I am building a triac sprinkler controller using BT136S-800,118 triacs with a microcontroller for control. The triac driver (MOC3021M) suggests a snubber circuit for an inductive load. I have two ...
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Are SSR Relays suitable for inductive and capacitive loads?

I want to knowingly buy a cheap knockoff SSR Realy from some online sellers. The SSR Relay is advertised as not to be used for inductive or capacitive loads. My application is switching on or off a ...
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3 answers
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TRIAC not triggering in 3rd quadrant but works perfectly in 1st

Good day. I am designing a power control circuit for dimming a 100W bulb using BTA16. In the circuit shown below, when I apply power to the circuit I only receive the positive pulse at the output (of ...
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TRIAC control of inductive load. Current ringing at higher power causes TRIAC to remain on

Here is the circuit I am using to control the motor. L2 is meant to represent the motor and C3 is the capacitor that comes with the motor. It is a single phase AC motor found here. This circuit is ...
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Triac testing out-of-circuit. Are my calculations right?

I've got a "T2550-12G triac" with the following datasheet (I gt = 50mA, I L = 80mA) and I want to test this little fellow with 12V DC (I will alternate the polarity; I don't have an ...
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Triacs other components resistors and capacitor as switch

Found this circuit on the internet but they don't elaborate the much. I understand other components function except for R2, R3, and C1. Can somebody explain them? As for my understanding, R1 - to ...
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SSR for Attiny85 using Optocoupler and Triac

Looking for some advice, I am trying to create an onboard SSR to control the switching of a 120VAC load (heater/lighting), with an operating power of around 1500W max. I chose the following parts and ...
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What are the disadvantages of using NZC Optocoupler as switch

I've bought some MOC3023 to use with a triac for turning some home appliance on/off using an EPS8266. The thing is.. every place that I search says that for on/off the best is a zero crossing detector ...
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Problem with TRIAC-TDA1085c circuit

I have a problem with a TDA1085c circuit. The board has 2 terminal switch with a moving shaft.There are 3 positions. Position 0 (motor stopped) position 1 (right-handed rotation) and position 3 (left-...
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How to protect potentiometer in adjustable soldering iron?

I have an adjustable soldering iron and noticed that recently at some position of the adjustment potentiometer (R3 in the schematic below, this is the potentiometer ...
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Single phase motor does not stop

I have a circuit that controls sine phase motor with three triacs. When I turn it on it works properly, I can regulate the speed, but when I turn it off the motor does not stop, it still spins but not ...
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