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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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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2 answers
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Cheapest solid-state way to turn a 240 VAC, 15 W resistive load on/off

I need to be able to pulse a 240 VAC, 15 W resistive load on and back off. I need it to turn on only for a single line cycle, then it will remain off for at least 60 seconds, so perhaps the components ...
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FODM3083 + Q6016NH2 switching 230V and 110V up to 16A

I have to be able to switch on and off a heater of 1500W total powered at 110AC and 230AC but I have some additional doubts. First doubt is about the proposed FODM design for hot-line switch (https://...
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What is the importance of R1 connected in this circuit?

What is the importance of R1 in this circuit? What would happen if I removed R1 and kept VR1?
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Triac voltage and delay time relation

I am trying to find a formula for voltage and delay time, but I don't know if there is a relation between delay time and voltage. For example if I need 100V, I should use X ms delay time. I found this ...
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What is a "snubberless" TRIAC? How does it compare to a standard device?

I was searching for a TRIAC to be used as part of a pre-charge circuit for large DC link capacitors, and found one (T435T-600FP) that is described as "snubberless". An on-line search did not ...
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Help me to simulate this DIAC-TRIAC circuit

I was given to simulate the circuit in the lab. The picture of the circuit from the manual is given below. I made the same circuit in LTspice. The problem is that I do not get the expected output as ...
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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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Using AC solenoids with rectified DC [closed]

If one wanted to avoid triac opto-couplers for AC solenoids, would it be OK to rectify the AC, without filter capacitance or regulation, then drive from a transistor opto-coupler? I would think the ...
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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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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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BT136 TRIAC waveform

I am using a TRIAC to switch an AC signal (a typical example is shown in question Triac Switch Circuit using MOC3021 and BT136). When a BT136 TRIAC is used to switch a pure sinewave signal, I want to ...
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ESP MCU, directly drive BT136

I have questions about driving a BT136 TRIAC using a port of ESP8266-NodeMCU-12E. I have tested BT136: if you apply 1.2V from a AA cell between Gate and T2, this result in T1 and T2 conducting for ...
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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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How do I calculate the potentiometer value for the controlling of Alpha angle of a phase control IC? [closed]

The datasheet suggests to use a 10Kohm pot to control the Alpha angle, however no matter how much I try I can't control it. I used 1Mohm pot instead and now I can control it more, but still with very ...
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2 answers
206 views

Transistor keeps failing in a capacitive dropper circuit with TRIAC

I'm trying to build an automatic night light circuit based on some designs I found online. Here's the circuit I built: The problem is that the transistor BC327 ...
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2 answers
115 views

Why TRIAC is not triggering?

I'm trying to trigger a TRIAC BTA16-800 using an MCO3021 optocoupler. I have a two-channel power supply, in one of them I'm pulsing the optocoupler at 120 Hz and the other channel is configured as a ...
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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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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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Is it a good idea to drive 24VAC solenoid valves with triacs?

I want to build irrigation system for my garden. Most solenoid valves for that purpose work at 24VAC. I'm wondering if I could use triacs to drive them. They are cheap and small (in comparison with ...
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Most accurate way to measure universal (AC) motor current?

I'm designing a control circuit for a universal (AC) motor (single phase, brushed). I've simulated the control circuit and it works as expected. Circuit below is controlled by a STM32G4 series ...
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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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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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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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Snubber Filter Circuit Not Working Triac Dimmer

Hi I am working on a project using a triac to do phase control dimming of 120V ac powered devices. I recently translated my project from perfboard to SMT using an SMT fabrication service. The project ...
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3 answers
102 views

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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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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1 answer
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Drive TRIAC with photo TRIAC

Can anyone tell me in the attached circuit why use always-on optotriac to drive TRIAC? What is the purpose of using phototriac in the circuit? This circuit is used to control the speed of ac motor and ...
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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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Make a string of Christmas lights slowly brighten and dim

OK, here's my Christmas light project and I didn't see this one asked yet on StackExchange. What I am trying to achieve: have a single string of incandescent Christmas lights slowly dim and brighten ...
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2 answers
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Control a 120 Vac relay with a triac. Good idea?

I'm beginning the design of a light control system based on a microcontroller. This is to activate the lights, what is usually used are continuous voltage relays, in ranges of 5, 12 or up to 24 VDC. ...
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1 answer
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I don't understand dimming on 3 quadrant TRIACs

Can someone help me understand how dimming works on 3-quadrant triacs? I understand they are great because they have higher reliability and don't need snubbers. What I don't understand is how 0-100% ...
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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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TRIAC motor control. Why is my resistor burning?

I have designed a digital motor controller using the following circuit. One of my resistors keeps overheating. There is a zero-cross detector elsewhere in the circuit used to time the firing of the ...
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1 answer
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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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Phase cut dimming driver for panel lights having occasional flick

I am designing a phase-cut dimming driver for Incandescent bulbs as well as LED panel lights with dimmable drivers. Using a BTA24 Triac and VOT8121AB Optocoupler driven by my MCU. For zero-cross ...
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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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In the PCB design, how should the a2 terminal island of a triac in the 252 sheath be?

For the A2 terminal of the triac in pcb design, I want to use both the front and back surfaces of the pcb. How should the vias be between the back and front surface?(actually zone areas in surfaces)I ...
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Does the PWM generated by the 555 make sense in this circuit?

This circuit I doubt very much that it works with the led lamp since it is not a linear load. But assuming that I replace it with an incandescent lamp, with the first logical 0 to 1 edge of the PWM ...
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How to measure AC voltage using non-linear opto-couplers?

I am designing a TRIAC LED dimmer circuit. Depending on the AC voltage applied, I control the gate trigger angle for the TRIAC to reduce/limit the current at 15 amperes to the load. Gate trigger ...
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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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1 answer
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Diagnosing dead soldering-iron

My soldering iron was working fine for a few years. One day, I used it and it worked fine again, then I unplugged it then tried to use it again a couple of hours later but it wouldn't heat up. I took ...
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Thermal protection of triac in floor heating controller

Hello there fellow engineers. I'm in the middle of design controller for floor heating. The idea is to have a triac based design with zero detection circuit, for each control point (each heating cable ...
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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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How to calculate wattage for gate/base protection resistor for a TRIAC

I am working on a project using the following circuit, which uses an Arduino type microcontroller to do pulse width dimming of AC circuitry using a TRIAC: I am wondering what wattage I should choose ...
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TRIAC BT136 as DIAC BD3 conversion both have MT1 and MT2

A DIAC looks like a diode. A TRIAC looks like transistor. I have project that uses a DB3 and a BT136, but the BD3 is not available in the local market. Can I cut the gate terminal off of a BT136 to ...
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