A TRIAC is an 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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Mixing AC and DC power in a circuit

This is likely a noob question, apologies if the answer is obvious. I'm trying to control a furnace using a 3.3V microcontroller. The furnace operates by connecting a common 21V AC "hot" line to one ...
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776 views

How do I select an optoisolator to both provide zero crossing to a uC and controll a triac?

This application note states that zero crossing detection can be achieved in an AVR with just a couple of resistors. However, it forgoes galvanic isolation and this is not acceptable for me. I would ...
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344 views

Triac connection for my project

TRIAC can be connected in series of 230 V. Shall I use mutivibrator for giving gate triggering this TRIAC? Also, how can I turn off this triggering by giving an external signal?
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Validate Triac circuit

I'm designing a device to switch a heating device driven by mains power. I've done quite a lot of research and realize there's a lot of information out there but as i'm dealing with potentially deadly ...
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336 views

Help me understand triac maximum current and when to use a heatsink

Datasheets list , under Absolute Maximum Ratings RMS on-state current = 16 A, for example. 1)How do I know if this is free air maximum current or properly heatsinked? 2)How can two triacs in ...
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285 views

How do I limit the maximum power, delivered to a heater, through a triac?

I am using the following circuit to turn ON/OFF a heater. Works like a charm. However, I would like to limit the maximum power delivered to the heater. The reasons for this are: the heater is a ...
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Choose TRIAC snubber resistor for multi-purpose switching

I'm designing a circuit to switch a 240V AC load and haven't done a lot with AC power control before. I'm planning to use a Fairchild MC3043-M optically coupled TRIAC driver along with a BT138-600 NXP ...
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2answers
455 views

Can electronics be damaged by plugging into a lighting dimmer circuit?

So my stupid room is wired so all of the lower receptacles are driven from the electronic wall dimmer. Stupid me plugged in my brand spanking new brother laser printer into the lower receptacle. It ...
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372 views

Why do they add a TRIAC after an MCP3020 optocoupler?

I have a relay circuit (I use it instead of a relay) that uses a MCP3020, which I think does the physical separation of the two circuits (it's a LED and a photo cell inside a chip) and a BTA08 TRIAC. ...
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228 views

Triac datasheet values

I have a Triac that I want to use to control low voltage (~16 V) AC. The data sheet is found here. It specifies that the peak gate voltage is 5 V with a peak current rating of 2 A (which seems quite ...
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250 views

Calculating max wattage load for opto-triac

Are there any guidelines? Do the guidelines differ depending on resistive/inductive/reactive loads? For example, the Vishay VO2223A is rated up to 1A. At 110V it seems it can switch up to a 1 A x ...
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What is the holding current on a triac?

What does the Holding Current characteristic mean on a triac? What does this mean for switching loads less than the Holding Current? For example the Sharp S108T02 has a max 50 mA Holding Current.
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is there any spice model for optoisolator triac driver circuit?

I have to design a phase angle dimmer using a triac. For this, I have read How do I drive a TRIAC from a microcontroller (for low voltages)? This forum really turns out to give me a good solution ...
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What does a TRIAC do?

I'm hoping someone on here can give me a simple explanation of what a TRIAC does. To give this request some context, I'm an embedded systems software engineer, so I interface with hardware, but I ...
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1answer
2k views

simple triac current limiter

I have a 20 liter electric storage water heater which has a 230V AC, 2KW electric heating element. The heating element is failing frequently primarily due to bad quality of water inducing faster ...
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TRIAC dimmer, circuit design help (resistive load)

Okay guys, I've been tasked with making a light-dimming control system for a 240V heat lamp dissipating around 250W. I need to adjust the heat output on the lamp by control from a microprocessor. I'm ...
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308 views

Sometimes the triac actuator doesn't turn off

The TRIAC actuator of a DC motor through a bridge rectifier. I activate a DC motor from the mains through a TRIAC (BTA16) in series with a 10 Ohms resistor for the inrush current limitation, in ...
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853 views

Multiple motor speed control with a single triac

I have a requirement where I have to control the speed of 10 motors. The motors are 230V AC single phase motors. The speed of the motors need to be increased or decreased using a electronic controller ...
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2answers
343 views

I need help matching parts

Link1: http://ww1.microchip.com/downloads/en/appnotes/00954A.pdf Link2: http://arduino.cc/playground/Code/ACPhaseControl Simple version: I want to use a picMicro 5v microcontroller combined with the ...
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384 views

Do multi-channel opto-triacs with common pins exist?

I am designing a circuit with many (4-128) copies of the same component. It's a 4-pin opto-isolator with opto-triac output. I am aware that the pin spacing and package width can't be much less in ...
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660 views

Questions regarding Triac Driver circuit

Sparkfun's EL Escudo Dos breakout board uses this circuit for an EL wire driver channel, with R2 = R3 = 330. I was wondering what the function of R2 and R3 is? Are they required? What would happen ...
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Digital Dimmer With Microcontroller

I want to build a digital dimmer for resistive Loads. I have found this circuit for that: The input voltage is 220VAC 50Hz. The red box in the picture is for ...
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TRIAC Dimming for LED Buck controller circuits

How can you create a solution for a LED constant current driver that can handle TRIAC dimming? Can you convert the waveform into a PWM and is there a simple solution?
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How do I get proportional 240V AC output from an Arduino-based PID controller to “dim” a rice cooker for a Sous-Vide project?

I'm making a PID controller for Sous-Vide, using an Arduino. I'm trying to decide how to control the output. Using an SSR as an on-off switch on 240V AC will probably give me the result I'm looking ...
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2answers
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How do I drive a TRIAC from a microcontroller (for low voltages)?

As a followup to this question, I would like to figure out how exactly one might go about driving a TRIAC from a microcontroller (for low-voltage applications, such as 24VAC). Imagine a scenario where ...
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What would a professional use to switch sprinkler solenoids?

As evidenced by several previous questions of mine, I'm working a project to design a sprinkler controller. This involves driving one of 16 solenoids (well, probably only one at a time...) based on a ...
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Trouble with triac driven dimmer circuit

I have a dimmer circuit that produces the following wave forms. Red: Triac Gate Signal Yellow: 120v 60Hz AC Wave (not triac output) I would assume that given this signal, the triac should flip on ...
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Troubleshooting a Triac Motor Control Circuit

I have a Xytronic 988 soldering station. It has a regular soldering iron on the left and an iron with a vacuum pump on the right. It has served me well over the years and one day when I was swapping ...
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Arduino triggering a TRIAC for EL Wire, no optoisolator

I have been researching and looking up how to control EL wire online and I will be using the same layout as the EL Escudo shield from Sparkfun but just for one strand. Basically: Arduino (+ resistor) ...
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Optotriac doesn't turn off

I'm using an opto triac, specifically the MOC3041, with a zero crossing circuit to switch the Tx pinout on an RS-232 interface. I have no problems turning it on, but after I unload the input (no ...
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Modding a dremel to accept 230volts

I purchased a Dremel tool from the United States and using it in India. As always, the trouble is with the power inputs. A step down converter is simply too expensive for those power ratings (>2 Amps ...
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Looking for and SMD optocoupled TRIAC

I'm looking for a SMD optocoupled TRIAC part for driving EL Wire (110VAC, 1000Hz, low current non-resistive load) with an ATTiny85 pin (TTL, 20mA max) running at 3.3V. The previous design used the ...
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SSR vs optocoupler with TRIAC output

I've designed (and mostly implemented, now) a system for turning on and off 24VAC solenoids. In order to achieve this, I used optocouplers with TRIAC output (Sharp PR26MF1xNSZ series). The datasheet ...
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When should I fire the TRIAC's gate when controlling an inductive load (AC motor)?

I'm using a combination of opto-triac + TRIAC to control a 230V AC motor with a microcontroller. For detecting the zero-crossing of the voltage I'm using another optocoupler. I know that the AC ...
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975 views

What does 'random phase' means in a triac driver?

I'm using this triac driver to control a triac. In its datasheet it says 'provide random phase control of high current triacs [...]'. What does that mean? It doesn't have zero-crossing detection?
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Is a protection diode needed on a TRIAC optocoupler and what for?

Please refer to page nine of the Sharp S108T01 / S108T02 datasheet: Is this diode needed - why/why not? How do I choose the correct diode, if yes? UPDATE: Thank you all for your educational ...
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Difference between Zero-Crossing Optoisolator and Regular Optoisolator

I am trying to find any documentation on what the purpose is of a Zero-Crossing Circuit TRIAC Optoisolator. The datasheets don't explain the concept well enough. If you do answer, please include ...
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How to calculate minimum gate current and voltage of a TRIAC

I want to use this TRIAC: http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_Thyristor_Lxx06xx_Qxx06xx_Qxx06xHx.pdf but only the maximum Igt and Vgt are given (25mA and 1.3V). How much ...
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Choosing components for a triac's snubber

I'm interfacing the BT139-600 TRIAC with this MOC3051-M Opto-triac. I want to build a snubber circuit for the TRIAC as shown in the MOC3051M opto-triac's datasheet @ page 8, figure 12. The load ...
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474 views

TRIAC heatsinking

I am thinking of using a BTA04 type TRIAC in a project to switch a power hungry mains appliance, which could draw up to 12A. I can't find a forward voltage anywhere in the datasheet, or an on-state ...
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541 views

Triac Turn-on Stress Calculation

When snubbing a triac, one of the concerns is minimizing turn-on stress as your snubber triac discharges across the newly-shorted terminals of the triac. This paper says that the main concern is ...
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Sanity-check on snubber design

I keep frying resistors in the following optocoupler and triac snubber circuit, and I'm not sure whether to attribute this to bad design, or to faulty components. There are no observable sparks at ...
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1answer
1k views

Using a triac to switch on/off a single phase AC motor

I want to use a triac controlled by a suitable optoisolator such as a MOC3020 to switch a single phase AC motor on and off, like the ones you'd find in a typical desk fan or a blender or similar. I ...
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2answers
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Why Snub an Optoisolator?

I am using an optocoupler and a power triac to switch 120VAC supply to an ~108 watt fan. The datasheet for my optocoupler requires me to snub the optocoupler output when I'm switching an inductive ...
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Current limiting at mains voltage

I am driving a BTB16-600BW triac using a MOC3052 exactly as suggested in the MOC3052 datasheet: The current into the power triac gate is limited using the highlighted resistor. My triac requires at ...
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How to use a phototriac coupler to trigger the main triac?

I have in my box of parts a phototriac coupler, namely a Sharp PC3SD21NTZ (datasheet), which is a zero cross type. I don't know how to use it, but I've been meaning to learn for a while. This part is ...
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What's the difference between 3 and 4 quadrant triacs?

I'm looking at triac datasheets, in particular this datasheet for BTA16 series triac. The "electrical characteristics" section is split into two parts: snubberless/logic level (3 quadrants) and ...
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Are TRIACs symmetrical?

When debugging a circuit using a micro-controller and triac to control AC current I ran into an issue (the triac wouldn't switch off) that was only resolved by flipping the polarity of the triac. The ...
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716 views

Microcontroller + Triac without an optoisolator

I have a project that needs to be in use on saturday (afterwards I'll be able to complete it properly) and my optoisolators haven't come in yet. I'm using an arduino to switch mains power (on/off) ...
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Controlling water pump speed

How can you control the speed of an AC water pump? In particular this one. My guess is that PWM won't work on an AC motor? I've heard that controlling the voltage will change it's speed...is this ...