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.

learn more… | top users | synonyms

2
votes
3answers
1k views

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.
0
votes
1answer
1k views

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 ...
14
votes
3answers
3k views

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 ...
2
votes
1answer
1k 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 ...
6
votes
3answers
4k views

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 ...
4
votes
1answer
299 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 ...
4
votes
3answers
807 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 ...
4
votes
2answers
335 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 ...
1
vote
1answer
341 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 ...
2
votes
2answers
582 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 ...
9
votes
4answers
13k views

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 ...
3
votes
3answers
299 views

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?
5
votes
6answers
6k views

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 ...
5
votes
2answers
11k views

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 ...
5
votes
5answers
3k views

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 ...
3
votes
3answers
4k views

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 ...
5
votes
1answer
1k views

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 ...
2
votes
1answer
2k views

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) ...
1
vote
4answers
910 views

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 ...
3
votes
1answer
1k views

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 ...
2
votes
2answers
465 views

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 ...
4
votes
3answers
3k views

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 ...
7
votes
3answers
7k views

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 ...
1
vote
2answers
896 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?
5
votes
2answers
1k views

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 ...
4
votes
2answers
2k views

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 ...
1
vote
2answers
3k views

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 ...
1
vote
1answer
4k views

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 ...
1
vote
2answers
460 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 ...
6
votes
1answer
515 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 ...
4
votes
4answers
1k views

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 ...
4
votes
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 ...
10
votes
2answers
1k views

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 ...
6
votes
1answer
2k views

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 ...
2
votes
1answer
3k views

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 ...
10
votes
2answers
1k views

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 ...
6
votes
3answers
757 views

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 ...
1
vote
2answers
690 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) ...
3
votes
4answers
3k views

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 ...
19
votes
4answers
9k views

Triac versus Relay

What are the scenarios where Triacs can not replace a relay or vice-versa?
11
votes
3answers
2k views

Controlling High Voltage device with Arduino

I want to control lava lamps using Arduino. I think it shouldn't be hard project, but I have no experience with hardware projects so I'm not sure witch design will feet best for me. I consider using ...