Is This the Ideal Solution for Switching 120V 3A AC Lines?

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In summary, the conversation discusses a proposed solution for switching 120V 3A AC lines. It involves using a TRIAC and an optoisolator, which have specific parameters and ratings. The design also includes a diode current limiting resistor and a gate current limiting resistor. The use of snubbers is suggested for potential inductive loads.
  • #1
jordanstreet
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Hey guys I'd like to run a few things by you guys. I will be switching 120V 3A AC lines and am considering the following solution. I do not need synchronous switching by the way.

This TRIAC
http://www.digikey.com/product-detail/en/BT134-600E,127/568-5015-5-ND/1155119
The datasheet says its rated up to 4A and has a max gate current of 2A.

This Optoisolator
http://www.digikey.com/product-detail/en/MOC3021/160-1374-5-ND/385844
The datasheet lists the trigger current at about 15mA so I'll go with 20mA to be safe, and has a peak surge current of 1A.

I will be triggering the optoisolator with 3.3V signals.

So with these parameters I've gone with
(3.3V - 1.3V) / .02A = 100 Ohms for the diode current limiting resistor on the optoisolator input.
170Vpk / .95A ~= 180 Ohms for the gate current limiting resistor on the triac

I will be using this schematic
http://www.simpleio.com/design/triacout/images/TriacOut4Sch_L.gif

Does this all sound good?
 
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  • #2
To me the design looks good. The only thing I can think of is that if the load is at all inductive, you should have snubbers on the main triacs.
 

Related to Is This the Ideal Solution for Switching 120V 3A AC Lines?

1. What is an optoisolator and how does it work?

An optoisolator is a device that uses light to transmit signals between two electrically isolated circuits. It typically consists of an LED on one side, which emits light when a current is applied, and a phototransistor on the other side, which detects the light and converts it into an electrical signal. This allows for isolation between the input and output circuits, providing protection against voltage surges and noise.

2. What is a triac and what is its role in an optoisolator circuit?

A triac is a type of semiconductor device that can control the flow of alternating current (AC) by acting as a switch. In an optoisolator circuit, the triac is connected to the output side of the optoisolator and is used to switch the AC power on and off based on the input signal received from the optoisolator. This allows for the isolation of the input signal from the high voltage AC power, providing safety and protection for the connected devices.

3. How is an optoisolator + triac circuit used in electronic devices?

An optoisolator + triac circuit is commonly used in electronic devices to provide isolation between low voltage control signals and high voltage AC power. It can be used to control the switching of AC loads, such as lights or motors, through a low voltage control signal, making it useful in applications such as home automation, motor control, and lighting control.

4. What are the advantages of using an optoisolator + triac circuit?

One of the main advantages of using an optoisolator + triac circuit is the added safety and protection it provides by isolating the input and output circuits. This can prevent damage to connected devices and ensure the safety of users. Additionally, optoisolator + triac circuits are compact, cost-effective, and have a long lifespan, making them a popular choice for electronic devices.

5. What are some common issues that can occur in an optoisolator + triac circuit?

Some common issues that can occur in an optoisolator + triac circuit include false triggering due to noise or voltage spikes, overheating of the triac, and failure of the optoisolator or triac component. These issues can be mitigated by using proper circuit design, selecting high-quality components, and implementing appropriate protection measures such as snubber circuits. Regular maintenance and testing can also help identify and prevent potential issues in the circuit.

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