A basic TRIAC 120V circuit

This is the schematic diagram of the circuit used in my other video of the basic TRIAC circuit where 120V load is switched on or off by the signal at the opto-isolator IC.

For my actuall circuit, I used:

5Vdc to signal the opto-isolator chip
R1 - 220 ohms (set for the 5Vdc to limit to the current needed, if you use another voltage in, then you should adjust this value of the resistor, higher for higher voltages).
R2 - 270 ohms (sets the current for the switching of the triac on/off - check the literature that comes with your triac for a recomended value. This basically allows and limits some of the ac current tapped from the 120vac line to be used for switching the triac on and off.).

NC = no connection

The dot in the upper left corner of the MOC3010, and most other IC chip/packages indicates Pin 1, and the other pins are increasingly numbered counter-clockwise.


I also had a mylar capacitor (optional, must test) that is supposed to reduce noise for motor type circuits or fast constant switching. A good way to see if a capacitor is needed is to test the circuit with an oscilloscope and look for noise.

The Opto-Isolator (here on a chip/IC package) is used to isolate one circuit from another. For the circuit in the video, it isolates a DC circuit, here 5Vdc, from dangerous high voltage and current from the 120V wall socket/plug receptical.

I show a ground in the video, and thats for the 5Vdc supply circuit for the Opto-Isolator circuit. You may or may not have problems if this is connected to the "ground" of the 120VAC system. It is best to avoid grounding to that due possible "different ground potentials" or "stray voltages".

Use a Triac of sufficient or higher power rating than necessary for the load. Basically how much current it will need to pass; will it be capable with a few volts ac "lost or dropped" across the triacs terminals. You will also have to look on the packaging of the triac to find the pinouts for it, specifically, which one is the gate or control terminal that is used to switch it on. Check for the required gate currents (max. and on/off state).

Please see my playlist with some related videos.

Here is a premade triac circuit you can buy for cheap and it has a heat sink also: http://www.ereshop.com/index.php?main_page=product_info&products_id=198

Category:

Science & Technology

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• triac