Here is datasheet: http://pdf.datasheetcatalog.com/datasheet/fairchild/IRF630B.pdf

From my wall is 220 VAC, but from datasheet I think this MOSFET alow just 200VAC (I am not sure please check).

Should I just connect drain and source to the AC wire?

  • 1
    \$\begingroup\$ Only if you want a small explosion! The 200V rating is absolute maximum 200V DC. 200VAC will peak at 280V DC and -280V DC... \$\endgroup\$ – user_1818839 Jan 15 '16 at 22:51
  • \$\begingroup\$ Which triac is good for 220VAC? \$\endgroup\$ – Vladimir Djukic Jan 15 '16 at 23:02

You cannot use a MOSFET this way. If you want to switch 220VAC then use a relay.

  • \$\begingroup\$ I don't want to use relay because I need dimming... \$\endgroup\$ – Vladimir Djukic Jan 15 '16 at 23:01
  • \$\begingroup\$ Why not buy a dimmer switch? \$\endgroup\$ – Steve G Jan 15 '16 at 23:07
  • \$\begingroup\$ Because I wana create one... I need to know how to control high AC voltage with low DC... \$\endgroup\$ – Vladimir Djukic Jan 15 '16 at 23:09

You can use a MOSFET to control an AC load as shown here: http://tahmidmc.blogspot.com/2012/11/controlling-ac-load-with-mosfet.html

With this scheme, you cannot control an inductive load unless you come up with some way to deal with the inductive kickback. You can also get rid of the rectifier by connecting 2 series MOSFETs as such:

Controlling AC load with 2 MOSFETs

Source: http://forum.allaboutcircuits.com/blog/controlling-an-ac-load-with-a-mosfet.518/


You don't (normally) switch mains with MOSFET. You use a solid-state relay using a triac internally.


simulate this circuit – Schematic created using CircuitLab

Figure 1. Solid state relay.

SSRs come in two flavours - zero-cross and non zero-cross. For your dimming application you need non zero-cross so that you can switch on at any point in the cycle.

Triac controlled waveform

Figure 2. Dimming by phase control.

Your controller circuit will need to detect the zero-crossing point and trigger the triac after the required delay.

Choose a triac to match your line voltage and the required current.

You are working with main voltages. Keep these very separate from your low-voltage circuits. Use good wiring practices.

  • \$\begingroup\$ Nice answer, but But still unclear. I will also need zero cross optoisolator to detect zero crossing on 220VAC, is that true? And if it is, which optoisolator I can use on 220VAC? \$\endgroup\$ – Vladimir Djukic Jan 16 '16 at 12:34
  • 2
    \$\begingroup\$ You are taking on an ambitious project given your current knowledge. Look up mains zero-cross detection circuits. This has been answered hundreds of times on this site. Consider developing your system using a low voltage transformer supply (12 to 50 V AC) where a short circuit with your probes or hands won't be lethal. \$\endgroup\$ – Transistor Jan 16 '16 at 12:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.