Using MOSFETs as a 110VAC 'dimmer', of sorts?

[schweini]

Hi!

I am new to this fun world of electronics, so please excuse any incredibly stupid things I come up with!

I was just switching my first couple of light bulbs with a relay, and now i'd like to dimm them, just for the fun of it. I did find something online using triacs, but it seemd a bit complex, for starters. Thus, another idea popped into my mind:

Could I use two MOSFETs (as far as I could see, there seem to be a couple that can handle 110V) for this? I'd build a basic rectifier bridge with them, and if i switch one MOSFET on, the light bulb should only become powered half of the time of the AC frequency, right? So it should roughly be half as bright?
When I switch the second MOSFET on, then the full sine wave of the AC should reach the light bulb, and it should shine at full capacity?

If this is somehow not complete nonsense, what would be a cheap MOSFET that could accomplish this? Would a heatsink be obligatory?

Thanks,

M.

 

[Boncuk]

Hi schweini,

instead of using MosFet transistors (which are limited in source - drain voltage) I suggest to check out insulated gate transistors (IGBTs).

You might use them to dim your lights using 110VAC.

Boncuk

 

[MikeMl]

Bad idea to use FETs (or IGBTs) for 120VAC lamp dimming unless you use Pulse Width Modulation (ney Phase Control) so that the FET is fully on or fully off. Otherwise you will need to mount the FET on a HUGE HeatSink. Use an SCR or a TRIAC instead.

 

[crutschow]

You are making it too complicated. If you just want half-wave and full-wave power then all you need is a rectifier in series with the load. A switch across the diode will allow full-wave or half-wave as desired.

 

[Ubergeek63]

Bad idea to use FETs (or IGBTs) for 120VAC lamp dimming unless you use Pulse Width Modulation (ney Phase Control) so that the FET is fully on or fully off. Otherwise you will need to mount the FET on a HUGE HeatSink. Use an SCR or a TRIAC instead.

WHAT?!? phase control IS a primitive form of PWM and there are PLENTY of affordable FETs available now to do it. the would generally be MORE efficient than TRIACs or IGBTs since at low currents they can get very low voltage drops.

 

[Mr RB]

To get half voltage and full voltage as he asked he just needs one diode, and a switch in parallel with that diode.

 

[MikeMl]

WHAT?!? phase control IS a primitive form of PWM..

IS what I said!

 

[Ubergeek63]

IS what I said!

sorry, it did not seem that way to me. seemed like a distinction instead of a comparison