120/240ac Triac Dimmer

[cjdelphi]

An arduino controlled triac caught my attention on fb, after reading about it occurred to me that a mc controlled triac controlled dimmers are expensive vs a triac/diac and a potentiometer to give dimming control

Then i realized this is only of any use for old incandescent bulbs, theactrics essentially fluro and 120/240ac led bulbs are ruled out, but why do i say 240vac led bulbs? Well they can be, but why? They operate on low dc voltage, so why waste money on an optocoupler, measuring the zero crossing then varying it's delay from that point to give a dimming effect..

Ok you say but what if all they have is 240ac in a room, ok then sure but it still has to convert 110/240ac to 3 - 12v either a transformer or capacitor fed supply at which point, if the goal is to dim a set of leds then why control the 240v side? Would it be not easier to open up the led bulb, extract the led board and pwm via a mosfet and get complete control over it!

Rant over but i hope you got the jist of it

http://m.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/

 

[AnalogKid]

"open up the led bulb," - No. These things usually are glued or ultrasonically welded, so opening up is a destructive process. It also *instantly* invalidates all safety certifications. Dimming is done on the AC side because that is where is it the most convenient, safest, and lowest cost for the vast majority of applications. The Edison-base light bulb is almost 100 years old, and there is a 60+ year infrastructure is in place for TRIAC dimming. Even though there are a ton of engineering reasons for doing it differently, we're stuck with it until the world shifts new home construction to low voltage lighting circuits.

Change has happened - there are TRIAC-dimmable fluorescent lamps, and many dimmable LED lamps.

ak

 

[cjdelphi]

Most led 240ac bulbs [edit i said usb, i meant 240ac ]lights people buy are not like that at all they are all cap driven, warranty means nothing to a lot of people when the "led 240ac bulb" costs you more in postage to send back to china, in these instances dissasembly is safer

 

[AnalogKid]

120/240ac led bulbs are ruled out,
Rant over but i hope you got the jist of it

Barely. Why are LED bulbs ruled out?

 

[cjdelphi]

Because cheap 240ac led bulbs are safer to run on low voltage by removing the led board and hooking up low voltage to control the leds to make it dim, rather than control 240v to make it dim ..

Just look at the link i posted, that's somehow safer ?

 

[AnalogKid]

Would it be not easier to open up the led bulb, extract the led board and pwm via a mosfet and get complete control over it!

No.

Not in this or any other known universe.

Rewiring my entire house, and cutting open up and gutting all of my light bulbs so they work only with a custom-made lamp dimmer that does not fit in a wall box, and coming up with an adapter for every lamp socket in the house or replacing all of them with something else - that is a ***huge*** "waste of money", and nowhere near "easier". And do you really think that a custom circuit with a PWM controller and a power MOSFET is going to cost less? Even without a pc board or perf board or any labor at all, the bare parts list will cost more than a purchased TRIAC dimmer, and it absolutely will when you figure in the cost of a whole-house AC/DC power supply.

And did I mention the wiring? Ah, yes, see above.

ak

 

[cjdelphi]

What?

I posted a link to a mc controlled 240vac dimmer circuit, are you claiming it's easier to build a mc dimmer (live mains voltage on the pcb)for every led "bulb" in your house???

That's somehow safer?

 

[cjdelphi]

If you read my post correctly you'd see my reasons for NOT using the arduino dimmer circuit

I stated that a traditional TRIAC / diac / pot combo is fine to use, even though as you said led bulbs can now dim probably using some method, either before or after stepping down the voltage

This was about a mc 240ac circuit being useless not to mention more dangerous than a traditional triac circuits

 

[AnalogKid]

Hmmm...we may be mis-communicating here. Scrambling now, will re-read later.

ak