A SIMPLE (not for me) Question about 4n25 Optoisolator!!!!

[DragonSisiw]

I am designing a circuit to control a 10W light bulb plugged in directly to 220V mains.
I am going to use logic gates for my control so I will have to isolate my control circuit (with 6VDC input) from the lamp (with 220VAC).

My professor ( a newbie professor, though i respect him ) said I can use 4N25 but after reviewing its datasheet, I highly doubt it will work.

Datasheets say the the maximum collector current is 100mA,
If P=IV then I=P/V   then in my case  I = 10W/220V  , the current is 45mA (am i correct to assume this is OK?)

BUT the problem is with the voltage
Datasheets say that the collector-emitter Breakdown Voltage is 70V and 220V is too much 

Any suggestions on how can i make this circuit work?
Or rather can you suggest other optoisolator that can withstand a direct 220VAC connection??

Thanks!!

[Rerouter]

Opto-triac, for AC stuff they are very commonly

[tggzzz]

You are correct: the optoisolator cannot directly switch the lamp.

You would use the optoisolator output to control a high current, high voltage switch. Note that the initial current transient can be much higher than 45mA (e.g. in the case of a cold incandescant bulb's filament), and there might be high voltage transients due to sudden current changes in inductors.

There are many examples on the web of how to do this - learning how to find such things is an essential part of engineering. (You have already done the first part: noticing that a 4N24 isn't sufficient)

[Simon]

opto isolators are rarely used to drive loads unless your talking a small relay or LED's, usually their job is to provide as their name suggests isolation between two sections of a circuit. You will have a low voltage and a high voltage circuit, the two will not electrically be connected but will be coupled and communicate with the optoisolator.

[DragonSisiw]

Thank you very much for clearing those out for me!! 

Actually I already have the MOC3011 optotriac in mind and a circuit to drive my 10W light bulb, but I guess I was just being stubborn on using 4N25 because I have it ready,

Guess I have to travel again to get me an optotriac or an AC relay in that case. 

Your help is greatly appreciated.



(This is a nice blog anyway  )