satyajeet:
I and others have suggested that you consider the use of a standard off the sheld IR remote control device to control your heater power because it is possibly the simplest to implement and gives you the most
sophisticated result.

If you built the 555 timer solution that you proposed you have to undertake the building of the hand held
device. If you are doing this as a one time type project then you end up with a messy hand held prototype. If you were intending a production type design then you have to tool up to build a whole product which is expensive.

On the other hand for either the home project OR the production design an off the shelf IR remote control
(which are available everywhere either retail or OEM for very easy to take prices) you end up with a nice
clean hand held device that includes battery holder, keypad, and IR emitter. Certainly if it was a retail
universal remote type device it has simple Channel UP/DOWN or Volume UP/DOWN byttons that you can use for the heater controls. And who knows maybe later on you will dream up other ways to control the heater by direct numeric input of the power level.

I suspect that the detection of the IR remote control key codes will take VERY similar software to that which
the funky 555 timer design would have taken. If you take just a short time with Google and/or the search
feature on this forum you can certainly locate multiple free downloadable samples of 8051 code for decoding IR remote control sequences.

So I suggest if you look at the intent of the posts that were made to your thread you can see that you were
being encouraged to think outside the box. I for one always try to encourage the re-use of existing technology wherever possible. I also suspect that your project is a learning vehicle and not a design you did for a production project. If that being the case I certainly suggested the IR remote control concept knowing full well that you would probably learn more from working out software detect of an IR remote control than you would have detecting the two frquency 555 timer contraption.

One last comment. I for one happen to think that you will find that IR remote control, with the intrinsic
"protocol" embedded into its transmission scheme, is far more reliable and less susceptable to false
triggering; Which in the case of a power control type device is a GOOD thing.

Michael Karas