Modulating IR Emitter without 555

[ElectroBeacon]

Hi,

I'm in need of ideas on how to go about this.
I need to modulate IR emitters at various frequencies (30Khz to 50Khz as is the norm, but not for remote control purposes).
I'm told I cannot use 555 timer given the cumbersome setup of resistors and the fluctuation of the voltage dividers with respect to temperature. Cannot also use any micro-processor either.
I do not need to encode any data either. Just need to emit a modulated IR signal.

I am novice in this field and would appreciate any help I can get.

 

[MikeMl]

There is a CMOS chip which will has a built-in inverter which when combined with an external ceramic resonator or crystal, will make a stable oscillator. The chip has an internal binary divider chain which divides down the oscillator freq by powers of two, ie 4096, 8192, ... This one chip, a crystal, and a couple of capacitors will give you a stable frequency of your choice.

Here it is 4060

 

[ElectroBeacon]

Thanks! I'll look into that.

Also,
I don't know if you can entertain my question further but, what would you make of a PIC 08M doing this dirty work?
It would be a single chip with no crystal required.

Is this a good idea?

 

[MikeMl]

The internal oscillator inside a 12F683 is accurate to about +-2%, which is only slightly better than the 555. If you want sub 1% accuracy, then you will have to use a crystal, either with a PIC or with the 4060...

 

[Boncuk]

Experiments prove that IR-receivers are not as narrow banded as assumed.

A 40KHz receiver works from 38KHz to 42KHz without problems.

All you have to take care of is emitting the carrier signal within the time limits as posted in the data sheet which are bursts of 600µs with the same pause duration.

Longer bursts reduce the receiver sensitivity because of the built in AGC.

Boncuk

 

[crutschow]

I do not need to encode any data either. Just need to emit a modulated IR signal.

Unfortunately you triggered my nit picker mode.

If you are not encoding data then you are not modulating the IR emitter. You are just generating a steady carrier signal. You modulate the carrier to transmit data.

 

[Boncuk]

Here is a circuit which should work accurately.

You might be able to increase the crystal frequency slightly resulting in a higher carrier frequency and shorter bursts.

Boncuk