for Anand Dhuru

Hi Dave, thank you very much for the pointer; I found it very informative and can certainly take some pointers from the math they have explained.

BTW, some folks at the piclist also directed me to an app. note on the X10 site that essentially uses a 16F877A as an X10 controller. Of special interest was the way they had connected to the mains *without* a transformer. I wonder if the coupling would be as effecient?

You might be surprised by my reluctance in using a transformer, but thats basically because trasnformers available here are kind of generic; they do not have any markings, nor brand mentioned. One just goes by the color of the slug, and hope for the best. In my case, I've found the one with the white slug (2nd stage IFT?) seems to work the best.

Again, thanks.

Anand

Anand,

If you look at p12 of the TDA5051A app note, it details coupling to 230V mains with an LC bandpass filter (no transformer).

I've also seen AN236 (?) from Microchip which I think is the one you're referring to. I've tried that coupling on a breadboard using a PIC12F683 and found it difficult to get much signal to the powerline.

If you plan a serial interface to the PIC you'll need isolation.

I recalled another app note that uses the same Toko T1002N transformer but with a transistor line amplifier. It's for the ST7537 which has been replaced by the ST7538. These are FSK modems but I think you're mostly interested in the line coupling.

Which PIC are you plann>Hi Dave, thank you very much for the pointer; I found it very

Anand,

There is another >You might be surprised by my reluctance in using a transformer, but

Thanks for the valuable pointers again, Dave.

I now have a collection of mains front end circuits, and am tring to decide on one (or a combination with ideas borrowed from some).

I have one query, Dave; correct me if I am wrong.

Assume that only an injector is required (reception not required).

You have X10 data coming out of the PIC. *The transformer generates the

120 KHz carrier*, and PIC data modulates this so one ends up with 120 KHz modulated X10 data coupled by the transformer into the mains.

Am I right so far? or is it that the data coming out of the PIC is already pre-modulated by the PIC at 120KHz (regardless of whether a direct or a transformer coupling is used)? I know the latter happens with the AN236 design.

If my earlier assumption is correct, then in transformerless designs one would have to also generate the 120 KHz within the PIC (as in AN236), or externally using an oscillator to modulate the X10 data.

You mentioned you did not get a decent transfer using the circuit in app. note AN236. This could perhaps be on account of the front end using 5 volts, as against the 18 - 30 volts hat X10 uses?

I use a 16F877 when I connect using a PL513; I prefer to use a bootloader as far as possible. But when I'm experimenting with my own interface, I prefer to use a 16F628, as I wouldnt like to share any line with the PC with either a bootloader or an ICSP cable.

Regards,

Anand

Anand,

In some X-10 designs (e.g. TW523, CM15A) they use one of the windings of a transformer as the inductor in an oscillator tank circuit and modulate that from the PIC (or other controller). In others (e.g. RR501) they generate the modulated 120kHz with the PIC. In both, they then use a tuned transformer to couple the signal to the powerline. I would generate the 120kHz with the PIC (easier than designing a stable oscillator and easier to tune). Even the

8-pin 12F683 has hardware PWM you can use for this. One of the app notes on Bruce Reynolds site has PWM code (for another PIC) which you can adapt.

I think the difficulty in the AN236 type coupling is that it cannot supply enough current. The X-10 transformer has a 5:1 turns ratio which steps down the voltage but steps up the current. (For receiving it steps up the voltage.)

The ST7537 app note has an excellent section on the powerline as a communications network beginning on p4.

The "IT800 Line Driver Performance" app note from...

has tables showing current & Vpp vs. network impedance at frequencies near the 120kHz used by X-10.

Another advantage of using the line driver shown in the ST7537 app note is that it is only activated during transmissions reducing signal attenuation during reception.

The PIC16F88 is similar to the PIC16F628 but the 16F88 can use a bootloader. There's a free bootloader available from

The PIC itself does not provide isolation so you need a transformer power supply and line coupler if you want to make a connection from a PC.

If you d>Thanks for the valuable pointers again, Dave.

Thanks, Dave; I now have a lot of information that I'll assimilate, and take it from there.

I shall keep the list updated on my progress.

BTW, talking of bootloaders, I use the one that is part of Microcode Studio, and am pretty happy with it. However, there is another one at

that also looks pretty good. A very wide device support, a small footprint, and the ability to generate one's own .hex files for custom configurations. And many more useful features such as automatic device detection etc.

Regards,

Anand.

Here's just a little more information.

The TDA5051A datasheet also >Thanks, Dave; I now have a lot of information that I'll assimilate, and

One more tidbit and I promise I'll try to stop. ;)

Mouser stocks the 78250 transformers.

*78250*&terms=78250&crc=true&N=142&Ns=SField They were >Thanks, Dave; I now have a lot of information that I'll assimilate, and

Anand,

Here's >Thanks, Dave; I now have a lot of information that I'll assimilate, and