a little help with capacitive power supply values

[Dennis]

Just to throw a 'spanner in the works' , if I do eventually use a transformer based supply like the dimmer attachment, what would be the smallest footprint 220V to 9V/5V transformer I could use ?

Kind regards
Dennis

[Dennis]

My questions ....

Are they perhaps profane , not correctly formulated, without direction , off-the beaten track, stupid ?

I realise there is google, encyclopedias, textbooks, etc. , but nothing can replace the power of human thoughts and minds !!

Is not our very nature to question how a system works and why ? When new technology is built or invented don't we find ourselves asking how it works ? How did someone think of that ?

Don't questions and discussions prompt new thoughts and ideas ?

In this instance I am asking for advice, information and thoughts regarding how others power PIC's and their circuitry.
I have not even attempted to build any such circuit yet and I have been researching this particular topic for two weeks already, gathering info.

Did the inventors of X10 and the likes of know all the odds before they started dabbling ?

What was life like before transformers?

Are there alternatives to transformers ?

I thank you all once again for answering some or most of my questions as well as for your concern for my safety !

I apologize for my lack of knowledge BUT I have a desire to learn more and I have found this forum to be the most interesting in this field thus far! Hats off to all of you !! THANK YOU!

So I have two options .. I recede back into cyberspace and lurk around in the shadows silently OR I summon the courage to ask the questions that other may/may not have thought of or asked before !

Thank you

Kind regards
Dennis

[Pic_User]

Hi Dennis,

Please continue to ask questions on this forum.

-Adam-

[dhouston]

Did the inventors of X10 ... know all the odds before they started dabbling ?

I'm sure they did as they had designed many other products before X10. They chose a capacitive supply because it cost less and had a smaller footprint. Their devices are enclosed in plastic cases so there's no shock potential. They also chose to make neutral their hot lead because they thought there was less noise near ZC (where they do their signalling) that way.

What was life like before transformers?

DC all the way. That's how Edison started out. Tesla was the one who pushed AC.

[dhouston]

Just to throw a 'spanner in the works' , if I do eventually use a transformer based supply like the dimmer attachment, what would be the smallest footprint 220V to 9V/5V transformer I could use ?

One alternative would be to use a switchmode wall transformer that supplies regulated +5V. That way, it's external to your device and has minimal effect on the footprint.

[Byte_Butcher]

Just to throw a 'spanner in the works' , if I do eventually use a transformer based supply like the dimmer attachment, what would be the smallest footprint 220V to 9V/5V transformer I could use ?

Kind regards
Dennis

Dunno what the smallest available size would be, but I like these quite a lot for only $2.67USD each in 10 quantity:
http://ww2.pulseeng.com/products/dat.../LT2007_04.pdf

I use 6 volt output... rectified and filtered it's perfect for powering a LDO to get 5 volts at up to 80mA.

Size is 22mm x 23mm x 19mm.

Small, cheap, safer than transformerless supplies, and able to produce plenty of current for powering a PIC + accessories.

For circuits where an "external" power supply (wall wart) is acceptable, I use these or something similar:
http://search.digikey.com/scripts/Dk...P6P-ND&stock=1



steve

[Dennis]

Adam ..will do , thank you!

Dave thanks again definitely checking out the switch mode stuff too.
And agrred on the Edison and Tesla facts :-)

Steve.. thank you will check asap!
>> I think these look awesome .. so tiny ! Thank YOU

Melanie/Amgen(Don) , please check the updated Capacitive Transformerless AC-DC PSU diagram attached. Common neutral this time (correct me if I am wrong!)

So now the circuit should be floating 5 Volts ABOVE NEUTRAL and not 5 Volts below LIVE right ?

Kind regards

Dennis

[anonymouse]

Adam ..will do , thank you!

Dave thanks again definitely checking out the switch mode stuff too.
And agrred on the Edison and Tesla facts :-)

Steve.. thank you will check asap!
>> I think these look awesome .. so tiny ! Thank YOU

Melanie/Amgen(Don) , please check the updated Capacitive Transformerless AC-DC PSU diagram attached. Common neutral this time (correct me if I am wrong!)

So now the circuit should be floating 5 Volts ABOVE NEUTRAL and not 5 Volts below LIVE right ?

Kind regards

Dennis

Dennis no its not safe, never never put a fuse in the neutral leg when it is at zero potential to earth. The fuse may blow the appliance looks like it is dead, somebody opens it up touches the phase/neutral, they could be dead. Try a transformer, that way you can sleep at night without worrying about the device killing somebody or smouldering away and catching fire.
all the best

[Byte_Butcher]

Yep, like anonymouse said, fuse in the neutral is bad!

If you really *must* build a transformerless supply, goto the document I referenced in post #17, scroll down to page 10, figure 10 and build it just like that. They've already figured out the right way.

Correctly designed transformerless supplies are plenty safe, especially since the commercial devices that usually contain them are invariably well sealed in a well insulated (plastic) housing to keep curious fingers away. Lots of insulation between the device and the user is the key.

But most of my projects involve a lot of testing, fiddling, finger poking, and experimentation (with the guts open and exposed), so most of the time I much prefer a good isolated supply.
I buy little transformers 10 at a time for under $3 each and don't have to worry about what parts are "hot" when I connect my 'scope ground or poke at a part with my finger.

If the size and weight of your project is REALLY critical (but if you're sending it up in a rocket, it probably won't be mains powered), or if you're building a product by the 1000's where saving $1 worth of parts becomes a pretty big deal, then maybe xformerless is the way to go. But for most applications (especially hobbiest) I have to ask... Why? What's to be gained that offsets the risks?

So... why do you want a xformerless supply? What benefits does it have for your project?


steve

[Melanie]

You're getting there...

Loose the Neutral Fuse as suggested.

Your Triac isn't completely wired... it's a three legged device. The LIVE goes through the TRIAC from the Supply Connector and goes out to the LIVE pin on the LOAD Connector. The NEUTRAL is common between the Supply and the Load, correct as you have it.

For those keeping an eye on this thread, if you use an isolated Supply for the PIC, it's low-voltage side will become LIVE the moment you connect it to the TRIACs gate. If you want your PIC to be isolated, then you will need an Opto-Isolator (or Pulse Transformer) of some sort between the Gate and the PIC.

Again, going back to an earlier question, yes, zero-cross is important - for many reasons (even if it's just to keep the peace with your neighbours). Go read up about it.

[dhouston]

If you really *must* build a transformerless supply, goto the document I referenced in post #17, scroll down to page 10, figure 10 and build it just like that.

Steve, isn't that the same document Dennis referenced in post #1 of this thread?

[dhouston]

Dennis,

You might also find Microchip AN236 helpful. It has a capacitive supply, a ZC detector and a triac.

• http://www.microchip.com/stellent/id...pnote=en012050

And there are more schematics of X10 modules on NASA engineer Dr. Ed Cheung's site.

• http://www.edcheung.com/automa/circuit.htm