a little help with capacitive power supply values

[Byte_Butcher]

Hmmm. 0.4 to 1.4 watts when idle sounds like quite a chunk to me.

Say, I've got a couple of Kill-A-Watt's lounging around here somewhere... I'll take one of these little transformers and put it to the 100 hour test like you did with the X-10 modules.

Edit: I just plugged one in and these little transformers, unloaded, show .02W and .09VA. I'll let it run for a few days and see how the watt-hours add up.

I kind of forget about the Kill-A-Watt's unless the grid power is down and I'm running on backup generator. Then I drag 'em out to keep track of voltage and frequency...

steve

[dhouston]

Hmmm. 0.4 to 1.4 watts when idle sounds like quite a chunk to me.

The 0.4 was the capacitive supply that really was idle; the 1.3 & 1.4 have superregenerative RF receivers which are never truly idle. The point was that capacitive supplies are not inherently wasteful.

Tle last 5 devices all use transformer PSUs as they have serial ports and require isolation.

[Pic_User]

More sites:
Step-down rectifier makes a simple dc power supply
[Electronic Design News]
http://www.edn.com/ednmag/archives/1...98/08df_06.htm
http://www.edn.com/ednmag/archives/1...98/08df_06.pdf

A Capacitor-Fed, Voltage-Step-Down, Single-Phase, Non-Isolated ...
http://www.grix.it/UserFiles/Powermo...L_acfvsdsp.pdf

+++++++++++++++++++ You may skip this part:

In my very best Rod Serling, Twilight Zone, imitation:

“Picture if you will; A man bent over his electronics’ workbench.
A man, with many decades of experience, working for a living, doing precisely what he is doing at this moment.
Analyzing an electronic circuit.

Not just any circuit, but a circuit made by X10.
A consumer circuit, brand new, just out of it’s pristine box, for the first time since it left the factory floor.
The device is powered through a two prong, AC, 120V (USA) power cord.

Only today, instead of analyzing the circuit to repair it, or analyzing it to modify the circuit, he is trying to learn something else.
He is attaching his multi thousand dollar oscilloscope to the X10 device, to find out how it works.
To learn the secrets of it’s communication wave form, if you will. (Rod Serling speak)
To SEE what is going on in this particular mysterious device.

He has done this countless times, to repair, to alter, to learn and to expand, on the knowledge gained by this analysis.

There is no schematic included.
The two wire cord lulls this “searcher of the truth”, into a false impression that the device MUST be isolated, MUST have a small power transformer, somewhere hidden from the casual observer.

Enter - The Twilight Zone:
He FAILS to notice, that there are NO outside connections needed, except the cord.
Just an all plastic case, with all plastic buttons. No jacks, no other cords, just a dead end for the power cord.
Cleverly designed by people who do this for a living.

Just a power cord attached to a plastic case with eight plastic switches.
The output for the device is really, signals going back down the power cord.
Signals riding on the 120V AC power line.
This is know but not thought about by the investigator at this time, overlooked.
He is not aware that this device is powered by a “transformerless” power supply.

With the standard, properly functioning oscilloscope, attached through a 100 times (100x) probe (for conservative safety), the examiner is ready to begin. He has carefully attached the probe, ground on the minus of the filter capacitor, probe on the plus of the low voltage supply.
He has done this, before he energizes the circuit, for obvious reasons.

He now, without the least hesitation, picks up the x10 power plug and plugs it directly into the 120Voutlet.

Also without the least hesitation, he watches half of the printed circuit traces disappear.
A loud bang, a bright flash, a lot of smoke are all that is left of that half of the circuit.

What does he do?
He doesn’t even examine the burnt x10. He knows what happened and why.
He unplugs the warm cord.
He wraps the cord around the unit.
He puts the burnt x10 switch back into its box.
He opens the second identical x10 unit box (an extra, back-up unit).
He opens the unit.
He places the oscilloscope probe on the identical place, only on the new x10 circuit board.
AND
He plugs the new x10 into 120V AC!

DE DE DE DE – DE DE DE DE (that’s Twilight Zone theme music, look it up)

NOT into the same normal AC receptacle, but INTO an isolation transformer. His bench-top isolation transformer.

He would have done this with the first x10 but he wasn’t paying attention.”

That inattentive investigator was... ME. This is a true story.
I had plugged the first (now ruined) x10 into the normal AC receptacle with the neutral side and the line side flipped.

This is why they make and we use line isolation transformers.
++++++++++++++++++++++

You should never service a transformerless supply without one.

-Adam-

[mackrackit]

Adam,

I am glad it was not a
Tales from the Crypt
rendition.

[Pic_User]

Adam,

I am glad it was not a
Tales from the Crypt
rendition.

Hey Dave,
It might have been, “Tales from the Crypt”, is I was a little bit more careless.
Half of MY circuit traces could have been blown off, if I had touched the circuit board anywhere.
DE DE DE DE... (I gotta stop that theme music)
-Adam-

[Dennis]

Tales from the crypt indeed !

So who ended up shocked and who ended up de-lighted ?

And to create a shift in the TIME-SPACE CONTINUUM .......

You could try wiring LIVE and NEUTRAL across a single pole double throw switch making sure you have the correct current rating , place the project box on the floor making sure your friend is leaning over the box monitoring the power LED (Make sure the top lid of the box is removeable - all securing screws removed) THEN plug your procjet in with the wall switch in the OFF position and THEN ....using a broomstick and jokingly tell your friend it's for safety sake and THEN...from a distance flip the switch to the ON position.
RESULT :
1 X very surprised friend
1 X totally blackened pc board
1 X extremely well toasted and burned out SPDT switch (all ratings ignored) :-)

ISOLATION ISOLATION ISOLATION !

Now try to maintain proper stabilization of this channel without creating a situation of over-modulation

Steve, Adam .. are you guys kinda volunteering yourselves to be PSU testers for this one ??
Could we get captures for each stage of testing ? one cam on you and one on the circuit ?
....and the scene begins with a skull and cross-bones with a caption saying something like DON'T DO THIS AT HOME ?

Kind regards
Dennis

[Byte_Butcher]

Steve, Adam .. are you guys kinda volunteering yourselves to be PSU testers for this one ??

Me? Sure, I'll test it. I'm not afraid. I've got an isolation transformer and know how to use it.

I suppose one of my more memorable "120V bench accidents" was repairing an old radio that had the neutral connected to its metal chassis. And an old worn 2 wire cord that could plug in backwards in certain outlets.
I managed to plug it in so that the neutral chassis was actually a hot (120VAC) chassis. When I went to clip my scope probe ground onto the chassis, there was a brilliant flash and bang. I was dazed but unharmed, and the scope probe was destroyed.

Live(d) and learn(ed)...


steve

[dhouston]

To learn the secrets of it’s communication wave form, if you will.

Simpler and safer is to use a stepdown transformer connected to the powerline and view the communication wave form through it. You don't even have to open the X-10 modules. A high pass filter passes 120kHz and blocks the 60Hz.

[Dennis]

Yes agreed or use a lower AC voltage at the same frequency running completely off the mains ?

Dennis