Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[pomonabill221]

BrianH.... you mis read my post...
I did NOT say put the resistors across the line!
I said put the pot across the transformer's output!

[Brian H]

I read your post correctly.

I never said you suggested resistors across the AC Line. If it sounded like I did. I am sorry for the confusion.

I was referring to the earlier post mentioning that some methods could be dangerous.
Like some used resistors directly across the AC Line or the ACT ScopeTest2 scope adapter comes to mind.

My post said the transformer was 100% safe.

[pomonabill221]

Well... excuse me too!  I didn't read YOUR post carefully!!!  I apologize!
Yes, I agree that ANYTHING dealing with line is VERY dangerous (although I don't head my warnings sometimes and have gotten bit before, but that's another story).
I would NEVER suggest that anyone do this, although an isolation transformer can help IF you do need line voltage.  That's another more advanced method.
But with the transformer that the OP suggested from ratshack, the line terminals ARE exposed because it is a PC board mount, so a method MUST be used to protect them from coming in contact with earth and/or a person and/or a piece of test equipment!
After the transformer (excluding a short across the secondary), it should be safe.

[Brian H]

Oh. The ratshack one is a PCB mounted one with exposed pins. Yes easy to touch the terminal.
Wired lead type would have been easier to tape the bare stripped part of the wires.

My old Heathkit Scope has a 1 volt AC output winding on its power transformer.
I thought gee this could be easy. Then reality set in and I thought. Maybe it may have noise on it from the other windings, powering the scope.

I did find a few old AC out wall warts. Few from telephone answering machines, an old USR Modem and a B&D rechargeable hand vac.
 

[bkenobi]

It may not matter afterall.  I stopped at costco on the way home tonight. They have a champion branded generator with what they call clean power. From what there pictures show, they suggest that this generator makes a really nice sine wave. It costs a bit more, but it also includes some things i was going to have to pay extra for at harbor freight (warranty, battery, remote start).

[Brian H]

Well the information maybe helpful to others wanting to use a generator.
You could also see exactly how clean its output is.

I may try mine myself. Or run my scope with the 1 volt AC signal on the horizontal sweep. To compare it to how close the generators AC is to 60 cycles.
X10 is fairly tolerant from what I have read. Insteon is not as forgiving.

[Noam]

I stopped at costco on the way home tonight. They have a champion branded generator with what they call clean power.

Is that the one that was recalled?
http://abclocal.go.com/kabc/story?section=news/consumer/recalls&id=8871258

[bkenobi]

Same model, but customer service told me they pulled all affected models (if their store had any).

[dhouston]

X10 is fairly tolerant from what I have read.

I've seen reports that X10 would not work unless the generator outputs a clean sine wave. However, I haven't investigated it. I would think it's the area around ZC, especially rise/fall time, that is important. And, any noise around ZC and spikes anywhere would likely be a problem.

[pomonabill221]

How could a rotating field, produced by the armature in the alternator, create anything but a sine wave?  Where could the noise come from?
The frequency is set by the armature (engine) speed, the voltage mainly by the field strength/number of turns on the stator and partially by speed.
Normally on small alternators, the armature is permanently magnetized (or charged), but may have slip rings that drive windings on the rotor and are controlled by a regulator to control the voltage output, but this I would imagine is on larger, more expensive gensets.  The smaller portable ones don't have this because of the expense involved. (I think).

[Brian H]

On my newer 6KW generator. It has the stationary windings for the output and a rotating field. A voltage regulator changes the rotating fields strength. I suspect it is a sine wave. Though I have not had a chance to look at it yet.

My old Sears 6KW had some sort of inductive regulation but I gave it away and the schematics along with it. It may have had a strange output but I can't say for sure.

[pomonabill221]

I see... so my guess would be IF the field's energizing drive were "noisy", then that would be reflected in the stator's output, but it should be ONLY a quiet DC voltage with a little change just to keep the output regulated.
Might be interesting to see how quiet the output is with no load/full load/step load... should be pretty good though.

[bkenobi]

Just curious if this description would be accurate in building an oscilloscope adapter for mains?  I missed this when I asked before, but found it in reviewing a recent topic.

http://www.idobartana.com/hakb/oscope.htm

[dave w]

Yes

[Brian H]

Just read the RED warnings and follow the instructions.
There is Line Voltage floating around and if reversed. The whole case of the scope. In theory would be at line voltage.