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JimmyDee
Admin
USA
4179 Posts |
 Posted - 01/30/2010 : 09:35:39
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quote:
Originally posted by bytemylobster
scary,
I will entrust my fluke for analytical.
I have a comment on the dimmers. Dimmers utilize silicon controlled rectifiers (SLR) which do not cut the peak of voltage but do cut into the full wave of power. Full power is reduced, because of the SLR slicing into the wave. The peak voltage is still there; however, it is not enough to light the light.
I think they actually have a triac instead of a SCR. Kind of the same principal but the SCR has a DC output and the triac produces an AC output chopping both the positive and negative sides of the wave form.
A UJT circuit fires the triac to chop the wave form at the desired voltage.
Now this is why we need to look at the voltage with a load on it. The Wiggies will produce the needed load. The triac will leak the full voltage through its junction points but at a very high resistance when in the off state. DVOM will see full voltage, Wiggies will read a variable voltage depending on the dimmers position.
Input impedance on Wiggies is low causing a load to be seen by the circuit. Input impedance on a DVOM is between 10 - 20 meg ohms and will read full voltage out of the electronic device.
An interesting test is to read the voltage from a 12 volt car battery that is completely dead. DVOM will read 12 + volts. Put a load on the battery like a light bulb and it will not light, voltage will be zero. As I have stated in a previous post, reading voltage with a DVOM can catch ya make ya look like, not too good.
I have told a story about where 2 instrument men caused a piece of machinery to be down for an entire day and they replaced sever $100s worth of parts before a RE (real electrician) checked the circuit with a Wiggies and found that an output card on a PLC had a bad triac output. An understanding of input impedance is imperative to trouble shooting.
Jim
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A moderator on this site is a member, just like you're a member. My opinions are no more valid than your opinions, so feel free to disagree with me on any subject. A Spell Checker for Your Forum Posts, By IESpell; CLICK HERE for a Free Copy. CLICK HERE for Mozilla Foxfire 3.5. Spell check built in. They are free and they work! |
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rabbitgun
Forum Magnate
USA
2035 Posts |
Posted - 01/30/2010 : 15:27:16
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quote:
Originally posted by JimmyDee
..........before a RE (real electrician) checked the circuit with a Wiggies and found that an output card on a PLC................
 I think I will change my sig........... "Only real electricians use wiggies"................ |
An analog man in a digital world.
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JimmyDee
Admin
USA
4179 Posts |
Posted - 01/30/2010 : 17:46:08
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quote:
Originally posted by rabbitgun
quote:
Originally posted by JimmyDee
I think I will change my sig........... "Only real electricians use wiggies"................
Oh that such truth would be seen in something as common as a signature.
Jim |
A moderator on this site is a member, just like you're a member. My opinions are no more valid than your opinions, so feel free to disagree with me on any subject. A Spell Checker for Your Forum Posts, By IESpell; CLICK HERE for a Free Copy. CLICK HERE for Mozilla Foxfire 3.5. Spell check built in. They are free and they work! |
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rabbitgun
Forum Magnate
USA
2035 Posts |
Posted - 01/30/2010 : 18:14:36
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quote:
Originally posted by JimmyDee
Oh that such truth would be seen in something as common as a signature.
Jim
Oh!...... Now Jimmy is a poet!
Where forth art thou my wiggy where forth art thou? Yee wiggy with two simple leads?
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An analog man in a digital world.
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macmikeman
Forum Magnate
1428 Posts |
Posted - 01/31/2010 : 18:19:37
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| What is getting hard to find is good belt holders for my wiggy. I should have picked up a dozen extra ones when I could find the right width size for my belt at the local hardware. Now they don't carry them anymore and I looked for a good replacement but cannot find. waaaaaaaaaaa.... |
F--- em all but six son, you need six to carry the coffin..... |
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John A. Peters
Forum Magnate
USA
1852 Posts |
Posted - 03/18/2010 : 15:10:15
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| Yep - Always suspect the dimmer since it is delicate electronics. First thing to do is open the dimmer outlet and put the two wires together. Do this even before testing the light bulbs or lamps and you will save time. bytemylobster is right. |
Same Day Service 415-239-5393 SF Electrician SF John A. Peters, San Francisco CA www.BrooklineElectric.com/ |
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bytemylobster
Avid Member
Canada
414 Posts |
Posted - 03/20/2010 : 17:48:51
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Jimmy,
Actually, I think the circuit of the dimmer slices the sine wave, not chop it. Think of a line up and down through the sine wave. If power is represented by the whole wave, then we have merely taken some of the power away because of the triac's action. That is why we still measure full voltage at the dimmer and or luminaire. |
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rabbitgun
Forum Magnate
USA
2035 Posts |
Posted - 03/20/2010 : 20:17:31
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quote:
Originally posted by bytemylobster
Jimmy,
Actually, I think the circuit of the dimmer slices the sine wave, not chop it. Think of a line up and down through the sine wave. If power is represented by the whole wave, then we have merely taken some of the power away because of the triac's action. That is why we still measure full voltage at the dimmer and or luminaire.
Oh....... Should I then slice or chop the chicken that I am preparing for our dinner? |
An analog man in a digital world.
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Dimmers Failing
