A/C detection in wires

[toozie]

I have a simple pencil A/C detector for figuring out if a wire is hot in the home that works great. Last night I was using it to determine which bulb was out on a string of Christmas lights and it worked like a champ, but it appears the line has to be running at 120Vac.

My question is does anyone know how to make one of these detectors, and is it possible to modify it to test ~24Vac (modifying the 120Vac home unit is fine as well). I have a Christmas display with 10 bulb sections of lights running at 24Vac that are a pain to debug when a light goes out (it seems like the internal shunt doesn't blow right when running at this voltage, so the whole set of 10 just goes dark. I tried my pencil tester, but it wouldn't work (even when I adjusted the sensitivity on it). Any thoughts??

~Jason

 

[jpanhalt]

The principle of detecting 120 VAC or 24 VAC is the same. As you suspected, it really is just a matter of sensitivity. You don't give the brand of tester you have. Zircon makes a live wire detector that may work, but I have not tried it myself. Just checked DigiKey. It has a Fluke 20 to 90 VAC tester for $23 USD, Cat # 614-1025-nd. John

 

[toozie]

The tester I have is a "Sperry Volt Sensor with circuit alert technology" It is a cheapo one, but works fine in the house and with standard Christmas lights. I just went out to try again and I can adjust the sensitivity to the point that it beeps when placed next to each bulb. Unfortunately, it also beeps on the segments not being lit (guess it is picking up some of the field from other segments).

My tester says it works from 12 - 1000Vac, but I get the feeling that for what I want to do, it isn't going to be reliable enough down in the 24Vac range (when the current is only ~170mA).
~J

 

[audioguru]

Replace your burning out, power hungry incandescent Christmas tree lights with LED ones.

My electrical Utility company gave away for free and traded new LED strings of lights for old incandescent ones to save energy.

The LED ones are not bright so use plenty of them.

 

[wmmullaney]

it worked like a champ

haha

 

[3v0]

Replace your burning out, power hungry incandescent Christmas tree lights with LED ones.

My electrical Utility company gave away for free and traded new LED strings of lights for old incandescent ones to save energy.

The LED ones are not bright so use plenty of them.

I know this is picking a nit. But they are they really free?

Maybe better to say, at no additional charge.

If anything is really free there are no strings attached. No prerequesite purchase or membership...

 

[wmmullaney]

So leds consume more power then regular bulbs?

 

[audioguru]

Regular incandescent light bulbs produce 90% of their power as heat and only 10% as light.
LEDs produce maybe 10% of their power as heat and maybe 90% of their power as light.

The LED Christmas tree lights draw about 1/30th the power of old incandescent bulbs. That is why the electrical utility company was giving away LED lights for free to save a lot of power so new generators won't be needed.

 

[Leftyretro]

Regular incandescent light bulbs produce 90% of their power as heat and only 10% as light.
LEDs produce maybe 10% of their power as heat and maybe 90% of their power as light.

The LED Christmas tree lights draw about 1/30th the power of old incandescent bulbs. That is why the electrical utility company was giving away LED lights for free to save a lot of power so new generators won't be needed.

Well the power companies could just ban Christmas all together, think of the power saved.

Lefty

 

[audioguru]

Well the power companies could just ban Christmas all together, think of the power saved.

Some religions are forcing us to say "Seasons Greetings" or "Holidays" instead of saying Christmas. The head people at the power company are not all of those religions.

 

[wmmullaney]

Oh well, I see what you mean.

 

[dknguyen]

Heh, christmas is the time when I'm least likely to see my friends since they're all away! It's quite ironic and lonely.

 

[3v0]

Well the power companies could just ban Christmas all together, think of the power saved.

Lefty

That would mean less money in their pockets.

Much of the power saving efforts by power companies is a PR thing.
The electric load is the largest during the summer.
They have more then enough to go around during the winter.

 

[audioguru]

Much of the power saving efforts by power companies is a PR thing.
The electric load is the largest during the summer.
They have more then enough to go around during the winter.

Not here.
The highest electric power consumption in my area occured 2 years ago at 2 weeks before Christmas. it was increasing each year. Foreign electricity needed to be purchased at a very high price to meet the demand to power inefficient Christmas lights.
Adding new generators would cost a fortune.

For silly Christmas lights?
So they gave away LED lights and the electric power consumption is dropping in winter.

In summer the electric utility company gives away "smart thermostats" where they can turn off your air conditioner when demand for power is high.
They will have a timed tier pricing for electric power which will be expensive when the demand is high and will be cheaper in the middle of the night.

 

[RODALCO]

Free LED Christmas lights ??

I will ask my POCO if they agree to a do a swap.

I have upgraded already a lot of my incandescent lamps with LED's. Look forward to a few freebies but i doubt it here in NZ.

 

[Hero999]

Regular incandescent light bulbs produce 90% of their power as heat and only 10% as light.
LEDs produce maybe 10% of their power as heat and maybe 90% of their power as light.

That's not true, no light is 90% efficient.

https://en.wikipedia.org/wiki/Luminous_efficacy#Examples_2

LED Christmas tree lights are so much more efficient because small incandescents are even worse than large incandescents and they can be produced in different colours rather than filtering a white light.