Building a house - making it "smart" and/or geek ready

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Aredwood

3885 posts

Uber Geek

#1173163 11-Nov-2014 22:08

pdh:

Also, not that it's very important at this level of power use, but am I correct in thinking that our power meters don't care about PWM dimming ? In other words, if you run all your lights at full whack - or dim them (using PWM) - the meter will 'spin' the same and show the same chargeable consumption ?

From my testing so far, power meters do actually read less when dimming has been preformed. My test rig - Billing meter (so called smart meter) daisy chained to a non smart digital meter, then a Ferris meter (spinning disc type), Then a 4kW rated light dimmer (leading edge phase angle control type). To finally a 2.4kW oil column heater. Switched off all circuits in house except for the power point that the test rig was plugged into. Used the inverter in my van to run the oscilloscope. Power draw as indicated by all 3 meters varied steadily as light dimmer varied throughout it's range. Didn't bother taking any voltage / current or power readings. As I don't own a true RMS multimeter.

Next test will be to modify a computer power supply so I can disable and re enable the active PFC stage while it is running. This means I will have a test load that I can vary the power factor of. While maintaining the same load. Need to buy a true RMS multimeter as well.

Niel

3267 posts

Uber Geek

Trusted

#1175232 13-Nov-2014 14:11

From my training mayne, many years ago: Power meters measure (supposed to) "real" (in phase) power so if a dimmer causes a phase shift between voltage and current then it will reduce the amount you are charged. But for lights (especially low power LEDs) the difference on your (much larger) power bill is minimal. Most of your high power equipment are resistive (hot water cylinder, stove, kettle).

You can never have enough Volvos!

heylinb4nz

656 posts

Ultimate Geek
Inactive user

#1175246 13-Nov-2014 14:33

Some tips

1) running Cat 6 for CCTV cameras before the lining and ceiling go in is much eaiser. have them all terminate to a locked closet or some hidden location where your networked DVR will be housed. Some good 720P IR 4ch systems for <$400NZ on ebay, the zmodo brand utilises power over cat6 so you only have to run cat 6 and not power as well.

2) digging out under house to make a man cave, or space for one in future

3) reinforcing a central closet \ storage space for valuables, housing cctv, or making a safe room.

pdh

343 posts

Ultimate Geek

#1175412 13-Nov-2014 19:48

Neil said: From my training many, many years ago: Power meters measure (supposed to) "real" (in phase) power so if a dimmer causes a phase shift between voltage and current then it will reduce the amount you are charged.

But do the modern PWM dimming circuits create any phase shift ? My understanding is that a modern dimmer simply turns the LED off and back on (at 400+ Hz) and the ratio of on & off time tricks your eye into experiencing brighter or dimmer light. In that case, the old rotating wheel meters (are there any of these still in action ?) would have to react very smartly to see a 50% dimmed circuit - where the power comes on & off 400 times a second....

Even a modern electronic meter not track it - it might just smooth things out. I would assume that any smoothing is to the benefit of the power company ;-)

You have a valid point that 50% dimmed LEDs are consuming a lot less power than 50% dimmed incandescents - but that's not really the point. If you want to adjust light levels and 'mood', then you can either use one dimmable circuit or else create redundant fixed circuits with different levels & focus. Saving power (and cost of power) by dimming a room full of fixtures should be more cost effective than turning off the bright lights and turning on a bunch of secondary lights with a lower output - just because you don't need to buy two sets of lights. Both solutions save you power, but you're not saving any money with the dimming solution - if the meter doesn't notice you doing it.

pdh

343 posts

Ultimate Geek

#1175414 13-Nov-2014 19:57

In a number of Whirlpool discussions, there is much hair-tearing over dimming LEDs.

Obviously, most of the domestic market is focussed on trying to make work the dimming of replacement LED bulbs on existing dimmers - and most new construction seems to follow on from this and make use of the old HPM & Clipsal dimmers. All of these seem to have issues - and some counsel that the issues are better sidestepped (in new construction) entirely - by following tried & true commercial lighting practice - where the dimming is done in the LED driver - using a 0-10 V control circuit.

I'm not really asking for examples of 'working examples' of 240 VAC dimming - many people do get lucky and 'only' suffer when ripple-control signals come in, or there's noise on the line, or the dimming level is set below 'x', or whatever. So, while it can all be sweet, there's ample proof that you have to be a bit lucky for it to be so.

Anyone have any experience with using 0-10 V control circuits domestically in NZ ?

Aredwood

3885 posts

Uber Geek

#1175534 14-Nov-2014 00:28

More info on LEDs and dimmers. http://sound.westhost.com/lamps/dimmers+leds.html Basicly using a leading edge dimmer on any type of electronic power supply at best can only be described as a kludge or bodge. This includes dimming 12V halogen power supplies. If you are going to use dimmers on electronic power supplies, You need trailing edge ones. But wirewound (magnetic type) halogen transformers require leading edge dimmers.

As for how the meter interprets the dimming. First you need to know how the dimming is carried out. And exactly how the mains to DC conversion, and the voltage stepdown is done. And then you look at what stage is the dimming process carried out. The best being inside the LED driver.

I have been doing my tests. Due to trying to figure out why my power bills are approx $200 in winter. $120 to $150 in Summer. Despite only 2 people in the house and almost no resistive loads. The only resistive loads I can think of are: kettle, dishwashers heating element, my soldering iron.

Niel

3267 posts

Uber Geek

Trusted

#1175548 14-Nov-2014 07:00

pdh: Neil said: From my training many, many years ago: Power meters measure (supposed to) "real" (in phase) power so if a dimmer causes a phase shift between voltage and current then it will reduce the amount you are charged.

But do the modern PWM dimming circuits create any phase shift ? My understanding is that a modern dimmer simply turns the LED off and back on (at 400+ Hz) and the ratio of on & off time tricks your eye into experiencing brighter or dimmer light. In that case, the old rotating wheel meters (are there any of these still in action ?) would have to react very smartly to see a 50% dimmed circuit - where the power comes on & off 400 times a second....

Modern electronics has caught up with this, but it takes a long time before the industry uses it. It gets forced by compliance standards (just like e.g. power supply energy efficiency). I'm not sure where the standards are at, but my comment was focused on how meters work. Only industrial sites (afaik) need to measure power factor and correct it (or pay extra rates). Overall, the phase shifts from consumers are small and averages out so the effect on the distribution network is small (but I have not quantified this).

It is not the dimming causing the phase shift, that is done on DC. It is the SMPSU front-end.

You can never have enough Volvos!

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pdh

343 posts

Ultimate Geek

#1175913 14-Nov-2014 15:34

Thanks Neil & Arenwood. Brilliant reference to the site explaining dimmers - best explanation of LED dimming I have read.

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