Zero Crossing Detector as high voltage power detector?

Projects General Guidance
1

Hi,

I'm looking for a way to check if some devices have power.
There are solutions like cheap 5V wall warts, relays, neon glow lamp...
But from my point of view the power waste is to big.
Also relays have the problem that most of them are not build for high and low voltage switching.
It would be easy to use a double switching relay if not both switches would be AgSnO2.

But there is another problem i have.
I use this dimmers in my house for LED lamps: http://www.eltako.com/fileadmin/downloads/en/datasheets/B_datasheet_EUD12NPN.pdf
And i want to check if they are on or off.

I found this circuit that wastes just 120mW: http://www.dextrel.net/diyzerocrosser.htm
Is this an option to detect power?
And will it work behind my dimmers?

2

What about a cheap hall effect sensor? To detect current...

3

I need voltage. I want to know if the relay, dimmer, switch, plug is on even if
the device behind it is off.

4

MrGlasspoole:
I'm looking for a way to check if some devices have power.

To check if there is power you have to check current and voltage.
If you only need voltage, then it's not power what you want to detect, just voltage.

PS: Power= V * I

5

Ok, sorry if the german guy on the other end used the wrong word :slight_smile:
For me Power = On - like it is printed on all the on switches :smiley:
If you look at it from the physics side then you are right.

6

There are solutions like cheap 5V wall warts, relays, neon glow lamp...
But from my point of view the power waste is to big.

You can detect voltage with very low power consumption, but you still need some power to drive your circuit and/or to drive an LED. For example, a digital multimeter might have in input impedance of 10-100 megohms, but it's powered by a battery.

How much power does one of those little neon lamps require? It can't very significant.

7

The neon lamps use ~0,35W.
From my point of view thats allot. In times where we change to LEDs in our house (incandescent light bulbs are already
banned here in Europe) and with the electricity price....
10 of this neon lamps running 24x365 is near $10 a year.
So if you look at all the stuff around the house, every watt counts.

Also the neon lamps will not work on the dimmers.

8

Must be walloper size neons....most i've seen draw around 400 microAmp 90 volt

9

58mW

Interesting to see a circuit that can draw less.

10

I imagine that the 58 mW rating is the maximum power dissipation.

I can light up those neon bulbs with static electricity from a hair comb, so a few microwatts ought to suffice for enough light to indicate that voltage (greater than about 90 V) is applied.

11

0.6mA at 90V is about 58mW, so I think that is the rated power under normal use. Bright enough to see in a panel indicator, with a sensitive detector you could certainly reduce the drive.

12

Ah ok, i looked and found some 230V 0.5 mA neons.
I was looking ad the ones we have here for the stwitches in our house.
But they are 20 years old and orange. I thought neons are always orange.
It looks like orange neons draw more power: http://www.conrad.de/ce/de/product/725013/Farbige-Glimmlampe-230-V-025-W-14-mA-Orange-Barthelme-Inhalt-1-St

But:

  1. They lose brightness over years.
  2. What happens with them behind a dimmer?
13
  1. What happens with them behind a dimmer?

Most dimmers just cut out part of the AC cycle, so that the ON time is shorter. A neon lamp will still light "behind" such a dimmer.

14

Until the part left over doesn't reach a high enough peak to turn on the neon. But that'll be getting rather dim.

15

As you can see in the datasheet from my dimmers they can do everything (leading phase angle / trailing phase angle).
I use electronic transformers for my LEDs.

The datasheet says:

Mixing of L loads (inductive loads, e.g. wound transformers) and C loads (capacitive loads,
e.g. electronic transformers) is not permitted. R loads (ohmic loads, e.g. 230V incandescent
lamps and halogen lamps) may be added anytime.

Hm, sounds save to put the neon lamp in parallel to the transformer.

Also from the datasheet:

Glow lamp current up to 5mA starting at 110V

I really don't want to kill such a expensive dimmer and need to be sure it will work.

16

polymorph:
0.6mA at 90V is about 58mW, so I think that is the rated power under normal use. Bright enough to see in a panel indicator, with a sensitive detector you could certainly reduce the drive.

The neons on the back of camera flashes run at about 40 uA and are still bright enough to see.

17

jremington:

  1. What happens with them behind a dimmer?

Most dimmers just cut out part of the AC cycle, so that the ON time is shorter. A neon lamp will still light "behind" such a dimmer.

Assuming there is a neutral present.

18

Sorry for the delay - very busy...

I have now the idea to be able to also set the brightness of my lamps via the Arduino.
If i use the neon lamps behind the dimmer and they also get dimmed it should be
possible with some logic in the code.
The question is what would work best: LDR, Photodiode or Phototransistor?

Then i have now another problem.
I need this self made optocoupler one time on some cable that is ~10 meter but just on and off (no dimmer) and it doesn't need
to be fast. It's J-Y(St)Y cable (~ AWG 23) and i think 5V over 10 meter and an LDR is not a good idea.
But i also have 24VDC there...
LDR + 24V + voltage divider possible or what can i do?

19

You should have written this all down on paper and sent it in to the people that run this site. Have you any idea how many LEDs have been twinkled by your packets being routed around the internet to get this subject posted?

No wonder we're all suffering such financial hardships!