Which is stupid: this design or me?

[Technoguy3]

So I have this light-sensitive nightlight that barely puts out any light, so I decided to open it up and see what's inside. I find... this. Is it just me or is this poor design? The resistor is a 47K Ohm if my math is right (unlikely). It looks like that this thing runs up my electricity bill even when it isn't on. Am I wrong? That's like 3A of current going through it even when the light isn't on, right?

EDIT: 120V/47K = 2.6mA. Silly me. Still, though, shouldn't there be some sort of mechanism to shut off the current when not in use?

[Simon]

that is piss poor design to be sure. Just abouts teaches what a NOT gate is.

[IanB]

Wow, you really broke that light well. No chance of putting that back together again... 

2.6 mA from the mains is no big deal. It's 1/4 W so things will get warm, but not especially hot. It looks like there is a CdS cell to bypass the neon and turn it off during daylight? I'm really not sure why that is needed.

[Simon]

It looks like there is a CdS cell to bypass the neon and turn it off during daylight? I'm really not sure why that is needed.

Sort of makes it look way more sophisticated than it is.....

[SeanB]

This is the deluxe model, with daylight switching. Production cost is around 5c more than the standard model, but the profit margin is three times as much, as you can sell the deluxe for 60c, as opposed to 20c for the regular model.

It is good this is so hard to open, you do not want a night light potentially where a young child can contact it with a flimsy case that falls off after a few months due to a cheap glue being used.

Just remember that this uses less than the 2mA quoted, as the neon lamp drops around 90V when lit, and the ldr will likely have a on resistance of around 20K when it is bright enough to not light the neon lamp.

[Simon]

Very good point.

[vk6zgo]

It is horrible,& not fit for purpose,but it actually is a very elegant design.

If for some reason you wanted to turn on a neon globe when it becomes dark,it does the job well.
The fact that it is too dull to be a proper nightlight,is a different matter altogether,as is the poor construction,& the possibility that the CdS cell may breakdown in service.
The Boss probably was very happy with this product,as they could use all those neons & CdS cells which had been lying around for 20 years.

[SeanB]

Not likely, more like the company also makes photoswitches, so has a contract that gives a good price for the CDS cells.