How to get rid of stuff?

[klugesmith]

Came to share a thing learned from looking up "grounding" switches, whose green screw is in fact there for safety ground connection to the mounting tabs and cover plate screws.

In most old house wiring, the cable to a light switch on wall has only 2 wires, "Hot" and "Switched Hot". 

Later codes required a safety ground wire.
In NEC it's formally identified as the equipment Grounding conductor (green, or bare copper, or metallic tube protecting the other wires).
Generally there is no need for a Grounded conductor (white "neutral" wire) at a light switch.

That's changing, because of the proliferation of active light switches, for example with Occupancy Sensing, and now fancy dimmers and color controllers.

The control electronics in those switches requires some standby current, customarily not more than 0.5 mA.  For years, the makers provided connection points and instructions to use the Grounding conductor as "neutral" connection for the control circuit. 

The two or three NEC revisions in past decade have been playing catch-up.  First by mandating that Grounded wire (neutral) be routed to new light-switch boxes, except listed cases that are unlikely to ever get an occupancy-sensing switch.  Then phasing out the permission to intentionally put current (even 0.5 mA) into the equipment grounding wire system.  It adds up when every room in a building has an active switch.

It's consistent with the general principle, after more than 130 years of electrical code evolution, that the Grounding conductor is not for current except under fault conditions. 

Kind of like changing rules about connections between electricity and metal water pipes. 
Long ago, a water pipe was a place you could divert electricity into,  to protect users of faulty electric appliances.  Not any more.  In new work, the only intentional ground connection to a water pipe is to take electricity out of the pipe, to protect plumbers and plumbing fixture users.

What's the story in jurisdictions outside of USA?

[klugesmith]

All 7 months of electronics flea market were cancelled this year because of the pandemic.  Need to find other ways to move things along.
Some items saved for projects are finally being abandoned, but that is hard to do.  It's easy to give them more time than they deserve.

Fluorescent lamps, set out with recyclables for weekly collection, were separated from their electronics.
An electric heating pad made for gardening was discarded, after becoming dry and stiff.


A dead microwave oven was reduced to metal frame (for ordinary recycling) and a pile of guts.
This specimen has a short section of conventional rectangular waveguide between magnetron probe and cooker box.


The heart from gut pile was able to beat, after I remembered need for ground connection between transformer core and magnetron yoke.  Not a demonstration to be undertaken by beginners; there are hazards other than electrocution.

[klugesmith]

Re. the old pink neon shapes from movie theater demolition.  I had a long talk with Bruce Suba the other day, and am inspired to put a bit of work into finding a new home for the neon stuff.  And maybe light some up as art in the back yard.

Here is a bit of "neon" serving to check the power unit from another MWO that was taken apart for scrap.  Packing up after the photo shoot, I was reminded again that the HV circuit depends on contact between magnetron yoke and transformer core. Picking up the magnetron by hand, while energized, would invite lethal electric shock (mixed DC and AC).


What good are old CRT television sets and video monitors? I am about to take at least three to e-waste. 
Had been saving them to measure the anode voltage and current -- maybe keep one for that.
Will the HV generator work if we save just the main circuit board?  With or without connection to deflection yoke?

[klugesmith]

Got a warning about adding to a post that had been idle for more than 120 days.   What's wrong with that?  Old threads are better than new if the topic is the same.

Interesting that my last post is about CRT TV's, because that's what's on my mind.   
Our electronics flea market organizers canceled all 7 meetings in 2020, and the first 6 (so far) in 2021.
There was a local e-waste drop off event today, inspiring me to dig into long-hidden piles.

I had scrounged two rear-projection TV sets, with RGB CRT's, a style that was widely being retired 10 or 15 years ago.   Giant Fresnel lens panels were the easiest part to play with (I melted some quarters using focused sunlight), but the electronic guts were saved too.


Figured it would be fun to light up a monochromatic blue or red CRT, perhaps for a CRT clock.
Originally at least one of these units powered up with rasters on all three "lamps".

Then they were stored outdoors under a tarp, and became rat nests.  In the second pictured unit, most components on main board were completely buried in rat guano before I got at it with a vacuum cleaner.
Would it be crazy to consider cleaning and powering up the board?

Anybody here want a small high intensity CRT with deflection yoke?  Got ideas for projects?
Any experience lighting up TV CRT's with scratch-built electronics? 
Billions of TV's were made with that technology. Now it's about as rare as film cameras, and takes up more space in collections.

[Uspring]

Got a warning about adding to a post that had been idle for more than 120 days.   What's wrong with that?  Old threads are better than new if the topic is the same.

I agree. But what do you expect from the forum software with a thread name like this?

[Mads Barnkob]

I have saved some smaller CRTs for the same project, small retro clocks

Looking at how vintage computers are rising in prices, I could only imagine that other electronic things in good condition with through-hole components will follow the same trend. Something that can be repaired and maintained.

I raised the warning limit from 120 days to 365 days, I think its just some default forum etiquette to warn users on bumping old threads. I agree with you, that keeping the information in a single same thread is better than multiply threads with years apart.