New is not always better

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Lenp
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New is not always better

Post by Lenp »

Just to blow away some cobwebs form the forum, I'll throw this one out.

I have an outside porch light. For years it was on a digital, astro wall timer, and it was never right!
I decided to install a photocell control that I found at the local super box. It was designed to fit pointing down, inside the light canopy and surprisingly, it only had 2 wires. It was to be wired in series with the line and lamp?

At dusk the night after installation, I could have sold disco tickets. The cell was 'seeing' the lamp and turning on and off quickly, then as it got darker it fluttered then finally the light was full on. At dawn, it repeated this performance until it became brighter and the lamp went out. I tried shields, a tube pointing away from the fixture, incantations, but nothing worked. The lamp would switch on and off with immediately when black tape was applied or removed from the cell.

Off to another super box, and there I found a different unit, one with 3 wires. Ah ha, the package said '..may take up to two minutes to operate"! The photocells were swapped and it now works perfectly. Nary a flicker.

But why?
Well, without destructive disassembly (AKA hitting it with a hammer) the first one must have been solid state. Perhaps based around a a triac and the photocell. In the shop it turned on and off immediately following the room lights, without delay.
The second one acts just like the older designs that used a bi-metal switch and a heater, and indeed, that is what causes the inherent delay, and no flicker. The price was almost the same for either unit, so now I'm off again to the super box..to get a spare before technology attacks again!

Neat...yes. Better..no!
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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dacflyer
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Re: New is not always better

Post by dacflyer »

i remember some of the even older ones on street lights, before the days of heated Bi-Metal, the old ones just had a CDS cell in series with a coil that pulled a switch open during the day.. and as the sun went down the coil lost energy, til the switch closed.
very robust and lasted for eons,, only down side was that any bright enough light at night, like lightning would cause the light to go out for a second, and if it was a mercury light, you had to wait for it to cool down before it re-struck the arc.
armed with such knowledge as a kid, i used to be mischievous and go around with a pin spot light ( 6v 30w ) and shine it on the fotocells and make the light go out..lol was real fun when you found one connected to a whole string of them down the block..
was a fun thing to show to friends...the old ones were great for instant response,
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