[sdiy] my annual DIY holiday project

[Oren Leavitt]

If you want a "soft on", an old carbon filament lamp in series with the 
load works great. Look for some of those old 260 watt 1930's heat lamp 
bulbs or smaller bulbs for smaller loads. These appear frequently on 
eBay, estate sales, and sometimes in antique shops:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6135977134
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6131016296
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2292286534
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6135212781

Carbon has a high resistance when cold that resistance drops as the 
filament heats up. Tungsten behaves the other way - low resistance when 
cold (high inrush current) and increases as it heats up.

Oren

KA4HJH wrote:

>>A way to increase the "cross-twinkler modulation" is to raise the power
>>source impedance. I use a 2nd string of non-twinkers wired in series. The
>>more of these bulbs unscrewed, the less power for the twinklers to fight
>>over.
> 
> 
> Do you mean that you're putting a parallel string in series with another
> parallel string?
> 
> 
>>Changes from independent blinkers to a chaotic system. I think that's
>>chaotic. But I'm not too sure what chaos is and isn't.
> 
> 
> Remember that incandescent light bulbs are PTC thermistors so their
> behavior isn't linear to begin with. That could crank up the chaos quite a
> bit.
> 
> 
>>Also, I was thinking that a string of non-blinking bulbs would be good in
>>series with something you wanted to power up slowly. Like something with old
>>caps. Screw in bulbs one at a time. Kind of like a cross between a single
>>light bulb and a variac. Kind of a "soft variac".
> 
> 
> This would work in a pinch. When you screw in each bulb there'll be rush of
> current until the filament heats up. In some situations this may be
> undesirable.
>