DIYbanter - View Single Post

wrote:

snipped

The bulbs are a dull red-to-orange at 1/10th to 1/5th voltage, and it
takes one-to-several seconds to warm up to final brightness, but they
generally do light. I said "5 to 10 bulbs" because it depends somewhat
on the particular traits of the bulbs. By adding more in series, each
runs at a lower voltage and takes longer to come to final brightness,
such that your eye has enough time to follow the changing luminosity,
up to the point where there are too many to see them light at all.

You spoke the truth and tought me something I didn't know.

I wouldn't have believed that there'd be any light in the visible
spectrum at 1/10 voltage, but I just played around with a few small "12
volt" automotive bulbs and my bench supply and they all put out a red
glow visible in dim light right down to 1 volt; and some even below.

I found one bulb which at 0.7 volts produced a little dull red in the
middle of the filament (The furthest point from where the filament
supports were sinking the heat away.)

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"