# Fastest incandescent lamp?

Discussion in 'Electronic Basics' started by Bill Bowden, Nov 21, 2005.

1. ### Bill BowdenGuest

What type of low voltage incandescent would be best to use for fastest
response time, or is there any difference?

I'm looking for a approximate 2 watt low voltage lamp to use with a
electronic roulette wheel. The pulse width is about 15 milliseconds
when the wheel starts and gets wider from there as the wheel slows
down. I tried using a 12 volt, 3 watt lamp with some bias to keep it
warm but that didn't help much. The lamp is fairly dim on short short
pulses with or without the bias.

Is there any particular incandescent lamp that is better than others in
terms of response time?

-Bill

2. ### Tim WilliamsGuest

For a given filament temperature (and thus life, intensity and color),
there's a certain amount of mass (volume) behind the surface area emitting
that light. Your best bet would be grain-of-wheat types, if smaller don't
exist (grain of dust lights? LOL).

Trivia: you can operate incandescents up to many kHz, but it's a small delta
T (small delta intensity) at a high bias temperature (where heat loss is
rapid = high thermal slew rate).

Tim

3. ### Bob MastaGuest

If response time is an issue, why not convert to LEDs?

Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

4. ### Jasen BettsGuest

for your lamps you could try a series capacitor with a parallel resistor
ad drive them with a higher voltage.

you may do better switching to some other type of display.

neons are fast but not low voltage,

LEDs are fast and low voltage.

Bye.
Jasen

5. ### Bill BowdenGuest

If response time is an issue, why not convert to LEDs?

Yes, I thought of using white LEDs but I don't think a single LED would
be bright enough and has a narrow viewing angle. Most of the light
would go straight up to the ceiling. I suppose the Luxon star 1 watts
might work, but are too expensive.

Anyway, I picked up a couple 14 volt 120mA bulbs at Radio Shack today
for \$1.71. I'll give them a try and report back. They are cheap enough
to run at higher voltage with a little less lifetime.

Do you know what the reduced lifetime would be running at excessive
voltage?

-Bill

6. ### John - kd5yiGuest

Life expectancy is roughly inversely proportional to the applied voltage
raised to the 12th power.

So rumor has it.

http://members.misty.com/don/bulb1.html

Cheers,
John

7. ### John PopelishGuest

In general, higher voltage bulbs of the same wattage will turn on and
off faster, because their thinner filaments have a higher surface to
volume ratio. A 4 watt 120 volt night light lamp should have a higher
flicker frequency capability than a 12 volt 4 watt lamp.

8. ### Bill BowdenGuest

In general, higher voltage bulbs of the same wattage will turn on and
Yes, I hooked up the 14 volt, 120mA Radio Shack lamp and the results
are impressive. With a 15 millisecond pulse, the bulb lights up white
with no orange color at all. Looks like this bulb will be usable.

The only problem is the rated lifetime is only 30 hours. Seems a bit
short to me, maybe it's a misprint?

-Bill

9. ### Bob MastaGuest

I have an old bicycle flasher that uses a 9V battery
to drive a 6V bulb. It is very bright, but the flashes
are very brief. At about 2 flashes per second, it
has run hundreds of hours without bulb failure,
while I've gone through many batteries over the
years. This was a complete surprise to me, since
I knew about the 12th power law, and also expected
that the power bursts would cause some sort of
thermal / mechanical fatigue.

So as long as your flashes are short, you
may likewise get a long bulb life. YMMV <g>

Best regards,

Bob Masta