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On Wed, 14 Jun 1995 Gavin_Bill@la*.nc*.na*.mi* wrote:
> PERSONALLY, I DON'T LIKE THE DISPERSED BEAM OF MR16 BULBS BECAUSE IT
> SEEMS TO CAUSE A LOT OF BACK SCATTER IN TURBID WATER. IN CLEAR WATER IT
> IS BETTER.
> THE LIFE RATINGS ON BULBS USUALLY REFLECT DIFFERENCES IN COLOR SPECTRUM.
> THE SHORTER RATED (50 HOUR BULBS) BURN HOTTER AND HAVE (TO ME) A MUCH
> MORE PLEASING LIGHT. THE USHIO BRL 12V, 50 WATT, IS A 50 HOUR BULB THAT
> HAS A COLOR TEMP OF 3300 DEG KELVIN. 3000 HOUR RATED BULBS WILL HAVE A
> LOWER COLOR SPECTRUM (PROBABLY 2800 - 2900 DEG KELVIN) AND DEPENDING ON
> YOUR PERSONAL VIEWPOINT, MAY NOT LOOK AS GOOD
The original question was about mr16 and mr11 bulbs. The high color temp.
bulbs are indeed nicer but the mr16 bulbs that I have seen that do burn
hot also have weird beam patterns. I do not advocate overvoltage to
"hot" low life bulbs. That is why I was careful to specify the long-life
"display" bulbs. Actually, by putting an overvoltage to These bulbs, they
can be made to have the higher color temp. we prefer.
>
> Also, you need not worry to much about overvoltage. First you are likely
> to be losing as much as a volt to your wires, switches, connectors, etc.
> before the power reaches the bulb.
>
> I WAS TEMPTED TO DISPUTE THAT BUT THOUGHT I'D BETTER CHECK FIRST. TO MY
> SURPRISE I FOUND ALMOST 0.5 VOLT DROP BETWEEN THE BATTERIES AND BULB ON
> MY OWN LIGHT (WHICH I BUILT WITH LOVING CARE). ROUGHLY 220 mV ON EACH
> LEG. THIS AT 12.6 VOLTS AND 4.2 AMPS. OKAY, SO V=IR MEANS I HAVE A TOTAL
> RESISTANCE OF ABOUT .44 V / 4.2 A = .1 OHM. STRANDED WIRE DATA SUGGESTS
> THAT ABOUT .02 OHMS OF THIS COMES FROM THE WIRE ITSELF. I SUSPECT THE
> BULB CONNECTOR ACCOUNTS FOR A SIGNIFICANT AMOUNT. SOMETHING TO
> INVESTIGATE! ANYWAY, I'D STILL BE CAREFUL ABOUT OVERVOLTING, THOUGH IT
> DOES SOMETIMES PRODUCE AN AWESOME LIGHT.
I learned about the voltage drop from a talk by Bob Goodman at a CDS
workshop when it was held at the women's club.
John was concerned that his battery was showing over 12 volts, especially
just after coming off of charge. This "overvoltage" I think we are not
going to worry about.
> Second, bulbs lose a fairly low percentage
> of their rated life to overvoltage as long as it is not much over 10 percent.
> (sorry, forget exact numbers).
>
> ACCORDING TO THE USHIO MANUAL "IF 90% OF THE RATED VOLTAGE IS SUPPLIED,
> THE LAMP LIFE WILL BE EXTENDED BY 3.5 TIMES. IF 110% OF THE RATED
> VOLTAGE IS SUPPLIED, THE LIFE WILL BE 1/3." ON A 3000 HOUR BULB THIS
> MIGHT NOT SEEM SIGNIFICANT, BUT ON A 50 HOUR BULB IT IS.
Thanks for looking it up. You are right, 50 hour bulbs should not be
"hopped up".
>
> CAN'T REALLY COMMENT AS I DISLIKE MR-16 BULBS IN GENERAL. BUT THEN,
> WE'RE DIVING BIG CAVE WHERE THE LASER BEAM ON THE 50 WATT TEST TUBE IS A
> REAL PLUS FOR PUNCHING ACROSS A 60 OR 80 FT WIDE TUNNEL AND LOOKING AT A
> POSSIBLE SIDE LEAD. I SUSPECT IT HAS TO DO WITH WHERE YOU DIVE THE MOST.
Yes, a good diver uses the best tools for the particular job. If I was
zooming through huge "power cave" I would want a tight bright "hole
spotter" too.
>
Good 'ol red tops, still have a bunch- too bad they leak so much.
These new "plug in and forget about it" chargers and batteries have
spoiled me.
Bill, thanks for your letter, I enjoyed it, Paul
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