Gonna change the oil
 

With few people at work, its hard to get much done. Today I woulda got
more done on the boat but spent it at work. I'll go to the boat to
change the oil and engine zinc on my Yanmar 2GM tomorrow.
Tried to find some 600 ohm resistors at Radio Shack for my homemade
ultra-bright LED anchor light but no luck, will havta order em.

Gonna change the oil
 

wrote in message
oups.com...
With few people at work, its hard to get much done. Today I woulda got
more done on the boat but spent it at work. I'll go to the boat to
change the oil and engine zinc on my Yanmar 2GM tomorrow.
Tried to find some 600 ohm resistors at Radio Shack for my homemade
ultra-bright LED anchor light but no luck, will havta order em.


How much less power draw will that new LED anchor light have over a standard
12v light?

Gonna change the oil
 

" JimH" wrote in message
. ..

wrote in message
oups.com...
With few people at work, its hard to get much done. Today I woulda got
more done on the boat but spent it at work. I'll go to the boat to
change the oil and engine zinc on my Yanmar 2GM tomorrow.
Tried to find some 600 ohm resistors at Radio Shack for my homemade
ultra-bright LED anchor light but no luck, will havta order em.


How much less power draw will that new LED anchor light have over a
standard 12v light?


I'd like to know also. Truckers are putting them all over their rigs and
they are *bright*. One my last trip to Florida, while driving at night, I
gave a trucker who was passing me the lights off/on routine to let him know
it was safe to pull back over. He flashed all his lights in a "thanks" and
damn near blinded me.

Eisboch

Gonna change the oil
 

wrote in message
oups.com...
When I drop by work on the way to the coast tomorrow, I'll get the
specs from the LED package for current draw and calculate the power. I
am using 6 of the LEDs so it oughta be fairly bright. If I remember
right, it was less than 1/2 of a 12 watt bulb. I am speccing 1 watt
resistors for it though (6 resistors in parallel each in series with an
LED).


Are the LEDs part of the parallel branches of the circuit? Meaning:

12v_________/\/\/\/\/\/\/\_________LED_________Ground
12v_________/\/\/\/\/\/\/\_________LED_________Ground
12v_________/\/\/\/\/\/\/\_________LED_________Ground
12v_________/\/\/\/\/\/\/\_________LED_________Ground
12v_________/\/\/\/\/\/\/\_________LED_________Ground
12v_________/\/\/\/\/\/\/\_________LED_________Ground


or are they:

12v__________/\/\/\/\/\/\/\____________LED_____Ground
12v__________/\/\/\/\/\/\/\_____l______ LED_____Ground
12v__________/\/\/\/\/\/\/\_____l______ LED_____Ground
12v__________/\/\/\/\/\/\/\_____l______ LED_____Ground
12v__________/\/\/\/\/\/\/\_____l______ LED_____Ground
12v__________/\/\/\/\/\/\/\_____l______ LED_____Ground


???

Eisboch

Gonna change the oil
 

First version, otherwise why use 6 resistors instead of one single
lower ohmage one of higher power.

Gonna change the oil
 

On 29 Dec 2005 17:47:55 -0800, "
wrote:

If I remember
right, it was less than 1/2 of a 12 watt bulb. I am speccing 1 watt
resistors for it though (6 resistors in parallel each in series with an
LED).

=========================================

How many LEDs in series would it take to use no resistors at all?

Six 1 watt resistors per LED sounds like a lot of wasted power to me.

Gonna change the oil
 

wrote in message
ups.com...
First version, otherwise why use 6 resistors instead of one single
lower ohmage one of higher power.


I was trying to roughly calculate the power requirements. You said 600 ohm
resistors, correct? The voltage drop on the LED will be minimal when
forward biased or "on", so each branch must be about .02 amps, times six
equals .12 amps, so the power must be about 12v times .12 or about 1.4
watts. Probably a bit more when you factor in the LED drop, whatever it is.
Significantly less than a regular light bulb!

Eisboch

Gonna change the oil
 

"Eisboch" wrote in message
...

wrote in message
ups.com...
First version, otherwise why use 6 resistors instead of one single
lower ohmage one of higher power.


I was trying to roughly calculate the power requirements. You said 600
ohm resistors, correct? The voltage drop on the LED will be minimal when
forward biased or "on", so each branch must be about .02 amps, times six
equals .12 amps, so the power must be about 12v times .12 or about 1.4
watts. Probably a bit more when you factor in the LED drop, whatever it
is. Significantly less than a regular light bulb!

Eisboch


In fact, the more I think about it, somethings wrong here. I must have
misunderstood your hookup. Do you plan to use six, 600 ohm resistors in
parallel for *each* of the LED segments? If so, the power consumed will go
up big time. Or is it a single 600 ohm resistor per LED segment. If so,
one watt resistors won't hack it.

Eisboch

Gonna change the oil
 

"Eisboch" wrote in message
...

wrote in message
ups.com...
First version, otherwise why use 6 resistors instead of one single
lower ohmage one of higher power.


I was trying to roughly calculate the power requirements. You said 600
ohm resistors, correct? The voltage drop on the LED will be minimal when
forward biased or "on", so each branch must be about .02 amps, times six
equals .12 amps, so the power must be about 12v times .12 or about 1.4
watts. Probably a bit more when you factor in the LED drop, whatever it
is. Significantly less than a regular light bulb!

Eisboch


Most LED's are in the 400mw range.

Gonna change the oil
 

"Wayne.B" wrote in message
...
On 29 Dec 2005 17:47:55 -0800, "
wrote:

If I remember
right, it was less than 1/2 of a 12 watt bulb. I am speccing 1 watt
resistors for it though (6 resistors in parallel each in series with an
LED).

=========================================

How many LEDs in series would it take to use no resistors at all?

Six 1 watt resistors per LED sounds like a lot of wasted power to me.


1 watt resistor can dissipate 1 watt of power across it, does not mean there
will be that much power. We always used 1/4w resisters.