I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve

Steve B wrote:
... Could I put them on a rheostat so that I could dim them down?

Yes. Do you know how much current they use? How many are there? Run
on 12v, I assume.

"Bob Engelhardt" wrote in message
...
Steve B wrote:
... Could I put them on a rheostat so that I could dim them down?

Yes. Do you know how much current they use? How many are there? Run on
12v, I assume.

Actually, it will not necessarily work. It depends on how the current is
regulated to the LED. If these are meant to be energy efficient, they will
have a constant current driver. Reduce the supply voltage a small amount
will not effect the current to the LED. Reducing the supply voltage below a
certain threshold will make the driver work erratically and it may even
increase the current to the LED. In this case you would have to open up
the unit and install the pot In parallel between the driver and LED and
accept efficiency losses when dimmed.

If the LED fixtures are cheap and not made for efficiency, they will simply
have a resistor in series with the LED to limit the maximum current at any
given voltage. In that case reducing the supply voltage will dim the LED.

Bob Engelhardt fired this volley in
:

Yes. Do you know how much current they use? How many are there? Run
on 12v, I assume.

Not well, though. It won't be nearly linear over the spin of the dial,
because of the tremendous "knee" in the avalanche current characteristics
of LEDs.

The best (but more complex) way to vary an LED's brightness is with pulse
width modulation. A 555 timer set up as an adjustable one-shot will
build you a fairly effective PWM source for this sort of application.

Keep the fundamental frequency above 100Hz to reduce visible flicker
artifacts (like when you move your eyes, and it seems to make a dotted
line instead of a streak).

LLoyd

"Bob Engelhardt" wrote in message
...
Steve B wrote:
... Could I put them on a rheostat so that I could dim them down?

Yes. Do you know how much current they use? How many are there? Run on
12v, I assume.

Yes, 12v dc. Low amps, low watts, just good bright light. I got the
shipment today, and went out and played with them. They give a nice clear
light, maybe too bright, which is why I want to tone it down a bit. When
fishing under a full moon like it is now, you don't need a lot of light, and
when you do, you can use one of the LED headlamps aimed at the right spot.
Guess just a run of the mill device would work. What would that be called
at Radio Shack? Rheostat?

Steve

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
Bob Engelhardt fired this volley in
:

Yes. Do you know how much current they use? How many are there? Run
on 12v, I assume.

Not well, though. It won't be nearly linear over the spin of the dial,
because of the tremendous "knee" in the avalanche current characteristics
of LEDs.

The best (but more complex) way to vary an LED's brightness is with pulse
width modulation. A 555 timer set up as an adjustable one-shot will
build you a fairly effective PWM source for this sort of application.

Keep the fundamental frequency above 100Hz to reduce visible flicker
artifacts (like when you move your eyes, and it seems to make a dotted
line instead of a streak).

LLoyd

I was never any good at electronics. What would I buy at Radio Shack?

Steve

"Steve B" fired this volley in news:jvesen$jnf$1
@speranza.aioe.org:

I was never any good at electronics. What would I buy at Radio Shack?

They wouldn't carry a built-up unit to do it. You'd have to buy parts
and cobble it up yourself.

If you're not an electronics type, I'd suggest just going with a
rheostat, and see if that works to your satisfaction.

Keep in mind that it will get hot in use (when it's dimming), so you'll
want a wire-wound unit rated at least 2/3 of the wattage of the lamps you
want to control, and you'll have to mount it in a ventilated *metal*
enclosure that will keep your fingers off the hot parts when it's in
operation.

LLoyd

On Thu, 02 Aug 2012 14:44:52 -0700, Steve B wrote:


Yes, 12v dc. Low amps, low watts, just good bright light. I got the
shipment today, and went out and played with them. They give a nice
clear light, maybe too bright, which is why I want to tone it down a
bit.

Get a bit of dark transparent plastic and cover them.

On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"Steve B" wrote in message
...
I was never any good at electronics. What would I buy at Radio
Shack?

Steve

You could try a few different Zener diodes in series to drop the
voltage. Pick physically large ones to get higher power dissipation.
They drop 1V one way and the rated voltage the other.

The dash light dimmer control from a junkyard might work.

jsw

Steve B wrote:
Yes, 12v dc. Low amps, low watts, ...

Well, you will need to be more specific. Without knowing the number of
lights and the current each draws, you can't know what rheostat to get.
E.g., a randomly picked one could be such that a very small turn could
turn the lights off entirely, or a complete turn could have very little
effect. And the wrong power sizing could result in it going up in smoke.

Did any information come with them? You certainly know how many of them
there are. How many LEDs in each fixture? We gotta have something
here. What you're asking is like "My car won't run, what size bolt do I
need?".

Bob

On 8/2/2012 8:12 PM, DoN. Nichols wrote:
On 2012-08-02, Spehro wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.


If it has an internal power supply then nothing short of radical surgery
will work.

LEDs themselves are current operated devices, not so much voltage.
So reducing the current flowing through them will cause them to dim.

But with an internal supply (and I'd suspect solar powered means just
that) - nope...

On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Did you look? There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Spehro Pefhany wrote :
On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Did you look? There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!


Best regards,
Spehro Pefhany

Reference or link?????

--
John G

On 3 Aug 2012 01:12:23 GMT, "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.
Cheers,
John B.

On Fri, 03 Aug 2012 16:29:43 +1000, John G
wrote:

Spehro Pefhany wrote :
On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Did you look? There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!


Best regards,
Spehro Pefhany

Reference or link?????

Here you go:-
http://bit.ly/NXGspy

Spehro Pefhany wrote on 4/08/2012 :
On Fri, 03 Aug 2012 16:29:43 +1000, John G
wrote:

Spehro Pefhany wrote :
On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard
wired. Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Did you look? There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!


Best regards,
Spehro Pefhany

Reference or link?????

Here you go:-
http://bit.ly/NXGspy

Thanks. I did not realize there were so many 12 volt dimmers and should
have looked myself.

--
John G

On 2012-08-03, Spehro Pefhany wrote:
On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:

[ ... ]

Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Did you look?

I wasn't sure of a proper search string to distinguish them from
AC line powered dimmers.

There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!

Your typing is expensive. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2012-08-03, Spehro Pefhany wrote:
On Fri, 03 Aug 2012 16:29:43 +1000, John G
wrote:

Spehro Pefhany wrote :
On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:

[ ... ]

Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

[ ... ]

Did you look? There are ones that are 12V and 12/24V and they cost
like $3-5 US delivered. Argh.. it's costing more than that for me to
type this!!!


Best regards,
Spehro Pefhany

Reference or link?????

Here you go:-
http://bit.ly/NXGspy

Hmm ... LMGTFY wants me to enable javascript. I'll do without,
since I'm not familiar with LMGTFY anyway.

Thanks,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"John B." wrote:

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.


Can and should are two different things. The proper way to dim them
is with a PWM controller which is dirt cheap on Ebay.

On Sat, 04 Aug 2012 10:25:10 -0400, "Michael A. Terrell"
wrote:


"John B." wrote:

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.


Can and should are two different things. The proper way to dim them
is with a PWM controller which is dirt cheap on Ebay.

How so "proper"? More efficient as no resisters used to generate heat
but the O.P just wanted to make the lights less bright and a rheostat
will do that with the usual 12 VDC LED lights.
Cheers,
John B.

"John B." wrote:

On Sat, 04 Aug 2012 10:25:10 -0400, "Michael A. Terrell"
wrote:


"John B." wrote:

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.


Can and should are two different things. The proper way to dim them
is with a PWM controller which is dirt cheap on Ebay.

How so "proper"? More efficient as no resisters used to generate heat
but the O.P just wanted to make the lights less bright and a rheostat
will do that with the usual 12 VDC LED lights.


He would need a wirewound Rheostat, and the control would be very
touch, since LEDS are current operated devices, unlike incandescents.
They will change brightness with temperature changes when such a crude
method id used. A decent Rheostat willl cost more than a PWM
controller. Some LEDs will start to emit light at the microamp level.

On 8/5/2012 3:44 AM, Michael A. Terrell wrote:

"John B." wrote:

On Sat, 04 Aug 2012 10:25:10 -0400, "Michael A. Terrell"
wrote:


"John B." wrote:

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.


Can and should are two different things. The proper way to dim them
is with a PWM controller which is dirt cheap on Ebay.

How so "proper"? More efficient as no resisters used to generate heat
but the O.P just wanted to make the lights less bright and a rheostat
will do that with the usual 12 VDC LED lights.


He would need a wirewound Rheostat, and the control would be very
touch, since LEDS are current operated devices, unlike incandescents.
They will change brightness with temperature changes when such a crude
method id used. A decent Rheostat willl cost more than a PWM
controller. Some LEDs will start to emit light at the microamp level.


Well, true enough.

But ALL

On Sun, 05 Aug 2012 04:44:53 -0400, "Michael A. Terrell"
wrote:


"John B." wrote:

On Sat, 04 Aug 2012 10:25:10 -0400, "Michael A. Terrell"
wrote:


"John B." wrote:

A great many of those 12 VDC lights are just series circuits made up
of LED's and resisters. Try a resister in series with one side of the
circuit. It may well dim your lights. If that works you can replaced
the resister with a variable resister (potentiometer, rheostat,
whatever) for finer control.


Can and should are two different things. The proper way to dim them
is with a PWM controller which is dirt cheap on Ebay.

How so "proper"? More efficient as no resisters used to generate heat
but the O.P just wanted to make the lights less bright and a rheostat
will do that with the usual 12 VDC LED lights.


He would need a wirewound Rheostat, and the control would be very
touch, since LEDS are current operated devices, unlike incandescents.
They will change brightness with temperature changes when such a crude
method id used. A decent Rheostat willl cost more than a PWM
controller. Some LEDs will start to emit light at the microamp level.

I'm not arguing that a PWM isn't efficient. I'm merely pointing out
that the general, run of the mill, 12 VDC LED fixture is either a
series wired bunch of LEDs or a series parallel wired bunch of LEDs,
possible with resisters in the series circuits. They normally draw so
little current that there is no necessity for a wire wound resister.
If I remember correctly I used either a 1/4 or 1/2 watt carbon
resister to dim the lights in my previous boat. The OP just wanted to
dim some fishing lights and a variable resister will do the job.

At least it did on my 40 ft. sailboat that I converted from
incandescent/fluorescent to LED. I had no problems with the lights in
the three years before I sold the boat. Power came from the 12 volt,
600 amp hour house bank who's voltage would have ranged between 14+
volts when charging and probably 11.5 volts.
Cheers,
John B.

"John B." wrote in message
...

I'm not arguing that a PWM isn't efficient. I'm merely pointing out
that the general, run of the mill, 12 VDC LED fixture is either a
series wired bunch of LEDs or a series parallel wired bunch of LEDs,
possible with resisters in the series circuits. They normally draw
so
little current that there is no necessity for a wire wound resister.
John B.

FWIW, the 24" LED rope light that illuminates my keyboard shelf
indicates 8W on a KAW.

On 3 Aug 2012 01:12:23 GMT, the renowned "DoN. Nichols"
wrote:

On 2012-08-02, Spehro Pefhany wrote:
On Thu, 2 Aug 2012 09:27:45 -0700, the renowned "Steve B"
wrote:

I have some LED pole lights coming for my boat. They are for inside the
boat for when we are fishing, and want a dim light. They come hard wired.
Could I put them on a rheostat so that I could dim them down?

Steve


Buy an electronic control from China on eBay. Costs just about
nothing.

But he wants to run it from DC on the boat, not 60 Hz AC, so I
think that the light dimmers (if that is what you are suggesting) won't
work without first converting to AC.

Enjoy,
DoN.

Just as a follow-up, I bought one and it's made pretty well. The
design uses an 80A MOSFET and a PWM made with a comparator and 555
generating sawtooth waves. Drive to the mosfet gate is quite pokey
(microseconds rise/fall), so I imagine RFI would be minimal (no RFI
filtering). I would derate it a bit at 24V because of the switching
losses.

Protection against input reversal (series diode), but no protection
against short circuit on the output or applying reverse voltage to the
output (either will destroy the unit almost instantly). No low voltage
lockout either- don't know if it could die from that or not (eg. run
battery down slowly and the MOSFET should go ohmic at some point). No
instructions at all.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com