Why not?
"chuck" wrote in message
nk.net...
No, that won't work at all.

Johnhh wrote:
Or go down to the hardware store and buy a light switch dimmer. It would
probably rust out in short order, but I'll bet the resistance would be
close enough to work.


"Jack Erbes" wrote in message
...

William Andersen wrote:


Anyone know what I need to buy to add a dimmer to my instrument lights?

snip

Just about every automobile has one, I'd visit a wrecking yard and
probably look for one of the newer ones that has the dimmer control
mounted separately from the light switch (like a dash mounted
thumbwheel).

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

Hardware store dimmers only work on AC power, not DC. They use a solid-state
device called a Triac, not a variable resistor.

Blue Sea makes dimmer units in several different amp ranges for 12 and 24
volt DC systems specifically for this type of application. They also sell a
switch to control it already labeled "Bright" and "Dim". These are available
through West Marine and several other distributors. I have one installed in
my custom engine instrument panel and it works like a champ.

Rusty O

"William Andersen" wrote in message
news:ta1Ce.14832$HV1.13600@fed1read07...
Anyone know what I need to buy to add a dimmer to my instrument lights?
I want to be able to control the intensity of my instrument lights. They
are not shielded and reflect on the windshield, making it impossible to
sit and look through the windshield. We have to stand while at the wheel
at night. I've changed to red light bulbs, but the instrument panel is
tilted so much there's no way to shield the windshield from the reflected
light.
I went to a Radio Shack today and all they could come up with was to offer
a volume control knob mounted on a wall switch plate. Since I'm not a
techie, I need to know exactly what to ask for, since they seem to know
even less than me.

I guess I just always assumed they were just variable resistors. There I go
assuming again--it gets me every time. Were they ever made with variable
resistors?

How do the Blue Sea one's work?

"Rusty" wrote in message
...
Hardware store dimmers only work on AC power, not DC. They use a
solid-state device called a Triac, not a variable resistor.

Blue Sea makes dimmer units in several different amp ranges for 12 and 24
volt DC systems specifically for this type of application. They also sell
a switch to control it already labeled "Bright" and "Dim". These are
available through West Marine and several other distributors. I have one
installed in my custom engine instrument panel and it works like a champ.

Rusty O

"William Andersen" wrote in message
news:ta1Ce.14832$HV1.13600@fed1read07...
Anyone know what I need to buy to add a dimmer to my instrument lights?
I want to be able to control the intensity of my instrument lights. They
are not shielded and reflect on the windshield, making it impossible to
sit and look through the windshield. We have to stand while at the wheel
at night. I've changed to red light bulbs, but the instrument panel is
tilted so much there's no way to shield the windshield from the reflected
light.
I went to a Radio Shack today and all they could come up with was to
offer a volume control knob mounted on a wall switch plate. Since I'm not
a techie, I need to know exactly what to ask for, since they seem to know
even less than me.

The Blue Sea dimmers are about two by three inches and about one inch thick.
They have five wires coming out one end. These wires go to 1) Ground, 2)
Power, 3) Bright, 4) Dim, 5) Light. The wires themselves are labeled for
their use. The switch you use to control the dimmer is designated (ON) OFF
(ON).

(ON) means 'Momentary On' so the switch returns with a spring when you press
on the top or the bottom and returns to the middle OFF position when you
release it. Switches like this connect a circuit from the center connection
to the bottom connection when you push on the top of the switch. They
connect the center position to the top connection when you push on the
bottom of the switch. Note: This is backwards to what you might expect.

To wire the dimmer you connect the 'Ground' lead to DC negative, the 'Power'
lead, and the center connection on the switch, to DC positive. The 'Bright'
lead connects to the bottom of the switch and the 'Dim' lead connects to the
top of the switch. The 'Light' lead goes to your light bulbs and of course
you connect the other end of each light bulb to DC negative. Don't forget
that DC positive lead to the center connection of the switch, it won't work
without it.

Now when you push on the top of the switch the lights will get brighter and
when you push on the bottom of the switch they will get dimmer. Another good
feature is the dimmer will 'remember' the last setting and return to it if
you turn off the power and later turn it back on again.

These dimmer units are available in 2 amp, 5 amp, and 10 amp versions. They
can also be used to control the speed of DC powered fans.

If you just want a simple rotary knob dimmer, Cole Hersee makes two
different models also available through West Marine and several other
suppliers. These, and the low amp Blue Sea system, all run about the same
price.

I answer to Johnhh's question, home dimmer switches haven't been made with
variable power resistors in more than thirty years.

Rusty O


"Johnhh" wrote in message
...
I guess I just always assumed they were just variable resistors. There I
go assuming again--it gets me every time. Were they ever made with
variable resistors?

How do the Blue Sea one's work?

A very cheap solution would be to put a resistor in series with the
lights and an SPST switch in parrallel with the resistor (to short it
out). You need to figure out the resistance on the chain of bulbs, find
a suitable similar resistance (for 1/2 power... more for less light,
etc) Power rating needs to be figured out as well. For 1/2 power, it
should match the total of all the lights... less if you raise the
resistance.

THis doesn't give you the variable resistance but it is a couple dollar
solution that may solve the problem.



Rusty wrote:
The Blue Sea dimmers are about two by three inches and about one inch thick.
They have five wires coming out one end. These wires go to 1) Ground, 2)
Power, 3) Bright, 4) Dim, 5) Light. The wires themselves are labeled for
their use. The switch you use to control the dimmer is designated (ON) OFF
(ON).

(ON) means 'Momentary On' so the switch returns with a spring when you press
on the top or the bottom and returns to the middle OFF position when you
release it. Switches like this connect a circuit from the center connection
to the bottom connection when you push on the top of the switch. They
connect the center position to the top connection when you push on the
bottom of the switch. Note: This is backwards to what you might expect.

To wire the dimmer you connect the 'Ground' lead to DC negative, the 'Power'
lead, and the center connection on the switch, to DC positive. The 'Bright'
lead connects to the bottom of the switch and the 'Dim' lead connects to the
top of the switch. The 'Light' lead goes to your light bulbs and of course
you connect the other end of each light bulb to DC negative. Don't forget
that DC positive lead to the center connection of the switch, it won't work
without it.

Now when you push on the top of the switch the lights will get brighter and
when you push on the bottom of the switch they will get dimmer. Another good
feature is the dimmer will 'remember' the last setting and return to it if
you turn off the power and later turn it back on again.

These dimmer units are available in 2 amp, 5 amp, and 10 amp versions. They
can also be used to control the speed of DC powered fans.

If you just want a simple rotary knob dimmer, Cole Hersee makes two
different models also available through West Marine and several other
suppliers. These, and the low amp Blue Sea system, all run about the same
price.

I answer to Johnhh's question, home dimmer switches haven't been made with
variable power resistors in more than thirty years.

Rusty O


"Johnhh" wrote in message
...

I guess I just always assumed they were just variable resistors. There I
go assuming again--it gets me every time. Were they ever made with
variable resistors?

How do the Blue Sea one's work?

If the main goal is to see how cheap you can do it....

Try painting the bottom contact on each light bulb with resistance paint. If
it's still too bright, just add another coat.

Rusty O

"Ed" wrote in message
.. .
A very cheap solution would be to put a resistor in series with the lights
and an SPST switch in parrallel with the resistor (to short it out). You
need to figure out the resistance on the chain of bulbs, find a suitable
similar resistance (for 1/2 power... more for less light, etc) Power rating
needs to be figured out as well. For 1/2 power, it should match the total
of all the lights... less if you raise the resistance.

THis doesn't give you the variable resistance but it is a couple dollar
solution that may solve the problem.



Rusty wrote:
The Blue Sea dimmers are about two by three inches and about one inch
thick. They have five wires coming out one end. These wires go to 1)
Ground, 2) Power, 3) Bright, 4) Dim, 5) Light. The wires themselves are
labeled for their use. The switch you use to control the dimmer is
designated (ON) OFF (ON).

(ON) means 'Momentary On' so the switch returns with a spring when you
press on the top or the bottom and returns to the middle OFF position
when you release it. Switches like this connect a circuit from the center
connection to the bottom connection when you push on the top of the
switch. They connect the center position to the top connection when you
push on the bottom of the switch. Note: This is backwards to what you
might expect.

To wire the dimmer you connect the 'Ground' lead to DC negative, the
'Power' lead, and the center connection on the switch, to DC positive.
The 'Bright' lead connects to the bottom of the switch and the 'Dim' lead
connects to the top of the switch. The 'Light' lead goes to your light
bulbs and of course you connect the other end of each light bulb to DC
negative. Don't forget that DC positive lead to the center connection of
the switch, it won't work without it.

Now when you push on the top of the switch the lights will get brighter
and when you push on the bottom of the switch they will get dimmer.
Another good feature is the dimmer will 'remember' the last setting and
return to it if you turn off the power and later turn it back on again.

These dimmer units are available in 2 amp, 5 amp, and 10 amp versions.
They can also be used to control the speed of DC powered fans.

If you just want a simple rotary knob dimmer, Cole Hersee makes two
different models also available through West Marine and several other
suppliers. These, and the low amp Blue Sea system, all run about the same
price.

I answer to Johnhh's question, home dimmer switches haven't been made
with variable power resistors in more than thirty years.

Rusty O


"Johnhh" wrote in message
...

I guess I just always assumed they were just variable resistors. There I
go assuming again--it gets me every time. Were they ever made with
variable resistors?

How do the Blue Sea one's work?

I don't deny being cheap. But I was looking for variable control.
I guess this will wait - there's better things I can do with $45
"Rusty" wrote in message
...
If the main goal is to see how cheap you can do it....

Try painting the bottom contact on each light bulb with resistance paint.
If it's still too bright, just add another coat.

Rusty O

"Ed" wrote in message
.. .
A very cheap solution would be to put a resistor in series with the lights
and an SPST switch in parrallel with the resistor (to short it out). You
need to figure out the resistance on the chain of bulbs, find a suitable
similar resistance (for 1/2 power... more for less light, etc) Power
rating needs to be figured out as well. For 1/2 power, it should match
the total of all the lights... less if you raise the resistance.

THis doesn't give you the variable resistance but it is a couple dollar
solution that may solve the problem.



Rusty wrote:
The Blue Sea dimmers are about two by three inches and about one inch
thick. They have five wires coming out one end. These wires go to 1)
Ground, 2) Power, 3) Bright, 4) Dim, 5) Light. The wires themselves are
labeled for their use. The switch you use to control the dimmer is
designated (ON) OFF (ON).

(ON) means 'Momentary On' so the switch returns with a spring when you
press on the top or the bottom and returns to the middle OFF position
when you release it. Switches like this connect a circuit from the
center connection to the bottom connection when you push on the top of
the switch. They connect the center position to the top connection when
you push on the bottom of the switch. Note: This is backwards to what
you might expect.

To wire the dimmer you connect the 'Ground' lead to DC negative, the
'Power' lead, and the center connection on the switch, to DC positive.
The 'Bright' lead connects to the bottom of the switch and the 'Dim'
lead connects to the top of the switch. The 'Light' lead goes to your
light bulbs and of course you connect the other end of each light bulb
to DC negative. Don't forget that DC positive lead to the center
connection of the switch, it won't work without it.

Now when you push on the top of the switch the lights will get brighter
and when you push on the bottom of the switch they will get dimmer.
Another good feature is the dimmer will 'remember' the last setting and
return to it if you turn off the power and later turn it back on again.

These dimmer units are available in 2 amp, 5 amp, and 10 amp versions.
They can also be used to control the speed of DC powered fans.

If you just want a simple rotary knob dimmer, Cole Hersee makes two
different models also available through West Marine and several other
suppliers. These, and the low amp Blue Sea system, all run about the
same price.

I answer to Johnhh's question, home dimmer switches haven't been made
with variable power resistors in more than thirty years.

Rusty O


"Johnhh" wrote in message
...

I guess I just always assumed they were just variable resistors. There
I go assuming again--it gets me every time. Were they ever made with
variable resistors?

How do the Blue Sea one's work?