circuit for running two bulbs from one run of 2 conductor wire?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

ray lunder - 21 Aug 2006 10:01 GMT

I saw this once using an off-on-off 3 pole switch (? it had 6 lugs)
and some diodes but I can't remember where. The switch is connected to
a 2 conductor wire that goes to a lense with two different bulbs in
it. In one switch position one bulb lights, in the other position the
first bulb goes off and the second bulbs lights instead. (the bulbs
could be different wattage or color). In the center position both
bulbs are off. You saved one wire run. Any ideas?

Reply to this Message

Heikki - 21 Aug 2006 11:24 GMT

> I saw this once using an off-on-off 3 pole switch (? it had 6 lugs)
> and some diodes but I can't remember where. The switch is connected to
[quoted text clipped - 3 lines]
> could be different wattage or color). In the center position both
> bulbs are off. You saved one wire run. Any ideas?

Elementary, dear Watson: Connect diodes in series with the bulbs, so they
only work in one "direction". Depending which of the two wires you connect
to plus and which to minus, one or the other bulb lights.

-H

Reply to this Message

jim.isbell - 22 Aug 2006 15:41 GMT

> > I saw this once using an off-on-off 3 pole switch (? it had 6 lugs)
> > and some diodes but I can't remember where. The switch is connected to
[quoted text clipped - 9 lines]
>
> -H

Its easier than that and it doesnt require diodes. With 6 lugs you are
talking about a 2 pole 3 throw switch. connect the two wires to the
wipper lugs and one bulb to each of the pairs at the ends. There are
no lugs for the center position.

BUT, you really need only a single pole three throw switch because you
only need to switch one of the wires, the other can go to both bulbs
all the time. AND again, you dont need diodes whether you are talking
DC or AC

Reply to this Message

OldSailor - 22 Aug 2006 16:01 GMT

> BUT, you really need only a single pole three throw switch because you
> only need to switch one of the wires, the other can go to both bulbs
> all the time. AND again, you dont need diodes whether you are talking
> DC or AC

If the switch is located at remote point - say on the boat's electrical
panel and the light is for example a 2-bulb steaming light/deck light, then
would your scheme not require 3 wires from the switch to the lights?

I have also seen diodes used - presumably they overcome this problem by only
requiring 2 wires up the mast?

Reply to this Message

Glenn Ashmore - 22 Aug 2006 18:26 GMT

You need two diodes and a Double throw double pole (DPDT) switch with center
off. The switch will have 6 poles. A pair at each end and a pair in the
middle. Connect the middle pair to your DC power and ground. Connect the
end poles diagonally across from each other and run from either end pair to
the lights. I use that method to control the direction of my fuel and water
transfer pumps.

At each of the two lights add a diode in series with the direction opposite
each other as Heikki described.

With 3 wires and a double gang rotary switch you can control 6 lights.

Signature

Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

>> BUT, you really need only a single pole three throw switch because you
>> only need to switch one of the wires, the other can go to both bulbs
[quoted text clipped - 9 lines]
> only
> requiring 2 wires up the mast?

Reply to this Message

ray lunder - 23 Aug 2006 05:54 GMT

Va-voom! thanks.

>You need two diodes and a Double throw double pole (DPDT) switch with center
>off. The switch will have 6 poles. A pair at each end and a pair in the
[quoted text clipped - 7 lines]
>
>With 3 wires and a double gang rotary switch you can control 6 lights.

Reply to this Message

derbyrm - 23 Aug 2006 14:08 GMT

But remember that you lose about one half volt thru the diode. For
incandescent light bulbs, the change from 12 volts to 11.5 is significant.
Better have bulbs with more than the required range/brightness.

Roger
derbyrm@NOSPAMinsightbbNOSPAM.com
http://home.insightbb.com/~derbyrm

> Va-voom! thanks.
>
[quoted text clipped - 13 lines]
>>
>>With 3 wires and a double gang rotary switch you can control 6 lights.

Reply to this Message

Heikki - 23 Aug 2006 19:51 GMT

> But remember that you lose about one half volt thru the diode. For
> incandescent light bulbs, the change from 12 volts to 11.5 is significant.
> Better have bulbs with more than the required range/brightness.

Or use LEDs as bulbs - they have the diode built in (actually, they *are*
diodes). As a side effect, you get more light for the same amount of
electricity, which translates to a longer battery life. May not be a
problem on a motor boat, but on a sailboat it may make a difference...

-Heikki

Reply to this Message

RLM - 24 Aug 2006 16:18 GMT

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
You will have to COPY and PASTE diagrams to a text editor such as
'Notepad' with fixed font to read. No diodes required.
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

DPDT Switch

Up position Center Position Down position

A-B connected None connectred B-C connected
D-E connected E-F connected

A D A D A D
) )
)------)
) ) ) ) B E
B E B) E) ) )
)------) )-------)
) )
C F C F C F

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

One light or the other, but only one at a time using SPDT switch.

Center off
Switch in up position L1 ON while L2 is Off
Switch in down position L2 ON while L1 is Off
Each light can be a different wattage.

A______________L1_____
|
|
|
|
Positive------ B |
|
|
|
C_______________L2___|________Neg.

SPDT switch On-Off-On

A,B,C, = terminals on switch
L1 = light or load 1
L2 = light or load 2

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

Dim or Bright lighting

Center off
Up position = L1 on
Bottom position both L1 & L2 on

This could be used in up position only anchor light is on.
In the down position running lights & anchor lights are on
when L1 = anchor light, L2 = port & starboard running lights.

Could also be used for a dim light in cabin in up position or
a brighten cabin where both lights are on in the down position
L1 and L2 can be different wattages or LEDs w/resistors.

j---A D
u
m
p
e
r B-jumper-E----- Positive
|
|
|
|---C F
| |
| |
L1 L2
| |
Neg.________________|________|

DPDT switch. On-Off-On
Jumper between A & C terminals on one side.
Jumper between B & E terminals
A,B,C,D,E,F = terminals on switch
L1 & L2 are lights or load

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

Small DC Motor Reverser
Using DPDT Switch
on-off-on

Polarity changes on motor as switch is
moved from top to bottom position.
Motor off in center position.

A D
\ /
\ /
\ /
\ /
Neg. B / E Pos.
/ \
/ \
/ \
/ \
C F
| |
| |
| |
|____M____|

A,B,C,D,E,F = terminals on switch
M = small DC motor (perm. magnet w/two poles, non-grounded frame)
May want small capacitor across motor terminals.

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

Hope this helps.

Reply to this Message

Heikki - 24 Aug 2006 19:00 GMT

>> I saw this once using an off-on-off 3 pole switch (? it had 6 lugs)
>> and some diodes but I can't remember where. The switch is connected to
>> a 2 conductor wire that goes to a lense with two different bulbs in
>> it. [...]

> You will have to COPY and PASTE diagrams to a text editor such as
> 'Notepad' with fixed font to read. No diodes required.

I think the key point in the original question was that 2 conductor wire.
Your diagrams seemed to need three conductors. If there can be three
conductors between the switch and the bulbs, your solution works fine (or
if you can use something else (metal hull?) for return). But with only two
wires available, some trickery is needed. The solution with 2 diodes is
probably the simplest.

- Heikki

Reply to this Message

RLM - 24 Aug 2006 19:46 GMT

>>> I saw this once using an off-on-off 3 pole switch (? it had 6 lugs)
>>> and some diodes but I can't remember where. The switch is connected to
[quoted text clipped - 12 lines]
>
> - Heikki

Copy and paste to notepad. This should work.
I see what you mean now! Thanks, I'll remember that.

A D
\ /
\ /
\ /
\ /
Neg. B / E Pos.
/ \
/ \
/ \
/ \
C F
| |
| |
| |
|___>|_L1_|
| |
| |
| |
|__|<__L2_|

>| = Diode

Reply to this Message

Boat Forum / Building / August 2006

circuit for running two bulbs from one run of 2 conductor wire?