Grex Do-it-yourself Conference

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Grex Do-it-yourself Item 33: Basic Switch Wiring
Entered by ea on Sat Jan 13 19:29:47 UTC 2001:

I have a device (it's a little flashing LED light thing) that runs off 2 
AA batteries, and I would like to add a switch to it.  This should not 
be hard, I just don't know how to complete the circuit.

The switch has 6 prongs.  I'll try to draw it, and number the prongs.  
It is a basic rocker switch with 2 positions, on and off.  The light has 
2 wires, red and black, which I assume get severed and attached to the 
switch in some manner.  I also have some spare cable that I can use, as 
the red and black wires are rather short.  Which wire goes to which 
prong?

|---------------|
| 1    3     5  |
|               |
| 2    4     6  |
|---------------|

5 responses total.

#1 of 5 by scott on Sat Jan 13 20:42:09 2001:

This is what is known as a "Double pole, double throw" switch (DPDT). 
Basically you have *four* on-off switches operated by one toggle.  A "single
pole, single throw" switch (SPST, get the acronym system?) would look like:

|-------
| 1  2  |
|-------|

while a SPDT switch would look like:

|-----------|
| 1   2   3 |
|-----------|

A double-pole switch just puts two of the same thing into one unit;

Anyway, the 4 on-off switches from your diagram are connected to:
Switch 1:  1-3
Switch 2:  3-5
Switch 3:  2-4
Switch 4:  4-6

So basically just pick one of those combinations and hook up.  You might need
to play around with it to figure out which side makes the "On Off" markings
correspond to what you have the switch doing.

#2 of 5 by ea on Sat Jan 13 21:07:14 2001:

Thanks!  That's just what I needed to know.

#3 of 5 by scott on Sat Jan 13 22:35:54 2001:

To expand on my response above, a DPDT switch is really like two SPTD switches
in the same box.  Eric's diagram would be more like:
|------------|
| 1    2   3 |
|------------|
| 4    5   6 |
|------------|

Internally, each section has two switches hooked up sort of like this:
|---------------|
| 1    2+3    4 |
|---------------|
That is, one switch is 1-2, and the other is 3-4.  2 and 3 are connected, and
only one of the two switches is on at a time (so when 1-2 is on, 3-4 is off).

#4 of 5 by rcurl on Sat Jan 13 23:04:58 2001:

Most DPDT toggle switches have only one swinging contact assemble at 3 (in
ea's diagram). That is, one SPDT component is either [1--3  5] or [1  3--5].

#5 of 5 by gull on Sun Jan 14 20:39:54 2001:

Also, a tip:  On toggle switches, the connection is made to the contacts 
on the opposite end from the one the handle is pointing towards.  On 
slide switches, the connection is made on the same end the handle is 
slid towards.

Internally, the mechanism is much the same, but toggles involve a lever 
action.

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