This must be simple but I can't seem to think it out in my head.

I have a DPDT switch, and I want to control a fan and a LED power source....120VAC to 12VDC converter that I pulled out of a wall wart.

When the switch is flipped one way it should run just the fan, when switched the other way it should run the fan and the light.

How can I wire this up without feeding power back into the light circuit?

 

When the switch is flipped one way it should run just the fan, when switched the other way it should run the fan and the light.

So when is the fan off?
It sounds like you just wire the fan directly to the power.

Or is DPDT with center-off?
If so, just wire the appropriate power to each of the center (wiper terminals).
Then connect both sides of one pole to the fan, but only one side of the other pole to the LED.

 

yeah it is center off...forgot to mention that.
The original design uses a DPST switch to break both hot and neutral.

it's in a small airbrush paint booth, I'm adding a light. so the switch I bought drops right in perfectly.

 

So here's how to wire it:

 

Fan power and LED power are coming from the same 120V source not separate.
so one side of the switch would go to the fan only, and the other side of the switch would go to the fan and the led power supply.

If I hook it up like that, because both common and hot are on the switch legs, when I switch only the fan on it'll send power to the LED power supply, but since neutral would be broken at the switch it would still work without powering on the LEDs right?

 

Maybe this will help a bit. The blue and red wires are hot and neutral going into the switch. The two black wires are for the fan.
the white wire is for the LED power supply..... I need to hook this up to the empty terminals on the switch with the fan as well but want to avoid any backfeeding if possible.

 

Fan power and LED power are coming from the same 120V source not separate.
so one side of the switch would go to the fan only, and the other side of the switch would go to the fan and the led power supply.

No.
120V hot goes to both left pins.
The right of the switch stays as I showed.

If I hook it up like that, because both common and hot are on the switch legs,

No.
Only hot goes to the switch.
Neutral (common) is not switched.

 

Yes, neutral is switched, I checked it with my meter. Both hot and neutral are switched. If it were wired as you say then the fan would be connected to two hot wires.

 

There must be a way to do this with both wires switched, but I can't seem to figure it out in multisim.....i've apparently forgotten a lot of what I used to know....

 

Yes, neutral is switched, I checked it with my meter. Both hot and neutral are switched. If it were wired as you say then the fan would be connected to two hot wires.

Neutral may now be switched, but you can't do what you want with a DPDT switch and control both hot and neutral.

There must be a way to do this with both wires switched, but I can't seem to figure it out in multisim.....i've apparently forgotten a lot of what I used to know.

You can't figure it out because it's not possible.
You need a 3PDT center-off switch, so you have an extra pole to switch the neutral.

 

eff.....I was really hoping to be able to have two modes to this thing, I got lucky finding a switch that dropped right in.
I guess I'm going to have to do what I didn't want to do and rewire it without the neutrals being switched.

 

So this keeps giving me a convergence error in multisim, but I'm not sure if it's because one of the poles is left disconnected or something else...... this hsould be correct, right?

 

So this keeps giving me a convergence error in multisim, but I'm not sure if it's because one of the poles is left disconnected or something else...... this hsould be correct, right?

I don't see a ground connection.
Spice simulators need some point in the circuit grounded for a proper simulation.

If that doesn't add a 1k resistor to ground to all the unused pins.

 

right, thanks..... It's been a number of years since I used this program and I forgot about that.

so If I wire it up like that it should work, I added ground to my simulation and it works fine.

 

I guess a SPDT would be better here since I'm wiring the neutrals together now and basically only need to use one half of this switch.

 

I guess a SPDT would be better here since I'm wiring the neutrals together now and basically only need to use one half of this switch.

How can that power the fan in both positions and the LED in only one?

 

I don't know, this is the trouble I'm having.......

so how do I have to wire this thing to achieve those ends? this should be simple and has taken far too long already.... this is the only aspect of this project left to finish.

 

screw it..... I'm going back to the original switch.....when the light is on the fan is on and when it's off it's all off.

 

screw it..... I'm going back to the original switch.....when the light is on the fan is on and when it's off it's all off.

Why do you think you have to switch the neutral/common?

 

I don't, it's how this stupid thing was designed. My life would've been a hell of a lot easier if they had just used a normal switch like normal people.

but it doesn't matter now anyway because you haven't actually helped me at all, just kept fixating on that neutral wire when all I wanted was some basic assistance trying to accomplish what I incorrectly thought would be a simple task.

I don't have the time or the space to have this thing sitting apart for days when it just needed a light. The light is installed and it's all working perfectly, just not entirely as planned.