I have this cigarette lighter adaptor installed:
http://www.blanford.com/AccessoryPowerOutlet/index.html

I want to install a toggle switch to turn it off, so I can leave my items plugged in and just turn off the power to the outlet versus pulling the power plugs out.

Do I need a DPST (dual pole, single throw) to turn off the live and ground or can I use a SPST (single pole, single throw) to turn off the live and keep the ground connected?

Are there any concerns with the SPST route?

Thanks in advance,
Jordan

 

You just need a simple ON/OFF switch - 2 terminals, simple lever or button for on or off. Put it on your ground wire. SPST is just fine.
Like this:
http://www.radioshack.com/product.asp?cata...BC11EF9E514E3A1

 

I thought I cut the live?

I've been looking on the internet to verify which one to cut. Everything I can find on Radioshack.com says LOAD and POWER, I assume that I cut the live line still...

Thanks in advance...again
Jordan

 

hehe, that link involves a pretty wide variety of types of circuits. It's probably too extensive. All you need to know is that on negative ground automotive DC circuits, most switches are on the ground wire. Putting it on the ground reduces the chance of accidental short circuits. I've used switches like what I linked up for all kinds of automotive devices, including hidden kill switches.

 

I usually put the switch in the "Hot" wire to the addapter plug. Both ways work BUT if the chassis of the appliance is metal and is grounded it will still be on when the ground wire to the cig. plug "socket" is opened with the switch. Or it will "spark" if it is bouncing around in the car and comes in contact with a grounded item. If it is a radio it will be grounded through the antenna shield/ground wire. So open the +12 Volt lead with the switch.
Andy

 

I bought the automotive rocker switch from Radio Shack for a whopping $2.XX...

I connected it to the hot wire. They said that way the device is always protected with a ground. The guy at the store said if I switched the ground it would be possible to fry a device since there was no ground protection. I decided to switch the hot wire.

Tested it out - works.

 

You know what they say - "You've got questions, we've got answers". Of course they didn't say it would be the right answer. Sometimes I think "RS" stands for "really stupid".

I'm not sure what "protection" the RS guy was referring to, but you did good by switching the +12v lead. Like Andy Kirk said, leaving the hot wire hot can cause problems on devices with a grounded housing.

Xviper - Over the years I've heard lots of interesting theories on why many automotive circuits switch ground instead of hot, one of the more interesting ones was that "all the current flows in the hot lead, so you can use a smaller switch or relay to switch ground". Uh-huh. And electrons make you fart.

In general, the safest method is to switch the +12v lead for anything electrical. The reason modern cars frequently switch negative is because of cost. Solid state switches (transistors and MOSFETs) are always cheaper and more efficient as N-channel devices, (meaning they switch negative currents). P-channel devices cost twice as much and still can't handle the same load currents as their N-channel counterparts.

.

 

And this whole time I've been reading automotive wiring diagrams, I've been thinking they knew what they were doing. All along, they've been just saving money. I shoulda known.
Anyway, all my switches are on the ground wire and I'm too lazy to go back and change them. (I don't really have that many.)

 

Xviper - Over the years I've heard lots of interesting theories on why many automotive circuits switch ground instead of hot, one of the more interesting ones was that "all the current flows in the hot lead, so you can use a smaller swiAnd electrons make you farttch or relay to switch ground". Uh-huh. .



I've been designing and installing electrical equipment in aircraft and cars for a heck of a long time, so that's why I fart so much.
Andy

 

It dosen't matter weather the switching device is in the negative or the positive lead, the current is exactly the same. However a solid state device like a FET is easier to switch on in the negative side as the "on" voltage is lower. If it is in the positive side the "on" voltage must be higher as in above +12 Volts. I think it is just easier to provide the switching voltage. A "P" device can be used in either the +12 Volt or the ground side.
Andy