Shutoff adapter

If I were to turn this into a project, it would be like this: Alternator runs batt V up to around 14.5V. When the car is off the batt drops down to ~12. Use this voltage as the automatic turn off. So... Voltage controlled switch. A low Rdson Mosfet switched by a threshold cct. ?? D from BC

Put a little leash on the plug that you clip to your key ring, and when you get out of the car, you can't take the key unless you unplug and unclip. :-)

Admittedly, this won't guarantee it gets unplugged, but it'd be a pretty effective reminder. :-)

Good Luck! Rich

In hot climates (aka Arizona) that can be as low as 13.3V

I don't know. I've been pondering a similar situation where I don't have switched A+ readily available... radar detector ;-)

...Jim Thompson

My escort radar detector uses an accelerometer to detect when the vehicle is not moving and turns off. maybe that's the way to go, but I was looking for something already available instead of a science project ;)

Like

or

plugged

A Relay?? The relay contacts go in series with the cigarette lighter and the coil is driven by the "engine running" voltage that is present somewhere (for the seat belt alarms, radio, e.t.c.). My car is like that from factory.

Yep. I feel an Instant ASCII drawing coming on.

IN ---+--------+--------+-------+---------+--------- | | | | | | 470k | 470k 2.2k 470k | | | | OUT | 100k | | | | pot ,-----|--10M--+ LED | | | __| | | | +--+--|+ \ | +--------- | | | >-----+ | +--------|-----|-__/ | |---' D \_|_ | | | G |

What about this idea (I feel the ASCII art coming)

| Butt | \\ / ^^^^/\\^^^^ ________________ | / switch | | ---/ o---- | | | .............| Cushion |................ car seat

i.e. microswitch embedded in the cushion so that the power is only supplied when you sit on it? I think it would fullfill your requirements unless you'd fall asleep in the parked car :)

many vehicles have the lighter socket connected to the accessories circuit (powers the wipers, vent/ac fan etc) so it cuts off when you turn off the key. it should be possible to add an additional socket on that circuit to power your hotseat.

Sorry, I meant LM393, the jellybean dual comparator. Three 470k resistors takes about 75uA, which isn't so bad, but an LM393 takes about 650uA, and is a bit of a hog. It's cheap and easy to get, but a comparator like LTC's LT1017, drawing 30uA, would be better.

IN ---+--------+--------+-------+---------+--------- | | | | | | 470k | 470k 2.2k 470k | | | | OUT | 100k | | | | pot ,-----|--10M--+ LED | | | __| | | | +--+--|+ \ | +--------- | | | >-----+ | +--------|-----|-__/ | |---' D \_|_ | | | G |

Sorry, I meant LM393, the jellybean dual comparator. Three 470k resistors take about 75uA, which isn't so bad, but an LM393 takes about 650uA, and is a bit of a hog. It's cheap and easy to get, but a low-power comparator like LTC's LT1017, drawing 30uA, would be better. The LT1017 has an active output pullup, so only two 470k resistors would be needed.

IN ---+--------+--------+-----------------+--------- | | | | | 470k | 2.2k 470k | | | OUT | 100k | | | pot ,-----|--10M--, LED | | | __| | | | +--+--|+ \ | +--------- | | | >-----+ | +--------|-----|-__/ | |---' D \_|_ | | | G |

Yes. Its called a relay. Get a 20A unit (for auxiliary lights, etc. at an auto supply shop) and cut the contacts into the cig. lighter circuit. Energize the coil from the auxiliary position on the ignition switch (downstream of a fuse). When the key is off, so is the lighter socket.

The lighter socket in my Ford Ranger isn't switched.

Most cigarette lighter sockets aren't. My new Q45 has extra "outlets" of that type, for accessories, phone chargers, etc., and THEY are switched.

...Jim Thompson

Neither the lighter nor auxiliary (same as a lighter without the lighter) in my '01 Ranger are switched. Good thing, they don't mess up my MP3 player.

Nor in my Mercury Cougar. I'm not enamored of solutions that require getting at the wiring under the dash. Under the hood, or in the trunk, etc., is OK, but behind and under the dash is murder. That's why I liked using the battery voltage to switch after the lighter outlet, e.g., with a simple circuit like the one I posted.

IN ---+--------+--------+-----------------+--------- | | | | | 470k | 2.2k 470k | | | OUT | 100k | | | pot ,-----|--10M--, LED | | | __| | | | +--+--|+ \\ | +--------- | | | >-----+ | +--------|-----|-__/ | |---' D \\_|_ | | | G |

The idea is to make it switched. All of my cars (dating back to 1979 models) have switched lighter sockets.

If that isn't desirable, I like the other guy's idea of a butt activated weight switch.

I don't remember any car or truck I've owned in the past 37 years that had a switched cigarette lighter socket. The radio is usually switched, and on its own fuse. There are adapter clips that snap on one leg of a fuse to tap the line. You pull the fuse, find the supply end and connect it there. Just make sure to use a fuse in the line, and as close to the fuse block as practical so that a short won't destroy the ignition switch. I was using this method in the early '70s because I never modify a wiring harness in a vehicle, and never buy one if there is any evidence that some moron has made any changes.

You're making it tooooo difficult. Open the cover to the fuses. You should find some spare LUGS that are on the accessory switch to simply slip a connector over.

Shouldn't. Read my alternator regulator patents... "cold" plateau is

Those of you in a severe climate will have trouble finding a low threshold that works year-round.

...Jim Thompson