seat heaters/momentary , latching circuit

I want to build or buy a relay to use on me car seat heaters that works in the following manner;

The circuit only becomes active when the car is running.
Each seat heater is activated by a momentary switch – Depress it once the heater turns on . Depress it again it turns off. Depress it again and it turns on. etc
When the Car is turned off all the seat heaters turn off.

Finally, Regardless of whether the seat heater was on or off when the car was running, all of the heaters return to an "OFF" state when the car is turned off. The next time the car is started the seat heaters are off.

I have units that heat up very quickly and have a large draw, I don't want any of the seat heaters to begin running when I next start the car. I looked through all of the information the site had on relays and this configuration seemed to get the closest to what I wanted to do but I do not think it was all the way there;

“Latched on/off using a single momentary pulse” seemed to take care of the on off portion seat heater portion but I do not know if cutting the 12vdc (by changing the source to accessory power) will return the entire system to an “off” state so that the heaters are not running the next time the car is used.

If this will do it then my journey is ended. If not can anyone direct me to a solution?

(Btw – special thanks to the 12volt administrator who put this app in place back in 2010)


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Rich
"Time flies like an arrow, Fruit flies like a banana"
DOG80pix.jpg

dosomething wrote:

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“Latched on/off using a single momentary pulse” seemed to take care of the on off portion seat heater portion but I do not know if cutting the 12vdc (by changing the source to accessory power) will return the entire system to an “off” state so that the heaters are not running the next time the car is used.

If this will do it then my journey is ended.

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Yes it will. Removing the power to the array, returns all relays to the relaxed state. Ie, waiting for ON. Your journey has ended. This circuit will do exactly what you desire.

Thank you thank you thank you!!!

I was reading in another post about using a much smaller set of mini relays so they would not take up as much space. Any idea what these are called and where I might purchase them?

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Rich
"Time flies like an arrow, Fruit flies like a banana"
DOG80pix.jpg

PCB relays, Radio Shack, Farnell, Mouser etc.
Be careful to check your power consumption, most will only switch 5-10 amps.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

dosomething wrote:

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I was reading in another post about using a much smaller set of mini relays so they would not take up as much space.

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In the 4-relay array above, 3 of the 4 relays have to be capable of carrying the heater current. To save space, you could use mini-relays in the 4-relay array, but then add a 5th high-current relay for the actual heater switching. Because the 4-relay array is only switching 120Ma of the 5th's relay coil, they can be very small.

Wire as follows:

85 = Ground
86 = "12volt Output" from the array. (Blue circuit)
30 = Power source for the heaters. (This can be a Hot at all times if desired).
87 = Output to heater.

There are electronic solutions which is my preference rather than several-relay logic - eg, that 2 inverter circuit I often posted to drive a relay via a transistor or MOSFET or simply drive a high current MOSFET; hence 3 "switches" per 14 pin hex inverter chip.

There is also the SPST single relay circuit but that requires a 2nd momentary to switch off, and a master +12V supply - eg, on extra IGN +12V relay - to enable & turn the lot off.

See both here.