using a relay for a latching circuit

[POD]

I've reupholstered the Defender seats and included seat heaters as my wife raves about them in my other car. The standard wiring that comes with the heater kit includes a fairly normal rocker switch albeit with a nice diagram of a seat heater. Problem I have with this is that if the heater is on when the ignition is turned off, it will come back on next time the ignition is turned on and will remain on until I remember to switch it off. I don't like this particularly for the passenger seat which could be inadvertently left on when unoccupied.
I want to set it up so that the heaters will not come back on after the ignition is switched off, unless they are again switched on. I believe I can achieve this with a simple 4-pin relay wired as shown in the attached diagram, with a 'start' (N.O.) and 'stop' (N.C.) switch.
I'd appreciate if the brains trust could check my diagram and confirm I have this correct (been a while)
I'm thinking also that the start and stop can probably be combined in a single 2-way momentary rocker switch with a N.O. and a N.C. function combined. If anyone can point me in the direction of such a switch that would also be great.
188410

[p38arover]

Can you post an image that’s not squashed.

[Blknight.aus]

What you've drawn up will work however the switchs will briefly be required to carry the full load

I'd add a resistor between the stop switch and the relay if the seat heaters pull full.cirrent on startup.

[POD]

Can you post an image that’s not squashed.

Yeah dunno what happened there. Trying again.
188417

Regarding carrying the full load, wouldn't that be for a poofteenth of a second before the relay latches? do you reckon that would be a problem? I can use this circuit to switch a second relay.

I was looking at Carling switches with an on-off-on momentary function, there are some that have eight terminals- would I be right in thinking that this makes one of the positions selectable between N.O. or N.C.?

[Blknight.aus]

Yeah dunno what happened there. Trying again.
188417

Regarding carrying the full load, wouldn't that be for a poofteenth of a second before the relay latches? do you reckon that would be a problem? I can use this circuit to switch a second relay.

I was looking at Carling switches with an on-off-on momentary function, there are some that have eight terminals- would I be right in thinking that this makes one of the positions selectable between N.O. or N.C.?

Yes it's only a fraction of a second but that fraction of a second is all it takes to arc the contacts and fuse them infused often enough.

[POD]

Yes good call. I'll run the heat power through a second relay.

[scarry]

Or use a latching relay with two sets of contacts,one for the load,using a hard 12V.
Just make sure the relay can carry the current needed.

[POD]

Or use a latching relay with two sets of contacts,one for the load,using a hard 12V.
Just make sure the relay can carry the current needed.

I guess that would be a DPDT relay- I'm going to start to get confused sorting out the separation of the circuits! I might be better off using this latching circuit to feed switching power to a second relay.
The challenge seems to be finding a NO / NC rocker switch. I'd far prefer a rocker switch for each seat to a pair of push switches.

[goingbush]

I answered before but had a brain fart, this is try 2.

You need a dual pole relay (or 2 relays, just parallel the coils) . The seat load need to come from battery not Ignition, dont forget to fuse it.

You need a push button switch for seat control , Not a toggle, Carling have push buttons.

188419

[POD]

I answered before but had a brain fart, this is try 2.

You need a dual pole relay (or 2 relays, just parallel the coils) . The seat load need to come from battery not Ignition, dont forget to fuse it.

You need a push button switch for seat control , Not a toggle, Carling have push buttons.

188419

Thanks for that. A problem with that schematic though, unless I'm missing something, is that the only way to turn the heater off is to turn the ignition off. Still leaves me needing a 'normally closed' switch to break the coil circuit.

[goingbush]

Thanks for that. A problem with that schematic though, unless I'm missing something, is that the only way to turn the heater off is to turn the ignition off. Still leaves me needing a 'normally closed' switch to break the coil circuit.

ahh yeah, I forgot about the off bit its like a logic problem.
that will be brain fart 2. This is why I dont do computer programming. I'll have another try.

[goingbush]

here we go, tested in my head , works,

push button for on, push again for off . you could add a pilot light across relay 5 coil so you know its on or off incase the boss says "I thought you turned seat warmer on"

this is as simple as it gets with relays, if you want a single pushbotton for on / off.
you will need 2 diodes. tbh much easier with transistors and more compact too .


188431

[POD]

It might take me a while to get my head around that! :)

[scarry]

Just put an ON/Off switch on ignition in feed,that will turn it off while ignition is on, if push button switch has been pushed.

As for diodes,transistors,i don't know as we normally work on 240,415V,etc,and don't use them.

[4bee]

Can you post an image that’s not squashed.



Or not vertical, my eyes ARE horizontal not vertical.[bigrolf]