Relay and switch wiring

[snoop6060]

Afternoon,

Another one of my probably stupid wiring questions...well, 2 actually .

I have wired my heated seats to a GSM controller which can basically trigger the relay without the dash switch being on. Works fine, the seats work either from the dash switch or from the GSM controller so I can switch them on remotely via SMS and even Alexa though Alexa is a bit flakey atm. Though... what happens if both the switch and the GSM controller are on and both providing 12volts to the relay for the heated seats, will this fry the relay? Something tells me not but just checking. Its wired on my desk atm so can just test, but may as well ask first.

Second one, and perhaps this actually is a stupid question. Obviously it would be normal to wire heated seats to a ignition switched supply, but I cannot due to wanting to remotely turn them on. So they are going to get wired to the leisure battery. Nice and simple as its under the seat. Though that means I could accidentally leave them on and drain the leisure battery which I almost certainly will do. So, could I wire the 12v input for the switch from a ignition controlled 12v from the main battery but wire the 12v+ to the relay which provides the actual current to the seats from the leisure battery? That way the switch will not operate without the engine on closing the relay, but when the GSM controller relay is on, that will bypass the switch so should work with the engine off. The GSM controller runs the heated seats for a max of 30mins so should not drain the battery under any circumstances. Cannot see why this would not work but again, may as well ask .

Cheers,
Si

 

[Pauly]

You need to be careful of dual supplies, in the first instance the control circuit feeds and in the second instance the main supply feeds.
In either case if both is switched on at the same time you will potentially be joining two circuits together and in turn pulling form two supplies on two different fuses !

In the first part i assume you are using the same supply to feed the manual switch and the GSM controller switch so whiles its not ideal cant see it would do any damage

In the second part if you fed one relay from engine batt and another relay from leisure batt if they both energise at the same time you would in effect link the two batteries together and that will cause problems as the batteries would try and equalise through your seat heater wiring, if they are at different states of charge current will flow and fuses will blow, i would think very carefully before going down this route as proper planning would be needed to keep the batteries electrically isolated, using multiple relays or some form of changeover switch rather than a normal relays maybe required, there are different ways you could go about it but seems to be over complicating a simple circuit ?

 

[snoop6060]

Over complicating things is just how I roll

I can feed both in the first example from the same supply and I had not considered that. The second question, it might just be better to forget that and if I flatten my lesuire battery then serves me right. That certainly simplifies it all

Can you move this to the electrics forum? Realised I posted in the wrong one.