Reply With QuoteIt seems overly complex and you can get chattering using one relay to switch another. A simpler method is to use a "retaining" contact, like in this drawing.
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ChatterBox
SubscriberLast year when I reupholstered my seats, I installed the optional heating pads to both seats. I have not yet wired them up. The loom that comes with the heaters is a simple on-off relay circuit with a rocker switch. The problem I have with this is, if I or a passenger switch the heater on and do not switch it off when exiting the vehicle, the heater will again be on next time the ignition is switched on. I want it to switch off with ignition off and not come back on unless intentionally switched on.
I've sketched up a very simple circuit diagram and would like some feedback regarding whether there are any problems using relays in this manner. I've acquired a couple of small DPDT momentary switches with a Normally Open (N.O.) and a Normally Closed (N.C.) in each. I propose to use the N.C. switch to switch on, this will latch the first relay in and activate the circuit until either the NC switch is pressed to turn the heater off, or the ignition is switched off.
Anyone see any problem with this? And yes I do know to put fuses in.
seat heater circuit.jpg
ForumSage
SupporterIt seems overly complex and you can get chattering using one relay to switch another. A simpler method is to use a "retaining" contact, like in this drawing.
download.png
2005 D3 TDV6 Present
1999 D2 TD5 Gone
ChatterBox
SubscriberOk thanks for that; the diagram above shows a 415v circuit with a contactor, I've used those many times with machines in my workshop but I could not find the equivalent for a 12v circuit (also they are horribly expensive in 415v) thus my attempt to replicate the system in 12v.
ForumSage
Supporter
There's a way to do it with what you have, using -ve switching, excuse my scrawl.....
20250821_191933.jpg
2005 D3 TDV6 Present
1999 D2 TD5 Gone
ChatterBox
SubscriberThanks for that, just got your PMs, wife had a remote meeting on our only computer...
I see the difference to my diagram is that the NC 'stop' switch is on the earth side of relay 1 coil rather than the +ve side, and that the N.O. start switch is connected to both relay coils. Does this avoid the chattering problem that Randlover mentioned? It looks like an elegant solution. Thanks again for taking the time.
ForumSage
SupporterYes, ignore what I said about chattering, as at first I thought the switches were relay contacts.
2005 D3 TDV6 Present
1999 D2 TD5 Gone
ChatterBox
SubscriberThat's great, thanks. Now I need to figure out a location on each side of the dash for two little push-buttons, and a way to label them.
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